Re: [PATCH v3 4/4] drm/panel: simple: add bus-format support for panel-dpi

[Max Krummenacher]

Hi Aradhya

Thanks for the review.

Rob's comment requires changes to panel-common.yaml in order for this to get in.
I think I know what needs to be done.

However, as there is no agreement on bus-format in the first place there is no
point in sorting that out now.

Regards
Max

On Wed, Aug 3, 2022 at 8:45 AM Aradhya Bhatia <a-bhatia1@xxxxxx> wrote:
>
>
>
> On 28-Jun-22 23:48, Max Krummenacher wrote:
> > From: Max Krummenacher <max.krummenacher@xxxxxxxxxxx>
> >
> > Evaluate the device tree bus-format property to set bus_format for
> > a 'panel-dpi' panel. Additionally infer the bpc value from the
> > given bus-format.
> >
> > Valid values for bus-format are found in:
> > <include/dt-bindings/display/dt-media-bus-format.h>
> >
> > This completes the addition of panel-dpi to completely specify
> > a panel-simple panel from the device tree.
> >
> > Signed-off-by: Max Krummenacher <max.krummenacher@xxxxxxxxxxx>
> >
> > ---
> >
> > Changes in v3:
> > - Moved the bus-format property under the port/endpoint node as
> >    suggested by Rob Herring
> >
> > Changes in v2:
> > - Fix errors found by dt_binding_check
> >
> >   drivers/gpu/drm/panel/panel-simple.c | 49 ++++++++++++++++++++++++++++
> >   1 file changed, 49 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/panel/panel-simple.c b/drivers/gpu/drm/panel/panel-simple.c
> > index 4a2e580a2f7b..f1a457f1069e 100644
> > --- a/drivers/gpu/drm/panel/panel-simple.c
> > +++ b/drivers/gpu/drm/panel/panel-simple.c
> > @@ -21,9 +21,11 @@
> >    * DEALINGS IN THE SOFTWARE.
> >    */
> >
> > +#include <dt-bindings/display/dt-media-bus-format.h>
> >   #include <linux/delay.h>
> >   #include <linux/gpio/consumer.h>
> >   #include <linux/module.h>
> > +#include <linux/of_graph.h>
> >   #include <linux/of_platform.h>
> >   #include <linux/platform_device.h>
> >   #include <linux/pm_runtime.h>
> > @@ -449,10 +451,12 @@ static int panel_dpi_probe(struct device *dev,
> >                          struct panel_simple *panel)
> >   {
> >       struct display_timing *timing;
> > +     struct device_node *endpoint;
> >       const struct device_node *np;
> >       struct panel_desc *desc;
> >       unsigned int bus_flags;
> >       struct videomode vm;
> > +     u32 bus_format;
> >       int ret;
> >
> >       np = dev->of_node;
> > @@ -477,6 +481,51 @@ static int panel_dpi_probe(struct device *dev,
> >       of_property_read_u32(np, "width-mm", &desc->size.width);
> >       of_property_read_u32(np, "height-mm", &desc->size.height);
> >
> > +     endpoint = of_graph_get_endpoint_by_regs(np, -1, -1);
> > +     if (endpoint &&
> > +         !of_property_read_u32(endpoint, "bus-format", &bus_format)) {
> > +             /* infer bpc from bus-format */
> > +             switch (bus_format) {
> > +             case DT_MEDIA_BUS_FMT_RGB565_1X16:
> > +                     desc->bus_format = MEDIA_BUS_FMT_RGB565_1X16;
> > +                     desc->bpc = 6;
> > +                     break;
> > +             case DT_MEDIA_BUS_FMT_RGB666_1X18:
> > +                     desc->bus_format = MEDIA_BUS_FMT_RGB666_1X18;
> > +                     desc->bpc = 6;
> > +                     break;
> > +             case DT_MEDIA_BUS_FMT_RGB666_1X24_CPADHI:
> > +                     desc->bus_format = MEDIA_BUS_FMT_RGB666_1X24_CPADHI;
> > +                     desc->bpc = 6;
> > +                     break;
> > +             case DT_MEDIA_BUS_FMT_BGR888_1X24:
> > +                     desc->bus_format = MEDIA_BUS_FMT_BGR888_1X24;
> > +                     desc->bpc = 8;
> > +                     break;
> > +             case DT_MEDIA_BUS_FMT_GBR888_1X24:
> > +                     desc->bus_format = MEDIA_BUS_FMT_GBR888_1X24;
> > +                     desc->bpc = 8;
> > +                     break;
> > +             case DT_MEDIA_BUS_FMT_RBG888_1X24:
> > +                     desc->bus_format = MEDIA_BUS_FMT_RBG888_1X24;
> > +                     desc->bpc = 8;
> > +                     break;
> > +             case DT_MEDIA_BUS_FMT_RGB888_1X24:
> > +                     desc->bus_format = MEDIA_BUS_FMT_RGB888_1X24;
> > +                     desc->bpc = 8;
> > +                     break;
> > +             case DT_MEDIA_BUS_FMT_RGB888_1X32_PADHI:
> > +                     desc->bus_format = MEDIA_BUS_FMT_RGB888_1X32_PADHI;
> > +                     desc->bpc = 8;
> > +                     break;
> > +             default:
> > +                     dev_err(dev, "%pOF: unknown bus-format property\n", np);
> > +                     return -EINVAL;
> > +             }
> > +     }
> > +
> > +     of_node_put(endpoint);
> > +
> >       /* Extract bus_flags from display_timing */
> >       bus_flags = 0;
> >       vm.flags = timing->flags;
>
> I understand that it is important to add a bus-format property for dumb
> dpi-panels, and I agree with the implementation in the patch-set.
>
> However,
> I do not yet fully understand Rob's comments on the dt-bindings side of
> patch set (patch 1/4) and what consequences it may cause if that remains
> unresolved.
>
> Given that the bus-format property gets added, I do not see any concern
> with the panel-simple driver patch.
>
>
> Reviewed-by: Aradhya Bhatia <a-bhatia1@xxxxxx>
>
>
> Regards
> Aradhya