[PATCH 1/2] of: Create platform devices for OF framebuffers
Thomas Zimmermann
tzimmermann at suse.de
Thu Apr 14 03:58:26 AEST 2022
Hi
Am 13.04.22 um 14:51 schrieb Rob Herring:
> On Wed, Apr 13, 2022 at 4:24 AM Thomas Zimmermann <tzimmermann at suse.de> wrote:
>>
>> Create a platform device for each OF-declared framebuffer and have
>> offb bind to these devices. Allows for real hot-unplugging and other
>> drivers besides offb.
>>
>> Originally, offb created framebuffer devices while initializing its
>> module by parsing the OF device tree. No actual Linux device was set
>> up. This tied OF framebuffers to offb and makes writing other drivers
>> for the OF framebuffers complicated. The absence of a Linux device
>> prevented real hot-unplugging. Adding a distinct platform device for
>> each OF framebuffer solves both problems. Specifically, a DRM drivers
>> can now provide graphics output with modern userspace.
>>
>> Some of the offb init code is now located in the OF initialization.
>> There's now also an implementation of of_platform_default_populate_init(),
>> which was missing before. The OF side creates different devices for
>> either OF display nodes or bootx displays as they require different
>> handling by the driver. The offb drivers picks up each type of device
>> and runs the appropriate fbdev initialization.
>>
>> Tested with OF display nodes on qemu's ppc64le target.
>>
>> Signed-off-by: Thomas Zimmermann <tzimmermann at suse.de>
>> ---
>> drivers/of/platform.c | 73 ++++++++++++++++++++++++++--
>> drivers/video/fbdev/offb.c | 98 +++++++++++++++++++++++++-------------
>> 2 files changed, 134 insertions(+), 37 deletions(-)
>>
>> diff --git a/drivers/of/platform.c b/drivers/of/platform.c
>> index a16b74f32aa9..4c63b9a73587 100644
>> --- a/drivers/of/platform.c
>> +++ b/drivers/of/platform.c
>> @@ -447,6 +447,60 @@ int of_platform_bus_probe(struct device_node *root,
>> }
>> EXPORT_SYMBOL(of_platform_bus_probe);
>>
>> +static int __init of_platform_populate_framebuffers(void)
>> +{
>> + struct device_node *boot_display = NULL;
>> + struct device_node *node;
>> + struct platform_device *dev;
>> + int ret;
>> +
>> + node = of_get_compatible_child(of_chosen, "simple-framebuffer");
>> + of_platform_device_create(node, NULL, NULL);
>> + of_node_put(node);
>> +
>
> The rest is PPC only, so bail out here if !PPC.
>
>> + /* Check if we have a MacOS display without a node spec */
>> + if (of_get_property(of_chosen, "linux,bootx-noscreen", NULL)) {
>> + /*
>> + * The old code tried to work out which node was the MacOS
>> + * display based on the address. I'm dropping that since the
>> + * lack of a node spec only happens with old BootX versions
>> + * (users can update) and with this code, they'll still get
>> + * a display (just not the palette hacks).
>> + */
>> + dev = platform_device_alloc("bootx-noscreen", 0);
>> + if (WARN_ON(!dev))
>> + return -ENOMEM;
>> + ret = platform_device_add(dev);
>> + if (WARN_ON(ret)) {
>> + platform_device_put(dev);
>> + return ret;
>> + }
>> + }
>> +
>> + /*
>> + * For OF framebuffers, first create the device for the boot display,
>> + * then for the other framebuffers. Only fail for the boot display;
>> + * ignore errors for the rest.
>> + */
>> + for_each_node_by_type(node, "display") {
>> + if (!of_get_property(node, "linux,opened", NULL) ||
>> + !of_get_property(node, "linux,boot-display", NULL))
>> + continue;
>> + dev = of_platform_device_create(node, "of-display", NULL);
>> + if (WARN_ON(!dev))
>> + return -ENOMEM;
>> + boot_display = node;
>> + break;
>> + }
>> + for_each_node_by_type(node, "display") {
>> + if (!of_get_property(node, "linux,opened", NULL) || node == boot_display)
>> + continue;
>> + of_platform_device_create(node, "of-display", NULL);
>> + }
>> +
>> + return 0;
>> +}
>> +
>> /**
>> * of_platform_populate() - Populate platform_devices from device tree data
>> * @root: parent of the first level to probe or NULL for the root of the tree
>> @@ -541,9 +595,7 @@ static int __init of_platform_default_populate_init(void)
>> of_node_put(node);
>> }
>>
>> - node = of_get_compatible_child(of_chosen, "simple-framebuffer");
>> - of_platform_device_create(node, NULL, NULL);
>> - of_node_put(node);
>> + of_platform_populate_framebuffers();
>>
>> /* Populate everything else. */
>> of_platform_default_populate(NULL, NULL, NULL);
>
> I'm pretty sure it's just this call that's the problem for PPC though
> none of the above existed when adding this caused a regression. Can we
> remove the ifdef and just make this call conditional on
> !IS_ENABLED(CONFIG_PPC).
Together with the changes in of_platform_populate_framebuffers(), the
code is more or less an "if-else" depending on PPC. I'll drop
of_platform_populate_framebuffers() from the patch and make a separate
implementation of of_platform_default_populate_init for PPC. Seems like
the easiest solution to me.
Best regards
Thomas
>
>
>> @@ -551,6 +603,20 @@ static int __init of_platform_default_populate_init(void)
>> return 0;
>> }
>> arch_initcall_sync(of_platform_default_populate_init);
>> +#else
>> +static int __init of_platform_default_populate_init(void)
>> +{
>> + device_links_supplier_sync_state_pause();
>> +
>> + if (!of_have_populated_dt())
>> + return -ENODEV;
>> +
>> + of_platform_populate_framebuffers();
>> +
>> + return 0;
>> +}
>> +arch_initcall_sync(of_platform_default_populate_init);
>> +#endif
>>
>> static int __init of_platform_sync_state_init(void)
>> {
>> @@ -558,7 +624,6 @@ static int __init of_platform_sync_state_init(void)
>> return 0;
>> }
>> late_initcall_sync(of_platform_sync_state_init);
>> -#endif
>>
>> int of_platform_device_destroy(struct device *dev, void *data)
>> {
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Ivo Totev
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