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Subject[PATCH v6 5/5] i2c-at91.c: add SMBUS_READ_BLOCK_DATA functionality
SMBus emulation uses I2C_M_RECV_LEN flag to indicate a SMBus block
read operation in which the length of a transfer is inicated by the
first received byte.

Make better use of clk_prepare()/clk_unprepare().

More sensible transfer timeout.

Signed-off-by: Nikolaus Voss <n.voss@weinmann.de>
---
drivers/i2c/busses/i2c-at91.c | 44 +++++++++++++++++++++++++++-------------
1 files changed, 30 insertions(+), 14 deletions(-)
diff --git a/drivers/i2c/busses/i2c-at91.c b/drivers/i2c/busses/i2c-at91.c
index 9f4e0d0..96f33f9 100644
--- a/drivers/i2c/busses/i2c-at91.c
+++ b/drivers/i2c/busses/i2c-at91.c
@@ -32,7 +32,7 @@
#include "i2c-at91.h"

#define TWI_CLK_HZ 100000 /* max 400 Kbits/s */
-#define AT91_I2C_TIMEOUT msecs_to_jiffies(10) /* transfer timeout */
+#define AT91_I2C_TIMEOUT msecs_to_jiffies(100) /* transfer timeout */

struct at91_twi_dev {
struct device *dev;
@@ -41,6 +41,7 @@ struct at91_twi_dev {
struct clk *clk;
u8 *buf;
size_t buf_len;
+ struct i2c_msg *msg;
int irq;
unsigned transfer_status;
struct i2c_adapter adapter;
@@ -113,9 +114,18 @@ static void at91_twi_write_next_byte(struct at91_twi_dev *dev)
static void at91_twi_read_next_byte(struct at91_twi_dev *dev)
{
*dev->buf = at91_twi_read(dev, AT91_TWI_RHR) & 0xff;
+ --dev->buf_len;
+
+ /* handle I2C_SMBUS_BLOCK_DATA */
+ if (unlikely(dev->msg->flags & I2C_M_RECV_LEN)) {
+ dev->msg->flags &= ~I2C_M_RECV_LEN;
+ dev->buf_len += *dev->buf;
+ dev->msg->len = dev->buf_len + 1;
+ dev_dbg(dev->dev, "received block length %d\n", dev->buf_len);
+ }

/* send stop if second but last byte has been read */
- if (--dev->buf_len == 1)
+ if (dev->buf_len == 1)
at91_twi_write(dev, AT91_TWI_CR, AT91_TWI_STOP);

dev_dbg(dev->dev, "read 0x%x, to go %d\n", *dev->buf, dev->buf_len);
@@ -144,17 +154,21 @@ static irqreturn_t atmel_twi_interrupt(int irq, void *dev_id)
return IRQ_HANDLED;
}

-static int at91_do_twi_transfer(struct at91_twi_dev *dev, bool is_read)
+static int at91_do_twi_transfer(struct at91_twi_dev *dev)
{
int ret;

+ dev_dbg(dev->dev, "transfer: %s %d bytes.\n",
+ (dev->msg->flags & I2C_M_RD) ? "read" : "write", dev->buf_len);
+
INIT_COMPLETION(dev->cmd_complete);
- if (is_read) {
- if (!dev->buf_len)
- at91_twi_write(dev, AT91_TWI_CR,
- AT91_TWI_START | AT91_TWI_STOP);
- else
- at91_twi_write(dev, AT91_TWI_CR, AT91_TWI_START);
+ if (dev->msg->flags & I2C_M_RD) {
+ unsigned start_flags = AT91_TWI_START;
+
+ /* if only one byte is to be read, immediately stop transfer */
+ if (dev->buf_len <= 1 && !(dev->msg->flags & I2C_M_RECV_LEN))
+ start_flags |= AT91_TWI_STOP;
+ at91_twi_write(dev, AT91_TWI_CR, start_flags);
at91_twi_write(dev, AT91_TWI_IER,
AT91_TWI_TXCOMP | AT91_TWI_RXRDY);
} else {
@@ -227,17 +241,17 @@ static int at91_twi_xfer(struct i2c_adapter *adap, struct i2c_msg *msg, int num)

dev->buf_len = m_start->len;
dev->buf = m_start->buf;
+ dev->msg = m_start;

- ret = at91_do_twi_transfer(dev, m_start->flags & I2C_M_RD);
- if (ret < 0)
- return ret;
+ ret = at91_do_twi_transfer(dev);

- return num;
+ return (ret < 0) ? ret : num;
}

static u32 at91_twi_func(struct i2c_adapter *adapter)
{
- return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
+ return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL
+ | I2C_FUNC_SMBUS_READ_BLOCK_DATA;
}

static struct i2c_algorithm at91_twi_algorithm = {
@@ -324,6 +338,7 @@ err_unuse_clocks:
iounmap(dev->base);
err_mem_ioremap:
clk_disable(dev->clk);
+ clk_unprepare(dev->clk);
clk_put(dev->clk);
err_free_mem:
kfree(dev);
@@ -341,6 +356,7 @@ static int __devexit at91_twi_remove(struct platform_device *pdev)

rc = i2c_del_adapter(&dev->adapter);
clk_disable(dev->clk);
+ clk_unprepare(dev->clk);
clk_put(dev->clk);
free_irq(dev->irq, dev);
iounmap(dev->base);
--
1.7.5.4


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