Re: [PATCH v2 00/13] OMAP Serial patches

From: Felipe Balbi
Date: Tue Aug 21 2012 - 09:05:58 EST

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Hi,

On Tue, Aug 21, 2012 at 03:15:58PM +0300, Felipe Balbi wrote:
> Hi guys,
>
> here's a series of cleanup patches to the OMAP serial
> driver. A later series could be made re-implementing
> DMA using the DMA Engine API. Note that for RX DMA
> we could be using RX Timeout IRQ as a hint that we better
> use PIO instead ;-)
>
> All patches were tested on my pandaboard, but I'd really
> like to receive Tested-by on other platforms.
>
> After this goes in, I'll probably try to get UART wakeup
> working again and only after that look at DMA.
>
> Changes since v1:
>
> . improved commit log on patch 9/13 (formerly 10/13)
> . removed patch 2/13
> . added a new patch switching from spin_lock_irqsave() to spin_lock and
> spin_unlock_irqrestore to spin_unlock
>
> Retested with my pandaboard, UART continues to work:
>
> # grep -i uart /proc/interrupts
> 106: 124 0 GIC OMAP UART2
> # grep -i uart /proc/interrupts
> 106: 189 0 GIC OMAP UART2
> # grep -i uart /proc/interrupts
> 106: 255 0 GIC OMAP UART2
> # grep -i uart /proc/interrupts
> 106: 321 0 GIC OMAP UART2
> # grep -i uart /proc/interrupts
> 106: 387 0 GIC OMAP UART2
> # grep -i uart /proc/interrupts
> 106: 453 0 GIC OMAP UART2
> # grep -i uart /proc/interrupts
> 106: 519 0 GIC OMAP UART2
>
> cheers
>
> ps: if anyone knows a better test for UART, let me know.
>
> for convenience of anyone testing, patches are available on my git tree [1] on
> branch uart
>
> [1] git://git.kernel.org/pub/scm/linux/kernel/git/balbi/usb.git uart

I have added one extra patch to this series:

From 6921efdb13dda7af216b331bb35535d4b53f004a Mon Sep 17 00:00:00 2001
From: Felipe Balbi <balbi@xxxxxx>
Date: Tue, 21 Aug 2012 15:48:35 +0300
Subject: [PATCH] serial: omap: drop pm_runtime_irq_safe() usage

pm_runtime_irq_safe() will essentially do an
unbalanced pm_runtime_get_sync() on our parent
device, which might cause problems when trying
to suspend.

In order to prevent that we drop pm_runtime_irq_safe
usage in exchange for a little performance hit
when we enter our IRQ handler while still suspended.

If that happens, what we will do is set the irq_pending
flag, do an asynchronous pm_runtime_get() call and
return IRQ_HANDLED. When our runtime_resume() callback
is executed, we check for that flag, and run our
IRQ handler so that we receive/transmit the pending
characters.

Signed-off-by: Felipe Balbi <balbi@xxxxxx>
---

One extra patch to OMAP UART driver. This seems to be working
pretty well even after echo mem > /sys/power/state. I can
see that I can even wake my pandaboard up by sending a character
through serial:

# echo mem > /sys/power/state
[ 1335.679260] PM: Syncing filesystems ... done.
[ 1335.684387] Freezing user space processes ... (elapsed 0.00 seconds) done.
[ 1335.691741] Freezing remaining freezable tasks ... (elapsed 0.02 seconds) done.
[ 1335.720886] Suspending console(s) (use no_console_suspend to debug)

[ 1335.734405] PM: suspend of devices complete after 5.492 msecs
[ 1335.735534] PM: late suspend of devices complete after 1.128 msecs
[ 1335.737518] PM: noirq suspend of devices complete after 1.952 msecs
[ 1335.737518] Disabling non-boot CPUs ...
[ 1335.738525] CPU1: shutdown
[ 1338.543762] Successfully put all powerdomains to target state
[ 1338.543853] Enabling non-boot CPUs ...
[ 1338.545654] CPU1: Booted secondary processor
[ 1338.546020] CPU1 is up
[ 1338.547027] PM: noirq resume of devices complete after 0.976 msecs
[ 1338.548400] PM: early resume of devices complete after 0.762 msecs
[ 1339.827087] PM: resume of devices complete after 1278.686 msecs
[ 1339.890960] Restarting tasks ... done.
# # grep -i uart /proc/interrupts
106: 3385 0 GIC OMAP UART2
# echo mem > /sys/power/state
[ 1358.015624] PM: Syncing filesystems ... done.
[ 1358.020812] Freezing user space processes ... (elapsed 0.00 seconds) done.
[ 1358.028167] Freezing remaining freezable tasks ... (elapsed 0.01 seconds) done.
[ 1358.055084] Suspending console(s) (use no_console_suspend to debug)

[ 1358.068847] PM: suspend of devices complete after 5.633 msecs
[ 1358.070007] PM: late suspend of devices complete after 1.126 msecs
[ 1358.072051] PM: noirq suspend of devices complete after 2.040 msecs
[ 1358.072051] Disabling non-boot CPUs ...
[ 1358.073211] CPU1: shutdown
[ 1359.104156] Successfully put all powerdomains to target state
[ 1359.104278] Enabling non-boot CPUs ...
[ 1359.106079] CPU1: Booted secondary processor
[ 1359.106475] CPU1 is up
[ 1359.107482] PM: noirq resume of devices complete after 1.004 msecs
[ 1359.108886] PM: early resume of devices complete after 0.761 msecs
[ 1360.414794] PM: resume of devices complete after 1305.836 msecs
[ 1360.478668] Restarting tasks ... done.
# # grep -i uart /proc/interrupts
106: 3511 0 GIC OMAP UART2

arch/arm/plat-omap/include/plat/omap-serial.h | 1 +
drivers/tty/serial/omap-serial.c | 16 +++++++++++++---
2 files changed, 14 insertions(+), 3 deletions(-)

diff --git a/arch/arm/plat-omap/include/plat/omap-serial.h b/arch/arm/plat-omap/include/plat/omap-serial.h
index 743ac80..52328ca 100644
--- a/arch/arm/plat-omap/include/plat/omap-serial.h
+++ b/arch/arm/plat-omap/include/plat/omap-serial.h
@@ -130,6 +130,7 @@ struct uart_omap_port {
u32 context_loss_cnt;
u32 errata;
u8 wakeups_enabled;
+ unsigned int irq_pending:1;

struct pm_qos_request pm_qos_request;
u32 latency;
diff --git a/drivers/tty/serial/omap-serial.c b/drivers/tty/serial/omap-serial.c
index a79658d..7e237f3 100644
--- a/drivers/tty/serial/omap-serial.c
+++ b/drivers/tty/serial/omap-serial.c
@@ -353,9 +353,13 @@ static inline irqreturn_t serial_omap_irq(int irq, void *dev_id)
irqreturn_t ret = IRQ_HANDLED;
int max_count = 256;

- spin_lock(&up->port.lock);
- pm_runtime_get_sync(up->dev);
+ if (pm_runtime_suspended(up->dev)) {
+ up->irq_pending = true;
+ pm_runtime_get(up->dev);
+ return IRQ_HANDLED;
+ }

+ spin_lock(&up->port.lock);
do {
iir = serial_in(up, UART_IIR);
if (iir & UART_IIR_NO_INT) {
@@ -400,6 +404,7 @@ static inline irqreturn_t serial_omap_irq(int irq, void *dev_id)
pm_runtime_mark_last_busy(up->dev);
pm_runtime_put_autosuspend(up->dev);
up->port_activity = jiffies;
+ up->irq_pending = false;

return ret;
}
@@ -1305,7 +1310,6 @@ static int serial_omap_probe(struct platform_device *pdev)
pm_runtime_set_autosuspend_delay(&pdev->dev,
omap_up_info->autosuspend_timeout);

- pm_runtime_irq_safe(&pdev->dev);
pm_runtime_enable(&pdev->dev);
pm_runtime_get_sync(&pdev->dev);

@@ -1416,6 +1420,9 @@ static int serial_omap_runtime_suspend(struct device *dev)
if (!up)
return -EINVAL;

+ if (up->irq_pending)
+ return -EBUSY;
+
if (!pdata)
return 0;

@@ -1452,6 +1459,9 @@ static int serial_omap_runtime_resume(struct device *dev)

up->latency = up->calc_latency;
schedule_work(&up->qos_work);
+
+ if (up->irq_pending)
+ serial_omap_irq(up->port.irq, up);
}

return 0;
--
1.7.12.rc3

--
balbi

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Next message: Catalin Marinas: "Re: [PATCH v2 14/31] arm64: DMA mapping API"
Previous message: Eric Dumazet: "[PATCH] task_work: add a scheduling point in task_work_run()"
In reply to: Felipe Balbi: "[PATCH v2 01/13] serial: omap: define and use to_uart_omap_port()"
Next in thread: Felipe Balbi: "Re: [PATCH v2 00/13] OMAP Serial patches"
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