[PATCH v8 3/6] drm/dp_mst: Add MST support to DP DPCD R/W functions

[Harry Wentland]

On 2019-08-26 2:05 p.m., David Francis wrote:
> Instead of having drm_dp_dpcd_read/write and
> drm_dp_mst_dpcd_read/write as entry points into the
> aux code, have drm_dp_dpcd_read/write handle both.
> 
> This means that DRM drivers can make MST DPCD read/writes.
> 
> v2: Fix spacing
> v3: Dump dpcd access on MST read/writes
> 
> Reviewed-by: Lyude Paul <lyude at redhat.com>

Reviewed-by: Harry Wentland <harry.wentland at amd.com>

Harry

> Signed-off-by: David Francis <David.Francis at amd.com>
> ---
>  drivers/gpu/drm/drm_dp_aux_dev.c | 12 ++----------
>  drivers/gpu/drm/drm_dp_helper.c  | 30 ++++++++++++++++++++----------
>  2 files changed, 22 insertions(+), 20 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_dp_aux_dev.c b/drivers/gpu/drm/drm_dp_aux_dev.c
> index 0cfb386754c3..418cad4f649a 100644
> --- a/drivers/gpu/drm/drm_dp_aux_dev.c
> +++ b/drivers/gpu/drm/drm_dp_aux_dev.c
> @@ -163,11 +163,7 @@ static ssize_t auxdev_read_iter(struct kiocb *iocb, struct iov_iter *to)
>  			break;
>  		}
>  
> -		if (aux_dev->aux->is_remote)
> -			res = drm_dp_mst_dpcd_read(aux_dev->aux, pos, buf,
> -						   todo);
> -		else
> -			res = drm_dp_dpcd_read(aux_dev->aux, pos, buf, todo);
> +		res = drm_dp_dpcd_read(aux_dev->aux, pos, buf, todo);
>  
>  		if (res <= 0)
>  			break;
> @@ -215,11 +211,7 @@ static ssize_t auxdev_write_iter(struct kiocb *iocb, struct iov_iter *from)
>  			break;
>  		}
>  
> -		if (aux_dev->aux->is_remote)
> -			res = drm_dp_mst_dpcd_write(aux_dev->aux, pos, buf,
> -						    todo);
> -		else
> -			res = drm_dp_dpcd_write(aux_dev->aux, pos, buf, todo);
> +		res = drm_dp_mst_dpcd_write(aux_dev->aux, pos, buf, todo);
>  
>  		if (res <= 0)
>  			break;
> diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
> index ffc68d305afe..2cc21eff4cf3 100644
> --- a/drivers/gpu/drm/drm_dp_helper.c
> +++ b/drivers/gpu/drm/drm_dp_helper.c
> @@ -30,6 +30,7 @@
>  #include <linux/seq_file.h>
>  
>  #include <drm/drm_dp_helper.h>
> +#include <drm/drm_dp_mst_helper.h>
>  #include <drm/drm_print.h>
>  #include <drm/drm_vblank.h>
>  
> @@ -251,7 +252,7 @@ static int drm_dp_dpcd_access(struct drm_dp_aux *aux, u8 request,
>  
>  /**
>   * drm_dp_dpcd_read() - read a series of bytes from the DPCD
> - * @aux: DisplayPort AUX channel
> + * @aux: DisplayPort AUX channel (SST or MST)
>   * @offset: address of the (first) register to read
>   * @buffer: buffer to store the register values
>   * @size: number of bytes in @buffer
> @@ -280,13 +281,18 @@ ssize_t drm_dp_dpcd_read(struct drm_dp_aux *aux, unsigned int offset,
>  	 * We just have to do it before any DPCD access and hope that the
>  	 * monitor doesn't power down exactly after the throw away read.
>  	 */
> -	ret = drm_dp_dpcd_access(aux, DP_AUX_NATIVE_READ, DP_DPCD_REV, buffer,
> -				 1);
> -	if (ret != 1)
> -		goto out;
> +	if (!aux->is_remote) {
> +		ret = drm_dp_dpcd_access(aux, DP_AUX_NATIVE_READ, DP_DPCD_REV,
> +					 buffer, 1);
> +		if (ret != 1)
> +			goto out;
> +	}
>  
> -	ret = drm_dp_dpcd_access(aux, DP_AUX_NATIVE_READ, offset, buffer,
> -				 size);
> +	if (aux->is_remote)
> +		ret = drm_dp_mst_dpcd_read(aux, offset, buffer, size);
> +	else
> +		ret = drm_dp_dpcd_access(aux, DP_AUX_NATIVE_READ, offset,
> +					 buffer, size);
>  
>  out:
>  	drm_dp_dump_access(aux, DP_AUX_NATIVE_READ, offset, buffer, ret);
> @@ -296,7 +302,7 @@ EXPORT_SYMBOL(drm_dp_dpcd_read);
>  
>  /**
>   * drm_dp_dpcd_write() - write a series of bytes to the DPCD
> - * @aux: DisplayPort AUX channel
> + * @aux: DisplayPort AUX channel (SST or MST)
>   * @offset: address of the (first) register to write
>   * @buffer: buffer containing the values to write
>   * @size: number of bytes in @buffer
> @@ -313,8 +319,12 @@ ssize_t drm_dp_dpcd_write(struct drm_dp_aux *aux, unsigned int offset,
>  {
>  	int ret;
>  
> -	ret = drm_dp_dpcd_access(aux, DP_AUX_NATIVE_WRITE, offset, buffer,
> -				 size);
> +	if (aux->is_remote)
> +		ret = drm_dp_mst_dpcd_write(aux, offset, buffer, size);
> +	else
> +		ret = drm_dp_dpcd_access(aux, DP_AUX_NATIVE_WRITE, offset,
> +					 buffer, size);
> +
>  	drm_dp_dump_access(aux, DP_AUX_NATIVE_WRITE, offset, buffer, ret);
>  	return ret;
>  }
>