Hi Dmitry, Thank you for reviewing the patches! On 10/20/24 17:27, Dmitry Baryshkov wrote: > 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. I haven't done a feasibility analysis of moving the CRTC bits of TIDSS into the encoder, but even if it were possible, it wouldn't solve the issue. The bridge_enable() sequence gets called _after_ the encoder has been enabled - causing the TIDSS's DPI (enabled from encoder) to still be up and running before the DSI has had a chance to be ready. Regards Aradhya > >> [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 >> >
