Re: [PATCH V2 4/6] drm: bridge: samsung-dsim: Dynamically configure DPHY timing

[Adam Ford]

On Mon, Apr 24, 2023 at 4:47 AM Marek Szyprowski
<m.szyprowski@xxxxxxxxxxx> wrote:
>
> On 24.04.2023 11:44, Chen-Yu Tsai wrote:
> > On Mon, Apr 24, 2023 at 5:31 PM Adam Ford <aford173@xxxxxxxxx> wrote:
> >> On Mon, Apr 24, 2023 at 1:12 AM Chen-Yu Tsai <wenst@xxxxxxxxxxxx> wrote:
> >>> On Sun, Apr 23, 2023 at 8:13 PM Adam Ford <aford173@xxxxxxxxx> wrote:
> >>>> The DPHY timings are currently hard coded. Since the input
> >>>> clock can be variable, the phy timings need to be variable
> >>>> too.  Add an additional variable to the driver data to enable
> >>>> this feature to prevent breaking boards that don't support it.
> >>>>
> >>>> The phy_mipi_dphy_get_default_config function configures the
> >>>> DPHY timings in pico-seconds, and a small macro converts those
> >>>> timings into clock cycles based on the pixel clock rate.
> >>>>
> >>>> Signed-off-by: Adam Ford <aford173@xxxxxxxxx>
> >>>> ---
> >>>>   drivers/gpu/drm/bridge/samsung-dsim.c | 79 +++++++++++++++++++++++----
> >>>>   include/drm/bridge/samsung-dsim.h     |  1 +
> >>>>   2 files changed, 70 insertions(+), 10 deletions(-)
> >>>>
> >>>> diff --git a/drivers/gpu/drm/bridge/samsung-dsim.c b/drivers/gpu/drm/bridge/samsung-dsim.c
> >>>> index 5b6e7825b92f..f165483d5044 100644
> >>>> --- a/drivers/gpu/drm/bridge/samsung-dsim.c
> >>>> +++ b/drivers/gpu/drm/bridge/samsung-dsim.c
> >>>> @@ -18,9 +18,7 @@
> >>>>   #include <linux/media-bus-format.h>
> >>>>   #include <linux/of_device.h>
> >>>>   #include <linux/phy/phy.h>
> >>>> -
> >>>>   #include <video/mipi_display.h>
> >>>> -
> >>>>   #include <drm/bridge/samsung-dsim.h>
> >>>>   #include <drm/drm_panel.h>
> >>>>   #include <drm/drm_print.h>
> >>>> @@ -218,6 +216,8 @@
> >>>>
> >>>>   #define OLD_SCLK_MIPI_CLK_NAME         "pll_clk"
> >>>>
> >>>> +#define PS_TO_CYCLE(PS, MHz) DIV64_U64_ROUND_CLOSEST(((PS) * (MHz)), 1000000000000ULL)
> >>>> +
> >>>>   static const char *const clk_names[5] = {
> >>>>          "bus_clk",
> >>>>          "sclk_mipi",
> >>>> @@ -487,6 +487,7 @@ static const struct samsung_dsim_driver_data imx8mm_dsi_driver_data = {
> >>>>          .m_min = 64,
> >>>>          .m_max = 1023,
> >>>>          .vco_min = 1050,
> >>>> +       .dynamic_dphy = 1,
> >>>>   };
> >>>>
> >>>>   static const struct samsung_dsim_driver_data *
> >>>> @@ -698,13 +699,50 @@ static void samsung_dsim_set_phy_ctrl(struct samsung_dsim *dsi)
> >>>>          const struct samsung_dsim_driver_data *driver_data = dsi->driver_data;
> >>>>          const unsigned int *reg_values = driver_data->reg_values;
> >>>>          u32 reg;
> >>>> +       struct drm_display_mode *m = &dsi->mode;
> >>>> +       int bpp = mipi_dsi_pixel_format_to_bpp(dsi->format);
> >>>> +       struct phy_configure_opts_mipi_dphy cfg;
> >>>> +       int clk_prepare, lpx, clk_zero, clk_post, clk_trail;
> >>>> +       int hs_exit, hs_prepare, hs_zero, hs_trail;
> >>>> +       unsigned long long clock_in_hz = m->clock * 1000;
> >>>>
> >>>>          if (driver_data->has_freqband)
> >>>>                  return;
> >>>>
> >>>> +       /* The dynamic_phy has the ability to adjust PHY Timing settings */
> >>>> +       if (driver_data->dynamic_dphy) {
> >>>> +               phy_mipi_dphy_get_default_config(clock_in_hz, bpp, dsi->lanes, &cfg);
> >>> This requires adding "select GENERIC_PHY_MIPI_DPHY" to DRM_SAMSUNG_DSIM,
> >>> otherwise with CONFIG_DRM_SAMSUNG_DSIM=m:
> >>>
> >>> ERROR: modpost: "phy_mipi_dphy_get_default_config"
> >>> [drivers/gpu/drm/bridge/samsung-dsim.ko] undefined!
> >>> make[5]: *** [scripts/Makefile.modpost:136: Module.symvers] Error 1
> >>> make[4]: *** [Makefile:1978: modpost] Error 2
> >>> make[3]: *** [Makefile:357: __build_one_by_one] Error 2
> >>>
> >>> I'm sure there'll be a similar error if CONFIG_DRM_SAMSUNG_DSIM=y.
> >> That's interesting, I didn't come across that.
> >> What did you use for a starting point when you applied the patches?
> >> I want to see if I can replicate it.
> > next-20230421. My config is pretty much tailored to the Hummingbird Pulse.
> > Device drivers for other hardware or things that I can't enable are all
> > disabled. For example I don't have PHY_MIXEL_MIPI_DPHY enabled.
> >
> > Maybe you have some other bridge or phy that selects it enabled?
>
>
> I've observed similar issue while building exynos_defconfig for arm 32bit.

Thanks to both of you for the head's up.  I'll add a patch to update
Kconfig to explicitly select that when I do V3.  I was just using the
base arm64 'defconfig' option without any customization.

adam
>
>
> Best regards
> --
> Marek Szyprowski, PhD
> Samsung R&D Institute Poland
>