Some small preparations around CAMSS D-PHY / C-PHY support

[PATCH 2/2] media: qcom: camss: Restrict endpoint bus-type to D-PHY

Posted by Luca Weiss 1 year ago

Currently the Qualcomm CAMSS driver only supports D-PHY while the
hardware on most SoCs also supports C-PHY. Until this support is added,
check for D-PHY to make it somewhat explicit that C-PHY won't work.

Signed-off-by: Luca Weiss <luca.weiss@fairphone.com>
---
 drivers/media/platform/qcom/camss/camss.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/media/platform/qcom/camss/camss.c b/drivers/media/platform/qcom/camss/camss.c
index 9fb31f4c18adee886cd0bcf84438a8f27635e07f..b99af35074cdf6fa794a0d2f0d54ecf12ac354d9 100644
--- a/drivers/media/platform/qcom/camss/camss.c
+++ b/drivers/media/platform/qcom/camss/camss.c
@@ -1855,6 +1855,15 @@ static int camss_of_parse_endpoint_node(struct device *dev,
 	if (ret)
 		return ret;
 
+	/*
+	 * Most SoCs support both D-PHY and C-PHY standards, but currently only
+	 * D-PHY is supported in the driver.
+	 */
+	if (vep.bus_type != V4L2_MBUS_CSI2_DPHY) {
+		dev_err(dev, "Unsupported bus type %d\n", vep.bus_type);
+		return -EINVAL;
+	}
+
 	csd->interface.csiphy_id = vep.base.port;
 
 	mipi_csi2 = &vep.bus.mipi_csi2;

-- 
2.47.1

Re: [PATCH 2/2] media: qcom: camss: Restrict endpoint bus-type to D-PHY

Posted by Vladimir Zapolskiy 1 year ago

Hi Luca.

On 12/9/24 14:01, Luca Weiss wrote:
> Currently the Qualcomm CAMSS driver only supports D-PHY while the
> hardware on most SoCs also supports C-PHY. Until this support is added,
> check for D-PHY to make it somewhat explicit that C-PHY won't work.
> 
> Signed-off-by: Luca Weiss <luca.weiss@fairphone.com>
> ---
>   drivers/media/platform/qcom/camss/camss.c | 9 +++++++++
>   1 file changed, 9 insertions(+)
> 
> diff --git a/drivers/media/platform/qcom/camss/camss.c b/drivers/media/platform/qcom/camss/camss.c
> index 9fb31f4c18adee886cd0bcf84438a8f27635e07f..b99af35074cdf6fa794a0d2f0d54ecf12ac354d9 100644
> --- a/drivers/media/platform/qcom/camss/camss.c
> +++ b/drivers/media/platform/qcom/camss/camss.c
> @@ -1855,6 +1855,15 @@ static int camss_of_parse_endpoint_node(struct device *dev,
>   	if (ret)
>   		return ret;
>   
> +	/*
> +	 * Most SoCs support both D-PHY and C-PHY standards, but currently only
> +	 * D-PHY is supported in the driver.
> +	 */
> +	if (vep.bus_type != V4L2_MBUS_CSI2_DPHY) {
> +		dev_err(dev, "Unsupported bus type %d\n", vep.bus_type);
> +		return -EINVAL;
> +	}
> +
>   	csd->interface.csiphy_id = vep.base.port;
>   
>   	mipi_csi2 = &vep.bus.mipi_csi2;

My cautious worries were futile, the change works as expected and
the regression testing on RB5 is passed:

===== begin parsing endpoint /soc@0/camss@ac6a000/ports/port@2/endpoint
fwnode video bus type not specified (0), mbus type not specified (0)
lane 0 position 0
lane 1 position 1
lane 2 position 2
lane 3 position 3
clock lane position 7
no lane polarities defined, assuming not inverted
assuming media bus type MIPI CSI-2 D-PHY (5)
===== end parsing endpoint /soc@0/camss@ac6a000/ports/port@2/endpoint

Tested-by: Vladimir Zapolskiy <vladimir.zapolskiy@linaro.org>
Reviewed-by: Vladimir Zapolskiy <vladimir.zapolskiy@linaro.org>

--
Best wishes,
Vladimir

Re: [PATCH 2/2] media: qcom: camss: Restrict endpoint bus-type to D-PHY

Posted by Bryan O'Donoghue 1 year ago

On 09/12/2024 12:01, Luca Weiss wrote:
> Currently the Qualcomm CAMSS driver only supports D-PHY while the
> hardware on most SoCs also supports C-PHY. Until this support is added,
> check for D-PHY to make it somewhat explicit that C-PHY won't work.
> 
> Signed-off-by: Luca Weiss <luca.weiss@fairphone.com>
> ---
>   drivers/media/platform/qcom/camss/camss.c | 9 +++++++++
>   1 file changed, 9 insertions(+)
> 
> diff --git a/drivers/media/platform/qcom/camss/camss.c b/drivers/media/platform/qcom/camss/camss.c
> index 9fb31f4c18adee886cd0bcf84438a8f27635e07f..b99af35074cdf6fa794a0d2f0d54ecf12ac354d9 100644
> --- a/drivers/media/platform/qcom/camss/camss.c
> +++ b/drivers/media/platform/qcom/camss/camss.c
> @@ -1855,6 +1855,15 @@ static int camss_of_parse_endpoint_node(struct device *dev,
>   	if (ret)
>   		return ret;
>   
> +	/*
> +	 * Most SoCs support both D-PHY and C-PHY standards, but currently only
> +	 * D-PHY is supported in the driver.
> +	 */
> +	if (vep.bus_type != V4L2_MBUS_CSI2_DPHY) {
> +		dev_err(dev, "Unsupported bus type %d\n", vep.bus_type);
> +		return -EINVAL;
> +	}
> +
>   	csd->interface.csiphy_id = vep.base.port;
>   
>   	mipi_csi2 = &vep.bus.mipi_csi2;
> 

Reviewed-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>

Re: [PATCH 2/2] media: qcom: camss: Restrict endpoint bus-type to D-PHY

Posted by Vladimir Zapolskiy 1 year ago

On 12/9/24 14:32, Bryan O'Donoghue wrote:
> On 09/12/2024 12:01, Luca Weiss wrote:
>> Currently the Qualcomm CAMSS driver only supports D-PHY while the
>> hardware on most SoCs also supports C-PHY. Until this support is added,
>> check for D-PHY to make it somewhat explicit that C-PHY won't work.
>>
>> Signed-off-by: Luca Weiss <luca.weiss@fairphone.com>
>> ---
>>    drivers/media/platform/qcom/camss/camss.c | 9 +++++++++
>>    1 file changed, 9 insertions(+)
>>
>> diff --git a/drivers/media/platform/qcom/camss/camss.c b/drivers/media/platform/qcom/camss/camss.c
>> index 9fb31f4c18adee886cd0bcf84438a8f27635e07f..b99af35074cdf6fa794a0d2f0d54ecf12ac354d9 100644
>> --- a/drivers/media/platform/qcom/camss/camss.c
>> +++ b/drivers/media/platform/qcom/camss/camss.c
>> @@ -1855,6 +1855,15 @@ static int camss_of_parse_endpoint_node(struct device *dev,
>>    	if (ret)
>>    		return ret;
>>    
>> +	/*
>> +	 * Most SoCs support both D-PHY and C-PHY standards, but currently only
>> +	 * D-PHY is supported in the driver.
>> +	 */
>> +	if (vep.bus_type != V4L2_MBUS_CSI2_DPHY) {
>> +		dev_err(dev, "Unsupported bus type %d\n", vep.bus_type);
>> +		return -EINVAL;
>> +	}
>> +

Looks like it would break all old board dtbs, which is not just bad, but NAK.

V4L2_MBUS_UNKNOWN shall be properly handled without the risk of regressions.

>>    	csd->interface.csiphy_id = vep.base.port;
>>    
>>    	mipi_csi2 = &vep.bus.mipi_csi2;
>>
> 
> Reviewed-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
> 

--
Best wishes,
Vladimir

Re: [PATCH 2/2] media: qcom: camss: Restrict endpoint bus-type to D-PHY

Posted by Luca Weiss 1 year ago

On Fri Dec 13, 2024 at 12:02 PM CET, Vladimir Zapolskiy wrote:
> On 12/9/24 14:32, Bryan O'Donoghue wrote:
> > On 09/12/2024 12:01, Luca Weiss wrote:
> >> Currently the Qualcomm CAMSS driver only supports D-PHY while the
> >> hardware on most SoCs also supports C-PHY. Until this support is added,
> >> check for D-PHY to make it somewhat explicit that C-PHY won't work.
> >>
> >> Signed-off-by: Luca Weiss <luca.weiss@fairphone.com>
> >> ---
> >>    drivers/media/platform/qcom/camss/camss.c | 9 +++++++++
> >>    1 file changed, 9 insertions(+)
> >>
> >> diff --git a/drivers/media/platform/qcom/camss/camss.c b/drivers/media/platform/qcom/camss/camss.c
> >> index 9fb31f4c18adee886cd0bcf84438a8f27635e07f..b99af35074cdf6fa794a0d2f0d54ecf12ac354d9 100644
> >> --- a/drivers/media/platform/qcom/camss/camss.c
> >> +++ b/drivers/media/platform/qcom/camss/camss.c
> >> @@ -1855,6 +1855,15 @@ static int camss_of_parse_endpoint_node(struct device *dev,
> >>    	if (ret)
> >>    		return ret;
> >>    
> >> +	/*
> >> +	 * Most SoCs support both D-PHY and C-PHY standards, but currently only
> >> +	 * D-PHY is supported in the driver.
> >> +	 */
> >> +	if (vep.bus_type != V4L2_MBUS_CSI2_DPHY) {
> >> +		dev_err(dev, "Unsupported bus type %d\n", vep.bus_type);
> >> +		return -EINVAL;
> >> +	}
> >> +
>
> Looks like it would break all old board dtbs, which is not just bad, but NAK.
>
> V4L2_MBUS_UNKNOWN shall be properly handled without the risk of regressions.

Please see drivers/media/v4l2-core/v4l2-fwnode.c around line 218.
The code there sets bus_type if it's UNKNOWN

    if (bus_type == V4L2_MBUS_UNKNOWN)
        vep->bus_type = V4L2_MBUS_CSI2_DPHY;

So setting "bus-type" in dt is not necessary, even if it makes things
more explicit from dt side. I don't think we'll ever get UNKNOWN here in
camss.

Regards
Luca


>
> >>    	csd->interface.csiphy_id = vep.base.port;
> >>    
> >>    	mipi_csi2 = &vep.bus.mipi_csi2;
> >>
> > 
> > Reviewed-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
> > 
>
> --
> Best wishes,
> Vladimir

Re: [PATCH 2/2] media: qcom: camss: Restrict endpoint bus-type to D-PHY

Posted by Vladimir Zapolskiy 1 year ago

On 12/13/24 13:22, Luca Weiss wrote:
> On Fri Dec 13, 2024 at 12:02 PM CET, Vladimir Zapolskiy wrote:
>> On 12/9/24 14:32, Bryan O'Donoghue wrote:
>>> On 09/12/2024 12:01, Luca Weiss wrote:
>>>> Currently the Qualcomm CAMSS driver only supports D-PHY while the
>>>> hardware on most SoCs also supports C-PHY. Until this support is added,
>>>> check for D-PHY to make it somewhat explicit that C-PHY won't work.
>>>>
>>>> Signed-off-by: Luca Weiss <luca.weiss@fairphone.com>
>>>> ---
>>>>     drivers/media/platform/qcom/camss/camss.c | 9 +++++++++
>>>>     1 file changed, 9 insertions(+)
>>>>
>>>> diff --git a/drivers/media/platform/qcom/camss/camss.c b/drivers/media/platform/qcom/camss/camss.c
>>>> index 9fb31f4c18adee886cd0bcf84438a8f27635e07f..b99af35074cdf6fa794a0d2f0d54ecf12ac354d9 100644
>>>> --- a/drivers/media/platform/qcom/camss/camss.c
>>>> +++ b/drivers/media/platform/qcom/camss/camss.c
>>>> @@ -1855,6 +1855,15 @@ static int camss_of_parse_endpoint_node(struct device *dev,
>>>>     	if (ret)
>>>>     		return ret;
>>>>     
>>>> +	/*
>>>> +	 * Most SoCs support both D-PHY and C-PHY standards, but currently only
>>>> +	 * D-PHY is supported in the driver.
>>>> +	 */
>>>> +	if (vep.bus_type != V4L2_MBUS_CSI2_DPHY) {
>>>> +		dev_err(dev, "Unsupported bus type %d\n", vep.bus_type);
>>>> +		return -EINVAL;
>>>> +	}
>>>> +
>>
>> Looks like it would break all old board dtbs, which is not just bad, but NAK.
>>
>> V4L2_MBUS_UNKNOWN shall be properly handled without the risk of regressions.
> 
> Please see drivers/media/v4l2-core/v4l2-fwnode.c around line 218.
> The code there sets bus_type if it's UNKNOWN
> 
>      if (bus_type == V4L2_MBUS_UNKNOWN)
>          vep->bus_type = V4L2_MBUS_CSI2_DPHY;
> 
> So setting "bus-type" in dt is not necessary, even if it makes things
> more explicit from dt side. I don't think we'll ever get UNKNOWN here in
> camss.

Thank you for pointing it out, I haven't tested the change yet, but hopefully
I will find time today to do it later on, it should exclude any doubts.

--
Best wishes,
Vladimir