Messages in this thread |  | | Date | Mon, 02 Dec 2013 15:42:05 -0500 | From | Peter Hurley <> | Subject | Re: [PATCH 03/10] tty: xuartps: Implement BREAK detection, add SYSRQ support |
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On 10/17/2013 05:08 PM, Soren Brinkmann wrote: > From: Vlad Lungu <vlad.lungu@windriver.com> > > The Cadence UART does not do break detection, even if the > datasheet says it does. This patch adds break detection in > software (tested in 8N1 mode only) and enables SYSRQ, > allowing for Break-g to enter KDB and all the other goodies. > > Signed-off-by: Vlad Lungu <vlad.lungu@windriver.com> > Signed-off-by: Soren Brinkmann <soren.brinkmann@xilinx.com> > --- > I ported this patch to 3.12 and fixed some style issues > --- > drivers/tty/serial/xilinx_uartps.c | 50 +++++++++++++++++++++++++++++++++++++- > 1 file changed, 49 insertions(+), 1 deletion(-) > > diff --git a/drivers/tty/serial/xilinx_uartps.c b/drivers/tty/serial/xilinx_uartps.c > index 8c0745951605..5d5557af4d22 100644 > --- a/drivers/tty/serial/xilinx_uartps.c > +++ b/drivers/tty/serial/xilinx_uartps.c > @@ -11,13 +11,17 @@ > * > */ > > +#if defined(CONFIG_SERIAL_XILINX_PS_UART_CONSOLE) && defined(CONFIG_MAGIC_SYSRQ) > +#define SUPPORT_SYSRQ > +#endif > + > #include <linux/platform_device.h> > #include <linux/serial.h> > +#include <linux/console.h> > #include <linux/serial_core.h> > #include <linux/slab.h> > #include <linux/tty.h> > #include <linux/tty_flip.h> > -#include <linux/console.h> > #include <linux/clk.h> > #include <linux/irq.h> > #include <linux/io.h> > @@ -128,6 +132,9 @@ > #define XUARTPS_IXR_RXEMPTY 0x00000002 /* RX FIFO empty interrupt. */ > #define XUARTPS_IXR_MASK 0x00001FFF /* Valid bit mask */ > > +/* Goes in read_status_mask for break detection as the HW doesn't do it*/ > +#define XUARTPS_IXR_BRK 0x80000000 > + > /** Channel Status Register > * > * The channel status register (CSR) is provided to enable the control logic > @@ -171,6 +178,23 @@ static irqreturn_t xuartps_isr(int irq, void *dev_id) > */ > isrstatus = xuartps_readl(XUARTPS_ISR_OFFSET); > > + /* > + * There is no hardware break detection, so we interpret framing > + * error with all-zeros data as a break sequence. Most of the time, > + * there's another non-zero byte at the end of the sequence. > + */ > + > + if (isrstatus & XUARTPS_IXR_FRAMING) { > + while (!(xuartps_readl(XUARTPS_SR_OFFSET) & > + XUARTPS_SR_RXEMPTY)) { > + if (!xuartps_readl(XUARTPS_FIFO_OFFSET)) { > + port->read_status_mask |= XUARTPS_IXR_BRK; > + isrstatus &= ~XUARTPS_IXR_FRAMING; > + } > + } > + xuartps_writel(XUARTPS_IXR_FRAMING, XUARTPS_ISR_OFFSET); > + } > + > /* drop byte with parity error if IGNPAR specified */ > if (isrstatus & port->ignore_status_mask & XUARTPS_IXR_PARITY) > isrstatus &= ~(XUARTPS_IXR_RXTRIG | XUARTPS_IXR_TOUT); > @@ -184,6 +208,30 @@ static irqreturn_t xuartps_isr(int irq, void *dev_id) > while ((xuartps_readl(XUARTPS_SR_OFFSET) & > XUARTPS_SR_RXEMPTY) != XUARTPS_SR_RXEMPTY) { > data = xuartps_readl(XUARTPS_FIFO_OFFSET); > + > + /* Non-NULL byte after BREAK is garbage (99%) */ > + if (data && (port->read_status_mask & > + XUARTPS_IXR_BRK)) { > + port->read_status_mask &= ~XUARTPS_IXR_BRK; > + port->icount.brk++; > + if (uart_handle_break(port)) > + continue; > + } > + > + /* > + * uart_handle_sysrq_char() doesn't work if > + * spinlocked, for some reason > + */ ^^^^^^^^^^^^^^^ Because the console write method, xuartps_console_write(), tries to lock the port->lock. Double-claim deadlock.
> + if (port->sysrq) { > + spin_unlock(&port->lock); > + if (uart_handle_sysrq_char(port, > + (unsigned char)data)) { > + spin_lock(&port->lock); > + continue; > + } > + spin_lock(&port->lock); > + } > + > port->icount.rx++; > > if (isrstatus & XUARTPS_IXR_PARITY) { >
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