linux-kernel - Re: [RFC][PATCH] drm: adv7511/33: Fix adv7511_cec

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Date:   Tue, 28 Nov 2017 13:32:47 -0800
From:   John Stultz <john.stultz@...aro.org>
To:     Archit Taneja <architt@...eaurora.org>
Cc:     Arnd Bergmann <arnd@...db.de>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        David Airlie <airlied@...ux.ie>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Bhumika Goyal <bhumirks@...il.com>,
        Inki Dae <inki.dae@...sung.com>,
        dri-devel@...ts.freedesktop.org,
        lkml <linux-kernel@...r.kernel.org>,
        Xinliang Liu <xinliang.liu@...aro.org>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        Sean Paul <seanpaul@...omium.org>,
        Hans Verkuil <hans.verkuil@...co.com>,
        Guodong Xu <guodong.xu@...aro.org>
Subject: Re: [RFC][PATCH] drm: adv7511/33: Fix adv7511_cec_init() failure handling

On Sun, Nov 26, 2017 at 4:56 AM, Archit Taneja <architt@...eaurora.org> wrote:
>
> On 11/17/2017 04:29 AM, John Stultz wrote:
>> diff --git a/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c
>> b/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c
>> index 0e14f15..939c3b9 100644
>> --- a/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c
>> +++ b/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c
>> @@ -1203,12 +1203,12 @@ static int adv7511_probe(struct i2c_client *i2c,
>> const struct i2c_device_id *id)
>>     #ifdef CONFIG_DRM_I2C_ADV7511_CEC
>>         ret = adv7511_cec_init(dev, adv7511, offset);
>> -       if (ret)
>> -               goto err_unregister_cec;
>>   #else
>> -       regmap_write(adv7511->regmap, ADV7511_REG_CEC_CTRL + offset,
>> -                    ADV7511_CEC_CTRL_POWER_DOWN);
>> +       ret = 1;
>>   #endif
>> +       if (ret)
>> +               regmap_write(adv7511->regmap, ADV7511_REG_CEC_CTRL +
>> offset,
>> +                            ADV7511_CEC_CTRL_POWER_DOWN);
>
>
> This would force CEC to be powered off even if adv7511_cec_init() returned
> 0, right?

I don't think so. The initent was its only powered off if
adv7511_cec_init returns an error or if  CONFIG_DRM_I2C_ADV7511_CEC is
not set.

> Do we know why the call to adv7511_cec_init() is failing on the Hikey board?
> If it's
> because there isn't a "cec" clock specified in DT, it's not really a fatal
> error, it
> just means that the platform hasn't been set up to support CEC. In that

Yea. I believe this is the case w/ HiKey.  I don't have deeply
detailed docs on the board so I'm not sure if we will be able to
enable that or not (Xinliang/Guodong: Do you know if its possible?).
In the meantime though, we shouldn't regress.

> case, we
> should just power down the CEC block. So, if adv7511_cec_init() would return
> a
> -ENOENT, which we could use as a hint to power down CEC. So, maybe something
> like this?:
>
> #ifdef CONFIG_DRM_I2C_ADV7511_CEC
>         ret = adv7511_cec_init(dev, adv7511, offset);
>         if (ret && ret != -ENOENT)
>                 goto err_unregister_cec;
> #endif
>         if (ret)
>             regmap_write(adv7511->regmap, ADV7511_REG_CEC_CTRL + offset,
>                         ADV7511_CEC_CTRL_POWER_DOWN);
>
> Apart from this, we should also move adv7511_cec_init() up in the probe so
> that
> it's called before the drm_bridge is registered.

Hans has since reworked the patch w/ a new version. You might want to
check his patches and see if they fit what your imagining.

thanks
-john