[PATCH v8 05/13] drm/bridge: cdns-dsi: Wait for Clk and Data Lanes to be ready

Aradhya Bhatia
2025-01-26T19:16:51Z

From: Aradhya Bhatia <a-bhatia1@ti.com>

Once the DSI Link and DSI Phy are initialized, the code needs to wait
for Clk and Data Lanes to be ready, before continuing configuration.
This is in accordance with the DSI Start-up procedure, found in the
Technical Reference Manual of Texas Instrument's J721E SoC[0] which
houses this DSI TX controller.

If the previous bridge (or crtc/encoder) are configured pre-maturely,
the input signal FIFO gets corrupt. This introduces a color-shift on the
display.

Allow the driver to wait for the clk and data lanes to get ready during
DSI enable.

[0]: See section 12.6.5.7.3 "Start-up Procedure" in J721E SoC TRM
TRM Link: http://www.ti.com/lit/pdf/spruil1

Fixes: e19233955d9e ("drm/bridge: Add Cadence DSI driver")
Cc: Stable List <stable@vger.kernel.org>
Tested-by: Dominik Haller <d.haller@phytec.de>
Reviewed-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>
---
drivers/gpu/drm/bridge/cadence/cdns-dsi-core.c | 15 ++++++++++++++-
1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/bridge/cadence/cdns-dsi-core.c b/drivers/gpu/drm/bridge/cadence/cdns-dsi-core.c
index 87921a748cdb..6a77ca36cb9d 100644
--- a/drivers/gpu/drm/bridge/cadence/cdns-dsi-core.c
+++ b/drivers/gpu/drm/bridge/cadence/cdns-dsi-core.c
@@ -769,7 +769,7 @@ static void cdns_dsi_bridge_enable(struct drm_bridge *bridge)
struct phy_configure_opts_mipi_dphy *phy_cfg = &output->phy_opts.mipi_dphy;
unsigned long tx_byte_period;
struct cdns_dsi_cfg dsi_cfg;
- u32 tmp, reg_wakeup, div;
+ u32 tmp, reg_wakeup, div, status;
int nlanes;

if (WARN_ON(pm_runtime_get_sync(dsi->base.dev) < 0))
@@ -786,6 +786,19 @@ static void cdns_dsi_bridge_enable(struct drm_bridge *bridge)
cdns_dsi_hs_init(dsi);
cdns_dsi_init_link(dsi);

+ /*
+ * Now that the DSI Link and DSI Phy are initialized,
+ * wait for the CLK and Data Lanes to be ready.
+ */
+ tmp = CLK_LANE_RDY;
+ for (int i = 0; i < nlanes; i++)
+ tmp |= DATA_LANE_RDY(i);
+
+ if (readl_poll_timeout(dsi->regs + MCTL_MAIN_STS, status,
+ (tmp == (status & tmp)), 100, 500000))
+ dev_err(dsi->base.dev,
+ "Timed Out: DSI-DPhy Clock and Data Lanes not ready.\n");
+
writel(HBP_LEN(dsi_cfg.hbp) | HSA_LEN(dsi_cfg.hsa),
dsi->regs + VID_HSIZE1);
writel(HFP_LEN(dsi_cfg.hfp) | HACT_LEN(dsi_cfg.hact),
--
2.34.1