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SubjectRe: [PATCH] drm/bridge: Ignore -EPROBE_DEFER when bridge attach fails
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On 12.10.2021 22:47, Guido Günther wrote:
> Hi Laurent,
> On Tue, Oct 12, 2021 at 11:17:07PM +0300, Laurent Pinchart wrote:
>> Hi Guido,
>>
>> Thank you for the patch.
>>
>> On Tue, Oct 12, 2021 at 09:58:58PM +0200, Guido Günther wrote:
>>> Otherwise logs are filled with
>>>
>>> [drm:drm_bridge_attach] *ERROR* failed to attach bridge /soc@0/bus@30800000/mipi-dsi@30a0 0000 to encoder None-34: -517
>>>
>>> when the bridge isn't ready yet.
>>>
>>> Fixes: fb8d617f8fd6 ("drm/bridge: Centralize error message when bridge attach fails")
>>> Signed-off-by: Guido Günther <agx@sigxcpu.org>
>>> ---
>>> drivers/gpu/drm/drm_bridge.c | 11 ++++++-----
>>> 1 file changed, 6 insertions(+), 5 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/drm_bridge.c b/drivers/gpu/drm/drm_bridge.c
>>> index a8ed66751c2d..f0508e85ae98 100644
>>> --- a/drivers/gpu/drm/drm_bridge.c
>>> +++ b/drivers/gpu/drm/drm_bridge.c
>>> @@ -227,14 +227,15 @@ int drm_bridge_attach(struct drm_encoder *encoder, struct drm_bridge *bridge,
>>> bridge->encoder = NULL;
>>> list_del(&bridge->chain_node);
>>>
>>> + if (ret != -EPROBE_DEFER) {
>>> #ifdef CONFIG_OF
>>> - DRM_ERROR("failed to attach bridge %pOF to encoder %s: %d\n",
>>> - bridge->of_node, encoder->name, ret);
>>> + DRM_ERROR("failed to attach bridge %pOF to encoder %s: %d\n",
>>> + bridge->of_node, encoder->name, ret);
>>> #else
>>> - DRM_ERROR("failed to attach bridge to encoder %s: %d\n",
>>> - encoder->name, ret);
>>> + DRM_ERROR("failed to attach bridge to encoder %s: %d\n",
>>> + encoder->name, ret);
>>> #endif
>>> -
>>> + }
>>
>> This looks fine as such, but I'm concerned about the direction it's
>> taking. Ideally, probe deferral should happen at probe time, way before
>> the bridge is attached. Doing otherwise is a step in the wrong direction
>> in my opinion, and something we'll end up regretting when we'll feel the
>> pain it inflicts.
>
> The particular case I'm seeing this is the nwl driver probe deferrals if
> the panel bridge isn't ready (which needs a bunch of components
> (dsi, panel, backlight wrapped led, ...) and it probes fine later on so I
> wonder where you see the actual error cause? That downstream of the
> bridge isn't ready or that the display controller is already attaching
> the bridge?

So it is something wrong there, nwl should not publish bridge interface
until it gather its resources (the panel in this case).

Regards
Andrzej


>
> Cheers,
> -- Guido
>
>>
>>> return ret;
>>> }
>>> EXPORT_SYMBOL(drm_bridge_attach);
>>
>> --
>> Regards,
>>
>> Laurent Pinchart
>>

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