Hi Prabhakar,
On Mon, May 12, 2025 at 07:23:23PM +0100, Prabhakar wrote:
> From: Lad Prabhakar <prabhakar.mahadev-lad...@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...@renesas.com>
> Signed-off-by: Fabrizio Castro <fabrizio.castro...@renesas.com>
> Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad...@bp.renesas.com>
> Reviewed-by: Biju Das <biju.das...@bp.renesas.com>
> ---
> 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 | 30 +++++++++++--------
> 1 file changed, 18 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 c5f698cd74f1..3f6988303e63 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 * MILLI))
No need for the inner parentheses.
> 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 * MILLI);
> +
> /*
> * Relationship between hsclk and vclk must follow
> * vclk * bpp = hsclk * 8 * lanes
> @@ -280,13 +288,11 @@ 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);
> + if (vclk_rate != mode->clock * MILLI)
> + dev_info(dsi->dev, "Requested vclk rate %lu, actual %lu
> mismatch\n",
> + mode->clock * MILLI, vclk_rate);
There's a high risk that the requested rate won't be achieved exactly.
Do we really want to print a non-debug message to the kernel log every
time ?
> + hsfreq = DIV_ROUND_CLOSEST_ULL(vclk_rate * bpp, dsi->lanes);
I doubt DIV_ROUND_CLOSEST_ULL() will make any difference in practice
given that you can't have more than 4 lanes, but that's fine.
>
> ret = rzg2l_mipi_dsi_dphy_init(dsi, hsfreq);
> if (ret < 0)
> @@ -304,12 +310,12 @@ 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;
> @@ -753,7 +759,7 @@ 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;
>
--
Regards,
Laurent Pinchart
