[PATCH v4 1/4] dt-bindings: simplefb: Specify node location and handoff related properties

[PATCH v4 1/4] dt-bindings: simplefb: Specify node location and handoff related properties

[Hans de Goede]

Since simplefb nodes do not relate directly to hw typically they have been
placed in the root of the devicetree. As the represent runtime information
having them as sub-nodes of /chosen is more logical, specify this.

Also specify when to set the chosen stdout-path property to a simplefb node.

For reliable handover to a hardware specific driver, that driver needs to
know which simplefb to unregister when taking over, specify how the hw driver
can find the matching simplefb node.

Last add some advice on how to fill and use simplefb nodes from a firmware
pov.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
Acked-by: Maxime Ripard <maxime.ripard@free-electrons.com>
--
Changes in v2:
-Add stdout-path to the example code
Changes in v3:
-Specify that the node name must be "framebuffer@<address>"
-Specify that the link to link simplefb node and display hw nodes to one
 another for handover goes into the simplefb node, and must be called "display"
-Specify how aliases may be used to tell the OS how to number displays
-Update the example to reflect these changes
Changes in v4:
-Keep the size of the reg property in the example as it was before
---
 .../bindings/video/simple-framebuffer.txt          | 49 +++++++++++++++++++++-
 1 file changed, 48 insertions(+), 1 deletion(-)

diff --git a/Documentation/devicetree/bindings/video/simple-framebuffer.txt b/Documentation/devicetree/bindings/video/simple-framebuffer.txt
index 8f35718..c548f33 100644
--- a/Documentation/devicetree/bindings/video/simple-framebuffer.txt
+++ b/Documentation/devicetree/bindings/video/simple-framebuffer.txt
@@ -4,6 +4,31 @@ A simple frame-buffer describes a frame-buffer setup by firmware or
 the bootloader, with the assumption that the display hardware has already
 been set up to scan out from the memory pointed to by the reg property.
 
+Since simplefb nodes represent runtime information they must be sub-nodes of
+the chosen node (*). Simplefb nodes must be named "framebuffer@<address>".
+
+If a simplefb node represents the preferred console for user interaction,
+then the chosen node's stdout-path property must point to it.
+
+If the devicetree contains nodes for the display hardware used by a simplefb,
+then the simplefb node must contain a property called "display", which
+contains a phandle pointing to the primary display hw node, so that the OS
+knows which simplefb to disable when handing over control to a driver for the
+real hardware. The bindings for the hw nodes must specify which node is
+considered the primary node.
+
+It is advised to add display# aliases to help the OS determine how to number
+things. If display# aliases are used, then if the simplefb node contains a
+"display" property then the /aliases/display# path must point to the display
+hw node the "display" property points to, otherwise it must point directly
+to the simplefb node.
+
+It is advised that devicetree files contain pre-filled, disabled framebuffer
+nodes, so that the firmware only needs to update the mode information and
+enable them. This way if e.g. later on support for more display clocks get
+added, the simplefb nodes will already contain this info and the firmware
+does not need to be updated.
+
 Required properties:
 - compatible: "simple-framebuffer"
 - reg: Should contain the location and size of the framebuffer memory.
@@ -19,14 +44,36 @@ Optional properties:
            are expected to already be configured correctly. The OS must
            ensure these clocks are not modified or disabled while the
            simple framebuffer remains active.
+- display : phandle pointing to the primary display hardware node
 
 Example:
 
-	framebuffer {
+aliases {
+	display0 = &lcdc0;
+}
+
+chosen {
+	framebuffer0: framebuffer@1d385000 {
 		compatible = "simple-framebuffer";
 		reg = <0x1d385000 (1600 * 1200 * 2)>;
 		width = <1600>;
 		height = <1200>;
 		stride = <(1600 * 2)>;
 		format = "r5g6b5";
+		clocks = <&ahb_gates 36>, <&ahb_gates 43>, <&ahb_gates 44>;
+		display = <&lcdc0>;
+	};
+	stdout-path = &framebuffer0;
+};
+
+soc@01c00000 {
+	lcdc0: lcdc@1c0c000 {
+		compatible = "allwinner,sun4i-a10-lcdc";
+		...
 	};
+};
+
+
+*) Older devicetree files may have a compatible = "simple-framebuffer" node
+in a different place, operating systems must first enumerate any compatible
+nodes found under chosen and then check for other compatible nodes.
-- 
2.1.0

[PATCH v4 2/4] simplefb: Add support for enumerating simplefb dt nodes in /chosen

[Hans de Goede]

Update simplefb to support the new preferred location for simplefb dt nodes
under /chosen.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
--
Changes in v2:
-Make name array larger in case we ever encounter more then 10000 framebuffers
Changes in v3:
-Switch to for_each_child_of_node to loop over the nodes under chosen
Changes in v4:
-Wrap the chosen enumeration code in #ifdef CONFIG_OF, as simplefb is used on
 non devicetree platforms too
-simplefb can only be built-in, so drop the module_exit function calling
 platform_driver_unregister
---
 drivers/video/fbdev/simplefb.c | 23 ++++++++++++++++++++++-
 1 file changed, 22 insertions(+), 1 deletion(-)

diff --git a/drivers/video/fbdev/simplefb.c b/drivers/video/fbdev/simplefb.c
index 868099a..e381a53 100644
--- a/drivers/video/fbdev/simplefb.c
+++ b/drivers/video/fbdev/simplefb.c
@@ -27,6 +27,7 @@
 #include <linux/platform_data/simplefb.h>
 #include <linux/platform_device.h>
 #include <linux/clk-provider.h>
+#include <linux/of_platform.h>
 
 static struct fb_fix_screeninfo simplefb_fix = {
 	.id		= "simple",
@@ -390,7 +391,27 @@ static struct platform_driver simplefb_driver = {
 	.probe = simplefb_probe,
 	.remove = simplefb_remove,
 };
-module_platform_driver(simplefb_driver);
+
+static int __init simplefb_init(void)
+{
+	int ret;
+	struct device_node __maybe_unused *np;
+
+	ret = platform_driver_register(&simplefb_driver);
+	if (ret)
+		return ret;
+
+#ifdef CONFIG_OF
+	for_each_child_of_node(of_chosen, np) {
+		if (of_device_is_compatible(np, "simple-framebuffer"))
+			of_platform_device_create(np, NULL, NULL);
+	}
+#endif
+
+	return 0;
+}
+
+module_init(simplefb_init);
 
 MODULE_AUTHOR("Stephen Warren <swarren@wwwdotorg.org>");
 MODULE_DESCRIPTION("Simple framebuffer driver");
-- 
2.1.0

[PATCH v4 3/4] fbcon: Change fbcon_init from module_init to fs_initcall

[Hans de Goede]

Various fb drivers register themselves before module_init so as to have a
console as early as possible, this is of little use if fbcon does not
initialize early too.

Fbcon cannot initialize earlier then fs_initcall, because then the creation
of /sys/class/graphics/fbcon will fail.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
---
 drivers/video/console/fbcon.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/video/console/fbcon.c b/drivers/video/console/fbcon.c
index eb976ee..ea43724 100644
--- a/drivers/video/console/fbcon.c
+++ b/drivers/video/console/fbcon.c
@@ -3624,7 +3624,7 @@ static int __init fb_console_init(void)
 	return 0;
 }
 
-module_init(fb_console_init);
+fs_initcall(fb_console_init);
 
 #ifdef MODULE
 
-- 
2.1.0

[PATCH v4 4/4] simplefb: Change simplefb_init from module_init to fs_initcall

[Hans de Goede]

One of the reasons for having the simplefb nodes in /chosen, and doing
explicit enumeration of the nodes there, is too allow enumerating them sooner,
so that we get a console earlier on.

Doing this earlier then fs_initcall is not useful, since the fb only turns
into a console when fbcon intializes, which is a fs_initcall too.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
--
Changes in v4 (of the patch-set):
-Drop the comment about using fs_initcall vs module_exit, as we no longer have
 a module_exit
---
 drivers/video/fbdev/simplefb.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/video/fbdev/simplefb.c b/drivers/video/fbdev/simplefb.c
index e381a53..1fc973c 100644
--- a/drivers/video/fbdev/simplefb.c
+++ b/drivers/video/fbdev/simplefb.c
@@ -411,7 +411,7 @@ static int __init simplefb_init(void)
 	return 0;
 }
 
-module_init(simplefb_init);
+fs_initcall(simplefb_init);
 
 MODULE_AUTHOR("Stephen Warren <swarren@wwwdotorg.org>");
 MODULE_DESCRIPTION("Simple framebuffer driver");
-- 
2.1.0

Re: [PATCH v4 1/4] dt-bindings: simplefb: Specify node location and handoff related properties

[Grant Likely]

On Thu, Nov 13, 2014 at 7:23 PM, Hans de Goede <hdegoede@redhat.com> wrote:
> Since simplefb nodes do not relate directly to hw typically they have been
> placed in the root of the devicetree. As the represent runtime information
> having them as sub-nodes of /chosen is more logical, specify this.
>
> Also specify when to set the chosen stdout-path property to a simplefb node.
>
> For reliable handover to a hardware specific driver, that driver needs to
> know which simplefb to unregister when taking over, specify how the hw driver
> can find the matching simplefb node.
>
> Last add some advice on how to fill and use simplefb nodes from a firmware
> pov.
>
> Signed-off-by: Hans de Goede <hdegoede@redhat.com>
> Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
> Acked-by: Maxime Ripard <maxime.ripard@free-electrons.com>
> --
> Changes in v2:
> -Add stdout-path to the example code
> Changes in v3:
> -Specify that the node name must be "framebuffer@<address>"
> -Specify that the link to link simplefb node and display hw nodes to one
>  another for handover goes into the simplefb node, and must be called "display"
> -Specify how aliases may be used to tell the OS how to number displays
> -Update the example to reflect these changes
> Changes in v4:
> -Keep the size of the reg property in the example as it was before
> ---
>  .../bindings/video/simple-framebuffer.txt          | 49 +++++++++++++++++++++-
>  1 file changed, 48 insertions(+), 1 deletion(-)
>
> diff --git a/Documentation/devicetree/bindings/video/simple-framebuffer.txt b/Documentation/devicetree/bindings/video/simple-framebuffer.txt
> index 8f35718..c548f33 100644
> --- a/Documentation/devicetree/bindings/video/simple-framebuffer.txt
> +++ b/Documentation/devicetree/bindings/video/simple-framebuffer.txt
> @@ -4,6 +4,31 @@ A simple frame-buffer describes a frame-buffer setup by firmware or
>  the bootloader, with the assumption that the display hardware has already
>  been set up to scan out from the memory pointed to by the reg property.
>
> +Since simplefb nodes represent runtime information they must be sub-nodes of
> +the chosen node (*). Simplefb nodes must be named "framebuffer@<address>".
> +
> +If a simplefb node represents the preferred console for user interaction,
> +then the chosen node's stdout-path property must point to it.

Since we've decided to point the display aliases at the display node
instead of the framebuffer, the stdout-path property should also point
to the display node. The simplefb driver can still work out which
framebuffer to use for stdout path in the same way that it figures out
how to resolve the display alias. This way the stdout details aren't
lost when the framebuffer is disabled and It also means that
stdout-path can be merely set to the alias ("display0") instead of the
full path ("/full/path/to/node").

> +
> +If the devicetree contains nodes for the display hardware used by a simplefb,
> +then the simplefb node must contain a property called "display", which
> +contains a phandle pointing to the primary display hw node, so that the OS
> +knows which simplefb to disable when handing over control to a driver for the
> +real hardware. The bindings for the hw nodes must specify which node is
> +considered the primary node.
> +
> +It is advised to add display# aliases to help the OS determine how to number
> +things. If display# aliases are used, then if the simplefb node contains a

s/then if/and if/

> +"display" property then the /aliases/display# path must point to the display
> +hw node the "display" property points to, otherwise it must point directly
> +to the simplefb node.
> +
> +It is advised that devicetree files contain pre-filled, disabled framebuffer
> +nodes, so that the firmware only needs to update the mode information and
> +enable them. This way if e.g. later on support for more display clocks get
> +added, the simplefb nodes will already contain this info and the firmware
> +does not need to be updated.

You should merge your guidance of naming pre-filled framebuffer nodes
into this patch. There is no need to have it separate.

> +
>  Required properties:
>  - compatible: "simple-framebuffer"
>  - reg: Should contain the location and size of the framebuffer memory.
> @@ -19,14 +44,36 @@ Optional properties:
>             are expected to already be configured correctly. The OS must
>             ensure these clocks are not modified or disabled while the
>             simple framebuffer remains active.
> +- display : phandle pointing to the primary display hardware node
>
>  Example:
>
> -       framebuffer {
> +aliases {
> +       display0 = &lcdc0;
> +}
> +
> +chosen {
> +       framebuffer0: framebuffer@1d385000 {
>                 compatible = "simple-framebuffer";
>                 reg = <0x1d385000 (1600 * 1200 * 2)>;
>                 width = <1600>;
>                 height = <1200>;
>                 stride = <(1600 * 2)>;
>                 format = "r5g6b5";
> +               clocks = <&ahb_gates 36>, <&ahb_gates 43>, <&ahb_gates 44>;
> +               display = <&lcdc0>;
> +       };
> +       stdout-path = &framebuffer0;
> +};
> +
> +soc@01c00000 {
> +       lcdc0: lcdc@1c0c000 {
> +               compatible = "allwinner,sun4i-a10-lcdc";
> +               ...
>         };
> +};
> +
> +
> +*) Older devicetree files may have a compatible = "simple-framebuffer" node
> +in a different place, operating systems must first enumerate any compatible
> +nodes found under chosen and then check for other compatible nodes.
> --
> 2.1.0
>

Re: [PATCH v4 2/4] simplefb: Add support for enumerating simplefb dt nodes in /chosen

[Grant Likely]

On Thu, Nov 13, 2014 at 7:23 PM, Hans de Goede <hdegoede@redhat.com> wrote:
> Update simplefb to support the new preferred location for simplefb dt nodes
> under /chosen.
>
> Signed-off-by: Hans de Goede <hdegoede@redhat.com>
> --
> Changes in v2:
> -Make name array larger in case we ever encounter more then 10000 framebuffers
> Changes in v3:
> -Switch to for_each_child_of_node to loop over the nodes under chosen
> Changes in v4:
> -Wrap the chosen enumeration code in #ifdef CONFIG_OF, as simplefb is used on
>  non devicetree platforms too
> -simplefb can only be built-in, so drop the module_exit function calling
>  platform_driver_unregister
> ---
>  drivers/video/fbdev/simplefb.c | 23 ++++++++++++++++++++++-
>  1 file changed, 22 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/video/fbdev/simplefb.c b/drivers/video/fbdev/simplefb.c
> index 868099a..e381a53 100644
> --- a/drivers/video/fbdev/simplefb.c
> +++ b/drivers/video/fbdev/simplefb.c
> @@ -27,6 +27,7 @@
>  #include <linux/platform_data/simplefb.h>
>  #include <linux/platform_device.h>
>  #include <linux/clk-provider.h>
> +#include <linux/of_platform.h>
>
>  static struct fb_fix_screeninfo simplefb_fix = {
>         .id             = "simple",
> @@ -390,7 +391,27 @@ static struct platform_driver simplefb_driver = {
>         .probe = simplefb_probe,
>         .remove = simplefb_remove,
>  };
> -module_platform_driver(simplefb_driver);
> +
> +static int __init simplefb_init(void)
> +{
> +       int ret;
> +       struct device_node __maybe_unused *np;
> +
> +       ret = platform_driver_register(&simplefb_driver);
> +       if (ret)
> +               return ret;
> +
> +#ifdef CONFIG_OF
> +       for_each_child_of_node(of_chosen, np) {
> +               if (of_device_is_compatible(np, "simple-framebuffer"))
> +                       of_platform_device_create(np, NULL, NULL);
> +       }
> +#endif

Nit: Kind of ugly. This should work instead:

        if (IS_ENABLED(CONFIG_OF_PLATFORM) && of_chosen) {
                for_each_child_of_node(of_chosen, np)
                        if (of_device_is_compatible(np, "simple-framebuffer"))
                                of_platform_device_create(np, NULL, NULL);
        }

And move the forward declaration of of_chosen in include/linux/of.h up
5 lines so that it is always declared. gcc will optimize it out, but
it will still get properly syntax checked on every build.

> +
> +       return 0;
> +}
> +
> +module_init(simplefb_init);
>
>  MODULE_AUTHOR("Stephen Warren <swarren@wwwdotorg.org>");
>  MODULE_DESCRIPTION("Simple framebuffer driver");
> --
> 2.1.0
>

Re: [PATCH v4 1/4] dt-bindings: simplefb: Specify node location and handoff related properties

[Hans de Goede]

Hi,

On 11/14/2014 10:19 AM, Grant Likely wrote:
> On Thu, Nov 13, 2014 at 7:23 PM, Hans de Goede <hdegoede@redhat.com> wrote:
>> Since simplefb nodes do not relate directly to hw typically they have been
>> placed in the root of the devicetree. As the represent runtime information
>> having them as sub-nodes of /chosen is more logical, specify this.
>>
>> Also specify when to set the chosen stdout-path property to a simplefb node.
>>
>> For reliable handover to a hardware specific driver, that driver needs to
>> know which simplefb to unregister when taking over, specify how the hw driver
>> can find the matching simplefb node.
>>
>> Last add some advice on how to fill and use simplefb nodes from a firmware
>> pov.
>>
>> Signed-off-by: Hans de Goede <hdegoede@redhat.com>
>> Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
>> Acked-by: Maxime Ripard <maxime.ripard@free-electrons.com>
>> --
>> Changes in v2:
>> -Add stdout-path to the example code
>> Changes in v3:
>> -Specify that the node name must be "framebuffer@<address>"
>> -Specify that the link to link simplefb node and display hw nodes to one
>>  another for handover goes into the simplefb node, and must be called "display"
>> -Specify how aliases may be used to tell the OS how to number displays
>> -Update the example to reflect these changes
>> Changes in v4:
>> -Keep the size of the reg property in the example as it was before
>> ---
>>  .../bindings/video/simple-framebuffer.txt          | 49 +++++++++++++++++++++-
>>  1 file changed, 48 insertions(+), 1 deletion(-)
>>
>> diff --git a/Documentation/devicetree/bindings/video/simple-framebuffer.txt b/Documentation/devicetree/bindings/video/simple-framebuffer.txt
>> index 8f35718..c548f33 100644
>> --- a/Documentation/devicetree/bindings/video/simple-framebuffer.txt
>> +++ b/Documentation/devicetree/bindings/video/simple-framebuffer.txt
>> @@ -4,6 +4,31 @@ A simple frame-buffer describes a frame-buffer setup by firmware or
>>  the bootloader, with the assumption that the display hardware has already
>>  been set up to scan out from the memory pointed to by the reg property.
>>
>> +Since simplefb nodes represent runtime information they must be sub-nodes of
>> +the chosen node (*). Simplefb nodes must be named "framebuffer@<address>".
>> +
>> +If a simplefb node represents the preferred console for user interaction,
>> +then the chosen node's stdout-path property must point to it.
> 
> Since we've decided to point the display aliases at the display node
> instead of the framebuffer, the stdout-path property should also point
> to the display node. The simplefb driver can still work out which
> framebuffer to use for stdout path in the same way that it figures out
> how to resolve the display alias. This way the stdout details aren't
> lost when the framebuffer is disabled and It also means that
> stdout-path can be merely set to the alias ("display0") instead of the
> full path ("/full/path/to/node").

Ok, will fix for V5.

> 
>> +
>> +If the devicetree contains nodes for the display hardware used by a simplefb,
>> +then the simplefb node must contain a property called "display", which
>> +contains a phandle pointing to the primary display hw node, so that the OS
>> +knows which simplefb to disable when handing over control to a driver for the
>> +real hardware. The bindings for the hw nodes must specify which node is
>> +considered the primary node.
>> +
>> +It is advised to add display# aliases to help the OS determine how to number
>> +things. If display# aliases are used, then if the simplefb node contains a
> 
> s/then if/and if/

Erm, no the then applies to both the musts following that sentence, in pseudo
code it looks like this:

if (display# aliases are used) {
	if (simplefb node contains a "display" property) {
		/aliases/display# path must point to the display hw node the "display" property points to
	} else {
		/aliases/display# path must point directly to the simplefb node.
	}
}

So no && between the (display# aliases are used) and (simplefb node contains a "display" property)
conditions.


> 
>> +"display" property then the /aliases/display# path must point to the display
>> +hw node the "display" property points to, otherwise it must point directly
>> +to the simplefb node.
>> +
>> +It is advised that devicetree files contain pre-filled, disabled framebuffer
>> +nodes, so that the firmware only needs to update the mode information and
>> +enable them. This way if e.g. later on support for more display clocks get
>> +added, the simplefb nodes will already contain this info and the firmware
>> +does not need to be updated.
> 
> You should merge your guidance of naming pre-filled framebuffer nodes
> into this patch. There is no need to have it separate.

Will do for v5.

Regards,

Hans

Re: [PATCH v4 2/4] simplefb: Add support for enumerating simplefb dt nodes in /chosen

[Hans de Goede]

Hi,

On 11/14/2014 10:28 AM, Grant Likely wrote:
> On Thu, Nov 13, 2014 at 7:23 PM, Hans de Goede <hdegoede@redhat.com> wrote:
>> Update simplefb to support the new preferred location for simplefb dt nodes
>> under /chosen.
>>
>> Signed-off-by: Hans de Goede <hdegoede@redhat.com>
>> --
>> Changes in v2:
>> -Make name array larger in case we ever encounter more then 10000 framebuffers
>> Changes in v3:
>> -Switch to for_each_child_of_node to loop over the nodes under chosen
>> Changes in v4:
>> -Wrap the chosen enumeration code in #ifdef CONFIG_OF, as simplefb is used on
>>  non devicetree platforms too
>> -simplefb can only be built-in, so drop the module_exit function calling
>>  platform_driver_unregister
>> ---
>>  drivers/video/fbdev/simplefb.c | 23 ++++++++++++++++++++++-
>>  1 file changed, 22 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/video/fbdev/simplefb.c b/drivers/video/fbdev/simplefb.c
>> index 868099a..e381a53 100644
>> --- a/drivers/video/fbdev/simplefb.c
>> +++ b/drivers/video/fbdev/simplefb.c
>> @@ -27,6 +27,7 @@
>>  #include <linux/platform_data/simplefb.h>
>>  #include <linux/platform_device.h>
>>  #include <linux/clk-provider.h>
>> +#include <linux/of_platform.h>
>>
>>  static struct fb_fix_screeninfo simplefb_fix = {
>>         .id             = "simple",
>> @@ -390,7 +391,27 @@ static struct platform_driver simplefb_driver = {
>>         .probe = simplefb_probe,
>>         .remove = simplefb_remove,
>>  };
>> -module_platform_driver(simplefb_driver);
>> +
>> +static int __init simplefb_init(void)
>> +{
>> +       int ret;
>> +       struct device_node __maybe_unused *np;
>> +
>> +       ret = platform_driver_register(&simplefb_driver);
>> +       if (ret)
>> +               return ret;
>> +
>> +#ifdef CONFIG_OF
>> +       for_each_child_of_node(of_chosen, np) {
>> +               if (of_device_is_compatible(np, "simple-framebuffer"))
>> +                       of_platform_device_create(np, NULL, NULL);
>> +       }
>> +#endif
> 
> Nit: Kind of ugly. This should work instead:
> 
>         if (IS_ENABLED(CONFIG_OF_PLATFORM) && of_chosen) {
>                 for_each_child_of_node(of_chosen, np)
>                         if (of_device_is_compatible(np, "simple-framebuffer"))
>                                 of_platform_device_create(np, NULL, NULL);
>         }
> 
> And move the forward declaration of of_chosen in include/linux/of.h up
> 5 lines so that it is always declared. gcc will optimize it out, but
> it will still get properly syntax checked on every build.

Ok, fixed for v5.

Regards,

Hans