* [PATCH] amba-pl011: clear previous interrupts before request_irq @ 2012-01-17 10:34 Shreshtha Kumar SAHU 2012-01-18 10:04 ` Shreshtha Kumar SAHU 0 siblings, 1 reply; 6+ messages in thread From: Shreshtha Kumar SAHU @ 2012-01-17 10:34 UTC (permalink / raw) To: gregkh, linux-serial, rmk+kernel; +Cc: linux-kernel, Shreshtha Kumar Sahu From: Shreshtha Kumar Sahu <shreshthakumar.sahu@stericsson.com> All previous interrupts should be cleared before installing interrupt handler i.e. before request_irq. pl011_shutdown clears the interrupt register but there may be case where bootloader transfers control to kernel and there are some pending interrupts. In this case interrupt handler will get called even before interrupt mask is enabled. Change-Id: Ie58ca0a36dec76ac38babc057ce1d66b3129d8f9 Acked-by: Linus Walleij <linus.walleij@linaro.org> --- drivers/tty/serial/amba-pl011.c | 9 +++++++++ 1 files changed, 9 insertions(+), 0 deletions(-) diff --git a/drivers/tty/serial/amba-pl011.c b/drivers/tty/serial/amba-pl011.c index 6958594..6dafaa2 100644 --- a/drivers/tty/serial/amba-pl011.c +++ b/drivers/tty/serial/amba-pl011.c @@ -1381,6 +1381,15 @@ static int pl011_startup(struct uart_port *port) uap->port.uartclk = clk_get_rate(uap->clk); /* + * Clear previous interrupts before installing interrupt handler + */ + spin_lock_irq(&uap->port.lock); + uap->im = 0; + writew(uap->im, uap->port.membase + UART011_IMSC); + writew(0xffff, uap->port.membase + UART011_ICR); + spin_unlock_irq(&uap->port.lock); + + /* * Allocate the IRQ */ retval = request_irq(uap->port.irq, pl011_int, 0, "uart-pl011", uap); -- 1.7.4.3 ^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH] amba-pl011: clear previous interrupts before request_irq 2012-01-17 10:34 [PATCH] amba-pl011: clear previous interrupts before request_irq Shreshtha Kumar SAHU @ 2012-01-18 10:04 ` Shreshtha Kumar SAHU 2012-01-18 10:15 ` Russell King 2012-01-18 11:41 ` Alan Cox 0 siblings, 2 replies; 6+ messages in thread From: Shreshtha Kumar SAHU @ 2012-01-18 10:04 UTC (permalink / raw) To: gregkh@suse.de, linux-serial@vger.kernel.org, rmk+kernel@arm.linux.org.uk Cc: linux-kernel@vger.kernel.org >From 0742fc49405b2a6f562981f61d93198e1595f30d Mon Sep 17 00:00:00 2001 From: Shreshtha Kumar Sahu <shreshthakumar.sahu@stericsson.com> Date: Tue, 17 Jan 2012 12:23:19 +0530 Subject: [PATCH v2] amba-pl011: clear previous interrupts before request_irq All previous interrupts should be cleared before installing interrupt handler i.e. before request_irq. pl011_shutdown clears the interrupt register but there may be case where bootloader transfers control to kernel and there are some pending interrupts. In this case interrupt handler will get called even before interrupt mask is enabled. Acked-by: Linus Walleij <linus.walleij@linaro.org> --- drivers/tty/serial/amba-pl011.c | 9 +++++++++ 1 files changed, 9 insertions(+), 0 deletions(-) diff --git a/drivers/tty/serial/amba-pl011.c b/drivers/tty/serial/amba-pl011.c index 6958594..6dafaa2 100644 --- a/drivers/tty/serial/amba-pl011.c +++ b/drivers/tty/serial/amba-pl011.c @@ -1381,6 +1381,15 @@ static int pl011_startup(struct uart_port *port) uap->port.uartclk = clk_get_rate(uap->clk); /* + * Clear previous interrupts before installing interrupt handler + */ + spin_lock_irq(&uap->port.lock); + uap->im = 0; + writew(uap->im, uap->port.membase + UART011_IMSC); + writew(0xffff, uap->port.membase + UART011_ICR); + spin_unlock_irq(&uap->port.lock); + + /* * Allocate the IRQ */ retval = request_irq(uap->port.irq, pl011_int, 0, "uart-pl011", uap); -- 1.7.4.3 ^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH] amba-pl011: clear previous interrupts before request_irq 2012-01-18 10:04 ` Shreshtha Kumar SAHU @ 2012-01-18 10:15 ` Russell King 2012-01-19 11:07 ` Shreshtha Kumar SAHU 2012-01-18 11:41 ` Alan Cox 1 sibling, 1 reply; 6+ messages in thread From: Russell King @ 2012-01-18 10:15 UTC (permalink / raw) To: Shreshtha Kumar SAHU Cc: gregkh@suse.de, linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org On Wed, Jan 18, 2012 at 03:34:11PM +0530, Shreshtha Kumar SAHU wrote: > > >From 0742fc49405b2a6f562981f61d93198e1595f30d Mon Sep 17 00:00:00 2001 > From: Shreshtha Kumar Sahu <shreshthakumar.sahu@stericsson.com> > Date: Tue, 17 Jan 2012 12:23:19 +0530 > Subject: [PATCH v2] amba-pl011: clear previous interrupts before request_irq > > All previous interrupts should be cleared before installing > interrupt handler i.e. before request_irq. pl011_shutdown > clears the interrupt register but there may be case where > bootloader transfers control to kernel and there are some > pending interrupts. In this case interrupt handler will get > called even before interrupt mask is enabled. > > Acked-by: Linus Walleij <linus.walleij@linaro.org> No sign-off, and I don't understand the problem being aluded to in the description above - particularly the last sentence. In theory, we should be prepared for the interrupt handler to be called immediately after request_irq() returns, and not have the driver misbehave because of that. Maybe a better solution would be to move request_irq() a bit later? But first, having a clearer description of the problem you're seeing would be beneficial. > --- > drivers/tty/serial/amba-pl011.c | 9 +++++++++ > 1 files changed, 9 insertions(+), 0 deletions(-) > > diff --git a/drivers/tty/serial/amba-pl011.c b/drivers/tty/serial/amba-pl011.c > index 6958594..6dafaa2 100644 > --- a/drivers/tty/serial/amba-pl011.c > +++ b/drivers/tty/serial/amba-pl011.c > @@ -1381,6 +1381,15 @@ static int pl011_startup(struct uart_port *port) > uap->port.uartclk = clk_get_rate(uap->clk); > > /* > + * Clear previous interrupts before installing interrupt handler > + */ > + spin_lock_irq(&uap->port.lock); > + uap->im = 0; > + writew(uap->im, uap->port.membase + UART011_IMSC); > + writew(0xffff, uap->port.membase + UART011_ICR); > + spin_unlock_irq(&uap->port.lock); > + > + /* > * Allocate the IRQ > */ > retval = request_irq(uap->port.irq, pl011_int, 0, "uart-pl011", uap); > -- > 1.7.4.3 > -- Russell King Linux kernel 2.6 ARM Linux - http://www.arm.linux.org.uk/ maintainer of: ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] amba-pl011: clear previous interrupts before request_irq 2012-01-18 10:15 ` Russell King @ 2012-01-19 11:07 ` Shreshtha Kumar SAHU 0 siblings, 0 replies; 6+ messages in thread From: Shreshtha Kumar SAHU @ 2012-01-19 11:07 UTC (permalink / raw) To: Russell King Cc: gregkh@suse.de, linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org On Wed, Jan 18, 2012 at 11:15:55 +0100, Russell King wrote: > On Wed, Jan 18, 2012 at 03:34:11PM +0530, Shreshtha Kumar SAHU wrote: > > > > >From 0742fc49405b2a6f562981f61d93198e1595f30d Mon Sep 17 00:00:00 2001 > > From: Shreshtha Kumar Sahu <shreshthakumar.sahu@stericsson.com> > > Date: Tue, 17 Jan 2012 12:23:19 +0530 > > Subject: [PATCH v2] amba-pl011: clear previous interrupts before request_irq > > > > All previous interrupts should be cleared before installing > > interrupt handler i.e. before request_irq. pl011_shutdown > > clears the interrupt register but there may be case where > > bootloader transfers control to kernel and there are some > > pending interrupts. In this case interrupt handler will get > > called even before interrupt mask is enabled. > > > > Acked-by: Linus Walleij <linus.walleij@linaro.org> > > No sign-off, and I don't understand the problem being aluded to in the > description above - particularly the last sentence. > Sorry for late reply and missing sign-off. In the setup where console is disabled and logs are diverted to buffer, it is observed that, continuous uart interrupts are coming. Even before IMSC (Interrupt mask set/clear register) is enabled for TX or RX interrupts, it is seen that interrupt handler getting called just after request_irq. It was found that this situation happens when RIS (raw interrupt register) has some pending interrupts (e.g. RI, CTS, DCD, RX etc. but IMO RX is main) when control gets transferred to kernel from bootloader. This refers that GIC (global interrupt controller) is providing interrupt even if interrupts for UART are masked/disabled in IMSC register. In this state problem elivated when cpu is looping in interrupt handler because of Rx interrupt set but Rx fifo is empty (hence rx_char is simply returning). How UART goes in to this state is still not completely understood. > In theory, we should be prepared for the interrupt handler to be called > immediately after request_irq() returns, and not have the driver misbehave > because of that. Maybe a better solution would be to move request_irq() > a bit later? > I tried doing this but problem persists. I understand that module should be robust enough and should not depend on state left by previous user of soc. I am still investigating and will come back with analysis. > But first, having a clearer description of the problem you're seeing > would be beneficial. > > > --- > > drivers/tty/serial/amba-pl011.c | 9 +++++++++ > > 1 files changed, 9 insertions(+), 0 deletions(-) > > > > diff --git a/drivers/tty/serial/amba-pl011.c b/drivers/tty/serial/amba-pl011.c > > index 6958594..6dafaa2 100644 > > --- a/drivers/tty/serial/amba-pl011.c > > +++ b/drivers/tty/serial/amba-pl011.c > > @@ -1381,6 +1381,15 @@ static int pl011_startup(struct uart_port *port) > > uap->port.uartclk = clk_get_rate(uap->clk); > > > > /* > > + * Clear previous interrupts before installing interrupt handler > > + */ > > + spin_lock_irq(&uap->port.lock); > > + uap->im = 0; > > + writew(uap->im, uap->port.membase + UART011_IMSC); > > + writew(0xffff, uap->port.membase + UART011_ICR); > > + spin_unlock_irq(&uap->port.lock); > > + > > + /* > > * Allocate the IRQ > > */ > > retval = request_irq(uap->port.irq, pl011_int, 0, "uart-pl011", uap); > > -- > > 1.7.4.3 > > > > -- > Russell King > Linux kernel 2.6 ARM Linux - http://www.arm.linux.org.uk/ > maintainer of: Thanks and Regards Shreshtha ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] amba-pl011: clear previous interrupts before request_irq 2012-01-18 10:04 ` Shreshtha Kumar SAHU 2012-01-18 10:15 ` Russell King @ 2012-01-18 11:41 ` Alan Cox 2012-01-19 11:15 ` Shreshtha Kumar SAHU 1 sibling, 1 reply; 6+ messages in thread From: Alan Cox @ 2012-01-18 11:41 UTC (permalink / raw) To: Shreshtha Kumar SAHU Cc: gregkh@suse.de, linux-serial@vger.kernel.org, rmk+kernel@arm.linux.org.uk, linux-kernel@vger.kernel.org > /* > + * Clear previous interrupts before installing interrupt handler > + */ > + spin_lock_irq(&uap->port.lock); > + uap->im = 0; > + writew(uap->im, uap->port.membase + UART011_IMSC); > + writew(0xffff, uap->port.membase + UART011_ICR); > + spin_unlock_irq(&uap->port.lock); I'm confused why you use spin_lock_irq before you've enabled the IRQ in the first place but looks fine. Alan ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] amba-pl011: clear previous interrupts before request_irq 2012-01-18 11:41 ` Alan Cox @ 2012-01-19 11:15 ` Shreshtha Kumar SAHU 0 siblings, 0 replies; 6+ messages in thread From: Shreshtha Kumar SAHU @ 2012-01-19 11:15 UTC (permalink / raw) To: Alan Cox Cc: gregkh@suse.de, linux-serial@vger.kernel.org, rmk+kernel@arm.linux.org.uk, linux-kernel@vger.kernel.org On Wed, Jan 18, 2012 at 12:41:00 +0100, Alan Cox wrote: > > /* > > + * Clear previous interrupts before installing interrupt handler > > + */ > > + spin_lock_irq(&uap->port.lock); > > + uap->im = 0; > > + writew(uap->im, uap->port.membase + UART011_IMSC); > > + writew(0xffff, uap->port.membase + UART011_ICR); > > + spin_unlock_irq(&uap->port.lock); > > I'm confused why you use spin_lock_irq before you've enabled the IRQ in > the first place but looks fine. > > Alan Yes, spin_lock_irq for the port is not required as request_irq is not yet called for the port. Thanks and Regards, Shreshtha ^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2012-01-19 11:16 UTC | newest] Thread overview: 6+ messages (download: mbox.gz follow: Atom feed -- links below jump to the message on this page -- 2012-01-17 10:34 [PATCH] amba-pl011: clear previous interrupts before request_irq Shreshtha Kumar SAHU 2012-01-18 10:04 ` Shreshtha Kumar SAHU 2012-01-18 10:15 ` Russell King 2012-01-19 11:07 ` Shreshtha Kumar SAHU 2012-01-18 11:41 ` Alan Cox 2012-01-19 11:15 ` Shreshtha Kumar SAHU
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