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

Hi Laurent,

Thank you for the review.

On Wed, May 6, 2026 at 9:14 PM Laurent Pinchart
[off-list ref] wrote:

On Wed, Apr 29, 2026 at 06:00:11PM +0100, Prabhakar wrote:

quoted

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.

Agreed, I will drop the info pointer for now.

quoted

-     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 ?

The RZ/G2UL SoC only supports DPAD0 so the check is redundant.

quoted

      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.

As agreed above I will drop this pointer for now.

Cheers,
Prabhakar