Re: [PATCH 2/4] drm/i915/dsi: Enable dithering for 6 bpc panels

From: Hans de Goede <hdegoede@redhat.com>
To: "Ville Syrjälä" <ville.syrjala@linux.intel.com>
Cc: intel-gfx <intel-gfx@lists.freedesktop.org>,
	dri-devel@lists.freedesktop.org
Subject: Re: [PATCH 2/4] drm/i915/dsi: Enable dithering for 6 bpc panels
Date: Mon, 21 Jan 2019 10:54:31 +0100	[thread overview]
Message-ID: <c8c80b2a-7366-14ab-9571-2c34790d3643@redhat.com> (raw)
In-Reply-To: <20190115145510.GK20097@intel.com>

Hi,

On 15-01-19 15:55, Ville Syrjälä wrote:
> On Sat, Dec 01, 2018 at 12:31:46PM +0100, Hans de Goede wrote:
>> The display engine has 2 dithering enable bits which both need to be set
>> for dithering to happen, 1 in the PIPECONF register which is taken care of
>> by i9xx_set_pipeconf() and a second bit at the encoder level.
>>
>> The dsi code was not setting the encoder level dithering enable bit causing
>> dithering to be disabled, this commit fixes this.
>>
>> Signed-off-by: Hans de Goede <hdegoede@redhat.com>
>> ---
>>   drivers/gpu/drm/i915/vlv_dsi.c | 4 ++++
>>   1 file changed, 4 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/i915/vlv_dsi.c b/drivers/gpu/drm/i915/vlv_dsi.c
>> index c10def5efa22..c21cbfa9653c 100644
>> --- a/drivers/gpu/drm/i915/vlv_dsi.c
>> +++ b/drivers/gpu/drm/i915/vlv_dsi.c
>> @@ -711,6 +711,10 @@ static void intel_dsi_port_enable(struct intel_encoder *encoder,
>>   					LANE_CONFIGURATION_DUAL_LINK_B :
>>   					LANE_CONFIGURATION_DUAL_LINK_A;
>>   		}
>> +
>> +		if (intel_dsi->pixel_format != MIPI_DSI_FMT_RGB888)
>> +			temp |= DITHERING_ENABLE;
> 
> The docs say this was only made to work in C0 stepping. Not sure any
> BYT-Ts were ever shipped with B2/3, nor am I sure if setting the bit
> would have any effect there. IMO let's just set the bit and hope for
> the best.
> 
> Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>

Thank you, I've pushed patches 1 and 2 of this series to dinq.

Regards,

Hans

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