RE: [PATCH V2] drm/imx: parallel-display: Remove bus flags check in imx_pd_bridge_atomic_check()

[Christoph Niedermaier <cniedermaier@dh-electronics.com>]

From: Max Krummenacher [mailto:max.oss.09@gmail.com]
Sent: Wednesday, February 9, 2022 10:38 AM
>> If display timings were read from the devicetree using
>> of_get_display_timing() and pixelclk-active is defined
>> there, the flag DISPLAY_FLAGS_SYNC_POSEDGE/NEGEDGE is
>> automatically generated. Through the function
>> drm_bus_flags_from_videomode() e.g. called in the
>> panel-simple driver this flag got into the bus flags,
>> but then in imx_pd_bridge_atomic_check() the bus flag
>> check failed and will not initialize the display. The
>> original commit fe141cedc433 does not explain why this
>> check was introduced. So remove the bus flags check,
>> because it stops the initialization of the display with
>> valid bus flags.
>>
>> Fixes: fe141cedc433 ("drm/imx: pd: Use bus format/flags provided by the bridge when available")
>> Signed-off-by: Christoph Niedermaier <cniedermaier@dh-electronics.com>
>> Cc: Marek Vasut <marex@denx.de>
>> Cc: Boris Brezillon <boris.brezillon@collabora.com>
>> Cc: Philipp Zabel <p.zabel@pengutronix.de>
>> Cc: David Airlie <airlied@linux.ie>
>> Cc: Daniel Vetter <daniel@ffwll.ch>
>> Cc: Shawn Guo <shawnguo@kernel.org>
>> Cc: Sascha Hauer <s.hauer@pengutronix.de>
>> Cc: Pengutronix Kernel Team <kernel@pengutronix.de>
>> Cc: Fabio Estevam <festevam@gmail.com>
>> Cc: NXP Linux Team <linux-imx@nxp.com>
>> Cc: linux-arm-kernel@lists.infradead.org
>> To: dri-devel@lists.freedesktop.org
>> ---
>> V2: - Add Boris to the Cc list
>> ---
>>  drivers/gpu/drm/imx/parallel-display.c | 8 --------
>>  1 file changed, 8 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/imx/parallel-display.c b/drivers/gpu/drm/imx/parallel-display.c
>> index a8aba0141ce7..06cb1a59b9bc 100644
>> --- a/drivers/gpu/drm/imx/parallel-display.c
>> +++ b/drivers/gpu/drm/imx/parallel-display.c
>> @@ -217,14 +217,6 @@ static int imx_pd_bridge_atomic_check(struct drm_bridge *bridge,
>>       if (!imx_pd_format_supported(bus_fmt))
>>               return -EINVAL;
>>
>> -     if (bus_flags &
>> -         ~(DRM_BUS_FLAG_DE_LOW | DRM_BUS_FLAG_DE_HIGH |
>> -           DRM_BUS_FLAG_PIXDATA_DRIVE_POSEDGE |
>> -           DRM_BUS_FLAG_PIXDATA_DRIVE_NEGEDGE)) {
>> -             dev_warn(imxpd->dev, "invalid bus_flags (%x)\n", bus_flags);
>> -             return -EINVAL;
>> -     }
>> -
>>       bridge_state->output_bus_cfg.flags = bus_flags;
>>       bridge_state->input_bus_cfg.flags = bus_flags;
>>       imx_crtc_state->bus_flags = bus_flags;
> 
> Tested on a Colibri iMX6DL with a panel-dpi based panel.
> 
> Tested-by: Max Krummenacher <max.krummenacher@toradex.com>

I still ask myself why this bus flag check is in the code.
Is there a reason not to remove that?

Regards
Christoph
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