linux-kernel - Re: [PATCH] drm/bridge: adv7511: Attach to DSI host at probe time

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Date:   Thu, 27 Jun 2019 15:14:52 +0000
From:   Matt Redfearn <matt.redfearn@...nci.com>
To:     Andrzej Hajda <a.hajda@...sung.com>,
        Archit Taneja <architt@...eaurora.org>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>
CC:     "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        Matthew Redfearn <matthew.redfearn@...nci.com>,
        Luc Van Oostenryck <luc.vanoostenryck@...il.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Jia-Ju Bai <baijiaju1990@...il.com>,
        Kieran Bingham <kieran.bingham+renesas@...asonboard.com>,
        David Airlie <airlied@...ux.ie>,
        Sean Paul <seanpaul@...omium.org>,
        Daniel Vetter <daniel@...ll.ch>
Subject: Re: [PATCH] drm/bridge: adv7511: Attach to DSI host at probe time



On 25/06/2019 11:54, Andrzej Hajda wrote:
> On 24.04.2019 15:22, Matt Redfearn wrote:
>> In contrast to all of the DSI panel drivers in drivers/gpu/drm/panel
>> which attach to the DSI host via mipi_dsi_attach() at probe time, the
>> ADV7533 bridge device does not. Instead it defers this to the point that
>> the upstream device connects to its bridge via drm_bridge_attach().
>> The generic Synopsys MIPI DSI host driver does not register it's own
>> drm_bridge until the MIPI DSI has attached. But it does not call
>> drm_bridge_attach() on the downstream device until the upstream device
>> has attached. This leads to a chicken and the egg failure and the DRM
>> pipeline does not complete.
>> Since all other mipi_dsi_device drivers call mipi_dsi_attach() in
>> probe(), make the adv7533 mipi_dsi_device do the same. This ensures that
>> the Synopsys MIPI DSI host registers it's bridge such that it is
>> available for the upstream device to connect to.
>>
>> Signed-off-by: Matt Redfearn <matt.redfearn@...nci.com>
>>
>> ---
>>
>>   drivers/gpu/drm/bridge/adv7511/adv7511_drv.c | 9 +++++----
>>   1 file changed, 5 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c b/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c
>> index e7ddd3e3db9..ea36ac3a3de 100644
>> --- a/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c
>> +++ b/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c
>> @@ -874,9 +874,6 @@ static int adv7511_bridge_attach(struct drm_bridge *bridge)
>>   				 &adv7511_connector_helper_funcs);
>>   	drm_connector_attach_encoder(&adv->connector, bridge->encoder);
>>   
>> -	if (adv->type == ADV7533)
>> -		ret = adv7533_attach_dsi(adv);
>> -
>>   	if (adv->i2c_main->irq)
>>   		regmap_write(adv->regmap, ADV7511_REG_INT_ENABLE(0),
>>   			     ADV7511_INT0_HPD);
>> @@ -1222,7 +1219,11 @@ static int adv7511_probe(struct i2c_client *i2c, const struct i2c_device_id *id)
>>   	drm_bridge_add(&adv7511->bridge);
>>   
>>   	adv7511_audio_init(dev, adv7511);
>> -	return 0;
>> +
>> +	if (adv7511->type == ADV7533)
>> +		return adv7533_attach_dsi(adv7511);
>> +	else
>> +		return 0;
> 
> 
> It seems that on failure of adv7533_attach_dsi cleanup is not performed.

Hi Andrzej,
Quite right - I will fix and resend.

> 
> Beside this change looks OK, but it would be good to test it on
> platforms with adv7533.

As in the commit message, I needed this change to get the driver to work 
at all on a platform with a Synopsys MIPI DSI interface. However I would 
be very grateful for feedback from people using the ADV7533 with other 
MIPI DSI hosts.

Thanks,
Matt

> 
> 
> Regards
> 
> Andrzej
> 
> 
>>   
>>   err_unregister_cec:
>>   	i2c_unregister_device(adv7511->i2c_cec);
> 
>