[PATCH 10/17] drm: renesas: rz-du: mipi_dsi: Use VCLK for HSFREQ calculation

Prabhakar
2025-03-30T21:08:15Z

From: Lad Prabhakar <prabhakar.mahadev-lad.rj@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@renesas.com>
Signed-off-by: Fabrizio Castro <fabrizio.castro.jz@renesas.com>
Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
---
.../gpu/drm/renesas/rz-du/rzg2l_mipi_dsi.c | 27 ++++++++++---------
1 file changed, 15 insertions(+), 12 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 746f82442c01..e0379f099659 100644
--- a/drivers/gpu/drm/renesas/rz-du/rzg2l_mipi_dsi.c
+++ b/drivers/gpu/drm/renesas/rz-du/rzg2l_mipi_dsi.c
@@ -8,6 +8,7 @@
#include <linux/delay.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>
@@ -15,6 +16,7 @@
#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>
@@ -199,7 +201,7 @@ static int rzg2l_mipi_dsi_dphy_init(struct rzg2l_mipi_dsi *dsi,
/* All DSI global operation timings are set with recommended setting */
for (i = 0; i < ARRAY_SIZE(rzg2l_mipi_dsi_global_timings); ++i) {
dphy_timings = &rzg2l_mipi_dsi_global_timings[i];
- if (hsfreq <= dphy_timings->hsfreq_max)
+ if (hsfreq <= (dphy_timings->hsfreq_max * KILO))
break;
}

@@ -258,7 +260,7 @@ 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;
@@ -269,6 +271,12 @@ static int rzg2l_mipi_dsi_startup(struct rzg2l_mipi_dsi *dsi,
u32 golpbkt;
int ret;

+ ret = pm_runtime_resume_and_get(dsi->dev);
+ if (ret < 0)
+ return ret;
+
+ clk_set_rate(dsi->vclk, mode->clock * KILO);
+
/*
* Relationship between hsclk and vclk must follow
* vclk * bpp = hsclk * 8 * lanes
@@ -280,13 +288,8 @@ 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);
+ vclk_rate = clk_get_rate(dsi->vclk);
+ hsfreq = DIV_ROUND_CLOSEST_ULL(vclk_rate * bpp, dsi->lanes);

ret = rzg2l_mipi_dsi_dphy_init(dsi, hsfreq);
if (ret < 0)
@@ -304,12 +307,12 @@ 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;
@@ -754,7 +757,7 @@ 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