linux-kernel - Re: [PATCH 4.13 30/53] drm/i915/bios: parse DDI ports also for CHV for HDMI DDC pin and DP AUX channel

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Date:   Tue, 17 Oct 2017 10:02:03 +0300
From:   Jani Nikula <jani.nikula@...el.com>
To:     Marek Wilczewski <marek.wilczewski@...tyElectronics.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org
Cc:     stable@...r.kernel.org,
        Ville Syrjälä <ville.syrjala@...ux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>
Subject: Re: [PATCH 4.13 30/53] drm/i915/bios: parse DDI ports also for CHV for HDMI DDC pin and DP AUX channel

On Mon, 16 Oct 2017, Marek Wilczewski <marek.wilczewski@...tyElectronics.com> wrote:
> Hi All,
>
> I can check this patch tomorrow on real HW, but this is rather not
> correct way to go.
>
> CherryView  / Braswell (N3xxx family) has got 3 DDI ports  - see EDS, 
> DDI0,1,2 - linked to PORTs B,C,D. (at least this is the Intel's naming).
>
> Making exception for CRB platform at this stage is stil a workaround.
>
> i915_pci.c should be patched - i can check it tomorrow and send patch if
> works ok on our platform.

CHV/BSW is not a DDI platform. This is not an exception for a CRB
platform or any platform for that matter. i915_pci.c should definitely
*not* be patched for this.

This patch is about parsing VBT data correctly. I don't know what you're
talking about, and why you think this is not the right way to fix the
parsing.

I pinged you about testing the patch on the bug you reported, I noted
the commit and closed the bug when we applied the patch. I gave you two
weeks in between. We applied the patch anyway because we believe it's
the right thing to do regardless of whether it actually fixes the bug
for you or not.

BR,
Jani.

>
> //Marek.
>
>
> W dniu 2017-10-16 o 18:16, Greg Kroah-Hartman pisze:
>> 4.13-stable review patch.  If anyone has any objections, please let me know.
>>
>> ------------------
>>
>> From: Jani Nikula <jani.nikula@...el.com>
>>
>> commit ea850f64c2722278f150dc11de2141baeb24211c upstream.
>>
>> While technically CHV isn't DDI, we do look at the VBT based DDI port
>> info for HDMI DDC pin and DP AUX channel. (We call these "alternate",
>> but they're really just something that aren't platform defaults.)
>>
>> In commit e4ab73a13291 ("drm/i915: Respect alternate_ddc_pin for all DDI
>> ports") Ville writes, "IIRC there may be CHV system that might actually
>> need this."
>>
>> I'm not sure why there couldn't be even more platforms that need this,
>> but start conservative, and parse the info for CHV in addition to DDI.
>>
>> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=100553
>> Reported-by: Marek Wilczewski <mw@...e.pl>
>> Reviewed-by: Ville Syrjälä <ville.syrjala@...ux.intel.com>
>> Signed-off-by: Jani Nikula <jani.nikula@...el.com>
>> Link: https://patchwork.freedesktop.org/patch/msgid/d0815082cb98487618429b62414854137049b888.1506586821.git.jani.nikula@intel.com
>> (cherry picked from commit 348e4058ebf53904e817eec7a1b25327143c2ed2)
>> Signed-off-by: Rodrigo Vivi <rodrigo.vivi@...el.com>
>> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
>>
>> ---
>>  drivers/gpu/drm/i915/intel_bios.c |    2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> --- a/drivers/gpu/drm/i915/intel_bios.c
>> +++ b/drivers/gpu/drm/i915/intel_bios.c
>> @@ -1231,7 +1231,7 @@ static void parse_ddi_ports(struct drm_i
>>  {
>>  	enum port port;
>>  
>> -	if (!HAS_DDI(dev_priv))
>> +	if (!HAS_DDI(dev_priv) && !IS_CHERRYVIEW(dev_priv))
>>  		return;
>>  
>>  	if (!dev_priv->vbt.child_dev_num)
>>
>>
>>
>

-- 
Jani Nikula, Intel Open Source Technology Center