Re: [PATCH V2 4/6] drm: bridge: samsung-dsim: Dynamically configure DPHY timing
From: Adam Ford
Date: Mon Apr 24 2023 - 05:31:59 EST
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.
adam
>
> > +
> > + /*
> > + * TODO:
> > + * The tech reference manual for i.MX8M Mini/Nano/Plus
> > + * doesn't state what the definition of the PHYTIMING
> > + * bits are beyond their address and bit position.
> > + * After reviewing NXP's downstream code, it appears
> > + * that the various PHYTIMING registers take the number
> > + * of cycles and use various dividers on them. This
> > + * calculation does not result in an exact match to the
> > + * downstream code, but it is very close, and it appears
> > + * to sync at a variety of resolutions. If someone
> > + * can get a more accurate mathematical equation needed
> > + * for these registers, this should be updated.
> > + */
> > +
> > + lpx = PS_TO_CYCLE(cfg.lpx, clock_in_hz);
> > + hs_exit = PS_TO_CYCLE(cfg.hs_exit, clock_in_hz);
> > + clk_prepare = PS_TO_CYCLE(cfg.clk_prepare, clock_in_hz);
> > + clk_zero = PS_TO_CYCLE(cfg.clk_zero, clock_in_hz);
> > + clk_post = PS_TO_CYCLE(cfg.clk_post, clock_in_hz);
> > + clk_trail = PS_TO_CYCLE(cfg.clk_trail, clock_in_hz);
> > + hs_prepare = PS_TO_CYCLE(cfg.hs_prepare, clock_in_hz);
> > + hs_zero = PS_TO_CYCLE(cfg.hs_zero, clock_in_hz);
> > + hs_trail = PS_TO_CYCLE(cfg.hs_trail, clock_in_hz);
> > + }
> > +
> > /* B D-PHY: D-PHY Master & Slave Analog Block control */
> > reg = reg_values[PHYCTRL_ULPS_EXIT] | reg_values[PHYCTRL_VREG_LP] |
> > reg_values[PHYCTRL_SLEW_UP];
> > +
> > samsung_dsim_write(dsi, DSIM_PHYCTRL_REG, reg);
> >
> > /*
> > @@ -712,7 +750,11 @@ static void samsung_dsim_set_phy_ctrl(struct samsung_dsim *dsi)
> > * T HS-EXIT: Time that the transmitter drives LP-11 following a HS
> > * burst
> > */
> > - reg = reg_values[PHYTIMING_LPX] | reg_values[PHYTIMING_HS_EXIT];
> > + if (driver_data->dynamic_dphy)
> > + reg = DSIM_PHYTIMING_LPX(lpx) | DSIM_PHYTIMING_HS_EXIT(hs_exit);
> > + else
> > + reg = reg_values[PHYTIMING_LPX] | reg_values[PHYTIMING_HS_EXIT];
> > +
> > samsung_dsim_write(dsi, DSIM_PHYTIMING_REG, reg);
> >
> > /*
> > @@ -728,10 +770,17 @@ static void samsung_dsim_set_phy_ctrl(struct samsung_dsim *dsi)
> > * T CLK-TRAIL: Time that the transmitter drives the HS-0 state after
> > * the last payload clock bit of a HS transmission burst
> > */
> > - reg = reg_values[PHYTIMING_CLK_PREPARE] |
> > - reg_values[PHYTIMING_CLK_ZERO] |
> > - reg_values[PHYTIMING_CLK_POST] |
> > - reg_values[PHYTIMING_CLK_TRAIL];
> > + if (driver_data->dynamic_dphy) {
> > + reg = DSIM_PHYTIMING1_CLK_PREPARE(clk_prepare) |
> > + DSIM_PHYTIMING1_CLK_ZERO(clk_zero) |
> > + DSIM_PHYTIMING1_CLK_POST(clk_post) |
> > + DSIM_PHYTIMING1_CLK_TRAIL(clk_trail);
> > + } else {
> > + reg = reg_values[PHYTIMING_CLK_PREPARE] |
> > + reg_values[PHYTIMING_CLK_ZERO] |
> > + reg_values[PHYTIMING_CLK_POST] |
> > + reg_values[PHYTIMING_CLK_TRAIL];
> > + }
> >
> > samsung_dsim_write(dsi, DSIM_PHYTIMING1_REG, reg);
> >
> > @@ -744,8 +793,17 @@ static void samsung_dsim_set_phy_ctrl(struct samsung_dsim *dsi)
> > * T HS-TRAIL: Time that the transmitter drives the flipped differential
> > * state after last payload data bit of a HS transmission burst
> > */
> > - reg = reg_values[PHYTIMING_HS_PREPARE] | reg_values[PHYTIMING_HS_ZERO] |
> > - reg_values[PHYTIMING_HS_TRAIL];
> > +
> > + if (driver_data->dynamic_dphy) {
> > + reg = DSIM_PHYTIMING2_HS_PREPARE(hs_prepare) |
> > + DSIM_PHYTIMING2_HS_ZERO(hs_zero) |
> > + DSIM_PHYTIMING2_HS_TRAIL(hs_trail);
> > + } else {
> > + reg = reg_values[PHYTIMING_HS_PREPARE] |
> > + reg_values[PHYTIMING_HS_ZERO] |
> > + reg_values[PHYTIMING_HS_TRAIL];
> > + }
> > +
> > samsung_dsim_write(dsi, DSIM_PHYTIMING2_REG, reg);
> > }
> >
> > @@ -1337,7 +1395,8 @@ static int samsung_dsim_init(struct samsung_dsim *dsi)
> > samsung_dsim_enable_clock(dsi);
> > if (driver_data->wait_for_reset)
> > samsung_dsim_wait_for_reset(dsi);
> > - samsung_dsim_set_phy_ctrl(dsi);
> > + if (!driver_data->has_freqband)
> > + samsung_dsim_set_phy_ctrl(dsi);
> > samsung_dsim_init_link(dsi);
> >
> > dsi->state |= DSIM_STATE_INITIALIZED;
> > diff --git a/include/drm/bridge/samsung-dsim.h b/include/drm/bridge/samsung-dsim.h
> > index a088d84579bc..25475d78adb3 100644
> > --- a/include/drm/bridge/samsung-dsim.h
> > +++ b/include/drm/bridge/samsung-dsim.h
> > @@ -62,6 +62,7 @@ struct samsung_dsim_driver_data {
> > u16 m_min;
> > u16 m_max;
> > u64 vco_min;
> > + bool dynamic_dphy;
> > };
> >
> > struct samsung_dsim_host_ops {
> > --
> > 2.39.2
> >