[PATCH v7 3/9] drm: renesas: rz-du: mipi_dsi: Use VCLK for HSFREQ calculation

[Prabhakar]

From: Lad Prabhakar <prabhakar.mahadev-lad.rj at bp.renesas.com>

Update the RZ/G2L MIPI DSI driver to calculate HSFREQ using the actual
VCLK rate instead of the mode clock. The relationship between HSCLK and
VCLK is:

    vclk * bpp <= hsclk * 8 * lanes

Retrieve the VCLK rate using `clk_get_rate(dsi->vclk)`, ensuring that
HSFREQ accurately reflects the clock rate set in hardware, leading to
better precision in data transmission.

Additionally, use `DIV_ROUND_CLOSEST_ULL` for a more precise division
when computing `hsfreq`. Also, update unit conversions to use correct
scaling factors for better clarity and correctness.

Since `clk_get_rate()` returns the clock rate in Hz, update the HSFREQ
threshold comparisons to use Hz instead of kHz to ensure correct behavior.

Co-developed-by: Fabrizio Castro <fabrizio.castro.jz at renesas.com>
Signed-off-by: Fabrizio Castro <fabrizio.castro.jz at renesas.com>
Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj at bp.renesas.com>
Reviewed-by: Biju Das <biju.das.jz at bp.renesas.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart+renesas at ideasonboard.com>
---
v6->v7:
- Stored frequency in Hz
- Added Reviewed-by from Laurent

v5->v6:
- Dropped parentheses around the calculation of `hsfreq_max`.
- Changed dev_info() to dev_dbg

v4->v5:
- Added dev_info() to print the VCLK rate if it doesn't match the
  requested rate.
- Added Reviewed-by tag from Biju

v3->v4:
- Used MILLI instead of KILO

v2->v3:
- No changes

v1->v2:
- No changes
---
 .../gpu/drm/renesas/rz-du/rzg2l_mipi_dsi.c    | 40 +++++++++++--------
 1 file changed, 23 insertions(+), 17 deletions(-)

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 7fa5bb2a62b6..b08274e5dfcf 100644
--- a/drivers/gpu/drm/renesas/rz-du/rzg2l_mipi_dsi.c
+++ b/drivers/gpu/drm/renesas/rz-du/rzg2l_mipi_dsi.c
@@ -11,6 +11,7 @@
 #include <linux/dma-mapping.h>
 #include <linux/io.h>
 #include <linux/iopoll.h>
+#include <linux/math.h>
 #include <linux/module.h>
 #include <linux/of.h>
 #include <linux/of_graph.h>
@@ -18,6 +19,7 @@
 #include <linux/pm_runtime.h>
 #include <linux/reset.h>
 #include <linux/slab.h>
+#include <linux/units.h>
 
 #include <drm/drm_atomic.h>
 #include <drm/drm_atomic_helper.h>
@@ -85,7 +87,7 @@ struct rzg2l_mipi_dsi_timings {
 
 static const struct rzg2l_mipi_dsi_timings rzg2l_mipi_dsi_global_timings[] = {
 	{
-		.hsfreq_max = 80000,
+		.hsfreq_max = 80000000,
 		.t_init = 79801,
 		.tclk_prepare = 8,
 		.ths_prepare = 13,
@@ -99,7 +101,7 @@ static const struct rzg2l_mipi_dsi_timings rzg2l_mipi_dsi_global_timings[] = {
 		.tlpx = 6,
 	},
 	{
-		.hsfreq_max = 125000,
+		.hsfreq_max = 125000000,
 		.t_init = 79801,
 		.tclk_prepare = 8,
 		.ths_prepare = 12,
@@ -113,7 +115,7 @@ static const struct rzg2l_mipi_dsi_timings rzg2l_mipi_dsi_global_timings[] = {
 		.tlpx = 6,
 	},
 	{
-		.hsfreq_max = 250000,
+		.hsfreq_max = 250000000,
 		.t_init = 79801,
 		.tclk_prepare = 8,
 		.ths_prepare = 12,
@@ -127,7 +129,7 @@ static const struct rzg2l_mipi_dsi_timings rzg2l_mipi_dsi_global_timings[] = {
 		.tlpx = 6,
 	},
 	{
-		.hsfreq_max = 360000,
+		.hsfreq_max = 360000000,
 		.t_init = 79801,
 		.tclk_prepare = 8,
 		.ths_prepare = 10,
@@ -141,7 +143,7 @@ static const struct rzg2l_mipi_dsi_timings rzg2l_mipi_dsi_global_timings[] = {
 		.tlpx = 6,
 	},
 	{
-		.hsfreq_max = 720000,
+		.hsfreq_max = 720000000,
 		.t_init = 79801,
 		.tclk_prepare = 8,
 		.ths_prepare = 9,
@@ -155,7 +157,7 @@ static const struct rzg2l_mipi_dsi_timings rzg2l_mipi_dsi_global_timings[] = {
 		.tlpx = 6,
 	},
 	{
-		.hsfreq_max = 1500000,
+		.hsfreq_max = 1500000000,
 		.t_init = 79801,
 		.tclk_prepare = 8,
 		.ths_prepare = 9,
@@ -268,7 +270,7 @@ static void rzg2l_mipi_dsi_dphy_exit(struct rzg2l_mipi_dsi *dsi)
 static int rzg2l_mipi_dsi_startup(struct rzg2l_mipi_dsi *dsi,
 				  const struct drm_display_mode *mode)
 {
-	unsigned long hsfreq;
+	unsigned long hsfreq, vclk_rate;
 	unsigned int bpp;
 	u32 txsetr;
 	u32 clstptsetr;
@@ -280,6 +282,16 @@ static int rzg2l_mipi_dsi_startup(struct rzg2l_mipi_dsi *dsi,
 	u32 dsisetr;
 	int ret;
 
+	ret = pm_runtime_resume_and_get(dsi->dev);
+	if (ret < 0)
+		return ret;
+
+	clk_set_rate(dsi->vclk, mode->clock * KILO);
+	vclk_rate = clk_get_rate(dsi->vclk);
+	if (vclk_rate != mode->clock * KILO)
+		dev_dbg(dsi->dev, "Requested vclk rate %lu, actual %lu mismatch\n",
+			mode->clock * KILO, vclk_rate);
+
 	/*
 	 * Relationship between hsclk and vclk must follow
 	 * vclk * bpp = hsclk * 8 * lanes
@@ -291,13 +303,7 @@ static int rzg2l_mipi_dsi_startup(struct rzg2l_mipi_dsi *dsi,
 	 * hsclk(bit) = hsclk(byte) * 8 = hsfreq
 	 */
 	bpp = mipi_dsi_pixel_format_to_bpp(dsi->format);
-	hsfreq = mode->clock * bpp / dsi->lanes;
-
-	ret = pm_runtime_resume_and_get(dsi->dev);
-	if (ret < 0)
-		return ret;
-
-	clk_set_rate(dsi->vclk, mode->clock * 1000);
+	hsfreq = DIV_ROUND_CLOSEST_ULL(vclk_rate * bpp, dsi->lanes);
 
 	ret = rzg2l_mipi_dsi_dphy_init(dsi, hsfreq);
 	if (ret < 0)
@@ -315,12 +321,12 @@ static int rzg2l_mipi_dsi_startup(struct rzg2l_mipi_dsi *dsi,
 	 * - data lanes: maximum 4 lanes
 	 * Therefore maximum hsclk will be 891 Mbps.
 	 */
-	if (hsfreq > 445500) {
+	if (hsfreq > 445500000) {
 		clkkpt = 12;
 		clkbfht = 15;
 		clkstpt = 48;
 		golpbkt = 75;
-	} else if (hsfreq > 250000) {
+	} else if (hsfreq > 250000000) {
 		clkkpt = 7;
 		clkbfht = 8;
 		clkstpt = 27;
@@ -942,7 +948,7 @@ static int rzg2l_mipi_dsi_probe(struct platform_device *pdev)
 	 * mode->clock and format are not available. So initialize DPHY with
 	 * timing parameters for 80Mbps.
 	 */
-	ret = rzg2l_mipi_dsi_dphy_init(dsi, 80000);
+	ret = rzg2l_mipi_dsi_dphy_init(dsi, 80000000);
 	if (ret < 0)
 		goto err_phy;
 
-- 
2.49.0