[PATCH v3 4/5] drm: renesas: rz-du: Move mode_valid logic to per-output 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-output
constraints stored in rzg2l_du_output_routing.

Previously, rzg2l_du_encoder_mode_valid() applied a hard-coded 83.5 MHz
upper limit specifically for DPAD0. This approach cannot scale across the
RZ DU family because pixel clock limits vary per SoC and per output
interface.

Add mode_clock_min and mode_clock_max fields to rzg2l_du_output_routing
so that clock constraints are expressed at the granularity of individual
output interfaces rather than globally per SoC. Update
rzg2l_du_encoder_mode_valid() to look up the routing entry for the active
output and return MODE_CLOCK_LOW or MODE_CLOCK_HIGH when the pixel clock
falls outside the declared range. A value of 0 for either field means no
bound is enforced in that direction.

Set the DPAD0 pixel clock limits for RZ/G2UL (R9A07G043U) to 20.875 MHz
minimum and 83.5 MHz maximum. RZ/G2L and RZ/G2LC (R9A07G044) share the
same DPAD0 pixel clock limits.

Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
---
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     | 4 ++++
 drivers/gpu/drm/renesas/rz-du/rzg2l_du_drv.h     | 4 ++++
 drivers/gpu/drm/renesas/rz-du/rzg2l_du_encoder.c | 6 +++++-
 3 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..d1bc205eb5f8 100644
--- a/drivers/gpu/drm/renesas/rz-du/rzg2l_du_drv.c
+++ b/drivers/gpu/drm/renesas/rz-du/rzg2l_du_drv.c
@@ -33,6 +33,8 @@ static const struct rzg2l_du_device_info rzg2l_du_r9a07g043u_info = {
 		[RZG2L_DU_OUTPUT_DPAD0] = {
 			.possible_outputs = BIT(0),
 			.port = 0,
+			.mode_clock_min = 20875,
+			.mode_clock_max = 83500,
 		},
 	},
 };
@@ -47,6 +49,8 @@ static const struct rzg2l_du_device_info rzg2l_du_r9a07g044_info = {
 		[RZG2L_DU_OUTPUT_DPAD0] = {
 			.possible_outputs = BIT(0),
 			.port = 1,
+			.mode_clock_min = 20875,
+			.mode_clock_max = 83500,
 		}
 	}
 };
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..307ae70dd382 100644
--- a/drivers/gpu/drm/renesas/rz-du/rzg2l_du_drv.h
+++ b/drivers/gpu/drm/renesas/rz-du/rzg2l_du_drv.h
@@ -30,6 +30,8 @@ enum rzg2l_du_output {
  * struct rzg2l_du_output_routing - Output routing specification
  * @possible_outputs: bitmask of possible outputs
  * @port: device tree port number corresponding to this output route
+ * @mode_clock_min: minimum pixel clock in kHz
+ * @mode_clock_max: maximum pixel clock in kHz
  *
  * The DU has 2 possible outputs (DPAD0, DSI0). Output routing data
  * specify the valid SoC outputs, which CRTC can drive the output, and the type
@@ -38,6 +40,8 @@ enum rzg2l_du_output {
 struct rzg2l_du_output_routing {
 	unsigned int possible_outputs;
 	unsigned int port;
+	int mode_clock_min;
+	int mode_clock_max;
 };
 
 /*
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..4af2ae09ff39 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 +50,12 @@ 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_output_routing *route = &rcdu->info->routes[renc->output];
 
-	if (renc->output == RZG2L_DU_OUTPUT_DPAD0 && mode->clock > 83500)
+	if (route->mode_clock_min && mode->clock < route->mode_clock_min)
+		return MODE_CLOCK_LOW;
+	if (route->mode_clock_max && mode->clock > route->mode_clock_max)
 		return MODE_CLOCK_HIGH;
 
 	return MODE_OK;
-- 
2.54.0