[v8,3/4] drm/atmel-hlcdc: iterate over all output endpoints
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Message ID 20180810130359.9882-4-peda@axentia.se
State New
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Series
  • drm/atmel-hlcdc: bus-width override support
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Commit Message

Peter Rosin Aug. 10, 2018, 1:03 p.m. UTC
This enables more flexible devicetrees. You can e.g. have two output
nodes where one is not enabled, without the ordering affecting things.

Prior to this patch the active node had to have endpoint id zero.

Signed-off-by: Peter Rosin <peda@axentia.se>
---
 drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_output.c | 32 ++++++++++++++++++------
 1 file changed, 25 insertions(+), 7 deletions(-)

Comments

jacopo mondi Aug. 13, 2018, 1:59 p.m. UTC | #1
Hi Peter,

On Fri, Aug 10, 2018 at 03:03:58PM +0200, Peter Rosin wrote:
> This enables more flexible devicetrees. You can e.g. have two output
> nodes where one is not enabled, without the ordering affecting things.
> 
> Prior to this patch the active node had to have endpoint id zero.
> 
> Signed-off-by: Peter Rosin <peda@axentia.se>
> ---
>  drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_output.c | 32 ++++++++++++++++++------
>  1 file changed, 25 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_output.c b/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_output.c
> index 8db51fb131db..16c1b2f54b42 100644
> --- a/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_output.c
> +++ b/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_output.c
> @@ -31,14 +31,16 @@ static const struct drm_encoder_funcs atmel_hlcdc_panel_encoder_funcs = {
>  	.destroy = drm_encoder_cleanup,
>  };
>  
> -static int atmel_hlcdc_attach_endpoint(struct drm_device *dev, int endpoint)
> +static int atmel_hlcdc_attach_endpoint(struct drm_device *dev,
> +				       struct of_endpoint *endpoint)
>  {
>  	struct drm_encoder *encoder;
>  	struct drm_panel *panel;
>  	struct drm_bridge *bridge;
>  	int ret;
>  
> -	ret = drm_of_find_panel_or_bridge(dev->dev->of_node, 0, endpoint,
> +	ret = drm_of_find_panel_or_bridge(dev->dev->of_node,
> +					  endpoint->port, endpoint->id,

You are refusing endpoint->port != 0 in the caller, so that could be
0.

Apart from that small nit:
Reviewed-by: Jacopo Mondi <jacopo+renesas@jmondi.org>

Thanks
  j

>  					  &panel, &bridge);
>  	if (ret)
>  		return ret;
> @@ -77,13 +79,29 @@ static int atmel_hlcdc_attach_endpoint(struct drm_device *dev, int endpoint)
>  
>  int atmel_hlcdc_create_outputs(struct drm_device *dev)
>  {
> -	int endpoint, ret = 0;
> -
> -	for (endpoint = 0; !ret; endpoint++)
> -		ret = atmel_hlcdc_attach_endpoint(dev, endpoint);
> +	struct of_endpoint endpoint;
> +	struct device_node *node = NULL;
> +	int count = 0;
> +	int ret = 0;
> +
> +	for_each_endpoint_of_node(dev->dev->of_node, node) {
> +		of_graph_parse_endpoint(node, &endpoint);
> +
> +		if (endpoint.port)
> +			continue;
> +
> +		ret = atmel_hlcdc_attach_endpoint(dev, &endpoint);
> +		if (ret == -ENODEV)
> +			continue;
> +		if (ret) {
> +			of_node_put(node);
> +			break;
> +		}
> +		count++;
> +	}
>  
>  	/* At least one device was successfully attached.*/
> -	if (ret == -ENODEV && endpoint)
> +	if (ret == -ENODEV && count)
>  		return 0;
>  
>  	return ret;
> -- 
> 2.11.0
>
Peter Rosin Aug. 13, 2018, 2:24 p.m. UTC | #2
On 2018-08-13 15:59, jacopo mondi wrote:
> Hi Peter,
> 
> On Fri, Aug 10, 2018 at 03:03:58PM +0200, Peter Rosin wrote:
>> This enables more flexible devicetrees. You can e.g. have two output
>> nodes where one is not enabled, without the ordering affecting things.
>>
>> Prior to this patch the active node had to have endpoint id zero.
>>
>> Signed-off-by: Peter Rosin <peda@axentia.se>
>> ---
>>  drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_output.c | 32 ++++++++++++++++++------
>>  1 file changed, 25 insertions(+), 7 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_output.c b/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_output.c
>> index 8db51fb131db..16c1b2f54b42 100644
>> --- a/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_output.c
>> +++ b/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_output.c
>> @@ -31,14 +31,16 @@ static const struct drm_encoder_funcs atmel_hlcdc_panel_encoder_funcs = {
>>  	.destroy = drm_encoder_cleanup,
>>  };
>>  
>> -static int atmel_hlcdc_attach_endpoint(struct drm_device *dev, int endpoint)
>> +static int atmel_hlcdc_attach_endpoint(struct drm_device *dev,
>> +				       struct of_endpoint *endpoint)
>>  {
>>  	struct drm_encoder *encoder;
>>  	struct drm_panel *panel;
>>  	struct drm_bridge *bridge;
>>  	int ret;
>>  
>> -	ret = drm_of_find_panel_or_bridge(dev->dev->of_node, 0, endpoint,
>> +	ret = drm_of_find_panel_or_bridge(dev->dev->of_node,
>> +					  endpoint->port, endpoint->id,
> 
> You are refusing endpoint->port != 0 in the caller, so that could be
> 0.

Yes, it could. However, I intentionally did not write 0 here, so that
the logic related to "port has to be zero" was in one place and not
scattered about. I guess it's up to Boris?

Maybe the port do not actually have to be zero at all? With the old
code, it was kind of understandable that the port number was fixed,
but for the code in my patch it does not matter at all AFAICT. There
is nothing in the binding docs (except for the example) that hints
that port has to be zero, so that's one thing in favor of just getting
rid of the port number checking altogether...

Cheers,
Peter


> Apart from that small nit:
> Reviewed-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
> 
> Thanks
>   j
> 
>>  					  &panel, &bridge);
>>  	if (ret)
>>  		return ret;
>> @@ -77,13 +79,29 @@ static int atmel_hlcdc_attach_endpoint(struct drm_device *dev, int endpoint)
>>  
>>  int atmel_hlcdc_create_outputs(struct drm_device *dev)
>>  {
>> -	int endpoint, ret = 0;
>> -
>> -	for (endpoint = 0; !ret; endpoint++)
>> -		ret = atmel_hlcdc_attach_endpoint(dev, endpoint);
>> +	struct of_endpoint endpoint;
>> +	struct device_node *node = NULL;
>> +	int count = 0;
>> +	int ret = 0;
>> +
>> +	for_each_endpoint_of_node(dev->dev->of_node, node) {
>> +		of_graph_parse_endpoint(node, &endpoint);
>> +
>> +		if (endpoint.port)
>> +			continue;
>> +
>> +		ret = atmel_hlcdc_attach_endpoint(dev, &endpoint);
>> +		if (ret == -ENODEV)
>> +			continue;
>> +		if (ret) {
>> +			of_node_put(node);
>> +			break;
>> +		}
>> +		count++;
>> +	}
>>  
>>  	/* At least one device was successfully attached.*/
>> -	if (ret == -ENODEV && endpoint)
>> +	if (ret == -ENODEV && count)
>>  		return 0;
>>  
>>  	return ret;
>> -- 
>> 2.11.0
>>
Rob Herring Aug. 13, 2018, 8:52 p.m. UTC | #3
On Mon, Aug 13, 2018 at 8:25 AM Peter Rosin <peda@axentia.se> wrote:
>
> On 2018-08-13 15:59, jacopo mondi wrote:
> > Hi Peter,
> >
> > On Fri, Aug 10, 2018 at 03:03:58PM +0200, Peter Rosin wrote:
> >> This enables more flexible devicetrees. You can e.g. have two output
> >> nodes where one is not enabled, without the ordering affecting things.

Your DTs are not supposed to be flexible. They should be well defined
by the binding.

> >>
> >> Prior to this patch the active node had to have endpoint id zero.
> >>
> >> Signed-off-by: Peter Rosin <peda@axentia.se>
> >> ---
> >>  drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_output.c | 32 ++++++++++++++++++------
> >>  1 file changed, 25 insertions(+), 7 deletions(-)
> >>
> >> diff --git a/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_output.c b/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_output.c
> >> index 8db51fb131db..16c1b2f54b42 100644
> >> --- a/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_output.c
> >> +++ b/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_output.c
> >> @@ -31,14 +31,16 @@ static const struct drm_encoder_funcs atmel_hlcdc_panel_encoder_funcs = {
> >>      .destroy = drm_encoder_cleanup,
> >>  };
> >>
> >> -static int atmel_hlcdc_attach_endpoint(struct drm_device *dev, int endpoint)
> >> +static int atmel_hlcdc_attach_endpoint(struct drm_device *dev,
> >> +                                   struct of_endpoint *endpoint)
> >>  {
> >>      struct drm_encoder *encoder;
> >>      struct drm_panel *panel;
> >>      struct drm_bridge *bridge;
> >>      int ret;
> >>
> >> -    ret = drm_of_find_panel_or_bridge(dev->dev->of_node, 0, endpoint,
> >> +    ret = drm_of_find_panel_or_bridge(dev->dev->of_node,
> >> +                                      endpoint->port, endpoint->id,
> >
> > You are refusing endpoint->port != 0 in the caller, so that could be
> > 0.
>
> Yes, it could. However, I intentionally did not write 0 here, so that
> the logic related to "port has to be zero" was in one place and not
> scattered about. I guess it's up to Boris?
>
> Maybe the port do not actually have to be zero at all? With the old
> code, it was kind of understandable that the port number was fixed,
> but for the code in my patch it does not matter at all AFAICT. There
> is nothing in the binding docs (except for the example) that hints
> that port has to be zero, so that's one thing in favor of just getting
> rid of the port number checking altogether...

The port numbering must be defined and fixed. If that is not clear in
the binding, fix the binding.

> >> @@ -77,13 +79,29 @@ static int atmel_hlcdc_attach_endpoint(struct drm_device *dev, int endpoint)
> >>
> >>  int atmel_hlcdc_create_outputs(struct drm_device *dev)
> >>  {
> >> -    int endpoint, ret = 0;
> >> -
> >> -    for (endpoint = 0; !ret; endpoint++)
> >> -            ret = atmel_hlcdc_attach_endpoint(dev, endpoint);
> >> +    struct of_endpoint endpoint;
> >> +    struct device_node *node = NULL;
> >> +    int count = 0;
> >> +    int ret = 0;
> >> +
> >> +    for_each_endpoint_of_node(dev->dev->of_node, node) {
> >> +            of_graph_parse_endpoint(node, &endpoint);

I'd really like to kill off of_graph_parse_endpoint, not add more
users (check the git history on this code). You should know what are
possible port and endpoint numbers, so iterate over those.

> >> +
> >> +            if (endpoint.port)
> >> +                    continue;
> >> +
> >> +            ret = atmel_hlcdc_attach_endpoint(dev, &endpoint);
> >> +            if (ret == -ENODEV)
> >> +                    continue;
> >> +            if (ret) {
> >> +                    of_node_put(node);
> >> +                    break;
> >> +            }
> >> +            count++;
> >> +    }
> >>
> >>      /* At least one device was successfully attached.*/
> >> -    if (ret == -ENODEV && endpoint)
> >> +    if (ret == -ENODEV && count)
> >>              return 0;
> >>
> >>      return ret;
> >> --
> >> 2.11.0
> >>
>
Peter Rosin Aug. 14, 2018, 6:35 a.m. UTC | #4
On 2018-08-13 22:52, Rob Herring wrote:
> On Mon, Aug 13, 2018 at 8:25 AM Peter Rosin <peda@axentia.se> wrote:
>>
>> On 2018-08-13 15:59, jacopo mondi wrote:
>>> Hi Peter,
>>>
>>> On Fri, Aug 10, 2018 at 03:03:58PM +0200, Peter Rosin wrote:
>>>> This enables more flexible devicetrees. You can e.g. have two output
>>>> nodes where one is not enabled, without the ordering affecting things.
> 
> Your DTs are not supposed to be flexible. They should be well defined
> by the binding.

I feel the need to explain the situation with more words...

We have a board with this atmel-hlcdc wired to both an LVDS encoder
and an HDMI encoder. Depending on how we integrate this board, only
one of these paths make sense. Hence, I would like to do the following
in a .dtsi for that board:

/ {
	hlcdc-display-controller {
		...
		port@0 {
			hlcdc_lvds: endpoint@0 {
				reg = <0>;
				remote-endpoint = <&lvds_encoder_input>;
			};

			hlcdc_hdmi: endpoint@1 {
				reg = <1>;
				remote-endpoint = <&hdmi_encoder_input>;
			};
		};
	};

	lvds_encoder: lvds-encoder {
		status = "disabled";

		...

		ports {
			#address-cells = <1>;
			#size-cells = <0>;

			port@0 {
				reg = <0>;

				lvds_encoder_input: endpoint {
					remote-endpoint = <&hlcdc_lvds>;
				};
			};

			port@1 {
				reg = <1>;

				lvds_encoder_output: endpoint {
				};
			};
		};
	};
};

&i2c2 {
	...
	hdmi_encoder: hdmi-encoder@70 {
		status = "disabled";

		...

		port {
			hdmi_encoder_input: endpoint {
				remote-endpoint = <&hlcdc_hdmi>;
			};
		};
	};
};


And then, depending on what components are fitted and what LVDS panel has
been attached to the LVDS encoder output, this can be used as follows
in the .dts file for LVDS case:

/ {
	panel: panel {
		compatible = "litemax,dlf2118", "panel-lvds";

		...

		port {
			panel_input: endpoint {
				remote-endpoint = <&lvds_encoder_output>;
			};
		};
	};
};


&lvds_encoder {
	status = "okay";
};

&lvds_encoder_output {
	remote-endpoint = <&panel_input>;
};


For the HDMI case, it would be this in the .dts file:

&hdmi_encoder {
	status = "okay";
};


The above seem so much better than just having the following in
the .dtsi file

/ {
	hlcdc-display-controller {
		...
		port@0 {
			hlcdc_lvds: endpoint {
				remote-endpoint = <&encoder_input>;
			};
		};
	};
};

and pushing the lvds-encoder and hdmi-encoder nodes (slightly modified) down
to the relevant .dts files. Especially so since we have to this point
delivered several variants with different LVDS panels. The duplication
is ugly, and the number of different panels is expected to grow...

But maybe I have misunderstood what endpoints are all about, but to me
the actual endpoint id is not that interesting and I see nothing in the
graph binding that suggests that endpoint id 0 has to be up and kicking
in order for endpoint id 1 to be examined at all.

For ports, yes, you are right that the port id needs to be defined and
fixed for a specific function, so scratch that. It was just a "maybe"
question anyway...

>>>>
>>>> Prior to this patch the active node had to have endpoint id zero.
>>>>
>>>> Signed-off-by: Peter Rosin <peda@axentia.se>
>>>> ---
>>>>  drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_output.c | 32 ++++++++++++++++++------
>>>>  1 file changed, 25 insertions(+), 7 deletions(-)
>>>>
>>>> diff --git a/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_output.c b/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_output.c
>>>> index 8db51fb131db..16c1b2f54b42 100644
>>>> --- a/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_output.c
>>>> +++ b/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_output.c
>>>> @@ -31,14 +31,16 @@ static const struct drm_encoder_funcs atmel_hlcdc_panel_encoder_funcs = {
>>>>      .destroy = drm_encoder_cleanup,
>>>>  };
>>>>
>>>> -static int atmel_hlcdc_attach_endpoint(struct drm_device *dev, int endpoint)
>>>> +static int atmel_hlcdc_attach_endpoint(struct drm_device *dev,
>>>> +                                   struct of_endpoint *endpoint)
>>>>  {
>>>>      struct drm_encoder *encoder;
>>>>      struct drm_panel *panel;
>>>>      struct drm_bridge *bridge;
>>>>      int ret;
>>>>
>>>> -    ret = drm_of_find_panel_or_bridge(dev->dev->of_node, 0, endpoint,
>>>> +    ret = drm_of_find_panel_or_bridge(dev->dev->of_node,
>>>> +                                      endpoint->port, endpoint->id,
>>>
>>> You are refusing endpoint->port != 0 in the caller, so that could be
>>> 0.
>>
>> Yes, it could. However, I intentionally did not write 0 here, so that
>> the logic related to "port has to be zero" was in one place and not
>> scattered about. I guess it's up to Boris?
>>
>> Maybe the port do not actually have to be zero at all? With the old
>> code, it was kind of understandable that the port number was fixed,
>> but for the code in my patch it does not matter at all AFAICT. There
>> is nothing in the binding docs (except for the example) that hints
>> that port has to be zero, so that's one thing in favor of just getting
>> rid of the port number checking altogether...
> 
> The port numbering must be defined and fixed. If that is not clear in
> the binding, fix the binding.

Ok, so the code in my patch does the right thing forcing the port
number to zero.

>>>> @@ -77,13 +79,29 @@ static int atmel_hlcdc_attach_endpoint(struct drm_device *dev, int endpoint)
>>>>
>>>>  int atmel_hlcdc_create_outputs(struct drm_device *dev)
>>>>  {
>>>> -    int endpoint, ret = 0;
>>>> -
>>>> -    for (endpoint = 0; !ret; endpoint++)
>>>> -            ret = atmel_hlcdc_attach_endpoint(dev, endpoint);
>>>> +    struct of_endpoint endpoint;
>>>> +    struct device_node *node = NULL;
>>>> +    int count = 0;
>>>> +    int ret = 0;
>>>> +
>>>> +    for_each_endpoint_of_node(dev->dev->of_node, node) {
>>>> +            of_graph_parse_endpoint(node, &endpoint);
> 
> I'd really like to kill off of_graph_parse_endpoint, not add more
> users (check the git history on this code). You should know what are
> possible port and endpoint numbers, so iterate over those.

So, add a comment to that effect in the docs of the of_graph_parse_endpoint
function.

How can the hlcdc driver know the actual number of endpoints? It's a
one-way signal path out from that port, and it can easily be routed to
1, 2, 3 or even more places. As shown above, forcing the endpoint id
to start at zero is a nuisance, and I don't see the point of it.

But I welcome suggestions on how to arrange the above dtsi/dts fragments
in a world where the endpoint id absolutely has to start at zero.

Cheers,
Peter

>>>> +
>>>> +            if (endpoint.port)
>>>> +                    continue;
>>>> +
>>>> +            ret = atmel_hlcdc_attach_endpoint(dev, &endpoint);
>>>> +            if (ret == -ENODEV)
>>>> +                    continue;
>>>> +            if (ret) {
>>>> +                    of_node_put(node);
>>>> +                    break;
>>>> +            }
>>>> +            count++;
>>>> +    }
>>>>
>>>>      /* At least one device was successfully attached.*/
>>>> -    if (ret == -ENODEV && endpoint)
>>>> +    if (ret == -ENODEV && count)
>>>>              return 0;
>>>>
>>>>      return ret;
>>>> --
>>>> 2.11.0
>>>>
>>
Rob Herring Aug. 14, 2018, 2:33 p.m. UTC | #5
On Tue, Aug 14, 2018 at 12:36 AM Peter Rosin <peda@axentia.se> wrote:
>
> On 2018-08-13 22:52, Rob Herring wrote:
> > On Mon, Aug 13, 2018 at 8:25 AM Peter Rosin <peda@axentia.se> wrote:
> >>
> >> On 2018-08-13 15:59, jacopo mondi wrote:
> >>> Hi Peter,
> >>>
> >>> On Fri, Aug 10, 2018 at 03:03:58PM +0200, Peter Rosin wrote:
> >>>> This enables more flexible devicetrees. You can e.g. have two output
> >>>> nodes where one is not enabled, without the ordering affecting things.
> >
> > Your DTs are not supposed to be flexible. They should be well defined
> > by the binding.
>
> I feel the need to explain the situation with more words...
>
> We have a board with this atmel-hlcdc wired to both an LVDS encoder
> and an HDMI encoder. Depending on how we integrate this board, only
> one of these paths make sense. Hence, I would like to do the following
> in a .dtsi for that board:
>
> / {
>         hlcdc-display-controller {
>                 ...
>                 port@0 {
>                         hlcdc_lvds: endpoint@0 {
>                                 reg = <0>;
>                                 remote-endpoint = <&lvds_encoder_input>;
>                         };
>
>                         hlcdc_hdmi: endpoint@1 {
>                                 reg = <1>;
>                                 remote-endpoint = <&hdmi_encoder_input>;
>                         };
>                 };
>         };
>
>         lvds_encoder: lvds-encoder {
>                 status = "disabled";
>
>                 ...
>
>                 ports {
>                         #address-cells = <1>;
>                         #size-cells = <0>;
>
>                         port@0 {
>                                 reg = <0>;
>
>                                 lvds_encoder_input: endpoint {
>                                         remote-endpoint = <&hlcdc_lvds>;
>                                 };
>                         };
>
>                         port@1 {
>                                 reg = <1>;
>
>                                 lvds_encoder_output: endpoint {
>                                 };
>                         };
>                 };
>         };
> };
>
> &i2c2 {
>         ...
>         hdmi_encoder: hdmi-encoder@70 {
>                 status = "disabled";
>
>                 ...
>
>                 port {
>                         hdmi_encoder_input: endpoint {
>                                 remote-endpoint = <&hlcdc_hdmi>;
>                         };
>                 };
>         };
> };
>
>
> And then, depending on what components are fitted and what LVDS panel has
> been attached to the LVDS encoder output, this can be used as follows
> in the .dts file for LVDS case:
>
> / {
>         panel: panel {
>                 compatible = "litemax,dlf2118", "panel-lvds";
>
>                 ...
>
>                 port {
>                         panel_input: endpoint {
>                                 remote-endpoint = <&lvds_encoder_output>;
>                         };
>                 };
>         };
> };
>
>
> &lvds_encoder {
>         status = "okay";
> };
>
> &lvds_encoder_output {
>         remote-endpoint = <&panel_input>;
> };
>
>
> For the HDMI case, it would be this in the .dts file:
>
> &hdmi_encoder {
>         status = "okay";
> };
>
>
> The above seem so much better than just having the following in
> the .dtsi file
>
> / {
>         hlcdc-display-controller {
>                 ...
>                 port@0 {
>                         hlcdc_lvds: endpoint {
>                                 remote-endpoint = <&encoder_input>;
>                         };
>                 };
>         };
> };
>
> and pushing the lvds-encoder and hdmi-encoder nodes (slightly modified) down
> to the relevant .dts files. Especially so since we have to this point
> delivered several variants with different LVDS panels. The duplication
> is ugly, and the number of different panels is expected to grow...
>
> But maybe I have misunderstood what endpoints are all about, but to me
> the actual endpoint id is not that interesting and I see nothing in the
> graph binding that suggests that endpoint id 0 has to be up and kicking
> in order for endpoint id 1 to be examined at all.

I guess it depends if the numbering is significant. For a one to many
fan out like this, not so much. For a muxed input, then it would be.

> For ports, yes, you are right that the port id needs to be defined and
> fixed for a specific function, so scratch that. It was just a "maybe"
> question anyway...
>
> >>>>
> >>>> Prior to this patch the active node had to have endpoint id zero.
> >>>>
> >>>> Signed-off-by: Peter Rosin <peda@axentia.se>
> >>>> ---
> >>>>  drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_output.c | 32 ++++++++++++++++++------
> >>>>  1 file changed, 25 insertions(+), 7 deletions(-)
> >>>>
> >>>> diff --git a/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_output.c b/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_output.c
> >>>> index 8db51fb131db..16c1b2f54b42 100644
> >>>> --- a/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_output.c
> >>>> +++ b/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_output.c
> >>>> @@ -31,14 +31,16 @@ static const struct drm_encoder_funcs atmel_hlcdc_panel_encoder_funcs = {
> >>>>      .destroy = drm_encoder_cleanup,
> >>>>  };
> >>>>
> >>>> -static int atmel_hlcdc_attach_endpoint(struct drm_device *dev, int endpoint)
> >>>> +static int atmel_hlcdc_attach_endpoint(struct drm_device *dev,
> >>>> +                                   struct of_endpoint *endpoint)
> >>>>  {
> >>>>      struct drm_encoder *encoder;
> >>>>      struct drm_panel *panel;
> >>>>      struct drm_bridge *bridge;
> >>>>      int ret;
> >>>>
> >>>> -    ret = drm_of_find_panel_or_bridge(dev->dev->of_node, 0, endpoint,
> >>>> +    ret = drm_of_find_panel_or_bridge(dev->dev->of_node,
> >>>> +                                      endpoint->port, endpoint->id,
> >>>
> >>> You are refusing endpoint->port != 0 in the caller, so that could be
> >>> 0.
> >>
> >> Yes, it could. However, I intentionally did not write 0 here, so that
> >> the logic related to "port has to be zero" was in one place and not
> >> scattered about. I guess it's up to Boris?
> >>
> >> Maybe the port do not actually have to be zero at all? With the old
> >> code, it was kind of understandable that the port number was fixed,
> >> but for the code in my patch it does not matter at all AFAICT. There
> >> is nothing in the binding docs (except for the example) that hints
> >> that port has to be zero, so that's one thing in favor of just getting
> >> rid of the port number checking altogether...
> >
> > The port numbering must be defined and fixed. If that is not clear in
> > the binding, fix the binding.
>
> Ok, so the code in my patch does the right thing forcing the port
> number to zero.
>
> >>>> @@ -77,13 +79,29 @@ static int atmel_hlcdc_attach_endpoint(struct drm_device *dev, int endpoint)
> >>>>
> >>>>  int atmel_hlcdc_create_outputs(struct drm_device *dev)
> >>>>  {
> >>>> -    int endpoint, ret = 0;
> >>>> -
> >>>> -    for (endpoint = 0; !ret; endpoint++)
> >>>> -            ret = atmel_hlcdc_attach_endpoint(dev, endpoint);
> >>>> +    struct of_endpoint endpoint;
> >>>> +    struct device_node *node = NULL;
> >>>> +    int count = 0;
> >>>> +    int ret = 0;
> >>>> +
> >>>> +    for_each_endpoint_of_node(dev->dev->of_node, node) {
> >>>> +            of_graph_parse_endpoint(node, &endpoint);
> >
> > I'd really like to kill off of_graph_parse_endpoint, not add more
> > users (check the git history on this code). You should know what are
> > possible port and endpoint numbers, so iterate over those.
>
> So, add a comment to that effect in the docs of the of_graph_parse_endpoint
> function.
>
> How can the hlcdc driver know the actual number of endpoints? It's a
> one-way signal path out from that port, and it can easily be routed to
> 1, 2, 3 or even more places. As shown above, forcing the endpoint id
> to start at zero is a nuisance, and I don't see the point of it.
>
> But I welcome suggestions on how to arrange the above dtsi/dts fragments
> in a world where the endpoint id absolutely has to start at zero.

Your dts file arrangement seems fine. Can't you just not exit the loop
on -ENODEV? IOW, just iterate til you find an enabled endpoint.

Rob
Peter Rosin Aug. 14, 2018, 3:05 p.m. UTC | #6
On 2018-08-14 16:33, Rob Herring wrote:
> On Tue, Aug 14, 2018 at 12:36 AM Peter Rosin <peda@axentia.se> wrote:
>>
>> On 2018-08-13 22:52, Rob Herring wrote:
>>> On Mon, Aug 13, 2018 at 8:25 AM Peter Rosin <peda@axentia.se> wrote:
>>>>
>>>> On 2018-08-13 15:59, jacopo mondi wrote:
>>>>> Hi Peter,
>>>>>
>>>>> On Fri, Aug 10, 2018 at 03:03:58PM +0200, Peter Rosin wrote:
>>>>>> This enables more flexible devicetrees. You can e.g. have two output
>>>>>> nodes where one is not enabled, without the ordering affecting things.
>>>
>>> Your DTs are not supposed to be flexible. They should be well defined
>>> by the binding.
>>
>> I feel the need to explain the situation with more words...
>>
>> We have a board with this atmel-hlcdc wired to both an LVDS encoder
>> and an HDMI encoder. Depending on how we integrate this board, only
>> one of these paths make sense. Hence, I would like to do the following
>> in a .dtsi for that board:
>>
>> / {
>>         hlcdc-display-controller {
>>                 ...
>>                 port@0 {
>>                         hlcdc_lvds: endpoint@0 {
>>                                 reg = <0>;
>>                                 remote-endpoint = <&lvds_encoder_input>;
>>                         };
>>
>>                         hlcdc_hdmi: endpoint@1 {
>>                                 reg = <1>;
>>                                 remote-endpoint = <&hdmi_encoder_input>;
>>                         };
>>                 };
>>         };
>>
>>         lvds_encoder: lvds-encoder {
>>                 status = "disabled";
>>
>>                 ...
>>
>>                 ports {
>>                         #address-cells = <1>;
>>                         #size-cells = <0>;
>>
>>                         port@0 {
>>                                 reg = <0>;
>>
>>                                 lvds_encoder_input: endpoint {
>>                                         remote-endpoint = <&hlcdc_lvds>;
>>                                 };
>>                         };
>>
>>                         port@1 {
>>                                 reg = <1>;
>>
>>                                 lvds_encoder_output: endpoint {
>>                                 };
>>                         };
>>                 };
>>         };
>> };
>>
>> &i2c2 {
>>         ...
>>         hdmi_encoder: hdmi-encoder@70 {
>>                 status = "disabled";
>>
>>                 ...
>>
>>                 port {
>>                         hdmi_encoder_input: endpoint {
>>                                 remote-endpoint = <&hlcdc_hdmi>;
>>                         };
>>                 };
>>         };
>> };
>>
>>
>> And then, depending on what components are fitted and what LVDS panel has
>> been attached to the LVDS encoder output, this can be used as follows
>> in the .dts file for LVDS case:
>>
>> / {
>>         panel: panel {
>>                 compatible = "litemax,dlf2118", "panel-lvds";
>>
>>                 ...
>>
>>                 port {
>>                         panel_input: endpoint {
>>                                 remote-endpoint = <&lvds_encoder_output>;
>>                         };
>>                 };
>>         };
>> };
>>
>>
>> &lvds_encoder {
>>         status = "okay";
>> };
>>
>> &lvds_encoder_output {
>>         remote-endpoint = <&panel_input>;
>> };
>>
>>
>> For the HDMI case, it would be this in the .dts file:
>>
>> &hdmi_encoder {
>>         status = "okay";
>> };
>>
>>
>> The above seem so much better than just having the following in
>> the .dtsi file
>>
>> / {
>>         hlcdc-display-controller {
>>                 ...
>>                 port@0 {
>>                         hlcdc_lvds: endpoint {
>>                                 remote-endpoint = <&encoder_input>;
>>                         };
>>                 };
>>         };
>> };
>>
>> and pushing the lvds-encoder and hdmi-encoder nodes (slightly modified) down
>> to the relevant .dts files. Especially so since we have to this point
>> delivered several variants with different LVDS panels. The duplication
>> is ugly, and the number of different panels is expected to grow...
>>
>> But maybe I have misunderstood what endpoints are all about, but to me
>> the actual endpoint id is not that interesting and I see nothing in the
>> graph binding that suggests that endpoint id 0 has to be up and kicking
>> in order for endpoint id 1 to be examined at all.
> 
> I guess it depends if the numbering is significant. For a one to many
> fan out like this, not so much. For a muxed input, then it would be.

Right, the endpoint numbering certainly *can* be important for some cases,
I can see that, and am not arguing against that part...

>> For ports, yes, you are right that the port id needs to be defined and
>> fixed for a specific function, so scratch that. It was just a "maybe"
>> question anyway...
>>
>>>>>>
>>>>>> Prior to this patch the active node had to have endpoint id zero.
>>>>>>
>>>>>> Signed-off-by: Peter Rosin <peda@axentia.se>
>>>>>> ---
>>>>>>  drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_output.c | 32 ++++++++++++++++++------
>>>>>>  1 file changed, 25 insertions(+), 7 deletions(-)
>>>>>>
>>>>>> diff --git a/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_output.c b/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_output.c
>>>>>> index 8db51fb131db..16c1b2f54b42 100644
>>>>>> --- a/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_output.c
>>>>>> +++ b/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_output.c
>>>>>> @@ -31,14 +31,16 @@ static const struct drm_encoder_funcs atmel_hlcdc_panel_encoder_funcs = {
>>>>>>      .destroy = drm_encoder_cleanup,
>>>>>>  };
>>>>>>
>>>>>> -static int atmel_hlcdc_attach_endpoint(struct drm_device *dev, int endpoint)
>>>>>> +static int atmel_hlcdc_attach_endpoint(struct drm_device *dev,
>>>>>> +                                   struct of_endpoint *endpoint)
>>>>>>  {
>>>>>>      struct drm_encoder *encoder;
>>>>>>      struct drm_panel *panel;
>>>>>>      struct drm_bridge *bridge;
>>>>>>      int ret;
>>>>>>
>>>>>> -    ret = drm_of_find_panel_or_bridge(dev->dev->of_node, 0, endpoint,
>>>>>> +    ret = drm_of_find_panel_or_bridge(dev->dev->of_node,
>>>>>> +                                      endpoint->port, endpoint->id,
>>>>>
>>>>> You are refusing endpoint->port != 0 in the caller, so that could be
>>>>> 0.
>>>>
>>>> Yes, it could. However, I intentionally did not write 0 here, so that
>>>> the logic related to "port has to be zero" was in one place and not
>>>> scattered about. I guess it's up to Boris?
>>>>
>>>> Maybe the port do not actually have to be zero at all? With the old
>>>> code, it was kind of understandable that the port number was fixed,
>>>> but for the code in my patch it does not matter at all AFAICT. There
>>>> is nothing in the binding docs (except for the example) that hints
>>>> that port has to be zero, so that's one thing in favor of just getting
>>>> rid of the port number checking altogether...
>>>
>>> The port numbering must be defined and fixed. If that is not clear in
>>> the binding, fix the binding.
>>
>> Ok, so the code in my patch does the right thing forcing the port
>> number to zero.
>>
>>>>>> @@ -77,13 +79,29 @@ static int atmel_hlcdc_attach_endpoint(struct drm_device *dev, int endpoint)
>>>>>>
>>>>>>  int atmel_hlcdc_create_outputs(struct drm_device *dev)
>>>>>>  {
>>>>>> -    int endpoint, ret = 0;
>>>>>> -
>>>>>> -    for (endpoint = 0; !ret; endpoint++)
>>>>>> -            ret = atmel_hlcdc_attach_endpoint(dev, endpoint);
>>>>>> +    struct of_endpoint endpoint;
>>>>>> +    struct device_node *node = NULL;
>>>>>> +    int count = 0;
>>>>>> +    int ret = 0;
>>>>>> +
>>>>>> +    for_each_endpoint_of_node(dev->dev->of_node, node) {
>>>>>> +            of_graph_parse_endpoint(node, &endpoint);
>>>
>>> I'd really like to kill off of_graph_parse_endpoint, not add more
>>> users (check the git history on this code). You should know what are
>>> possible port and endpoint numbers, so iterate over those.
>>
>> So, add a comment to that effect in the docs of the of_graph_parse_endpoint
>> function.
>>
>> How can the hlcdc driver know the actual number of endpoints? It's a
>> one-way signal path out from that port, and it can easily be routed to
>> 1, 2, 3 or even more places. As shown above, forcing the endpoint id
>> to start at zero is a nuisance, and I don't see the point of it.
>>
>> But I welcome suggestions on how to arrange the above dtsi/dts fragments
>> in a world where the endpoint id absolutely has to start at zero.
> 
> Your dts file arrangement seems fine. Can't you just not exit the loop
> on -ENODEV? IOW, just iterate til you find an enabled endpoint.

That would regress cases where two (or more) endpoints are enabled
(which is currently supported). As I see it, the driver will have a
very hard time knowing when to stop iterating with any solution not
involving the equivalent of the functions for_each_endpoint_of_node
and of_graph_parse_endpoint. Open-coding of_graph_parse_endpoint just
to avoid it is a bit more than silly IMHO...

Cheers,
Peter
Boris Brezillon Aug. 24, 2018, 7:47 a.m. UTC | #7
On Tue, 14 Aug 2018 17:05:29 +0200
Peter Rosin <peda@axentia.se> wrote:

> >>>>>> @@ -77,13 +79,29 @@ static int atmel_hlcdc_attach_endpoint(struct drm_device *dev, int endpoint)
> >>>>>>
> >>>>>>  int atmel_hlcdc_create_outputs(struct drm_device *dev)
> >>>>>>  {
> >>>>>> -    int endpoint, ret = 0;
> >>>>>> -
> >>>>>> -    for (endpoint = 0; !ret; endpoint++)
> >>>>>> -            ret = atmel_hlcdc_attach_endpoint(dev, endpoint);
> >>>>>> +    struct of_endpoint endpoint;
> >>>>>> +    struct device_node *node = NULL;
> >>>>>> +    int count = 0;
> >>>>>> +    int ret = 0;
> >>>>>> +
> >>>>>> +    for_each_endpoint_of_node(dev->dev->of_node, node) {
> >>>>>> +            of_graph_parse_endpoint(node, &endpoint);  
> >>>
> >>> I'd really like to kill off of_graph_parse_endpoint, not add more
> >>> users (check the git history on this code). You should know what are
> >>> possible port and endpoint numbers, so iterate over those.  
> >>
> >> So, add a comment to that effect in the docs of the of_graph_parse_endpoint
> >> function.
> >>
> >> How can the hlcdc driver know the actual number of endpoints? It's a
> >> one-way signal path out from that port, and it can easily be routed to
> >> 1, 2, 3 or even more places. As shown above, forcing the endpoint id
> >> to start at zero is a nuisance, and I don't see the point of it.
> >>
> >> But I welcome suggestions on how to arrange the above dtsi/dts fragments
> >> in a world where the endpoint id absolutely has to start at zero.  
> > 
> > Your dts file arrangement seems fine. Can't you just not exit the loop
> > on -ENODEV? IOW, just iterate til you find an enabled endpoint.  
> 
> That would regress cases where two (or more) endpoints are enabled
> (which is currently supported). As I see it, the driver will have a
> very hard time knowing when to stop iterating with any solution not
> involving the equivalent of the functions for_each_endpoint_of_node
> and of_graph_parse_endpoint. Open-coding of_graph_parse_endpoint just
> to avoid it is a bit more than silly IMHO...

I agree, and actually, I think this is Rob who suggested to do what we
do here :-) (iterate from 0 to X, and stop as soon as
-ENODEV is returned).
Rob Herring Aug. 24, 2018, 4:33 p.m. UTC | #8
On Fri, Aug 24, 2018 at 2:47 AM Boris Brezillon
<boris.brezillon@bootlin.com> wrote:
>
> On Tue, 14 Aug 2018 17:05:29 +0200
> Peter Rosin <peda@axentia.se> wrote:
>
> > >>>>>> @@ -77,13 +79,29 @@ static int atmel_hlcdc_attach_endpoint(struct drm_device *dev, int endpoint)
> > >>>>>>
> > >>>>>>  int atmel_hlcdc_create_outputs(struct drm_device *dev)
> > >>>>>>  {
> > >>>>>> -    int endpoint, ret = 0;
> > >>>>>> -
> > >>>>>> -    for (endpoint = 0; !ret; endpoint++)
> > >>>>>> -            ret = atmel_hlcdc_attach_endpoint(dev, endpoint);
> > >>>>>> +    struct of_endpoint endpoint;
> > >>>>>> +    struct device_node *node = NULL;
> > >>>>>> +    int count = 0;
> > >>>>>> +    int ret = 0;
> > >>>>>> +
> > >>>>>> +    for_each_endpoint_of_node(dev->dev->of_node, node) {
> > >>>>>> +            of_graph_parse_endpoint(node, &endpoint);
> > >>>
> > >>> I'd really like to kill off of_graph_parse_endpoint, not add more
> > >>> users (check the git history on this code). You should know what are
> > >>> possible port and endpoint numbers, so iterate over those.
> > >>
> > >> So, add a comment to that effect in the docs of the of_graph_parse_endpoint
> > >> function.
> > >>
> > >> How can the hlcdc driver know the actual number of endpoints? It's a
> > >> one-way signal path out from that port, and it can easily be routed to
> > >> 1, 2, 3 or even more places. As shown above, forcing the endpoint id
> > >> to start at zero is a nuisance, and I don't see the point of it.
> > >>
> > >> But I welcome suggestions on how to arrange the above dtsi/dts fragments
> > >> in a world where the endpoint id absolutely has to start at zero.
> > >
> > > Your dts file arrangement seems fine. Can't you just not exit the loop
> > > on -ENODEV? IOW, just iterate til you find an enabled endpoint.
> >
> > That would regress cases where two (or more) endpoints are enabled
> > (which is currently supported). As I see it, the driver will have a
> > very hard time knowing when to stop iterating with any solution not
> > involving the equivalent of the functions for_each_endpoint_of_node
> > and of_graph_parse_endpoint. Open-coding of_graph_parse_endpoint just
> > to avoid it is a bit more than silly IMHO...
>
> I agree, and actually, I think this is Rob who suggested to do what we
> do here :-) (iterate from 0 to X, and stop as soon as
> -ENODEV is returned).

By suggested, you mean implemented because that is what it currently
does. My suggestion now is to do this:

for (endpoint = 0; endpoint < SOME_REASONABLE_MAX_NUMBER_OF_ENDPOINTS;
endpoint++) {
  ret = atmel_hlcdc_attach_endpoint(dev, endpoint);
  if (ret == -ENODEV)
    continue;
  // handle other errors?
}

And SOME_REASONABLE_MAX_NUMBER_OF_ENDPOINTS is something you make up
based on how many connections any board will have and physics (I
suppose you could have trees worth of buffers, but really what is the
worst case in an actual board design?). I would think 4 would be
plenty. If not, double it to 8.

Rob

Patch
diff mbox series

diff --git a/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_output.c b/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_output.c
index 8db51fb131db..16c1b2f54b42 100644
--- a/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_output.c
+++ b/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_output.c
@@ -31,14 +31,16 @@  static const struct drm_encoder_funcs atmel_hlcdc_panel_encoder_funcs = {
 	.destroy = drm_encoder_cleanup,
 };
 
-static int atmel_hlcdc_attach_endpoint(struct drm_device *dev, int endpoint)
+static int atmel_hlcdc_attach_endpoint(struct drm_device *dev,
+				       struct of_endpoint *endpoint)
 {
 	struct drm_encoder *encoder;
 	struct drm_panel *panel;
 	struct drm_bridge *bridge;
 	int ret;
 
-	ret = drm_of_find_panel_or_bridge(dev->dev->of_node, 0, endpoint,
+	ret = drm_of_find_panel_or_bridge(dev->dev->of_node,
+					  endpoint->port, endpoint->id,
 					  &panel, &bridge);
 	if (ret)
 		return ret;
@@ -77,13 +79,29 @@  static int atmel_hlcdc_attach_endpoint(struct drm_device *dev, int endpoint)
 
 int atmel_hlcdc_create_outputs(struct drm_device *dev)
 {
-	int endpoint, ret = 0;
-
-	for (endpoint = 0; !ret; endpoint++)
-		ret = atmel_hlcdc_attach_endpoint(dev, endpoint);
+	struct of_endpoint endpoint;
+	struct device_node *node = NULL;
+	int count = 0;
+	int ret = 0;
+
+	for_each_endpoint_of_node(dev->dev->of_node, node) {
+		of_graph_parse_endpoint(node, &endpoint);
+
+		if (endpoint.port)
+			continue;
+
+		ret = atmel_hlcdc_attach_endpoint(dev, &endpoint);
+		if (ret == -ENODEV)
+			continue;
+		if (ret) {
+			of_node_put(node);
+			break;
+		}
+		count++;
+	}
 
 	/* At least one device was successfully attached.*/
-	if (ret == -ENODEV && endpoint)
+	if (ret == -ENODEV && count)
 		return 0;
 
 	return ret;