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

[Adam Ford]

On Mon, Apr 24, 2023 at 4:50 AM Adam Ford <aford173 at gmail.com> wrote:
>
> On Mon, Apr 24, 2023 at 4:47 AM Marek Szyprowski
> <m.szyprowski at samsung.com> wrote:
> >
> > On 24.04.2023 11:44, Chen-Yu Tsai wrote:
> > > On Mon, Apr 24, 2023 at 5:31 PM Adam Ford <aford173 at gmail.com> wrote:
> > >> On Mon, Apr 24, 2023 at 1:12 AM Chen-Yu Tsai <wenst at chromium.org> wrote:
> > >>> On Sun, Apr 23, 2023 at 8:13 PM Adam Ford <aford173 at gmail.com> 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 at gmail.com>
> > >>>> ---
> > >>>>   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.

Marek S & Chen-Yu,

I added a patch into the series to make this select
GENERIC_PHY_MIPI_DPHY, and I tested it with the 32-bit arm config,
exynos_defconfig and it now builds successfully.

I'm going to wait a few more hours to see if anyone else has any
feedback before I send V3.

adam



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