[PATCH v2] drm/bridge: ti-sn65dsi83: move clk setup to enable

[Jan Remmet]

Move enable PLL from pre_enable to sn65dsi83_atomic_pre_enable.

The base clocks may not be ready when pre_enable is called.

commit c9b1150a68d9 ("drm/atomic-helper: Re-order bridge chain pre-enable
		and post-disable") points out that pre_enable hook definition says that
"The display pipe (i.e. clocks and timing signals) feeding this bridge
will not yet be running when this callback is called".

Signed-off-by: Jan Remmet <j.remmet at phytec.de>
---
commit c9b1150a68d9 ("drm/atomic-helper: Re-order bridge chain pre-enable
and post-disable") caused our display [1] to flicker constantly.

Our setup is
i.MX8MM mxsfb -> samsung_dsim ->
 sn65dsi83 (MIPI to LVDS) -> ETML1010G3DRA (display)

Reverting the commit [2] let the display work again.
Only difference in clk_summary is the change of
dsi_phy_ref from 72400000 (flickering) to 18100000 (working)

The same behavior can be seen with a ph128800t006-zhc01 display
and dsi_phy_ref from 66500000 (flickering) to 16625000 (working)

The root cause seems to be that mxsfb_crtc_atomic_enable is called after
samsung_dsim_atomic_pre_enable. This changes the parent clock after
the PLL is already configured.

According to the commit [2] pre_enable hooks should not rely on clocks.
Both drivers used in our setup work with clocks in pre_enable.

Moving the clock setup from pre_enable to enable fix the issue for
our setup.

Please note that I am not deeply familiar with the DRM subsystem internals,
and there might be side effects of this change that I haven't considered.

[1] arch/arm64/boot/dts/freescale/imx8mm-phyboard-polis-peb-av-10.dtso
[2] https://lore.kernel.org/all/20250605171524.27222-4-aradhya.bhatia@linux.dev/
---
Changes in v2:
- remove samsung_dsim patch
- tested on top of https://lore.kernel.org/all/20250619-samsung-dsim-fix-v1-1-6b5de68fb115@ideasonboard.com/
- Link to v1: https://lore.kernel.org/r/20250925-wip-j-remmet-phytec-de-bspimx8m-3801_peb-av-10_with_ac209-v1-0-94f9f775ee62@phytec.de
---
 drivers/gpu/drm/bridge/ti-sn65dsi83.c | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/drivers/gpu/drm/bridge/ti-sn65dsi83.c b/drivers/gpu/drm/bridge/ti-sn65dsi83.c
index 033c44326552ab167d4e8d9b74957c585e4c6fb7..4cbdbafc3e85821ef6fcd9f74bf07faf6b9f84ff 100644
--- a/drivers/gpu/drm/bridge/ti-sn65dsi83.c
+++ b/drivers/gpu/drm/bridge/ti-sn65dsi83.c
@@ -474,7 +474,6 @@ static void sn65dsi83_atomic_pre_enable(struct drm_bridge *bridge,
 	struct drm_crtc *crtc;
 	bool lvds_format_24bpp;
 	bool lvds_format_jeida;
-	unsigned int pval;
 	__le16 le16val;
 	u16 val;
 	int ret;
@@ -614,6 +613,14 @@ static void sn65dsi83_atomic_pre_enable(struct drm_bridge *bridge,
 	regmap_write(ctx->regmap, REG_VID_CHA_VERTICAL_FRONT_PORCH,
 		     mode->vsync_start - mode->vdisplay);
 	regmap_write(ctx->regmap, REG_VID_CHA_TEST_PATTERN, 0x00);
+}
+
+static void sn65dsi83_atomic_enable(struct drm_bridge *bridge,
+				    struct drm_atomic_state *state)
+{
+	struct sn65dsi83 *ctx = bridge_to_sn65dsi83(bridge);
+	unsigned int pval;
+	int ret;
 
 	/* Enable PLL */
 	regmap_write(ctx->regmap, REG_RC_PLL_EN, REG_RC_PLL_EN_PLL_EN);
@@ -633,13 +640,6 @@ static void sn65dsi83_atomic_pre_enable(struct drm_bridge *bridge,
 
 	/* Wait for 10ms after soft reset as specified in datasheet */
 	usleep_range(10000, 12000);
-}
-
-static void sn65dsi83_atomic_enable(struct drm_bridge *bridge,
-				    struct drm_atomic_state *state)
-{
-	struct sn65dsi83 *ctx = bridge_to_sn65dsi83(bridge);
-	unsigned int pval;
 
 	/* Clear all errors that got asserted during initialization. */
 	regmap_read(ctx->regmap, REG_IRQ_STAT, &pval);

---
base-commit: 93213d0743010ac6a6a21e97e75c695a423b81b3
change-id: 20250925-wip-j-remmet-phytec-de-bspimx8m-3801_peb-av-10_with_ac209-058abe8477c6

Best regards,
-- 
Jan Remmet <j.remmet at phytec.de>