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[PATCH v5 3/6] drm/bridge: cadence: cdns-mhdp8546-core: Set the mhdp connector earlier in atomic_enable()

Harikrishna Shenoy posted 6 patches 1 month, 3 weeks ago
There is a newer version of this series
[PATCH v5 3/6] drm/bridge: cadence: cdns-mhdp8546-core: Set the mhdp connector earlier in atomic_enable()
Posted by Harikrishna Shenoy 1 month, 3 weeks ago 
From: Jayesh Choudhary <j-choudhary@ti.com>

In case if we get errors in cdns_mhdp_link_up() or cdns_mhdp_reg_read()
in atomic_enable, we will go to cdns_mhdp_modeset_retry_fn() and will hit
NULL pointer while trying to access the mutex. We need the connector to
be set before that. Unlike in legacy !(DBANC) cases, we do not have
connector initialised in bridge_attach(). So set the mhdp->connector
in atomic_enable() earlier to avoid possible NULL pointer.

Fixes: c932ced6b585 ("drm/tidss: Update encoder/bridge chain connect model")
Signed-off-by: Jayesh Choudhary <j-choudhary@ti.com>
---
 .../drm/bridge/cadence/cdns-mhdp8546-core.c   | 20 +++++++++----------
 1 file changed, 10 insertions(+), 10 deletions(-)

diff --git a/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c b/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c
index c2ce3d6e5a88..b2f5a48cac2d 100644
--- a/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c
+++ b/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c
@@ -1759,12 +1759,21 @@ static void cdns_mhdp_atomic_enable(struct drm_bridge *bridge,
 	struct drm_bridge_state *new_state;
 	const struct drm_display_mode *mode;
 	u32 resp;
-	int ret;
+	int ret = 0;
 
 	dev_dbg(mhdp->dev, "bridge enable\n");
 
 	mutex_lock(&mhdp->link_mutex);
 
+	mhdp->connector = drm_atomic_get_new_connector_for_encoder(state,
+								   bridge->encoder);
+	if (WARN_ON(!mhdp->connector))
+		goto out;
+
+	conn_state = drm_atomic_get_new_connector_state(state, mhdp->connector);
+	if (WARN_ON(!conn_state))
+		goto out;
+
 	if (mhdp->plugged && !mhdp->link_up) {
 		ret = cdns_mhdp_link_up(mhdp);
 		if (ret < 0)
@@ -1784,15 +1793,6 @@ static void cdns_mhdp_atomic_enable(struct drm_bridge *bridge,
 	cdns_mhdp_reg_write(mhdp, CDNS_DPTX_CAR,
 			    resp | CDNS_VIF_CLK_EN | CDNS_VIF_CLK_RSTN);
 
-	mhdp->connector = drm_atomic_get_new_connector_for_encoder(state,
-								   bridge->encoder);
-	if (WARN_ON(!mhdp->connector))
-		goto out;
-
-	conn_state = drm_atomic_get_new_connector_state(state, mhdp->connector);
-	if (WARN_ON(!conn_state))
-		goto out;
-
 	if (mhdp->hdcp_supported &&
 	    mhdp->hw_state == MHDP_HW_READY &&
 	    conn_state->content_protection ==
-- 
2.34.1
Re: [PATCH v5 3/6] drm/bridge: cadence: cdns-mhdp8546-core: Set the mhdp connector earlier in atomic_enable()
Posted by Tomi Valkeinen 1 month ago 
Hi,

On 11/08/2025 10:59, Harikrishna Shenoy wrote:
> From: Jayesh Choudhary <j-choudhary@ti.com>
> 
> In case if we get errors in cdns_mhdp_link_up() or cdns_mhdp_reg_read()
> in atomic_enable, we will go to cdns_mhdp_modeset_retry_fn() and will hit
> NULL pointer while trying to access the mutex. We need the connector to
> be set before that. Unlike in legacy !(DBANC) cases, we do not have
> connector initialised in bridge_attach(). So set the mhdp->connector
> in atomic_enable() earlier to avoid possible NULL pointer.
> 
> Fixes: c932ced6b585 ("drm/tidss: Update encoder/bridge chain connect model")
> Signed-off-by: Jayesh Choudhary <j-choudhary@ti.com>
> ---
>  .../drm/bridge/cadence/cdns-mhdp8546-core.c   | 20 +++++++++----------
>  1 file changed, 10 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c b/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c
> index c2ce3d6e5a88..b2f5a48cac2d 100644
> --- a/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c
> +++ b/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c
> @@ -1759,12 +1759,21 @@ static void cdns_mhdp_atomic_enable(struct drm_bridge *bridge,
>  	struct drm_bridge_state *new_state;
>  	const struct drm_display_mode *mode;
>  	u32 resp;
> -	int ret;
> +	int ret = 0;
>  
>  	dev_dbg(mhdp->dev, "bridge enable\n");
>  
>  	mutex_lock(&mhdp->link_mutex);
>  
> +	mhdp->connector = drm_atomic_get_new_connector_for_encoder(state,
> +								   bridge->encoder);
> +	if (WARN_ON(!mhdp->connector))
> +		goto out;
> +
> +	conn_state = drm_atomic_get_new_connector_state(state, mhdp->connector);
> +	if (WARN_ON(!conn_state))
> +		goto out;

You are just moving code here, but... Shouldn't these be errors? If I
read this right, ret is 0 here, and thus if we hit either of those
issues above, we'll return 0.

 Tomi

> +
>  	if (mhdp->plugged && !mhdp->link_up) {
>  		ret = cdns_mhdp_link_up(mhdp);
>  		if (ret < 0)
> @@ -1784,15 +1793,6 @@ static void cdns_mhdp_atomic_enable(struct drm_bridge *bridge,
>  	cdns_mhdp_reg_write(mhdp, CDNS_DPTX_CAR,
>  			    resp | CDNS_VIF_CLK_EN | CDNS_VIF_CLK_RSTN);
>  
> -	mhdp->connector = drm_atomic_get_new_connector_for_encoder(state,
> -								   bridge->encoder);
> -	if (WARN_ON(!mhdp->connector))
> -		goto out;
> -
> -	conn_state = drm_atomic_get_new_connector_state(state, mhdp->connector);
> -	if (WARN_ON(!conn_state))
> -		goto out;
> -
>  	if (mhdp->hdcp_supported &&
>  	    mhdp->hw_state == MHDP_HW_READY &&
>  	    conn_state->content_protection ==
Re: [PATCH v5 3/6] drm/bridge: cadence: cdns-mhdp8546-core: Set the mhdp connector earlier in atomic_enable()
Posted by Harikrishna Shenoy 1 month ago 
On 9/1/25 15:35, Tomi Valkeinen wrote:
> Hi,
>
> On 11/08/2025 10:59, Harikrishna Shenoy wrote:
>> From: Jayesh Choudhary <j-choudhary@ti.com>
>>
>> In case if we get errors in cdns_mhdp_link_up() or cdns_mhdp_reg_read()
>> in atomic_enable, we will go to cdns_mhdp_modeset_retry_fn() and will hit
>> NULL pointer while trying to access the mutex. We need the connector to
>> be set before that. Unlike in legacy !(DBANC) cases, we do not have
>> connector initialised in bridge_attach(). So set the mhdp->connector
>> in atomic_enable() earlier to avoid possible NULL pointer.
>>
>> Fixes: c932ced6b585 ("drm/tidss: Update encoder/bridge chain connect model")
>> Signed-off-by: Jayesh Choudhary <j-choudhary@ti.com>
>> ---
>>   .../drm/bridge/cadence/cdns-mhdp8546-core.c   | 20 +++++++++----------
>>   1 file changed, 10 insertions(+), 10 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c b/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c
>> index c2ce3d6e5a88..b2f5a48cac2d 100644
>> --- a/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c
>> +++ b/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c
>> @@ -1759,12 +1759,21 @@ static void cdns_mhdp_atomic_enable(struct drm_bridge *bridge,
>>   	struct drm_bridge_state *new_state;
>>   	const struct drm_display_mode *mode;
>>   	u32 resp;
>> -	int ret;
>> +	int ret = 0;
>>   
>>   	dev_dbg(mhdp->dev, "bridge enable\n");
>>   
>>   	mutex_lock(&mhdp->link_mutex);
>>   
>> +	mhdp->connector = drm_atomic_get_new_connector_for_encoder(state,
>> +								   bridge->encoder);
>> +	if (WARN_ON(!mhdp->connector))
>> +		goto out;
>> +
>> +	conn_state = drm_atomic_get_new_connector_state(state, mhdp->connector);
>> +	if (WARN_ON(!conn_state))
>> +		goto out;
> You are just moving code here, but... Shouldn't these be errors? If I
> read this right, ret is 0 here, and thus if we hit either of those
> issues above, we'll return 0.
>
>   Tomi
>
This is a void function, no need to return
>> +
>>   	if (mhdp->plugged && !mhdp->link_up) {
>>   		ret = cdns_mhdp_link_up(mhdp);
>>   		if (ret < 0)
>> @@ -1784,15 +1793,6 @@ static void cdns_mhdp_atomic_enable(struct drm_bridge *bridge,
>>   	cdns_mhdp_reg_write(mhdp, CDNS_DPTX_CAR,
>>   			    resp | CDNS_VIF_CLK_EN | CDNS_VIF_CLK_RSTN);
>>   
>> -	mhdp->connector = drm_atomic_get_new_connector_for_encoder(state,
>> -								   bridge->encoder);
>> -	if (WARN_ON(!mhdp->connector))
>> -		goto out;
>> -
>> -	conn_state = drm_atomic_get_new_connector_state(state, mhdp->connector);
>> -	if (WARN_ON(!conn_state))
>> -		goto out;
>> -
>>   	if (mhdp->hdcp_supported &&
>>   	    mhdp->hw_state == MHDP_HW_READY &&
>>   	    conn_state->content_protection ==

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