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[PATCH 1/3] drm/bridge: samsung-dsim: move bridge init sequence to atomic_enable

Kaustabh Chakraborty posted 3 patches 2 weeks, 1 day ago
There is a newer version of this series
[PATCH 1/3] drm/bridge: samsung-dsim: move bridge init sequence to atomic_enable
Posted by Kaustabh Chakraborty 2 weeks, 1 day ago 
Since commit c9b1150a68d9 ("drm/atomic-helper: Re-order bridge chain
pre-enable and post-disable"), pre-enable sequence is called before the
CRTC is enabled.

This causes unintended side-effects (abberation among potentially other
things) in the display when samsung_dsim_init() is called in the
pre-enable part of the sequence. Call it in samsung_dsim_atomic_enable()
instead.

Cc: stable@vger.kernel.org # v6.17 and later
Signed-off-by: Kaustabh Chakraborty <kauschluss@disroot.org>
---
 drivers/gpu/drm/bridge/samsung-dsim.c | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/bridge/samsung-dsim.c b/drivers/gpu/drm/bridge/samsung-dsim.c
index 1d85e706c74b9..975f8b50ae660 100644
--- a/drivers/gpu/drm/bridge/samsung-dsim.c
+++ b/drivers/gpu/drm/bridge/samsung-dsim.c
@@ -1655,6 +1655,13 @@ static void samsung_dsim_atomic_pre_enable(struct drm_bridge *bridge,
 	}
 
 	dsi->state |= DSIM_STATE_ENABLED;
+}
+
+static void samsung_dsim_atomic_enable(struct drm_bridge *bridge,
+				       struct drm_atomic_state *state)
+{
+	struct samsung_dsim *dsi = bridge_to_dsi(bridge);
+	int ret;
 
 	/*
 	 * For Exynos-DSIM the downstream bridge, or panel are expecting
@@ -1665,12 +1672,6 @@ static void samsung_dsim_atomic_pre_enable(struct drm_bridge *bridge,
 		if (ret)
 			return;
 	}
-}
-
-static void samsung_dsim_atomic_enable(struct drm_bridge *bridge,
-				       struct drm_atomic_state *state)
-{
-	struct samsung_dsim *dsi = bridge_to_dsi(bridge);
 
 	samsung_dsim_set_display_mode(dsi);
 	samsung_dsim_set_display_enable(dsi, true);

-- 
2.52.0
Re: [PATCH 1/3] drm/bridge: samsung-dsim: move bridge init sequence to atomic_enable
Posted by Marek Szyprowski 2 weeks ago 
On 24.01.2026 18:20, Kaustabh Chakraborty wrote:
> Since commit c9b1150a68d9 ("drm/atomic-helper: Re-order bridge chain
> pre-enable and post-disable"), pre-enable sequence is called before the
> CRTC is enabled.
>
> This causes unintended side-effects (abberation among potentially other
> things) in the display when samsung_dsim_init() is called in the
> pre-enable part of the sequence. Call it in samsung_dsim_atomic_enable()
> instead.
>
> Cc: stable@vger.kernel.org # v6.17 and later
> Signed-off-by: Kaustabh Chakraborty <kauschluss@disroot.org>

I'm not sure if this will be needed:

https://lore.kernel.org/all/20251205-drm-seq-fix-v1-0-fda68fa1b3de@ideasonboard.com/


> ---
>   drivers/gpu/drm/bridge/samsung-dsim.c | 13 +++++++------
>   1 file changed, 7 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/gpu/drm/bridge/samsung-dsim.c b/drivers/gpu/drm/bridge/samsung-dsim.c
> index 1d85e706c74b9..975f8b50ae660 100644
> --- a/drivers/gpu/drm/bridge/samsung-dsim.c
> +++ b/drivers/gpu/drm/bridge/samsung-dsim.c
> @@ -1655,6 +1655,13 @@ static void samsung_dsim_atomic_pre_enable(struct drm_bridge *bridge,
>   	}
>   
>   	dsi->state |= DSIM_STATE_ENABLED;
> +}
> +
> +static void samsung_dsim_atomic_enable(struct drm_bridge *bridge,
> +				       struct drm_atomic_state *state)
> +{
> +	struct samsung_dsim *dsi = bridge_to_dsi(bridge);
> +	int ret;
>   
>   	/*
>   	 * For Exynos-DSIM the downstream bridge, or panel are expecting
> @@ -1665,12 +1672,6 @@ static void samsung_dsim_atomic_pre_enable(struct drm_bridge *bridge,
>   		if (ret)
>   			return;
>   	}
> -}
> -
> -static void samsung_dsim_atomic_enable(struct drm_bridge *bridge,
> -				       struct drm_atomic_state *state)
> -{
> -	struct samsung_dsim *dsi = bridge_to_dsi(bridge);
>   
>   	samsung_dsim_set_display_mode(dsi);
>   	samsung_dsim_set_display_enable(dsi, true);
>
Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland
Re: [PATCH 1/3] drm/bridge: samsung-dsim: move bridge init sequence to atomic_enable
Posted by Kaustabh Chakraborty 1 week, 1 day ago 
On 2026-01-26 09:57 +01:00, Marek Szyprowski wrote:
> On 24.01.2026 18:20, Kaustabh Chakraborty wrote:
>> Since commit c9b1150a68d9 ("drm/atomic-helper: Re-order bridge chain
>> pre-enable and post-disable"), pre-enable sequence is called before the
>> CRTC is enabled.
>>
>> This causes unintended side-effects (abberation among potentially other
>> things) in the display when samsung_dsim_init() is called in the
>> pre-enable part of the sequence. Call it in samsung_dsim_atomic_enable()
>> instead.
>>
>> Cc: stable@vger.kernel.org # v6.17 and later
>> Signed-off-by: Kaustabh Chakraborty <kauschluss@disroot.org>
>
> I'm not sure if this will be needed:
>
> https://lore.kernel.org/all/20251205-drm-seq-fix-v1-0-fda68fa1b3de@ideasonboard.com/

Tested on v6.19-rc7, this is fixed now. This can be dropped.

>
>
>> ---
>>   drivers/gpu/drm/bridge/samsung-dsim.c | 13 +++++++------
>>   1 file changed, 7 insertions(+), 6 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/bridge/samsung-dsim.c b/drivers/gpu/drm/bridge/samsung-dsim.c
>> index 1d85e706c74b9..975f8b50ae660 100644
>> --- a/drivers/gpu/drm/bridge/samsung-dsim.c
>> +++ b/drivers/gpu/drm/bridge/samsung-dsim.c
>> @@ -1655,6 +1655,13 @@ static void samsung_dsim_atomic_pre_enable(struct drm_bridge *bridge,
>>   	}
>>   
>>   	dsi->state |= DSIM_STATE_ENABLED;
>> +}
>> +
>> +static void samsung_dsim_atomic_enable(struct drm_bridge *bridge,
>> +				       struct drm_atomic_state *state)
>> +{
>> +	struct samsung_dsim *dsi = bridge_to_dsi(bridge);
>> +	int ret;
>>   
>>   	/*
>>   	 * For Exynos-DSIM the downstream bridge, or panel are expecting
>> @@ -1665,12 +1672,6 @@ static void samsung_dsim_atomic_pre_enable(struct drm_bridge *bridge,
>>   		if (ret)
>>   			return;
>>   	}
>> -}
>> -
>> -static void samsung_dsim_atomic_enable(struct drm_bridge *bridge,
>> -				       struct drm_atomic_state *state)
>> -{
>> -	struct samsung_dsim *dsi = bridge_to_dsi(bridge);
>>   
>>   	samsung_dsim_set_display_mode(dsi);
>>   	samsung_dsim_set_display_enable(dsi, true);
>>
> Best regards
Re: [PATCH 1/3] drm/bridge: samsung-dsim: move bridge init sequence to atomic_enable
Posted by Marek Szyprowski 2 weeks ago 
On 26.01.2026 09:57, Marek Szyprowski wrote:
> On 24.01.2026 18:20, Kaustabh Chakraborty wrote:
>> Since commit c9b1150a68d9 ("drm/atomic-helper: Re-order bridge chain
>> pre-enable and post-disable"), pre-enable sequence is called before the
>> CRTC is enabled.
>>
>> This causes unintended side-effects (abberation among potentially other
>> things) in the display when samsung_dsim_init() is called in the
>> pre-enable part of the sequence. Call it in samsung_dsim_atomic_enable()
>> instead.
>>
>> Cc: stable@vger.kernel.org # v6.17 and later
>> Signed-off-by: Kaustabh Chakraborty <kauschluss@disroot.org>
>
> I'm not sure if this will be needed:
>
> https://lore.kernel.org/all/20251205-drm-seq-fix-v1-0-fda68fa1b3de@ideasonboard.com/ 
>

Even more, there is a pending similar patch:

https://lore.kernel.org/all/20250619-samsung-dsim-fix-v1-1-6b5de68fb115@ideasonboard.com/

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland

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