linux-kernel - Re: [PATCH v5 1/2] drm: tilcdc: implement palette loading for rev1

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Message-ID: <CAMpxmJUh8KypU_-HtGa+ieCpO46FBME8_VQCJvYkCjFhmuVWgg@mail.gmail.com>
Date:   Wed, 16 Nov 2016 12:34:18 +0100
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>,
        Peter Ujfalusi <peter.ujfalusi@...com>,
        arm-soc <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v5 1/2] drm: tilcdc: implement palette loading for rev1

2016-10-31 17:05 GMT+01:00 Jyri Sarha <jsarha@...com>:
> On 10/31/16 16:19, 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.
>>
>
> There is only one thing I do not like about this patch. The palette
> loading is done so late that the frame buffer address are already placed
> into DMA base and ceiling registers, and we need to read them from the
> registers and restore them back after the palette loading.
>
> Could you try if the palette loading function works without trouble when
> called from tilcdc_pm_resume() before drm_atomic_helper_resume() call?
> If it does it would be cleaner in the sense that you could get rid off
> the old dma address restore code. You could reinit the completion always
> there right before the palette loading.
>
> If you can not get the above suggestion to work, then I can take this
> patch.
>

Hi Jyri,

the problem is that tilcdc_pm_resume() is not called when tilcdc is
initialized. We would have to have two calls in different places for
that to work.

>> +static void tilcdc_crtc_load_palette(struct drm_crtc *crtc)
>> +{
>> +     u32 dma_fb_base, dma_fb_ceiling, raster_ctl;
>> +     struct tilcdc_crtc *tilcdc_crtc;
>> +     struct drm_device *dev;
>> +     u16 *first_entry;
>> +
>> +     dev = crtc->dev;
>> +     tilcdc_crtc = to_tilcdc_crtc(crtc);
>> +     first_entry = tilcdc_crtc->palette_base;
>> +
>> +     *first_entry = TILCDC_REV1_PALETTE_FIRST_ENTRY;
>> +
>> +     dma_fb_base = tilcdc_read(dev, LCDC_DMA_FB_BASE_ADDR_0_REG);
>> +     dma_fb_ceiling = tilcdc_read(dev, LCDC_DMA_FB_CEILING_ADDR_0_REG);
>> +     raster_ctl = tilcdc_read(dev, LCDC_RASTER_CTRL_REG);
>> +
>> +     /* Tell the LCDC where the palette is located. */
>> +     tilcdc_write(dev, LCDC_DMA_FB_BASE_ADDR_0_REG,
>> +                  tilcdc_crtc->palette_dma_handle);
>> +     tilcdc_write(dev, LCDC_DMA_FB_CEILING_ADDR_0_REG,
>> +                  (u32)tilcdc_crtc->palette_dma_handle
>
> Just a nit pick, but I would put the plus sign to the end of the line
> above instead of the beginning of the line bellow. However,
> check_patch.pl does not complain about this so I guess I can accept it too.
>
>> +                             + TILCDC_REV1_PALETTE_SIZE - 1);
>> +

I'll fix that in v6.

Thanks,
Bartosz Golaszewski