linux-kernel - Re: [PATCH 1/3] drm/msm/dpu: Add DPU_INTF_DATABUS

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Message-ID: <f4fb042c-1458-6077-3c49-8cc02638b27c@linaro.org>
Date:   Wed, 14 Jun 2023 15:01:59 +0300
From:   Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To:     Marijn Suijten <marijn.suijten@...ainline.org>,
        Jessica Zhang <quic_jesszhan@...cinc.com>
Cc:     Rob Clark <robdclark@...il.com>, Sean Paul <sean@...rly.run>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>, quic_abhinavk@...cinc.com,
        linux-arm-msm@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        freedreno@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] drm/msm/dpu: Add DPU_INTF_DATABUS_WIDEN feature flag
 for DPU >= 5.0

On 14/06/2023 14:42, Marijn Suijten wrote:
> On 2023-06-13 18:57:11, Jessica Zhang wrote:
>> DPU 5.x+ supports a databus widen mode that allows more data to be sent
>> per pclk. Enable this feature flag on all relevant chipsets.
>>
>> Signed-off-by: Jessica Zhang <quic_jesszhan@...cinc.com>
>> ---
>>   drivers/gpu/drm/msm/disp/dpu1/dpu_hw_catalog.c | 3 ++-
>>   drivers/gpu/drm/msm/disp/dpu1/dpu_hw_catalog.h | 2 ++
>>   2 files changed, 4 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_catalog.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_catalog.c
>> index 36ba3f58dcdf..0be7bf0bfc41 100644
>> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_catalog.c
>> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_catalog.c
>> @@ -103,7 +103,8 @@
>>   	(BIT(DPU_INTF_INPUT_CTRL) | \
>>   	 BIT(DPU_INTF_TE) | \
>>   	 BIT(DPU_INTF_STATUS_SUPPORTED) | \
>> -	 BIT(DPU_DATA_HCTL_EN))
>> +	 BIT(DPU_DATA_HCTL_EN) | \
>> +	 BIT(DPU_INTF_DATABUS_WIDEN))
> 
> This doesn't work.  DPU 5.0.0 is SM8150, which has DSI 6G 2.3.  In the
> last patch for DSI you state and enable widebus for DSI 6G 2.5+ only,
> meaning DPU and DSI are now desynced, and the output is completely
> corrupted.
> 
> Is the bound in dsi_host wrong, or do DPU and DSI need to communicate
> when widebus will be enabled, based on DPU && DSI supporting it?

I'd prefer to follow the second approach, as we did for DP. DPU asks the 
actual video output driver if widebus is to be enabled.

> 
> - Marijn
> 
>>   #define INTF_SC7280_MASK (INTF_SC7180_MASK | BIT(DPU_INTF_DATA_COMPRESS))
>>   
>> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_catalog.h b/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_catalog.h
>> index b860784ade72..b9939e00f5e0 100644
>> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_catalog.h
>> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_catalog.h
>> @@ -182,6 +182,7 @@ enum {
>>    *                                  than video timing
>>    * @DPU_INTF_STATUS_SUPPORTED       INTF block has INTF_STATUS register
>>    * @DPU_INTF_DATA_COMPRESS          INTF block has DATA_COMPRESS register
>> + * @DPU_INTF_DATABUS_WIDEN          INTF block has DATABUS_WIDEN register
>>    * @DPU_INTF_MAX
>>    */
>>   enum {
>> @@ -190,6 +191,7 @@ enum {
>>   	DPU_DATA_HCTL_EN,
>>   	DPU_INTF_STATUS_SUPPORTED,
>>   	DPU_INTF_DATA_COMPRESS,
>> +	DPU_INTF_DATABUS_WIDEN,
>>   	DPU_INTF_MAX
>>   };
>>   
>>
>> -- 
>> 2.40.1
>>

-- 
With best wishes
Dmitry