Hi Stefan,
Thankk you for the patch.
On Wednesday, 12 September 2018 21:32:15 EEST Stefan Agner wrote:
> The DRM bus flags conveys additional information on pixel data on
> the bus. All currently available bus flags might be of interest for
> a bridge. In the case at hand a dumb VGA bridge needs a specific
> data enable polarity (DRM_BUS_FLAG_DE_LOW).
>
> Replace the sampling_edge field with input_bus_flags and allow all
> currently documented bus flags.
>
> This changes the perspective from sampling side to the driving
> side for the currently supported flags. We assume that the sampling
> edge is always the opposite of the driving edge (hence we need to
> invert the DRM_BUS_FLAG_PIXDATA_[POS|NEG]EDGE flags). This is an
> assumption we already make for displays. For all we know it is a
> safe assumption for bridges too.
Please don't, that will get confusing very quickly. Flag names such as
DRM_BUS_FLAG_PIXDATA_NEGEDGE don't mention sampling or driving. There's only a
small comment next to their definition, which will easily be overlooked. I'd
rather update the definition to cover both sampling and driving, and document
the input_bus_flags field to explain that all flags refer to sampling.
> Signed-off-by: Stefan Agner <stefan@xxxxxxxx>
> ---
> drivers/gpu/drm/bridge/dumb-vga-dac.c | 6 +++---
> include/drm/drm_bridge.h | 11 +++++------
> 2 files changed, 8 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/gpu/drm/bridge/dumb-vga-dac.c
> b/drivers/gpu/drm/bridge/dumb-vga-dac.c index 9b706789a341..d5aa0f931ef2
> 100644
> --- a/drivers/gpu/drm/bridge/dumb-vga-dac.c
> +++ b/drivers/gpu/drm/bridge/dumb-vga-dac.c
> @@ -234,7 +234,7 @@ static int dumb_vga_remove(struct platform_device *pdev)
> */
> static const struct drm_bridge_timings default_dac_timings = {
> /* Timing specifications, datasheet page 7 */
> - .sampling_edge = DRM_BUS_FLAG_PIXDATA_POSEDGE,
> + .input_bus_flags = DRM_BUS_FLAG_PIXDATA_NEGEDGE,
> .setup_time_ps = 500,
> .hold_time_ps = 1500,
> };
> @@ -245,7 +245,7 @@ static const struct drm_bridge_timings
> default_dac_timings = { */
> static const struct drm_bridge_timings ti_ths8134_dac_timings = {
> /* From timing diagram, datasheet page 9 */
> - .sampling_edge = DRM_BUS_FLAG_PIXDATA_POSEDGE,
> + .input_bus_flags = DRM_BUS_FLAG_PIXDATA_NEGEDGE,
> /* From datasheet, page 12 */
> .setup_time_ps = 3000,
> /* I guess this means latched input */
> @@ -258,7 +258,7 @@ static const struct drm_bridge_timings
> ti_ths8134_dac_timings = { */
> static const struct drm_bridge_timings ti_ths8135_dac_timings = {
> /* From timing diagram, datasheet page 14 */
> - .sampling_edge = DRM_BUS_FLAG_PIXDATA_POSEDGE,
> + .input_bus_flags = DRM_BUS_FLAG_PIXDATA_NEGEDGE,
> /* From datasheet, page 16 */
> .setup_time_ps = 2000,
> .hold_time_ps = 500,
> diff --git a/include/drm/drm_bridge.h b/include/drm/drm_bridge.h
> index bd850747ce54..45e90f4b46c3 100644
> --- a/include/drm/drm_bridge.h
> +++ b/include/drm/drm_bridge.h
> @@ -244,14 +244,13 @@ struct drm_bridge_funcs {
> */
> struct drm_bridge_timings {
> /**
> - * @sampling_edge:
> + * @input_bus_flags:
> *
> - * Tells whether the bridge samples the digital input signal
> - * from the display engine on the positive or negative edge of the
> - * clock, this should reuse the DRM_BUS_FLAG_PIXDATA_[POS|NEG]EDGE
> - * bitwise flags from the DRM connector (bit 2 and 3 valid).
> + * Additional settings this bridge requires for the pixel data on
> + * the input bus (e.g. pixel signal polarity). See also
> + * &drm_display_info->bus_flags.
> */
> - u32 sampling_edge;
> + u32 input_bus_flags;
> /**
> * @setup_time_ps:
> *
--
Regards,
Laurent Pinchart
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