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

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Date: Mon, 20 May 2024 11:29:42 +0800
From: Liu Ying <victor.liu@....com>
To: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
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,
 aford173@...il.com, 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 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?

Regards,
Liu Ying