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[PATCH v2 3/8] drm: zynqmp_dp: Adjust training values per-lane

Sean Anderson posted 8 patches 1 year, 10 months ago
[PATCH v2 3/8] drm: zynqmp_dp: Adjust training values per-lane
Posted by Sean Anderson 1 year, 10 months ago 
The feedback we get from the DPRX is per-lane. Make changes using this
information, instead of picking the maximum values from all lanes. This
results in more-consistent training on marginal links.

Signed-off-by: Sean Anderson <sean.anderson@linux.dev>
---

(no changes since v1)

 drivers/gpu/drm/xlnx/zynqmp_dp.c | 23 ++++++++---------------
 1 file changed, 8 insertions(+), 15 deletions(-)

diff --git a/drivers/gpu/drm/xlnx/zynqmp_dp.c b/drivers/gpu/drm/xlnx/zynqmp_dp.c
index 98a32e6a0459..8635b5673386 100644
--- a/drivers/gpu/drm/xlnx/zynqmp_dp.c
+++ b/drivers/gpu/drm/xlnx/zynqmp_dp.c
@@ -605,28 +605,21 @@ static void zynqmp_dp_adjust_train(struct zynqmp_dp *dp,
 				   u8 link_status[DP_LINK_STATUS_SIZE])
 {
 	u8 *train_set = dp->train_set;
-	u8 voltage = 0, preemphasis = 0;
 	u8 i;
 
 	for (i = 0; i < dp->mode.lane_cnt; i++) {
-		u8 v = drm_dp_get_adjust_request_voltage(link_status, i);
-		u8 p = drm_dp_get_adjust_request_pre_emphasis(link_status, i);
+		u8 voltage = drm_dp_get_adjust_request_voltage(link_status, i);
+		u8 preemphasis =
+			drm_dp_get_adjust_request_pre_emphasis(link_status, i);
 
-		if (v > voltage)
-			voltage = v;
+		if (voltage >= DP_TRAIN_VOLTAGE_SWING_LEVEL_3)
+			voltage |= DP_TRAIN_MAX_SWING_REACHED;
 
-		if (p > preemphasis)
-			preemphasis = p;
-	}
+		if (preemphasis >= DP_TRAIN_PRE_EMPH_LEVEL_2)
+			preemphasis |= DP_TRAIN_MAX_PRE_EMPHASIS_REACHED;
 
-	if (voltage >= DP_TRAIN_VOLTAGE_SWING_LEVEL_3)
-		voltage |= DP_TRAIN_MAX_SWING_REACHED;
-
-	if (preemphasis >= DP_TRAIN_PRE_EMPH_LEVEL_2)
-		preemphasis |= DP_TRAIN_MAX_PRE_EMPHASIS_REACHED;
-
-	for (i = 0; i < dp->mode.lane_cnt; i++)
 		train_set[i] = voltage | preemphasis;
+	}
 }
 
 /**
-- 
2.35.1.1320.gc452695387.dirty
Re: [PATCH v2 3/8] drm: zynqmp_dp: Adjust training values per-lane
Posted by Tomi Valkeinen 1 year, 10 months ago 
On 20/03/2024 00:51, Sean Anderson wrote:
> The feedback we get from the DPRX is per-lane. Make changes using this
> information, instead of picking the maximum values from all lanes. This
> results in more-consistent training on marginal links.
> 
> Signed-off-by: Sean Anderson <sean.anderson@linux.dev>
> ---
> 
> (no changes since v1)
> 
>   drivers/gpu/drm/xlnx/zynqmp_dp.c | 23 ++++++++---------------
>   1 file changed, 8 insertions(+), 15 deletions(-)
> 
> diff --git a/drivers/gpu/drm/xlnx/zynqmp_dp.c b/drivers/gpu/drm/xlnx/zynqmp_dp.c
> index 98a32e6a0459..8635b5673386 100644
> --- a/drivers/gpu/drm/xlnx/zynqmp_dp.c
> +++ b/drivers/gpu/drm/xlnx/zynqmp_dp.c
> @@ -605,28 +605,21 @@ static void zynqmp_dp_adjust_train(struct zynqmp_dp *dp,
>   				   u8 link_status[DP_LINK_STATUS_SIZE])
>   {
>   	u8 *train_set = dp->train_set;
> -	u8 voltage = 0, preemphasis = 0;
>   	u8 i;
>   
>   	for (i = 0; i < dp->mode.lane_cnt; i++) {
> -		u8 v = drm_dp_get_adjust_request_voltage(link_status, i);
> -		u8 p = drm_dp_get_adjust_request_pre_emphasis(link_status, i);
> +		u8 voltage = drm_dp_get_adjust_request_voltage(link_status, i);
> +		u8 preemphasis =
> +			drm_dp_get_adjust_request_pre_emphasis(link_status, i);
>   
> -		if (v > voltage)
> -			voltage = v;
> +		if (voltage >= DP_TRAIN_VOLTAGE_SWING_LEVEL_3)
> +			voltage |= DP_TRAIN_MAX_SWING_REACHED;
>   
> -		if (p > preemphasis)
> -			preemphasis = p;
> -	}
> +		if (preemphasis >= DP_TRAIN_PRE_EMPH_LEVEL_2)
> +			preemphasis |= DP_TRAIN_MAX_PRE_EMPHASIS_REACHED;
>   
> -	if (voltage >= DP_TRAIN_VOLTAGE_SWING_LEVEL_3)
> -		voltage |= DP_TRAIN_MAX_SWING_REACHED;
> -
> -	if (preemphasis >= DP_TRAIN_PRE_EMPH_LEVEL_2)
> -		preemphasis |= DP_TRAIN_MAX_PRE_EMPHASIS_REACHED;
> -
> -	for (i = 0; i < dp->mode.lane_cnt; i++)
>   		train_set[i] = voltage | preemphasis;
> +	}
>   }
>   
>   /**

Looks fine to me, but a few cosmetic suggestions, feel free to ignore if 
not to your liking:

1)

u8 voltage, preemphasis;

voltage = drm_dp_get_adjust_request_voltage(link_status, i);
preemphasis = drm_dp_get_adjust_request_pre_emphasis(link_status, i);

2)

for (unsigned int i = 0; i < dp->mode.lane_cnt; i++)

3)

dp->train_set[i] = voltage | preemphasis;


Reviewed-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>

  Tomi
Re: [PATCH v2 3/8] drm: zynqmp_dp: Adjust training values per-lane
Posted by Sean Anderson 1 year, 10 months ago 
On 3/20/24 01:57, Tomi Valkeinen wrote:
> On 20/03/2024 00:51, Sean Anderson wrote:
>> The feedback we get from the DPRX is per-lane. Make changes using this
>> information, instead of picking the maximum values from all lanes. This
>> results in more-consistent training on marginal links.
>>
>> Signed-off-by: Sean Anderson <sean.anderson@linux.dev>
>> ---
>>
>> (no changes since v1)
>>
>>   drivers/gpu/drm/xlnx/zynqmp_dp.c | 23 ++++++++---------------
>>   1 file changed, 8 insertions(+), 15 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/xlnx/zynqmp_dp.c b/drivers/gpu/drm/xlnx/zynqmp_dp.c
>> index 98a32e6a0459..8635b5673386 100644
>> --- a/drivers/gpu/drm/xlnx/zynqmp_dp.c
>> +++ b/drivers/gpu/drm/xlnx/zynqmp_dp.c
>> @@ -605,28 +605,21 @@ static void zynqmp_dp_adjust_train(struct zynqmp_dp *dp,
>>                      u8 link_status[DP_LINK_STATUS_SIZE])
>>   {
>>       u8 *train_set = dp->train_set;
>> -    u8 voltage = 0, preemphasis = 0;
>>       u8 i;
>>         for (i = 0; i < dp->mode.lane_cnt; i++) {
>> -        u8 v = drm_dp_get_adjust_request_voltage(link_status, i);
>> -        u8 p = drm_dp_get_adjust_request_pre_emphasis(link_status, i);
>> +        u8 voltage = drm_dp_get_adjust_request_voltage(link_status, i);
>> +        u8 preemphasis =
>> +            drm_dp_get_adjust_request_pre_emphasis(link_status, i);
>>   -        if (v > voltage)
>> -            voltage = v;
>> +        if (voltage >= DP_TRAIN_VOLTAGE_SWING_LEVEL_3)
>> +            voltage |= DP_TRAIN_MAX_SWING_REACHED;
>>   -        if (p > preemphasis)
>> -            preemphasis = p;
>> -    }
>> +        if (preemphasis >= DP_TRAIN_PRE_EMPH_LEVEL_2)
>> +            preemphasis |= DP_TRAIN_MAX_PRE_EMPHASIS_REACHED;
>>   -    if (voltage >= DP_TRAIN_VOLTAGE_SWING_LEVEL_3)
>> -        voltage |= DP_TRAIN_MAX_SWING_REACHED;
>> -
>> -    if (preemphasis >= DP_TRAIN_PRE_EMPH_LEVEL_2)
>> -        preemphasis |= DP_TRAIN_MAX_PRE_EMPHASIS_REACHED;
>> -
>> -    for (i = 0; i < dp->mode.lane_cnt; i++)
>>           train_set[i] = voltage | preemphasis;
>> +    }
>>   }
>>     /**
> 
> Looks fine to me, but a few cosmetic suggestions, feel free to ignore if not to your liking:
> 
> 1)
> 
> u8 voltage, preemphasis;
> 
> voltage = drm_dp_get_adjust_request_voltage(link_status, i);
> preemphasis = drm_dp_get_adjust_request_pre_emphasis(link_status, i);

If the comment here is about the line break, I agree that this looks
better but the second line is over 80 characters.

> 2)
> 
> for (unsigned int i = 0; i < dp->mode.lane_cnt; i++)

Is this allowed now?

> 3)
> 
> dp->train_set[i] = voltage | preemphasis;

This would be undone in patch 7/8.

--Sean

> Reviewed-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
> 
>  Tomi
>

Patchew 2.1-devel-b67e4c2

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