[PATCH v11 6/7] drm: renesas: rz-du: mipi_dsi: Add LPCLK clock support

[Prabhakar]

From: Lad Prabhakar <prabhakar.mahadev-lad.rj@xxxxxxxxxxxxxx>

Add LPCLK clock handling to the RZ/G2L MIPI DSI driver to support proper
DSI timing parameter configuration on RZ/V2H SoCs. While lpclk is present
on both RZ/G2L and RZ/V2H SoCs, the RZ/V2H SoC specifically uses the lpclk
rate to configure the DSI timing parameter ULPSEXIT.

Introduce a new lpclk field in the rzg2l_mipi_dsi structure and acquire
the "lpclk" clock during probe to enable lpclk rate-based timing
calculations on RZ/V2H while maintaining compatibility with RZ/G2L.

Co-developed-by: Fabrizio Castro <fabrizio.castro.jz@xxxxxxxxxxx>
Signed-off-by: Fabrizio Castro <fabrizio.castro.jz@xxxxxxxxxxx>
Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@xxxxxxxxxxxxxx>
Reviewed-by: Biju Das <biju.das.jz@xxxxxxxxxxxxxx>
Reviewed-by: Tomi Valkeinen <tomi.valkeinen+renesas@xxxxxxxxxxxxxxxx>
---
v10->v11:
- No changes.

v9->v10:
- No changes.

v8->v9:
- Added reviewed-by tag from Tomi

v7->v8:
- Updated commit message
- Switched to use devm_clk_get() instead of devm_clk_get_optional()
  as lpclk clock is available on all SoCs.

v6->v7:
- New patch
Note, this patch was previously part of series [0].
[0] https://lore.kernel.org/all/20250609225630.502888-1-prabhakar.mahadev-lad.rj@xxxxxxxxxxxxxx/
---
 drivers/gpu/drm/renesas/rz-du/rzg2l_mipi_dsi.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/gpu/drm/renesas/rz-du/rzg2l_mipi_dsi.c b/drivers/gpu/drm/renesas/rz-du/rzg2l_mipi_dsi.c
index 3b52dfc0ea1e..bb03b49b1e85 100644
--- a/drivers/gpu/drm/renesas/rz-du/rzg2l_mipi_dsi.c
+++ b/drivers/gpu/drm/renesas/rz-du/rzg2l_mipi_dsi.c
@@ -68,6 +68,7 @@ struct rzg2l_mipi_dsi {
 	struct drm_bridge *next_bridge;
 
 	struct clk *vclk;
+	struct clk *lpclk;
 
 	enum mipi_dsi_pixel_format format;
 	unsigned int num_data_lanes;
@@ -979,6 +980,10 @@ static int rzg2l_mipi_dsi_probe(struct platform_device *pdev)
 	if (IS_ERR(dsi->vclk))
 		return PTR_ERR(dsi->vclk);
 
+	dsi->lpclk = devm_clk_get(dsi->dev, "lpclk");
+	if (IS_ERR(dsi->lpclk))
+		return PTR_ERR(dsi->lpclk);
+
 	dsi->rstc = devm_reset_control_get_optional_exclusive(dsi->dev, "rst");
 	if (IS_ERR(dsi->rstc))
 		return dev_err_probe(dsi->dev, PTR_ERR(dsi->rstc),
-- 
2.43.0