[PATCH v4 4/5] drm: renesas: rz-du: Move mode_valid logic to per-SoC clock limits

[Prabhakar <prabhakar.csengg@gmail.com>]

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 and RZ/G2L limit
the DPAD0 pixel clock to a narrow window, 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 check these bounds when evaluating
DPAD0 outputs, returning MODE_CLOCK_LOW when the pixel clock falls
below mode_clock_min and MODE_CLOCK_HIGH when it exceeds mode_clock_max.

Populate the pixel clock limits for both the RZ/G2UL (R9A07G043U) and
RZ/G2L (R9A07G044) variants to a minimum of 20875 kHz and a maximum of
83500 kHz.

Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
---
v3->v4:
- Dropped per pad limits
- Updated commit message to reflect the change in approach.

v2->v3:
- Moved clock limits from device_info to output_routing to allow
  per-output constraints.
- Updated commit message to reflect the change in approach.

v1->v2:
- Dropped storing info pointer in struct rzg2l_du_encoder as it's not needed.
---
 drivers/gpu/drm/renesas/rz-du/rzg2l_du_drv.c     | 6 +++++-
 drivers/gpu/drm/renesas/rz-du/rzg2l_du_drv.h     | 4 ++++
 drivers/gpu/drm/renesas/rz-du/rzg2l_du_encoder.c | 9 ++++++++-
 3 files changed, 17 insertions(+), 2 deletions(-)

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..1e4b9f38c55b 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 = {
@@ -48,7 +50,9 @@ static const struct rzg2l_du_device_info rzg2l_du_r9a07g044_info = {
 			.possible_outputs = BIT(0),
 			.port = 1,
 		}
-	}
+	},
+	.mode_clock_min = 20875,
+	.mode_clock_max = 83500,
 };
 
 static const struct rzg2l_du_device_info rzg2l_du_r9a09g057_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 0e567b57a408..56220139a149 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 +50,15 @@ rzg2l_du_encoder_mode_valid(struct drm_encoder *encoder,
 			    const struct drm_display_mode *mode)
 {
 	struct rzg2l_du_encoder *renc = to_rzg2l_encoder(encoder);
+	struct rzg2l_du_device *rcdu = to_rzg2l_du_device(renc->base.dev);
+	const struct rzg2l_du_device_info *info = rcdu->info;
 
-	if (renc->output == RZG2L_DU_OUTPUT_DPAD0 && mode->clock > 83500)
+	if (renc->output != RZG2L_DU_OUTPUT_DPAD0)
+		return MODE_OK;
+
+	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;
 
 	return MODE_OK;
-- 
2.54.0