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Subject[PATCH 6/7] [v2] tty/powerpc: introduce the ePAPR embedded hypervisor byte channel driver
Date
The ePAPR embedded hypervisor specification provides an API for "byte
channels", which are serial-like virtual devices for sending and receiving
streams of bytes. This driver provides Linux kernel support for byte
channels via three distinct interfaces:

1) An early-console (udbg) driver. This provides early console output
through a byte channel. The byte channel handle must be specified in a
Kconfig option.

2) A normal console driver. Output is sent to the byte channel designated
for stdout in the device tree. The console driver is for handling kernel
printk calls.

3) A tty driver, which is used to handle user-space input and output. The
byte channel used for the console is designated as the default tty.

Signed-off-by: Timur Tabi <timur@freescale.com>
---
arch/powerpc/include/asm/udbg.h | 1 +
arch/powerpc/kernel/udbg.c | 2 +
drivers/tty/Kconfig | 33 ++
drivers/tty/Makefile | 1 +
drivers/tty/ehv_bytechan.c | 888 +++++++++++++++++++++++++++++++++++++++
5 files changed, 925 insertions(+), 0 deletions(-)
create mode 100644 drivers/tty/ehv_bytechan.c
diff --git a/arch/powerpc/include/asm/udbg.h b/arch/powerpc/include/asm/udbg.h
index 11ae699..bb9f6b1 100644
--- a/arch/powerpc/include/asm/udbg.h
+++ b/arch/powerpc/include/asm/udbg.h
@@ -52,6 +52,7 @@ extern void __init udbg_init_44x_as1(void);
extern void __init udbg_init_40x_realmode(void);
extern void __init udbg_init_cpm(void);
extern void __init udbg_init_usbgecko(void);
+extern void __init udbg_init_ehv_bc(void);

#endif /* __KERNEL__ */
#endif /* _ASM_POWERPC_UDBG_H */
diff --git a/arch/powerpc/kernel/udbg.c b/arch/powerpc/kernel/udbg.c
index e39cad8..d117368 100644
--- a/arch/powerpc/kernel/udbg.c
+++ b/arch/powerpc/kernel/udbg.c
@@ -62,6 +62,8 @@ void __init udbg_early_init(void)
udbg_init_cpm();
#elif defined(CONFIG_PPC_EARLY_DEBUG_USBGECKO)
udbg_init_usbgecko();
+#elif defined(CONFIG_PPC_EARLY_DEBUG_EHV_BC)
+ udbg_init_ehv_bc();
#endif

#ifdef CONFIG_PPC_EARLY_DEBUG
diff --git a/drivers/tty/Kconfig b/drivers/tty/Kconfig
index 3fd7199..9fe0212 100644
--- a/drivers/tty/Kconfig
+++ b/drivers/tty/Kconfig
@@ -319,3 +319,36 @@ config N_GSM
This line discipline provides support for the GSM MUX protocol and
presents the mux as a set of 61 individual tty devices.

+config PPC_EPAPR_HV_BYTECHAN
+ tristate "ePAPR hypervisor byte channel driver"
+ depends on PPC
+ help
+ This driver creates /dev entries for each ePAPR hypervisor byte
+ channel, thereby allowing applications to communicate with byte
+ channels as if they were serial ports.
+
+config PPC_EARLY_DEBUG_EHV_BC
+ bool "Early console (udbg) support for ePAPR hypervisors"
+ depends on PPC_EPAPR_HV_BYTECHAN
+ help
+ Select this option to enable early console (a.k.a. "udbg") support
+ via an ePAPR byte channel. You also need to choose the byte channel
+ handle below.
+
+config PPC_EARLY_DEBUG_EHV_BC_HANDLE
+ int "Byte channel handle for early console (udbg)"
+ depends on PPC_EARLY_DEBUG_EHV_BC
+ default 0
+ help
+ If you want early console (udbg) output through a byte channel,
+ specify the handle of the byte channel to use.
+
+ For this to work, the byte channel driver must be compiled
+ in-kernel, not as a module.
+
+ Note that only one early console driver can be enabled, so don't
+ enable any others if you enable this one.
+
+ If the number you specify is not a valid byte channel handle, then
+ there simply will be no early console output. This is true also
+ if you don't boot under a hypervisor at all.
diff --git a/drivers/tty/Makefile b/drivers/tty/Makefile
index 690522f..4afebd2 100644
--- a/drivers/tty/Makefile
+++ b/drivers/tty/Makefile
@@ -24,5 +24,6 @@ obj-$(CONFIG_ROCKETPORT) += rocket.o
obj-$(CONFIG_SYNCLINK_GT) += synclink_gt.o
obj-$(CONFIG_SYNCLINKMP) += synclinkmp.o
obj-$(CONFIG_SYNCLINK) += synclink.o
+obj-$(CONFIG_PPC_EPAPR_HV_BYTECHAN) += ehv_bytechan.o

obj-y += ipwireless/
diff --git a/drivers/tty/ehv_bytechan.c b/drivers/tty/ehv_bytechan.c
new file mode 100644
index 0000000..e67f70b
--- /dev/null
+++ b/drivers/tty/ehv_bytechan.c
@@ -0,0 +1,888 @@
+/* ePAPR hypervisor byte channel device driver
+ *
+ * Copyright 2009-2011 Freescale Semiconductor, Inc.
+ *
+ * Author: Timur Tabi <timur@freescale.com>
+ *
+ * This file is licensed under the terms of the GNU General Public License
+ * version 2. This program is licensed "as is" without any warranty of any
+ * kind, whether express or implied.
+ *
+ * This driver support three distinct interfaces, all of which are related to
+ * ePAPR hypervisor byte channels.
+ *
+ * 1) An early-console (udbg) driver. This provides early console output
+ * through a byte channel. The byte channel handle must be specified in a
+ * Kconfig option.
+ *
+ * 2) A normal console driver. Output is sent to the byte channel designated
+ * for stdout in the device tree. The console driver is for handling kernel
+ * printk calls.
+ *
+ * 3) A tty driver, which is used to handle user-space input and output. The
+ * byte channel used for the console is designated as the default tty.
+ */
+
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/slab.h>
+#include <linux/err.h>
+#include <linux/interrupt.h>
+#include <linux/fs.h>
+#include <linux/poll.h>
+#include <asm/epapr_hcalls.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/cdev.h>
+#include <linux/console.h>
+#include <linux/tty.h>
+#include <linux/tty_flip.h>
+#include <linux/circ_buf.h>
+#include <asm/udbg.h>
+
+/* The size of the transmit circular buffer. This must be a power of two. */
+#define BUF_SIZE 2048
+
+/* Per-byte channel private data */
+struct ehv_bc_data {
+ struct device *dev;
+ struct tty_port port;
+ uint32_t handle;
+ unsigned int rx_irq;
+ unsigned int tx_irq;
+
+ spinlock_t lock; /* lock for transmit buffer */
+ unsigned char buf[BUF_SIZE]; /* transmit circular buffer */
+ unsigned int head; /* circular buffer head */
+ unsigned int tail; /* circular buffer tail */
+
+ int tx_irq_enabled; /* true == TX interrupt is enabled */
+};
+
+/* Array of byte channel objects */
+static struct ehv_bc_data *bcs;
+
+/* Byte channel handle for stdout (and stdin), taken from device tree */
+static unsigned int stdout_bc;
+
+/* Virtual IRQ for the byte channel handle for stdin, taken from device tree */
+static unsigned int stdout_irq;
+
+/**************************** SUPPORT FUNCTIONS ****************************/
+
+/*
+ * Enable the transmit interrupt
+ *
+ * Unlike a serial device, byte channels have no mechanism for disabling their
+ * own receive or transmit interrupts. To emulate that feature, we toggle
+ * the IRQ in the kernel.
+ *
+ * We cannot just blindly call enable_irq() or disable_irq(), because these
+ * calls are reference counted. This means that we cannot call enable_irq()
+ * if interrupts are already enabled. This can happen in two situations:
+ *
+ * 1. The tty layer makes two back-to-back calls to ehv_bc_tty_write()
+ * 2. A transmit interrupt occurs while executing ehv_bc_tx_dequeue()
+ *
+ * To work around this, we keep a flag to tell us if the IRQ is enabled or not.
+ */
+static void enable_tx_interrupt(struct ehv_bc_data *bc)
+{
+ if (!bc->tx_irq_enabled) {
+ enable_irq(bc->tx_irq);
+ bc->tx_irq_enabled = 1;
+ }
+}
+
+static void disable_tx_interrupt(struct ehv_bc_data *bc)
+{
+ if (bc->tx_irq_enabled) {
+ disable_irq_nosync(bc->tx_irq);
+ bc->tx_irq_enabled = 0;
+ }
+}
+
+/*
+ * find the byte channel handle to use for the console
+ *
+ * The byte channel to be used for the console is specified via a "stdout"
+ * property in the /chosen node.
+ *
+ * For compatible with legacy device trees, we also look for a "stdout" alias.
+ */
+static int find_console_handle(void)
+{
+ struct device_node *np, *np2;
+ const char *sprop = NULL;
+ const uint32_t *iprop;
+
+ np = of_find_node_by_path("/chosen");
+ if (np)
+ sprop = of_get_property(np, "stdout-path", NULL);
+
+ if (!np || !sprop) {
+ of_node_put(np);
+ np = of_find_node_by_name(NULL, "aliases");
+ if (np)
+ sprop = of_get_property(np, "stdout", NULL);
+ }
+
+ if (!sprop) {
+ of_node_put(np);
+ return 0;
+ }
+
+ /* We don't care what the aliased node is actually called. We only
+ * care if it's compatible with "epapr,hv-byte-channel", because that
+ * indicates that it's a byte channel node. We use a temporary
+ * variable, 'np2', because we can't release 'np' until we're done with
+ * 'sprop'.
+ */
+ np2 = of_find_node_by_path(sprop);
+ of_node_put(np);
+ np = np2;
+ if (!np) {
+ pr_warning("ehv-bc: stdout node '%s' does not exist\n", sprop);
+ return 0;
+ }
+
+ /* Is it a byte channel? */
+ if (!of_device_is_compatible(np, "epapr,hv-byte-channel")) {
+ of_node_put(np);
+ return 0;
+ }
+
+ stdout_irq = irq_of_parse_and_map(np, 0);
+ if (stdout_irq == NO_IRQ) {
+ pr_err("ehv-bc: no 'interrupts' property in %s node\n", sprop);
+ of_node_put(np);
+ return 0;
+ }
+
+ /*
+ * The 'hv-handle' property contains the handle for this byte channel.
+ */
+ iprop = of_get_property(np, "hv-handle", NULL);
+ if (!iprop) {
+ pr_err("ehv-bc: no 'hv-handle' property in %s node\n",
+ np->name);
+ of_node_put(np);
+ return 0;
+ }
+ stdout_bc = be32_to_cpu(*iprop);
+
+ of_node_put(np);
+ return 1;
+}
+
+/*************************** EARLY CONSOLE DRIVER ***************************/
+
+#ifdef CONFIG_PPC_EARLY_DEBUG_EHV_BC
+
+/*
+ * send a byte to a byte channel, wait if necessary
+ *
+ * This function sends a byte to a byte channel, and it waits and
+ * retries if the byte channel is full. It returns if the character
+ * has been sent, or if some error has occurred.
+ *
+ */
+static void byte_channel_spin_send(const char data)
+{
+ int ret, count;
+
+ do {
+ count = 1;
+ ret = ev_byte_channel_send(CONFIG_PPC_EARLY_DEBUG_EHV_BC_HANDLE,
+ &count, &data);
+ } while (ret == EV_EAGAIN);
+}
+
+/*
+ * The udbg subsystem calls this function to display a single character.
+ * We convert CR to a CR/LF.
+ */
+static void ehv_bc_udbg_putc(char c)
+{
+ if (c == '\n')
+ byte_channel_spin_send('\r');
+
+ byte_channel_spin_send(c);
+}
+
+/*
+ * early console initialization
+ *
+ * PowerPC kernels support an early printk console, also known as udbg.
+ * This function must be called via the ppc_md.init_early function pointer.
+ * At this point, the device tree has been unflattened, so we can obtain the
+ * byte channel handle for stdout.
+ *
+ * We only support displaying of characters (putc). We do not support
+ * keyboard input.
+ */
+void __init udbg_init_ehv_bc(void)
+{
+ unsigned int rx_count, tx_count;
+ unsigned int ret;
+
+ /* Check if we're running as a guest of a hypervisor */
+ if (!(mfmsr() & MSR_GS))
+ return;
+
+ /* Verify the byte channel handle */
+ ret = ev_byte_channel_poll(CONFIG_PPC_EARLY_DEBUG_EHV_BC_HANDLE,
+ &rx_count, &tx_count);
+ if (ret)
+ return;
+
+ udbg_putc = ehv_bc_udbg_putc;
+ register_early_udbg_console();
+
+ udbg_printf("ehv-bc: early console using byte channel handle %u\n",
+ CONFIG_PPC_EARLY_DEBUG_EHV_BC_HANDLE);
+}
+
+#endif
+
+/****************************** CONSOLE DRIVER ******************************/
+
+static struct tty_driver *ehv_bc_driver;
+
+/*
+ * Byte channel console sending worker function.
+ *
+ * For consoles, if the output buffer is full, we should just spin until it
+ * clears.
+ */
+static int ehv_bc_console_byte_channel_send(unsigned int handle, const char *s,
+ unsigned int count)
+{
+ unsigned int len;
+ int ret = 0;
+
+ while (count) {
+ len = min_t(unsigned int, count, EV_BYTE_CHANNEL_MAX_BYTES);
+ do {
+ ret = ev_byte_channel_send(handle, &len, s);
+ } while (ret == EV_EAGAIN);
+ count -= len;
+ s += len;
+ }
+
+ return ret;
+}
+
+/*
+ * write a string to the console
+ *
+ * This function gets called to write a string from the kernel, typically from
+ * a printk(). This function spins until all data is written.
+ *
+ * We copy the data to a temporary buffer because we need to insert a \r in
+ * front of every \n. It's more efficient to copy the data to the buffer than
+ * it is to make multiple hcalls for each character or each newline.
+ */
+static void ehv_bc_console_write(struct console *co, const char *s,
+ unsigned int count)
+{
+ unsigned int handle = (unsigned int)co->data;
+ char s2[EV_BYTE_CHANNEL_MAX_BYTES];
+ unsigned int i, j = 0;
+ char c;
+
+ for (i = 0; i < count; i++) {
+ c = *s++;
+
+ if (c == '\n')
+ s2[j++] = '\r';
+
+ s2[j++] = c;
+ if (j >= (EV_BYTE_CHANNEL_MAX_BYTES - 1)) {
+ if (ehv_bc_console_byte_channel_send(handle, s2, j))
+ return;
+ j = 0;
+ }
+ }
+
+ if (j)
+ ehv_bc_console_byte_channel_send(handle, s2, j);
+}
+
+/*
+ * When /dev/console is opened, the kernel iterates the console list looking
+ * for one with ->device and then calls that method. On success, it expects
+ * the passed-in int* to contain the minor number to use.
+ */
+static struct tty_driver *ehv_bc_console_device(struct console *co, int *index)
+{
+ *index = co->index;
+
+ return ehv_bc_driver;
+}
+
+static struct console ehv_bc_console = {
+ .name = "ttyEHV",
+ .write = ehv_bc_console_write,
+ .device = ehv_bc_console_device,
+ .flags = CON_PRINTBUFFER | CON_ENABLED,
+};
+
+/*
+ * Console initialization
+ *
+ * This is the first function that is called after the device tree is
+ * available, so here is where we determine the byte channel handle and IRQ for
+ * stdout/stdin, even though that information is used by the tty and character
+ * drivers.
+ */
+static int __init ehv_bc_console_init(void)
+{
+ if (!find_console_handle()) {
+ pr_debug("ehv-bc: stdout is not a byte channel\n");
+ return -ENODEV;
+ }
+
+#ifdef CONFIG_PPC_EARLY_DEBUG_EHV_BC
+ /* Print a friendly warning if the user chose the wrong byte channel
+ * handle for udbg.
+ */
+ if (stdout_bc != CONFIG_PPC_EARLY_DEBUG_EHV_BC_HANDLE)
+ pr_warning("ehv-bc: udbg handle %u is not the stdout handle\n",
+ CONFIG_PPC_EARLY_DEBUG_EHV_BC_HANDLE);
+#endif
+
+ ehv_bc_console.data = (void *)stdout_bc;
+
+ /* add_preferred_console() must be called before register_console(),
+ otherwise it won't work. However, we don't want to enumerate all the
+ byte channels here, either, since we only care about one. */
+
+ add_preferred_console(ehv_bc_console.name, ehv_bc_console.index, NULL);
+ register_console(&ehv_bc_console);
+
+ pr_info("ehv-bc: registered console driver for byte channel %u\n",
+ stdout_bc);
+
+ return 0;
+}
+console_initcall(ehv_bc_console_init);
+
+/******************************** TTY DRIVER ********************************/
+
+/*
+ * byte channel receive interupt handler
+ *
+ * This ISR is called whenever data is available on a byte channel.
+ */
+static irqreturn_t ehv_bc_tty_rx_isr(int irq, void *data)
+{
+ struct ehv_bc_data *bc = data;
+ struct tty_struct *ttys = tty_port_tty_get(&bc->port);
+ unsigned int rx_count, tx_count, len;
+ int count;
+ char buffer[EV_BYTE_CHANNEL_MAX_BYTES];
+ int ret;
+
+ /* ttys could be NULL during a hangup */
+ if (!ttys)
+ return IRQ_HANDLED;
+
+ /* Find out how much data needs to be read, and then ask the TTY layer
+ * if it can handle that much. We want to ensure that every byte we
+ * read from the byte channel will be accepted by the TTY layer.
+ */
+ ev_byte_channel_poll(bc->handle, &rx_count, &tx_count);
+ count = tty_buffer_request_room(ttys, rx_count);
+
+ /* 'count' is the maximum amount of data the TTY layer can accept at
+ * this time. However, during testing, I was never able to get 'count'
+ * to be less than 'rx_count'. I'm not sure whether I'm calling it
+ * correctly.
+ */
+
+ while (count > 0) {
+ len = min_t(unsigned int, count, sizeof(buffer));
+
+ /* Read some data from the byte channel. This function will
+ * never return more than EV_BYTE_CHANNEL_MAX_BYTES bytes.
+ */
+ ev_byte_channel_receive(bc->handle, &len, buffer);
+
+ /* 'len' is now the amount of data that's been received. 'len'
+ * can't be zero, and most likely it's equal to one.
+ */
+
+ /* Pass the received data to the tty layer. */
+ ret = tty_insert_flip_string(ttys, buffer, len);
+
+ /* 'ret' is the number of bytes that the TTY layer accepted.
+ * If it's not equal to 'len', then it means the buffer is
+ * full, which should never happen. If it does happen, we can
+ * exit gracefully, but we drop the last 'len - ret' characters
+ * that we read from the byte channel.
+ */
+ if (ret != len)
+ break;
+
+ count -= len;
+ }
+
+ /* Tell the tty layer that we're done. */
+ tty_flip_buffer_push(ttys);
+
+ tty_kref_put(ttys);
+
+ return IRQ_HANDLED;
+}
+
+/*
+ * dequeue the transmit buffer to the hypervisor
+ *
+ * This function, which can be called in interrupt context, dequeues as much
+ * data as possible from the transmit buffer to the byte channel.
+ */
+static void ehv_bc_tx_dequeue(struct ehv_bc_data *bc)
+{
+ unsigned int count;
+ unsigned int len, ret;
+ unsigned long flags;
+
+ do {
+ spin_lock_irqsave(&bc->lock, flags);
+ len = min_t(unsigned int,
+ CIRC_CNT_TO_END(bc->head, bc->tail, BUF_SIZE),
+ EV_BYTE_CHANNEL_MAX_BYTES);
+
+ ret = ev_byte_channel_send(bc->handle, &len, bc->buf + bc->tail);
+
+ /* 'len' is valid only if the return code is 0 or EV_EAGAIN */
+ if (!ret || (ret == EV_EAGAIN))
+ bc->tail = (bc->tail + len) & (BUF_SIZE - 1);
+
+ count = CIRC_CNT(bc->head, bc->tail, BUF_SIZE);
+ spin_unlock_irqrestore(&bc->lock, flags);
+ } while (count && !ret);
+
+ spin_lock_irqsave(&bc->lock, flags);
+ if (CIRC_CNT(bc->head, bc->tail, BUF_SIZE))
+ /*
+ * If we haven't emptied the buffer, then enable the TX IRQ.
+ * We'll get an interrupt when there's more room in the
+ * hypervisor's output buffer.
+ */
+ enable_tx_interrupt(bc);
+ else
+ disable_tx_interrupt(bc);
+ spin_unlock_irqrestore(&bc->lock, flags);
+}
+
+/*
+ * byte channel transmit interupt handler
+ *
+ * This ISR is called whenever space becomes available for transmitting
+ * characters on a byte channel.
+ */
+static irqreturn_t ehv_bc_tty_tx_isr(int irq, void *data)
+{
+ struct ehv_bc_data *bc = data;
+ struct tty_struct *ttys = tty_port_tty_get(&bc->port);
+
+ ehv_bc_tx_dequeue(bc);
+ if (ttys) {
+ tty_wakeup(ttys);
+ tty_kref_put(ttys);
+ }
+
+ return IRQ_HANDLED;
+}
+
+/*
+ * This function is called when the tty layer has data for us send. We store
+ * the data first in a circular buffer, and then dequeue as much of that data
+ * as possible.
+ *
+ * We don't need to worry about whether there is enough room in the buffer for
+ * all the data. The purpose of ehv_bc_tty_write_room() is to tell the tty
+ * layer how much data it can safely send to us. We guarantee that
+ * ehv_bc_tty_write_room() will never lie, so the tty layer will never send us
+ * too much data.
+ */
+static int ehv_bc_tty_write(struct tty_struct *ttys, const unsigned char *s,
+ int count)
+{
+ struct ehv_bc_data *bc = ttys->driver_data;
+ unsigned long flags;
+ unsigned int len;
+ unsigned int written = 0;
+
+ while (1) {
+ spin_lock_irqsave(&bc->lock, flags);
+ len = CIRC_SPACE_TO_END(bc->head, bc->tail, BUF_SIZE);
+ if (count < len)
+ len = count;
+ if (len) {
+ memcpy(bc->buf + bc->head, s, len);
+ bc->head = (bc->head + len) & (BUF_SIZE - 1);
+ }
+ spin_unlock_irqrestore(&bc->lock, flags);
+ if (!len)
+ break;
+
+ s += len;
+ count -= len;
+ written += len;
+ }
+
+ ehv_bc_tx_dequeue(bc);
+
+ return written;
+}
+
+/*
+ * This function can be called multiple times for a given tty_struct, which is
+ * why we initialize bc->ttys in ehv_bc_tty_port_activate() instead.
+ *
+ * The tty layer will still call this function even if the device was not
+ * registered (i.e. tty_register_device() was not called). This happens
+ * because tty_register_device() is optional and some legacy drivers don't
+ * use it. So we need to check for that.
+ */
+static int ehv_bc_tty_open(struct tty_struct *ttys, struct file *filp)
+{
+ struct ehv_bc_data *bc = &bcs[ttys->index];
+
+ if (!bc->dev)
+ return -ENODEV;
+
+ return tty_port_open(&bc->port, ttys, filp);
+}
+
+/*
+ * Amazingly, if ehv_bc_tty_open() returns an error code, the tty layer will
+ * still call this function to close the tty device. So we can't assume that
+ * the tty port has been initialized.
+ */
+static void ehv_bc_tty_close(struct tty_struct *ttys, struct file *filp)
+{
+ struct ehv_bc_data *bc = &bcs[ttys->index];
+
+ if (bc->dev)
+ tty_port_close(&bc->port, ttys, filp);
+}
+
+/*
+ * Return the amount of space in the output buffer
+ *
+ * This is actually a contract between the driver and the tty layer outlining
+ * how much write room the driver can guarantee will be sent OR BUFFERED. This
+ * driver MUST honor the return value.
+ */
+static int ehv_bc_tty_write_room(struct tty_struct *ttys)
+{
+ struct ehv_bc_data *bc = ttys->driver_data;
+ unsigned long flags;
+ int count;
+
+ spin_lock_irqsave(&bc->lock, flags);
+ count = CIRC_SPACE(bc->head, bc->tail, BUF_SIZE);
+ spin_unlock_irqrestore(&bc->lock, flags);
+
+ return count;
+}
+
+/*
+ * Stop sending data to the tty layer
+ *
+ * This function is called when the tty layer's input buffers are getting full,
+ * so the driver should stop sending it data. The easiest way to do this is to
+ * disable the RX IRQ, which will prevent ehv_bc_tty_rx_isr() from being
+ * called.
+ *
+ * The hypervisor will continue to queue up any incoming data. If there is any
+ * data in the queue when the RX interrupt is enabled, we'll immediately get an
+ * RX interrupt.
+ */
+static void ehv_bc_tty_throttle(struct tty_struct *ttys)
+{
+ struct ehv_bc_data *bc = ttys->driver_data;
+
+ disable_irq(bc->rx_irq);
+}
+
+/*
+ * Resume sending data to the tty layer
+ *
+ * This function is called after previously calling ehv_bc_tty_throttle(). The
+ * tty layer's input buffers now have more room, so the driver can resume
+ * sending it data.
+ */
+static void ehv_bc_tty_unthrottle(struct tty_struct *ttys)
+{
+ struct ehv_bc_data *bc = ttys->driver_data;
+
+ /* If there is any data in the queue when the RX interrupt is enabled,
+ * we'll immediately get an RX interrupt.
+ */
+ enable_irq(bc->rx_irq);
+}
+
+static void ehv_bc_tty_hangup(struct tty_struct *ttys)
+{
+ struct ehv_bc_data *bc = ttys->driver_data;
+
+ ehv_bc_tx_dequeue(bc);
+ tty_port_hangup(&bc->port);
+}
+
+/*
+ * TTY driver operations
+ *
+ * If we could ask the hypervisor how much data is still in the TX buffer, or
+ * at least how big the TX buffers are, then we could implement the
+ * .wait_until_sent and .chars_in_buffer functions.
+ */
+static const struct tty_operations ehv_bc_ops = {
+ .open = ehv_bc_tty_open,
+ .close = ehv_bc_tty_close,
+ .write = ehv_bc_tty_write,
+ .write_room = ehv_bc_tty_write_room,
+ .throttle = ehv_bc_tty_throttle,
+ .unthrottle = ehv_bc_tty_unthrottle,
+ .hangup = ehv_bc_tty_hangup,
+};
+
+/*
+ * initialize the TTY port
+ *
+ * This function will only be called once, no matter how many times
+ * ehv_bc_tty_open() is called. That's why we register the ISR here, and also
+ * why we initialize tty_struct-related variables here.
+ */
+static int ehv_bc_tty_port_activate(struct tty_port *port,
+ struct tty_struct *ttys)
+{
+ struct ehv_bc_data *bc = container_of(port, struct ehv_bc_data, port);
+ int ret;
+
+ ttys->driver_data = bc;
+
+ ret = request_irq(bc->rx_irq, ehv_bc_tty_rx_isr, 0, "ehv-bc", bc);
+ if (ret < 0) {
+ dev_err(bc->dev, "could not request rx irq %u (ret=%i)\n",
+ bc->rx_irq, ret);
+ return ret;
+ }
+
+ /* request_irq also enables the IRQ */
+ bc->tx_irq_enabled = 1;
+
+ ret = request_irq(bc->tx_irq, ehv_bc_tty_tx_isr, 0, "ehv-bc", bc);
+ if (ret < 0) {
+ dev_err(bc->dev, "could not request tx irq %u (ret=%i)\n",
+ bc->tx_irq, ret);
+ free_irq(bc->rx_irq, bc);
+ return ret;
+ }
+
+ /* The TX IRQ is enabled only when we can't write all the data to the
+ * byte channel at once, so by default it's disabled.
+ */
+ disable_tx_interrupt(bc);
+
+ return 0;
+}
+
+static void ehv_bc_tty_port_shutdown(struct tty_port *port)
+{
+ struct ehv_bc_data *bc = container_of(port, struct ehv_bc_data, port);
+
+ free_irq(bc->tx_irq, bc);
+ free_irq(bc->rx_irq, bc);
+}
+
+static const struct tty_port_operations ehv_bc_tty_port_ops = {
+ .activate = ehv_bc_tty_port_activate,
+ .shutdown = ehv_bc_tty_port_shutdown,
+};
+
+static int __devinit ehv_bc_tty_probe(struct platform_device *pdev)
+{
+ struct device_node *np = pdev->dev.of_node;
+ struct ehv_bc_data *bc;
+ const uint32_t *iprop;
+ unsigned int handle;
+ int ret;
+ static unsigned int index = 1;
+ unsigned int i;
+
+ iprop = of_get_property(np, "hv-handle", NULL);
+ if (!iprop) {
+ dev_err(&pdev->dev, "no 'hv-handle' property in %s node\n",
+ np->name);
+ return -ENODEV;
+ }
+
+ /* We already told the console layer that the index for the console
+ * device is zero, so we need to make sure that we use that index when
+ * we probe the console byte channel node.
+ */
+ handle = be32_to_cpu(*iprop);
+ i = (handle == stdout_bc) ? 0 : index++;
+ bc = &bcs[i];
+
+ bc->handle = handle;
+ bc->head = 0;
+ bc->tail = 0;
+ spin_lock_init(&bc->lock);
+
+ bc->rx_irq = irq_of_parse_and_map(np, 0);
+ bc->tx_irq = irq_of_parse_and_map(np, 1);
+ if ((bc->rx_irq == NO_IRQ) || (bc->tx_irq == NO_IRQ)) {
+ dev_err(&pdev->dev, "no 'interrupts' property in %s node\n",
+ np->name);
+ ret = -ENODEV;
+ goto error;
+ }
+
+ bc->dev = tty_register_device(ehv_bc_driver, i, &pdev->dev);
+ if (IS_ERR(bc->dev)) {
+ ret = PTR_ERR(bc->dev);
+ dev_err(&pdev->dev, "could not register tty (ret=%i)\n", ret);
+ goto error;
+ }
+
+ tty_port_init(&bc->port);
+ bc->port.ops = &ehv_bc_tty_port_ops;
+
+ dev_set_drvdata(&pdev->dev, bc);
+
+ dev_info(&pdev->dev, "registered /dev/%s%u for byte channel %u\n",
+ ehv_bc_driver->name, i, bc->handle);
+
+ return 0;
+
+error:
+ irq_dispose_mapping(bc->tx_irq);
+ irq_dispose_mapping(bc->rx_irq);
+
+ memset(bc, 0, sizeof(struct ehv_bc_data));
+ return ret;
+}
+
+static int ehv_bc_tty_remove(struct platform_device *pdev)
+{
+ struct ehv_bc_data *bc = dev_get_drvdata(&pdev->dev);
+
+ tty_unregister_device(ehv_bc_driver, bc - bcs);
+
+ irq_dispose_mapping(bc->tx_irq);
+ irq_dispose_mapping(bc->rx_irq);
+
+ return 0;
+}
+
+static const struct of_device_id ehv_bc_tty_of_ids[] = {
+ { .compatible = "epapr,hv-byte-channel" },
+ {}
+};
+
+static struct platform_driver ehv_bc_tty_driver = {
+ .driver = {
+ .owner = THIS_MODULE,
+ .name = "ehv-bc",
+ .of_match_table = ehv_bc_tty_of_ids,
+ },
+ .probe = ehv_bc_tty_probe,
+ .remove = ehv_bc_tty_remove,
+};
+
+/**
+ * ehv_bc_init - ePAPR hypervisor byte channel driver initialization
+ *
+ * This function is called when this module is loaded.
+ */
+static int __init ehv_bc_init(void)
+{
+ struct device_node *np;
+ unsigned int count = 0; /* Number of elements in bcs[] */
+ int ret;
+
+ pr_info("ePAPR hypervisor byte channel driver\n");
+
+ /* Count the number of byte channels */
+ for_each_compatible_node(np, NULL, "epapr,hv-byte-channel")
+ count++;
+
+ if (!count)
+ return -ENODEV;
+
+ /* The array index of an element in bcs[] is the same as the tty index
+ * for that element. If you know the address of an element in the
+ * array, then you can use pointer math (e.g. "bc - bcs") to get its
+ * tty index.
+ */
+ bcs = kzalloc(count * sizeof(struct ehv_bc_data), GFP_KERNEL);
+ if (!bcs)
+ return -ENOMEM;
+
+ ehv_bc_driver = alloc_tty_driver(count);
+ if (!ehv_bc_driver) {
+ ret = -ENOMEM;
+ goto error;
+ }
+
+ ehv_bc_driver->owner = THIS_MODULE;
+ ehv_bc_driver->driver_name = "ehv-bc";
+ ehv_bc_driver->name = ehv_bc_console.name;
+ ehv_bc_driver->type = TTY_DRIVER_TYPE_CONSOLE;
+ ehv_bc_driver->subtype = SYSTEM_TYPE_CONSOLE;
+ ehv_bc_driver->init_termios = tty_std_termios;
+ ehv_bc_driver->flags = TTY_DRIVER_REAL_RAW | TTY_DRIVER_DYNAMIC_DEV;
+ tty_set_operations(ehv_bc_driver, &ehv_bc_ops);
+
+ ret = tty_register_driver(ehv_bc_driver);
+ if (ret) {
+ pr_err("ehv-bc: could not register tty driver (ret=%i)\n", ret);
+ goto error;
+ }
+
+ ret = platform_driver_register(&ehv_bc_tty_driver);
+ if (ret) {
+ pr_err("ehv-bc: could not register platform driver (ret=%i)\n",
+ ret);
+ goto error;
+ }
+
+ return 0;
+
+error:
+ if (ehv_bc_driver) {
+ tty_unregister_driver(ehv_bc_driver);
+ put_tty_driver(ehv_bc_driver);
+ }
+
+ kfree(bcs);
+
+ return ret;
+}
+
+
+/**
+ * ehv_bc_exit - ePAPR hypervisor byte channel driver termination
+ *
+ * This function is called when this driver is unloaded.
+ */
+static void __exit ehv_bc_exit(void)
+{
+ tty_unregister_driver(ehv_bc_driver);
+ put_tty_driver(ehv_bc_driver);
+ kfree(bcs);
+}
+
+module_init(ehv_bc_init);
+module_exit(ehv_bc_exit);
+
+MODULE_AUTHOR("Timur Tabi <timur@freescale.com>");
+MODULE_DESCRIPTION("ePAPR hypervisor byte channel driver");
+MODULE_LICENSE("GPL v2");
--
1.7.3.4



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  Last update: 2011-05-19 20:37    [from the cache]
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