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drm/bridge: cdns-dsi: Use pre_enable/post_disable to enable/disable

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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.

[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@ideasonboard.com>
Tested-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Signed-off-by: Aradhya Bhatia <a-bhatia1@ti.com>
Signed-off-by: Aradhya Bhatia <aradhya.bhatia@linux.dev>
Tested-by: Devarsh Thakkar <devarsht@ti.com>
Link: https://lore.kernel.org/r/20250605171524.27222-5-aradhya.bhatia@linux.dev
Signed-off-by: Maxime Ripard <mripard@kernel.org>
This commit is contained in:
Aradhya Bhatia
2025-06-05 22:45:24 +05:30
committed by Maxime Ripard
parent c9b1150a68
commit 3e4e1f2543
1 changed files with 35 additions and 29 deletions
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64
drivers/gpu/drm/bridge/cadence/cdns-dsi-core.c
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@@ -670,13 +670,28 @@ 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_atomic_state *state)
static void cdns_dsi_bridge_atomic_post_disable(struct drm_bridge *bridge,
struct drm_atomic_state *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);
@@ -688,15 +703,6 @@ static void cdns_dsi_bridge_atomic_disable(struct drm_bridge *bridge,
if (dsi->platform_ops && dsi->platform_ops->disable)
dsi->platform_ops->disable(dsi);
pm_runtime_put(dsi->base.dev);
}
static void cdns_dsi_bridge_atomic_post_disable(struct drm_bridge *bridge,
struct drm_atomic_state *state)
{
struct cdns_dsi_input *input = bridge_to_cdns_dsi_input(bridge);
struct cdns_dsi *dsi = input_to_dsi(input);
dsi->phy_initialized = false;
dsi->link_initialized = false;
phy_power_off(dsi->dphy);
@@ -774,8 +780,8 @@ 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_atomic_state *state)
static void cdns_dsi_bridge_atomic_pre_enable(struct drm_bridge *bridge,
struct drm_atomic_state *state)
{
struct cdns_dsi_input *input = bridge_to_cdns_dsi_input(bridge);
struct cdns_dsi *dsi = input_to_dsi(input);
@@ -792,6 +798,21 @@ static void cdns_dsi_bridge_atomic_enable(struct drm_bridge *bridge,
u32 tmp, reg_wakeup, div, status;
int nlanes;
/*
* 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 (WARN_ON(pm_runtime_get_sync(dsi->base.dev) < 0))
return;
@@ -811,8 +832,8 @@ static void cdns_dsi_bridge_atomic_enable(struct drm_bridge *bridge,
mode = &crtc_state->adjusted_mode;
nlanes = output->dev->lanes;
cdns_dsi_hs_init(dsi);
cdns_dsi_init_link(dsi);
cdns_dsi_hs_init(dsi);
/*
* Now that the DSI Link and DSI Phy are initialized,
@@ -941,19 +962,6 @@ 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_atomic_state *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,
@@ -1048,9 +1056,7 @@ cdns_dsi_bridge_atomic_reset(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_reset = cdns_dsi_bridge_atomic_reset,