[Intel-gfx] [PATCH] drm/i915/hdmi: Prune modes that require HDMI2.1 FRL

[Nautiyal, Ankit K]

On 7/19/2022 12:32 PM, Murthy, Arun R wrote:
>> -----Original Message-----
>> From: Nautiyal, Ankit K <ankit.k.nautiyal at intel.com>
>> Sent: Tuesday, July 19, 2022 11:40 AM
>> To: Murthy, Arun R <arun.r.murthy at intel.com>; intel-
>> gfx at lists.freedesktop.org
>> Subject: Re: [Intel-gfx] [PATCH] drm/i915/hdmi: Prune modes that require
>> HDMI2.1 FRL
>>
>>
>> On 7/19/2022 8:45 AM, Murthy, Arun R wrote:
>>>> -----Original Message-----
>>>> From: Nautiyal, Ankit K <ankit.k.nautiyal at intel.com>
>>>> Sent: Friday, July 8, 2022 3:36 PM
>>>> To: Murthy, Arun R <arun.r.murthy at intel.com>; intel-
>>>> gfx at lists.freedesktop.org
>>>> Subject: Re: [Intel-gfx] [PATCH] drm/i915/hdmi: Prune modes that
>>>> require
>>>> HDMI2.1 FRL
>>>>
>>>> Hi Arun,
>>>>
>>>> Thanks for the comments.
>>>>
>>>> Please find my response inline.
>>>>
>>>> On 7/8/2022 9:30 AM, Murthy, Arun R wrote:
>>>>>> -----Original Message-----
>>>>>> From: Intel-gfx <intel-gfx-bounces at lists.freedesktop.org> On Behalf
>>>>>> Of Ankit Nautiyal
>>>>>> Sent: Thursday, July 7, 2022 10:57 AM
>>>>>> To: intel-gfx at lists.freedesktop.org
>>>>>> Subject: [Intel-gfx] [PATCH] drm/i915/hdmi: Prune modes that
>>>>>> require
>>>>>> HDMI2.1 FRL
>>>>>>
>>>>>> HDMI2.1 requires some higher resolution video modes to be
>>>>>> enumerated only if HDMI2.1 Fixed Rate Link (FRL) is supported.
>>>>>> Current platforms do not support FRL transmission so prune modes
>>>>>> that require HDMI2.1 FRL.
>>>>>>
>>>>> If the hardware doesn't support FRL then it basically blocks HDMI2.1
>>>> feature.
>>>>> Then it wont be possible to use any resolution above 4k60 is it?
>>>> Yes right. As I understand, the HDMI2.1a supersedes HDMI2.0b, and so
>>>> the
>>>>
>>>> platforms  supporting HDMI2.0 must now pass the HDMI2.1 CTS.
>>>> The HDMI2.1a spec introduces Marketing Feature names for 4K100,
>>>> 4K120, 8k at 50, 8k at 60 with suffix A, and B.
>>>> Suffix A meaning mode supported without compression, and B meaning,
>>>> mode supported with compression.
>>>>
>>>> There are CTS tests that expect these modes not to be enumerated, if
>>>> the source does support the given requirements.
>>>>
>>>>
>>> Thanks for the clarification.
>>>
>>>>>> Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal at intel.com>
>>>>>> ---
>>>>>>     drivers/gpu/drm/i915/display/intel_hdmi.c | 21
>>>> +++++++++++++++++++++
>>>>>>     1 file changed, 21 insertions(+)
>>>>>>
>>>>>> diff --git a/drivers/gpu/drm/i915/display/intel_hdmi.c
>>>>>> b/drivers/gpu/drm/i915/display/intel_hdmi.c
>>>>>> index ebd91aa69dd2..93c00b61795f 100644
>>>>>> --- a/drivers/gpu/drm/i915/display/intel_hdmi.c
>>>>>> +++ b/drivers/gpu/drm/i915/display/intel_hdmi.c
>>>>>> @@ -1974,6 +1974,20 @@ intel_hdmi_mode_clock_valid(struct
>>>>>> drm_connector *connector, int clock,
>>>>>>     	return status;
>>>>>>     }
>>>>>>
>>>>>> +/*
>>>>>> + * HDMI2.1 requires higher resolution modes like 8k60, 4K120 to be
>>>>>> + * enumerated only if FRL is supported. Platforms not supporting
>>>>>> +FRL
>>>>>> + * must prune these modes.
>>>>>> + */
>>>>>> +static bool
>>>>>> +hdmi21_frl_quirk(int dotclock, bool frl_supported) {
>>>>>> +	if (dotclock >= 600000 && !frl_supported)
>>>>>> +		return true;
>>>>>> +
>>>>>> +	return false;
>>>>>> +}
>>>>>> +
>>>>>>     static enum drm_mode_status
>>>>>>     intel_hdmi_mode_valid(struct drm_connector *connector,
>>>>>>     		      struct drm_display_mode *mode) @@ -2001,6 +2015,13
>>>> @@
>>>>>> intel_hdmi_mode_valid(struct drm_connector *connector,
>>>>>>     		clock *= 2;
>>>>>>     	}
>>>>>>
>>>>>> +	/*
>>>>>> +	 * Current Platforms do not support HDMI2.1 FRL mode of
>>>>>> transmission,
>>>>>> +	 * so prune the modes that require FRL.
>>>>>> +	 */
>>>>>> +	if (hdmi21_frl_quirk(clock, false))
>>>>>> +		return MODE_BAD;
>>>>>> +
>>>>> Instead of setting this frl_supported as false, can we get this info
>>>>> from hardware, so that when our hardware supports it later it would
>>>>> be
>>>> easy to enable this.
>>>>
>>>> We can have something like:
>>>>
>>>> src_supports_frl()
>>>>
>>>> {
>>>>
>>>> /* FRL not supported in
>>>>
>>>> return false;
>>>>
>>>> }
>>>>
>>> Yes something like this looks good. It would be a good design to judge
>>> this based on the Display version.
>> I do agree, we need to have this check when we have HDMI2.1 support for
>> any platform.
>>
>> In future patches, when FRL transmission will be enabled, at that time it
>> would make sense to check for display version, and parse from VBT about
>> what rate it allows  etc.
>>
> Awaiting patch with handling this properly!
> Reviewed-by: Arun R Murthy <arun.r.murthy at intel.com>


Thanks Arun for the for the review.

I have sent another version of the patch, with some changes.

As discussed, check for FRL support, will be added while enabling FRL in 
future platforms, so removed the function altogether.

Regards,

Ankit

>
> Thanks and Regards,
> Arun R Murthy
> -------------------