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

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Date: Mon, 20 May 2024 17:26:05 +0800
From: Liu Ying <victor.liu@....com>
To: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>, aford173@...il.com
Cc: 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,
 jani.nikula@...el.com, bli@...g-olufsen.dk, sui.jingfeng@...ux.dev
Subject: Re: [PATCH] drm/bridge: adv7511: Exit interrupt handling when
 necessary

On 5/20/24 17:08, Dmitry Baryshkov wrote:
> On Mon, 20 May 2024 at 06:29, Liu Ying <victor.liu@....com> wrote:
>>
>> 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?
>>
>> Then, adv7511_cec_irq_process() will have less chance to be called from
>> adv7511_irq_process() (assuming CONFIG_DRM_I2C_ADV7511_CEC is defined)
>> if adv7511->i2c_main->irq is zero.
>>
>> But, anyway, it seems that commit f3d9683346d6 ("drm/bridge: adv7511:
>> Allow IRQ to share GPIO pins") is even more broken to handle the CEC case,
>> as adv7511_cec_adap_enable() may enable some interrupts for CEC.
>>
>> This is a bit complicated.  Thoughts?
> 
> Send a revert and do it properly?

Good idea.  Adam, can you do that?