Re: [PATCH v3 7/7] drm/vc4: kms: Don't disable the muxing of an active CRTC

[Thomas Zimmermann <tzimmermann@suse.de>]

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Hi

Am 19.11.20 um 15:32 schrieb Maxime Ripard:
> On Thu, Nov 19, 2020 at 10:12:43AM +0100, Thomas Zimmermann wrote:
>> Hi
>>
>> Am 05.11.20 um 14:56 schrieb Maxime Ripard:
>>> The current HVS muxing code will consider the CRTCs in a given state to
>>> setup their muxing in the HVS, and disable the other CRTCs muxes.
>>>
>>> However, it's valid to only update a single CRTC with a state, and in this
>>> situation we would mux out a CRTC that was enabled but left untouched by
>>> the new state.
>>>
>>> Fix this by setting a flag on the CRTC state when the muxing has been
>>> changed, and only change the muxing configuration when that flag is there.
>>>
>>> Fixes: 87ebcd42fb7b ("drm/vc4: crtc: Assign output to channel automatically")
>>> Reviewed-by: Hoegeun Kwon <hoegeun.kwon@samsung.com>
>>> Tested-by: Hoegeun Kwon <hoegeun.kwon@samsung.com>
>>> Signed-off-by: Maxime Ripard <maxime@cerno.tech>
>>> ---
>>>    drivers/gpu/drm/vc4/vc4_drv.h |  1 +
>>>    drivers/gpu/drm/vc4/vc4_kms.c | 82 ++++++++++++++++++++---------------
>>>    2 files changed, 48 insertions(+), 35 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/vc4/vc4_drv.h b/drivers/gpu/drm/vc4/vc4_drv.h
>>> index 014113823647..325b53ff11b3 100644
>>> --- a/drivers/gpu/drm/vc4/vc4_drv.h
>>> +++ b/drivers/gpu/drm/vc4/vc4_drv.h
>>> @@ -524,6 +524,7 @@ struct vc4_crtc_state {
>>>    	struct drm_mm_node mm;
>>>    	bool feed_txp;
>>>    	bool txp_armed;
>>> +	bool needs_muxing;
>>
>> Maybe rather 'update_muxing'.
>>
>> More generally, I'd separate fields that contain actual CRTC state, such
>> assigned_channel, from those that only contain transitional state during
>> update-commit, such as needs_muxing.
> 
> How would you separate them?
> 
> I'll use your other suggestions, thanks!

I'd put the transitional state at the end of the struct and put a 
comment above. Something like 'Transitional state below; only valid 
during atomic commits'.

Best regards
Thomas

> Maxime
> 

-- 
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Felix Imendörffer

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