linux-kernel - Re: [PATCH] drm/bridge: adv7511: Exit interrupt handling when necessary

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Message-ID: <acc508e2-b067-47ef-b3e2-fcac51403fe0@linux.dev>
Date: Mon, 20 May 2024 19:48:46 +0800
From: Sui Jingfeng <sui.jingfeng@...ux.dev>
To: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
Cc: Liu Ying <victor.liu@....com>, dri-devel@...ts.freedesktop.org,
 linux-kernel@...r.kernel.org, andrzej.hajda@...el.com,
 neil.armstrong@...aro.org, rfoss@...nel.org,
 Laurent.pinchart@...asonboard.com, jonas@...boo.se,
 jernej.skrabec@...il.com, maarten.lankhorst@...ux.intel.com,
 mripard@...nel.org, tzimmermann@...e.de, airlied@...il.com, daniel@...ll.ch,
 biju.das.jz@...renesas.com, u.kleine-koenig@...gutronix.de,
 aford173@...il.com, jani.nikula@...el.com, bli@...g-olufsen.dk
Subject: Re: [PATCH] drm/bridge: adv7511: Exit interrupt handling when
 necessary

Hi,


On 5/20/24 19:13, Dmitry Baryshkov wrote:
> On Mon, 20 May 2024 at 14:11, Sui Jingfeng <sui.jingfeng@...ux.dev> wrote:
>>
>> Hi,
>>
>> On 5/20/24 06:11, Dmitry Baryshkov wrote:
>>> On Thu, May 16, 2024 at 06:10:06PM +0800, Liu Ying wrote:
>>>> Commit f3d9683346d6 ("drm/bridge: adv7511: Allow IRQ to share GPIO pins")
>>>> fails to consider the case where adv7511->i2c_main->irq is zero, i.e.,
>>>> no interrupt requested at all.
>>>>
>>>> Without interrupt, adv7511_wait_for_edid() could return -EIO sometimes,
>>>> because it polls adv7511->edid_read flag by calling adv7511_irq_process()
>>>> a few times, but adv7511_irq_process() happens to refuse to handle
>>>> interrupt by returning -ENODATA.  Hence, EDID retrieval fails randomly.
>>>>
>>>> Fix the issue by checking adv7511->i2c_main->irq before exiting interrupt
>>>> handling from adv7511_irq_process().
>>>>
>>>> Fixes: f3d9683346d6 ("drm/bridge: adv7511: Allow IRQ to share GPIO pins")
>>>> Signed-off-by: Liu Ying <victor.liu@....com>
>>>> ---
>>>>    drivers/gpu/drm/bridge/adv7511/adv7511_drv.c | 3 ++-
>>>>    1 file changed, 2 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c b/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c
>>>> index 6089b0bb9321..2074fa3c1b7b 100644
>>>> --- a/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c
>>>> +++ b/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c
>>>> @@ -479,7 +479,8 @@ static int adv7511_irq_process(struct adv7511 *adv7511, bool process_hpd)
>>>>               return ret;
>>>>
>>>>       /* If there is no IRQ to handle, exit indicating no IRQ data */
>>>> -    if (!(irq0 & (ADV7511_INT0_HPD | ADV7511_INT0_EDID_READY)) &&
>>>> +    if (adv7511->i2c_main->irq &&
>>>> +        !(irq0 & (ADV7511_INT0_HPD | ADV7511_INT0_EDID_READY)) &&
>>>>           !(irq1 & ADV7511_INT1_DDC_ERROR))
>>>>               return -ENODATA;
>>>
>>> I think it might be better to handle -ENODATA in adv7511_wait_for_edid()
>>> instead. WDYT?
>>>
>>
>> I think this is may deserve another patch.
> 
> My point is that the IRQ handler is fine to remove -ENODATA here,

[...]

> there is no pending IRQ that can be handled. 

But there may has other things need to do in the adv7511_irq_process()
function.

So instead of continuing
> the execution when we know that IRQ bits are not set, 

Even when IRQ bits are not set, it just means that there is no HPD
and no EDID ready-to-read signal. HDMI CEC interrupts still need
to process.


it's better to
> ignore -ENODATA in the calling code and go on with msleep().
> 

So, It's confusing to ignore the -ENODATA here.

-- 
Best regards
Sui