Re: [PATCH 3/4] drm: renesas: rz-du: Move mode_valid logic to per-SoC clock limits

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

On Wed, Apr 29, 2026 at 06:00:11PM +0100, Prabhakar wrote:
> From: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
> 
> Move pixel clock validation from a fixed encoder check to per SoC
> constraints stored in rzg2l_du_device_info.
> 
> Pixel clock limits differ across SoCs in the RZ DU family and cannot be
> expressed by a single shared rule. For example, RZ/G2UL (R9A07G043U)
> limits the DPAD0 pixel clock to 83.5 MHz, while other SoCs such as
> RZ/T2H require a wider operating range.
> 
> Add mode_clock_min and mode_clock_max fields to rzg2l_du_device_info to
> describe the supported pixel clock range for each SoC. Update
> rzg2l_du_encoder_mode_valid() to return MODE_CLOCK_LOW when the pixel
> clock falls below mode_clock_min and MODE_CLOCK_HIGH when it exceeds
> mode_clock_max.
> 
> Set the pixel clock limits for RZ/G2UL(R9A07G043U) to 20.875MHz minimum
> and 83.5MHz maximum.
> 
> Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
> ---
>  drivers/gpu/drm/renesas/rz-du/rzg2l_du_drv.c     | 2 ++
>  drivers/gpu/drm/renesas/rz-du/rzg2l_du_drv.h     | 4 ++++
>  drivers/gpu/drm/renesas/rz-du/rzg2l_du_encoder.c | 6 +++++-
>  drivers/gpu/drm/renesas/rz-du/rzg2l_du_encoder.h | 2 ++
>  4 files changed, 13 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/renesas/rz-du/rzg2l_du_drv.c b/drivers/gpu/drm/renesas/rz-du/rzg2l_du_drv.c
> index 0fef33a5a089..3b7162c6e1f4 100644
> --- a/drivers/gpu/drm/renesas/rz-du/rzg2l_du_drv.c
> +++ b/drivers/gpu/drm/renesas/rz-du/rzg2l_du_drv.c
> @@ -35,6 +35,8 @@ static const struct rzg2l_du_device_info rzg2l_du_r9a07g043u_info = {
>  			.port = 0,
>  		},
>  	},
> +	.mode_clock_min = 20875,
> +	.mode_clock_max = 83500,
>  };
>  
>  static const struct rzg2l_du_device_info rzg2l_du_r9a07g044_info = {
> diff --git a/drivers/gpu/drm/renesas/rz-du/rzg2l_du_drv.h b/drivers/gpu/drm/renesas/rz-du/rzg2l_du_drv.h
> index 58806c2a8f2b..885558eb9547 100644
> --- a/drivers/gpu/drm/renesas/rz-du/rzg2l_du_drv.h
> +++ b/drivers/gpu/drm/renesas/rz-du/rzg2l_du_drv.h
> @@ -44,10 +44,14 @@ struct rzg2l_du_output_routing {
>   * struct rzg2l_du_device_info - DU model-specific information
>   * @channels_mask: bit mask of available DU channels
>   * @routes: array of CRTC to output routes, indexed by output (RZG2L_DU_OUTPUT_*)
> + * @mode_clock_min: minimum pixel clock in kHz
> + * @mode_clock_max: maximum pixel clock in kHz
>   */
>  struct rzg2l_du_device_info {
>  	unsigned int channels_mask;
>  	struct rzg2l_du_output_routing routes[RZG2L_DU_OUTPUT_MAX];
> +	u32 mode_clock_min;
> +	u32 mode_clock_max;
>  };
>  
>  #define RZG2L_DU_MAX_CRTCS		1
> diff --git a/drivers/gpu/drm/renesas/rz-du/rzg2l_du_encoder.c b/drivers/gpu/drm/renesas/rz-du/rzg2l_du_encoder.c
> index d53068733c66..ad02efec1c23 100644
> --- a/drivers/gpu/drm/renesas/rz-du/rzg2l_du_encoder.c
> +++ b/drivers/gpu/drm/renesas/rz-du/rzg2l_du_encoder.c
> @@ -50,8 +50,11 @@ rzg2l_du_encoder_mode_valid(struct drm_encoder *encoder,
>  			    const struct drm_display_mode *mode)
>  {
>  	struct rzg2l_du_encoder *renc = to_rzg2l_encoder(encoder);
> +	const struct rzg2l_du_device_info *info = renc->info;

You could use

	struct rzg2l_du_device *rcdu = to_rzg2l_du_device(renc->base.dev);
	const struct rzg2l_du_device_info *info = rcdu->info;

and avoid the info pointer in struct rzg2l_du_encoder. Up to you.

>  
> -	if (renc->output == RZG2L_DU_OUTPUT_DPAD0 && mode->clock > 83500)
> +	if (info->mode_clock_min && mode->clock < info->mode_clock_min)
> +		return MODE_CLOCK_LOW;
> +	if (info->mode_clock_max && mode->clock > info->mode_clock_max)
>  		return MODE_CLOCK_HIGH;

The new check now applies to all outputs, not just the DPAD0 output. Is
that intentional ?

>  
>  	return MODE_OK;
> @@ -107,6 +110,7 @@ int rzg2l_du_encoder_init(struct rzg2l_du_device  *rcdu,
>  	if (IS_ERR(renc))
>  		return PTR_ERR(renc);
>  
> +	renc->info = rcdu->info;
>  	renc->output = output;
>  	drm_encoder_helper_add(&renc->base, &rzg2l_du_encoder_helper_funcs);
>  
> diff --git a/drivers/gpu/drm/renesas/rz-du/rzg2l_du_encoder.h b/drivers/gpu/drm/renesas/rz-du/rzg2l_du_encoder.h
> index 3e430c1f6132..39a1d178b856 100644
> --- a/drivers/gpu/drm/renesas/rz-du/rzg2l_du_encoder.h
> +++ b/drivers/gpu/drm/renesas/rz-du/rzg2l_du_encoder.h
> @@ -14,10 +14,12 @@
>  #include <linux/container_of.h>
>  
>  struct rzg2l_du_device;
> +struct rzg2l_du_device_info;
>  
>  struct rzg2l_du_encoder {
>  	struct drm_encoder base;
>  	enum rzg2l_du_output output;
> +	const struct rzg2l_du_device_info *info;

If you want to keep a pointer here to avoid going through
to_rzg2l_du_device(), I would store a backpointer to rzg2l_du_device
instead of just an info pointer, it could come handy in other places.

>  };
>  
>  static inline struct rzg2l_du_encoder *to_rzg2l_encoder(struct drm_encoder *e)

-- 
Regards,

Laurent Pinchart