linux-kernel - Re: [PATCH v2] drm: tilcdc: implement palette loading for rev1

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Date:   Mon, 24 Oct 2016 11:47:31 +0200
From:   Bartosz Golaszewski <bgolaszewski@...libre.com>
To:     Jyri Sarha <jsarha@...com>
Cc:     Tomi Valkeinen <tomi.valkeinen@...com>,
        David Airlie <airlied@...ux.ie>,
        Kevin Hilman <khilman@...libre.com>,
        Michael Turquette <mturquette@...libre.com>,
        Sekhar Nori <nsekhar@...com>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-drm <dri-devel@...ts.freedesktop.org>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Peter Ujfalusi <peter.ujfalusi@...com>
Subject: Re: [PATCH v2] drm: tilcdc: implement palette loading for rev1

2016-10-24 11:25 GMT+02:00 Jyri Sarha <jsarha@...com>:
> On 10/24/16 11:43, Bartosz Golaszewski wrote:
>> Revision 1 of the IP doesn't work if we don't load the palette (even
>> if it's not used, which is the case for the RGB565 format).
>>
>> Add a function called from tilcdc_crtc_enable() which performs all
>> required actions if we're dealing with a rev1 chip.
>>
>> Signed-off-by: Bartosz Golaszewski <bgolaszewski@...libre.com>
>> ---
>> v1 -> v2:
>> - only allocate dma memory for revision 1
>>
>
>
> Is it enough to load the palette only once? What if lcdc is powered down
> by power management in the middle?
>
> I think you should reinit the completion struct at least in
> tilcdc_pm_resume(), if not in tilcdc_crtc_disable().
>
> Cheers,
> Jyri
>

Hi Jyri,

I ran the following test:

- tilcdc_crtc_enable() was called on device init
- ran modetest -M tilcdc -s 26:800x600@...6 and quit
- waited for the screen to go blank
- tilcdc_crtc_disable() was called
- ran modetest again
- tilcdc_crtc_enable() was called again, this time without calling
tilcdc_crtc_load_palette()
- color bar still correctly displayed

Seems like it's only needed once.

Thanks,
Bartosz