[PATCH] drm/meson: encoder_dsi: load ENCL gamma table while ENCL is disabled

[PATCH] drm/meson: encoder_dsi: load ENCL gamma table while ENCL is disabled

[Shigeaki Asai via B4 Relay]

From: Shigeaki Asai <y-asai.0816@docomonet.jp>

meson_encoder_dsi_atomic_enable() programmed the ENCL gamma LUT right
after meson_venc_mipi_dsi_mode_set(), i.e. while the ENCL timing
generator was already running (ENCL_VIDEO_EN=1). Writing the LUT
during active video stalls the hardware: L_GAMMA_CNTL_PORT
WR_RDY/ADR_RDY deassert and the ENCL line counter (ENCL_INFO_READ)
freezes, so every remaining write times out (~8s total at boot) and
the panel ends up with a corrupted gamma table (wrong colors).

Instrumented boots on the ODROID-GO Ultra (S922X) show:

  failing:  start: VIDEO_EN=1 INFO 0000001a->002d0000 GAMMA_CNTL=00000030
            stall: INFO 002d0000->002d0000 GAMMA_CNTL=00000000
            (VID_CLK_CNTL2 / VIID_CLK_CNTL / VIID_CLK_DIV unchanged,
             i.e. the ENCL clock is still running)
  fixed:    start: VIDEO_EN=0 INFO 00000000->00000000 GAMMA_CNTL=00000030
            no stall, no timeout

Whether it failed depended only on timing, which is why enabling
lock debugging (LOCKDEP etc.) appeared to "fix" it most of the time.
It happens regardless of the bootloader (mainline or Hardkernel vendor
U-Boot).

The function already writes ENCL_VIDEO_EN=0 right afterwards before
re-enabling the encoder, so simply move meson_encl_load_gamma() after
that write. This matches the order used by the vendor U-Boot's own LCD
driver, which never times out.

Tested on the ODROID-GO Ultra with mainline U-Boot: 5 cold boots +
3 warm reboots, no timeouts, correct colors, LOCKDEP disabled.

Fixes: 42dcf15f901c ("drm/meson: add DSI encoder")
Cc: stable@vger.kernel.org
Tested-by: John Williams <porschemad911@gmail.com>
Signed-off-by: Shigeaki Asai <y-asai.0816@docomonet.jp>
---
This was found on the ODROID-GO Ultra while bringing it up on
Lakka / ROCKNIX. Happy to test any alternative approach.
---
 drivers/gpu/drm/meson/meson_encoder_dsi.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/meson/meson_encoder_dsi.c b/drivers/gpu/drm/meson/meson_encoder_dsi.c
index faa309cb97a6..912cd676bbe2 100644
--- a/drivers/gpu/drm/meson/meson_encoder_dsi.c
+++ b/drivers/gpu/drm/meson/meson_encoder_dsi.c
@@ -65,9 +65,9 @@ static void meson_encoder_dsi_atomic_enable(struct drm_bridge *bridge,
 	/* ENCL clock setup is handled by CCF */
 
 	meson_venc_mipi_dsi_mode_set(priv, &crtc_state->adjusted_mode);
-	meson_encl_load_gamma(priv);
 
 	writel_relaxed(0, priv->io_base + _REG(ENCL_VIDEO_EN));
+	meson_encl_load_gamma(priv);
 
 	writel_bits_relaxed(ENCL_VIDEO_MODE_ADV_VFIFO_EN, ENCL_VIDEO_MODE_ADV_VFIFO_EN,
 			    priv->io_base + _REG(ENCL_VIDEO_MODE_ADV));

---
base-commit: 70456f05d4b6396b22048c4b8cd3cb98ecf9f9e3
change-id: 20261004-meson-gamma-3306257c0d28

Best regards,
--  
Shigeaki Asai <y-asai.0816@docomonet.jp>

Re: [PATCH] drm/meson: encoder_dsi: load ENCL gamma table while ENCL is disabled

[Neil Armstrong]

On 10/4/26 16:50, Shigeaki Asai via B4 Relay wrote:
> From: Shigeaki Asai <y-asai.0816@docomonet.jp>
> 
> meson_encoder_dsi_atomic_enable() programmed the ENCL gamma LUT right
> after meson_venc_mipi_dsi_mode_set(), i.e. while the ENCL timing
> generator was already running (ENCL_VIDEO_EN=1). Writing the LUT
> during active video stalls the hardware: L_GAMMA_CNTL_PORT
> WR_RDY/ADR_RDY deassert and the ENCL line counter (ENCL_INFO_READ)
> freezes, so every remaining write times out (~8s total at boot) and
> the panel ends up with a corrupted gamma table (wrong colors).
> 
> Instrumented boots on the ODROID-GO Ultra (S922X) show:
> 
>    failing:  start: VIDEO_EN=1 INFO 0000001a->002d0000 GAMMA_CNTL=00000030
>              stall: INFO 002d0000->002d0000 GAMMA_CNTL=00000000
>              (VID_CLK_CNTL2 / VIID_CLK_CNTL / VIID_CLK_DIV unchanged,
>               i.e. the ENCL clock is still running)
>    fixed:    start: VIDEO_EN=0 INFO 00000000->00000000 GAMMA_CNTL=00000030
>              no stall, no timeout
> 
> Whether it failed depended only on timing, which is why enabling
> lock debugging (LOCKDEP etc.) appeared to "fix" it most of the time.
> It happens regardless of the bootloader (mainline or Hardkernel vendor
> U-Boot).
> 
> The function already writes ENCL_VIDEO_EN=0 right afterwards before
> re-enabling the encoder, so simply move meson_encl_load_gamma() after
> that write. This matches the order used by the vendor U-Boot's own LCD
> driver, which never times out.
> 
> Tested on the ODROID-GO Ultra with mainline U-Boot: 5 cold boots +
> 3 warm reboots, no timeouts, correct colors, LOCKDEP disabled.
> 
> Fixes: 42dcf15f901c ("drm/meson: add DSI encoder")
> Cc: stable@vger.kernel.org
> Tested-by: John Williams <porschemad911@gmail.com>
> Signed-off-by: Shigeaki Asai <y-asai.0816@docomonet.jp>
> ---
> This was found on the ODROID-GO Ultra while bringing it up on
> Lakka / ROCKNIX. Happy to test any alternative approach.
> ---
>   drivers/gpu/drm/meson/meson_encoder_dsi.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/meson/meson_encoder_dsi.c b/drivers/gpu/drm/meson/meson_encoder_dsi.c
> index faa309cb97a6..912cd676bbe2 100644
> --- a/drivers/gpu/drm/meson/meson_encoder_dsi.c
> +++ b/drivers/gpu/drm/meson/meson_encoder_dsi.c
> @@ -65,9 +65,9 @@ static void meson_encoder_dsi_atomic_enable(struct drm_bridge *bridge,
>   	/* ENCL clock setup is handled by CCF */
>   
>   	meson_venc_mipi_dsi_mode_set(priv, &crtc_state->adjusted_mode);
> -	meson_encl_load_gamma(priv);
>   
>   	writel_relaxed(0, priv->io_base + _REG(ENCL_VIDEO_EN));
> +	meson_encl_load_gamma(priv);
>   
>   	writel_bits_relaxed(ENCL_VIDEO_MODE_ADV_VFIFO_EN, ENCL_VIDEO_MODE_ADV_VFIFO_EN,
>   			    priv->io_base + _REG(ENCL_VIDEO_MODE_ADV));
> 
> ---
> base-commit: 70456f05d4b6396b22048c4b8cd3cb98ecf9f9e3
> change-id: 20261004-meson-gamma-3306257c0d28
> 
> Best regards,
> --
> Shigeaki Asai <y-asai.0816@docomonet.jp>

Thanks for figuring this out !

Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>

Thanks,
Neil