lkml.org 
[lkml]   [2015]   [Oct]   [2]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH 2/2] gpio: omap: convert to use generic irq handler
From
Date
On 10/02/2015 03:17 PM, Linus Walleij wrote:
> On Fri, Sep 25, 2015 at 12:28 PM, Grygorii Strashko
> <grygorii.strashko@ti.com> wrote:
>
>> This patch converts TI OMAP GPIO driver to use generic irq handler
>> instead of chained IRQ handler. This way OMAP GPIO driver will be
>> compatible with RT kernel where it will be forced thread IRQ handler
>> while in non-RT kernel it still will be executed in HW IRQ context.
>> As part of this change the IRQ wakeup configuration is applied to
>> GPIO Bank IRQ as it now will be under control of IRQ PM Core during
>> suspend.
>>
>> There are also additional benefits:
>> - on-RT kernel there will be no complains any more about PM runtime usage
>> in atomic context "BUG: sleeping function called from invalid context";
>> - GPIO bank IRQs will appear in /proc/interrupts and its usage statistic
>> will be visible;
>> - GPIO bank IRQs could be configured through IRQ proc_fs interface and,
>> as result, could be a part of IRQ balancing process if needed;
>> - GPIO bank IRQs will be under control of IRQ PM Core during
>> suspend to RAM.
>>
>> Disadvantage:
>> - additional runtime overhed as call chain till
>> omap_gpio_irq_handler() will be longer now
>> - necessity to use wa_lock in omap_gpio_irq_handler() to W/A warning
>> in handle_irq_event_percpu()
>> WARNING: CPU: 1 PID: 35 at kernel/irq/handle.c:149 handle_irq_event_percpu+0x51c/0x638()
>>
>> This patch doesn't fully follows recommendations provided by Sebastian
>> Andrzej Siewior [1], because It's required to go through and check all
>> GPIO IRQ pin states as fast as possible and pass control to handle_level_irq
>> or handle_edge_irq. handle_level_irq or handle_edge_irq will perform actions
>> specific for IRQ triggering type and wakeup corresponding registered
>> threaded IRQ handler (at least it's expected to be threaded).
>> IRQs can be lost if handle_nested_irq() will be used, because excecution
>> time of some pin specific GPIO IRQ handler can be very significant and
>> require accessing ext. devices (I2C).
>>
>> Idea of such kind reworking was also discussed in [2].
>>
>> [1] http://www.spinics.net/lists/linux-omap/msg120665.html
>> [2] http://www.spinics.net/lists/linux-omap/msg119516.html
>>
>> Tested-by: Tony Lindgren <tony@atomide.com>
>> Tested-by: Austin Schuh <austin@peloton-tech.com>
>> Signed-off-by: Grygorii Strashko <grygorii.strashko@ti.com>
>
> Patch applied.
>

Thanks.

> I'm thinking that we need some recommendations on how to write
> IRQ handlers in order to be RT-compatible. Can you help me lining
> up the requirements in Documentation/gpio/driver.txt?
>
> I will write an RFC patch and let you write some additional text
> to it in response then we can iterate it a bit.

Sure. I'll try to help.


--
regards,
-grygorii


\
 
 \ /
  Last update: 2015-10-03 01:01    [W:0.093 / U:4.788 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site