Re: [PATCH v3 12/38] drm/msm/dp: introduce max_streams for DP controller MST support

[Yongxing Mou <yongxing.mou@oss.qualcomm.com>]

On 8/26/2025 1:42 AM, Dmitry Baryshkov wrote:
> On Mon, Aug 25, 2025 at 10:15:58PM +0800, Yongxing Mou wrote:
>> From: Abhinav Kumar <quic_abhinavk@quicinc.com>
>>
>> Introduce the `mst_streams` field in each DP controller descriptor to
>> specify the number of supported MST streams. Most platforms support 2 or
>> 4 MST streams, while platforms without MST support default to a single
>> stream (`DEFAULT_STREAM_COUNT = 1`).
>>
>> This change also accounts for platforms with asymmetric stream support,
>> e.g., DP0 supporting 4 streams and DP1 supporting 2.
> 
> How?
> 
Each DP controller have it own msm_dp_desc ...
>>
>> Signed-off-by: Abhinav Kumar <quic_abhinavk@quicinc.com>
>> Signed-off-by: Yongxing Mou <yongxing.mou@oss.qualcomm.com>
>> ---
>>   drivers/gpu/drm/msm/dp/dp_display.c | 21 +++++++++++++++++++++
>>   drivers/gpu/drm/msm/dp/dp_display.h |  1 +
>>   2 files changed, 22 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/msm/dp/dp_display.c b/drivers/gpu/drm/msm/dp/dp_display.c
>> index 78d932bceb581ee54116926506b1025bd159108f..a8477a0a180137f15cbb1401c3964636aa32626c 100644
>> --- a/drivers/gpu/drm/msm/dp/dp_display.c
>> +++ b/drivers/gpu/drm/msm/dp/dp_display.c
>> @@ -33,6 +33,7 @@ module_param(psr_enabled, bool, 0);
>>   MODULE_PARM_DESC(psr_enabled, "enable PSR for eDP and DP displays");
>>   
>>   #define HPD_STRING_SIZE 30
>> +#define DEFAULT_STREAM_COUNT 1
>>   
>>   enum {
>>   	ISR_DISCONNECTED,
>> @@ -52,6 +53,7 @@ struct msm_dp_display_private {
>>   	bool core_initialized;
>>   	bool phy_initialized;
>>   	bool audio_supported;
>> +	bool mst_supported;
> 
> Why do we need the separate boot field here? Isn't it enough to check the max_stream?
> 
If remove mst_supported, condition "mst_streams > 1" will appear in 
multiple places.
>>   
>>   	struct drm_device *drm_dev;
>>   
>> @@ -84,12 +86,15 @@ struct msm_dp_display_private {
>>   
>>   	void __iomem *p0_base;
>>   	size_t p0_len;
>> +
>> +	int max_stream;
>>   };
>>   
>>   struct msm_dp_desc {
>>   	phys_addr_t io_start;
>>   	unsigned int id;
>>   	bool wide_bus_supported;
>> +	int mst_streams;
>>   };
>>   
>>   static const struct msm_dp_desc msm_dp_desc_sa8775p[] = {
>> @@ -1213,6 +1218,15 @@ static int msm_dp_display_get_io(struct msm_dp_display_private *display)
>>   	return 0;
>>   }
>>   
>> +int msm_dp_get_mst_max_stream(struct msm_dp *msm_dp_display)
>> +{
>> +	struct msm_dp_display_private *dp;
>> +
>> +	dp = container_of(msm_dp_display, struct msm_dp_display_private, msm_dp_display);
>> +
>> +	return dp->max_stream;
>> +}
>> +
>>   static int msm_dp_display_probe(struct platform_device *pdev)
>>   {
>>   	int rc = 0;
>> @@ -1239,6 +1253,13 @@ static int msm_dp_display_probe(struct platform_device *pdev)
>>   	dp->msm_dp_display.is_edp =
>>   		(dp->msm_dp_display.connector_type == DRM_MODE_CONNECTOR_eDP);
>>   	dp->hpd_isr_status = 0;
>> +	dp->max_stream = DEFAULT_STREAM_COUNT;
> 
> Just use 1 it's not that magic to define it.
> 
Will fix it.
>> +	dp->mst_supported = FALSE;
>> +
>> +	if (desc->mst_streams > DEFAULT_STREAM_COUNT) {
>> +		dp->max_stream = desc->mst_streams;
>> +		dp->mst_supported = TRUE;
>> +	}
>>   
>>   	rc = msm_dp_display_get_io(dp);
>>   	if (rc)
>> diff --git a/drivers/gpu/drm/msm/dp/dp_display.h b/drivers/gpu/drm/msm/dp/dp_display.h
>> index 37c6e87db90ce951274cdae61f26d76dc9ef3840..7727cf325a89b4892d2370a5616c4fa76fc88485 100644
>> --- a/drivers/gpu/drm/msm/dp/dp_display.h
>> +++ b/drivers/gpu/drm/msm/dp/dp_display.h
>> @@ -29,6 +29,7 @@ struct msm_dp {
>>   	bool psr_supported;
>>   };
>>   
>> +int msm_dp_get_mst_max_stream(struct msm_dp *msm_dp_display);
>>   int msm_dp_display_get_modes(struct msm_dp *msm_dp_display);
>>   bool msm_dp_display_check_video_test(struct msm_dp *msm_dp_display);
>>   int msm_dp_display_get_test_bpp(struct msm_dp *msm_dp_display);
>>
>> -- 
>> 2.34.1
>>
>