On Sun, Oct 20, 2024 at 01:35:30AM +0530, Aradhya Bhatia wrote: > From: Aradhya Bhatia <a-bhatia1@xxxxxx> > > The cdns-dsi controller requires that it be turned on completely before > the input DPI's source has begun streaming[0]. Not having that, allows > for a small window before cdns-dsi enable and after cdns-dsi disable > where the previous entity (in this case tidss's videoport) to continue > streaming DPI video signals. This small window where cdns-dsi is > disabled but is still receiving signals causes the input FIFO of > cdns-dsi to get corrupted. This causes the colors to shift on the output > display. The colors can either shift by one color component (R->G, G->B, > B->R), or by two color components (R->B, G->R, B->G). > > Since tidss's videoport starts streaming via crtc enable hooks, we need > cdns-dsi to be up and running before that. Now that the bridges are > pre_enabled before crtc is enabled, and post_disabled after crtc is > disabled, use the pre_enable and post_disable hooks to get cdns-dsi > ready and running before the tidss videoport to get pass the color shift > issues. > Not being an expert in the TI DSS driver, would it be more proper to handle that in the TI driver instead? I mean, sending out DPI signals isn't a part of the CRTC setup, it's a job of the encoder. > [0]: See section 12.6.5.7.3 "Start-up Procedure" in J721E SoC TRM > TRM Link: http://www.ti.com/lit/pdf/spruil1 > > Reviewed-by: Tomi Valkeinen <tomi.valkeinen@xxxxxxxxxxxxxxxx> > Signed-off-by: Aradhya Bhatia <a-bhatia1@xxxxxx> > Signed-off-by: Aradhya Bhatia <aradhya.bhatia@xxxxxxxxx> > --- > .../gpu/drm/bridge/cadence/cdns-dsi-core.c | 62 ++++++++++--------- > 1 file changed, 34 insertions(+), 28 deletions(-) > > diff --git a/drivers/gpu/drm/bridge/cadence/cdns-dsi-core.c b/drivers/gpu/drm/bridge/cadence/cdns-dsi-core.c > index 79d8c2264c14..dfeb53841ebc 100644 > --- a/drivers/gpu/drm/bridge/cadence/cdns-dsi-core.c > +++ b/drivers/gpu/drm/bridge/cadence/cdns-dsi-core.c > @@ -658,13 +658,28 @@ cdns_dsi_bridge_mode_valid(struct drm_bridge *bridge, > return MODE_OK; > } > > -static void cdns_dsi_bridge_atomic_disable(struct drm_bridge *bridge, > - struct drm_bridge_state *old_bridge_state) > +static void cdns_dsi_bridge_atomic_post_disable(struct drm_bridge *bridge, > + struct drm_bridge_state *old_bridge_state) > { > struct cdns_dsi_input *input = bridge_to_cdns_dsi_input(bridge); > struct cdns_dsi *dsi = input_to_dsi(input); > u32 val; > > + /* > + * The cdns-dsi controller needs to be disabled after it's DPI source > + * has stopped streaming. If this is not followed, there is a brief > + * window before DPI source is disabled and after cdns-dsi controller > + * has been disabled where the DPI stream is still on, but the cdns-dsi > + * controller is not ready anymore to accept the incoming signals. This > + * is one of the reasons why a shift in pixel colors is observed on > + * displays that have cdns-dsi as one of the bridges. > + * > + * To mitigate this, disable this bridge from the bridge post_disable() > + * hook, instead of the bridge _disable() hook. The bridge post_disable() > + * hook gets called after the CRTC disable, where often many DPI sources > + * disable their streams. > + */ > + > val = readl(dsi->regs + MCTL_MAIN_DATA_CTL); > val &= ~(IF_VID_SELECT_MASK | IF_VID_MODE | VID_EN | HOST_EOT_GEN | > DISP_EOT_GEN); > @@ -683,15 +698,6 @@ static void cdns_dsi_bridge_atomic_disable(struct drm_bridge *bridge, > pm_runtime_put(dsi->base.dev); > } > > -static void cdns_dsi_bridge_atomic_post_disable(struct drm_bridge *bridge, > - struct drm_bridge_state *old_bridge_state) > -{ > - struct cdns_dsi_input *input = bridge_to_cdns_dsi_input(bridge); > - struct cdns_dsi *dsi = input_to_dsi(input); > - > - pm_runtime_put(dsi->base.dev); > -} > - > static void cdns_dsi_hs_init(struct cdns_dsi *dsi) > { > struct cdns_dsi_output *output = &dsi->output; > @@ -760,8 +766,8 @@ static void cdns_dsi_init_link(struct cdns_dsi *dsi) > dsi->link_initialized = true; > } > > -static void cdns_dsi_bridge_atomic_enable(struct drm_bridge *bridge, > - struct drm_bridge_state *old_bridge_state) > +static void cdns_dsi_bridge_atomic_pre_enable(struct drm_bridge *bridge, > + struct drm_bridge_state *old_bridge_state) > { > struct cdns_dsi_input *input = bridge_to_cdns_dsi_input(bridge); > struct cdns_dsi *dsi = input_to_dsi(input); > @@ -776,6 +782,21 @@ static void cdns_dsi_bridge_atomic_enable(struct drm_bridge *bridge, > if (WARN_ON(pm_runtime_get_sync(dsi->base.dev) < 0)) > return; > > + /* > + * The cdns-dsi controller needs to be enabled before it's DPI source > + * has begun streaming. If this is not followed, there is a brief window > + * after DPI source enable and before cdns-dsi controller enable where > + * the DPI stream is on, but the cdns-dsi controller is not ready to > + * accept the incoming signals. This is one of the reasons why a shift > + * in pixel colors is observed on displays that have cdns-dsi as one of > + * the bridges. > + * > + * To mitigate this, enable this bridge from the bridge pre_enable() > + * hook, instead of the bridge _enable() hook. The bridge pre_enable() > + * hook gets called before the CRTC enable, where often many DPI sources > + * enable their streams. > + */ > + > if (dsi->platform_ops && dsi->platform_ops->enable) > dsi->platform_ops->enable(dsi); > > @@ -912,19 +933,6 @@ static void cdns_dsi_bridge_atomic_enable(struct drm_bridge *bridge, > writel(tmp, dsi->regs + MCTL_MAIN_EN); > } > > -static void cdns_dsi_bridge_atomic_pre_enable(struct drm_bridge *bridge, > - struct drm_bridge_state *old_bridge_state) > -{ > - struct cdns_dsi_input *input = bridge_to_cdns_dsi_input(bridge); > - struct cdns_dsi *dsi = input_to_dsi(input); > - > - if (WARN_ON(pm_runtime_get_sync(dsi->base.dev) < 0)) > - return; > - > - cdns_dsi_init_link(dsi); > - cdns_dsi_hs_init(dsi); > -} > - > static u32 *cdns_dsi_bridge_get_input_bus_fmts(struct drm_bridge *bridge, > struct drm_bridge_state *bridge_state, > struct drm_crtc_state *crtc_state, > @@ -968,9 +976,7 @@ static int cdns_dsi_bridge_atomic_check(struct drm_bridge *bridge, > static const struct drm_bridge_funcs cdns_dsi_bridge_funcs = { > .attach = cdns_dsi_bridge_attach, > .mode_valid = cdns_dsi_bridge_mode_valid, > - .atomic_disable = cdns_dsi_bridge_atomic_disable, > .atomic_pre_enable = cdns_dsi_bridge_atomic_pre_enable, > - .atomic_enable = cdns_dsi_bridge_atomic_enable, > .atomic_post_disable = cdns_dsi_bridge_atomic_post_disable, > .atomic_check = cdns_dsi_bridge_atomic_check, > .atomic_duplicate_state = drm_atomic_helper_bridge_duplicate_state, > -- > 2.34.1 > -- With best wishes Dmitry
