[linux-sunxi] [PATCH 3/3] Revert "drm/sun4i: dsi: Rework a bit the hblk calculation"
jagan at amarulasolutions.com
Thu Oct 3 04:23:54 UTC 2019
On Tue, Oct 1, 2019 at 1:34 PM Icenowy Zheng <icenowy at aosc.io> wrote:
> This reverts commit 62e7511a4f4dcf07f753893d3424decd9466c98b.
> This commit, although claimed as a refactor, in fact changed the
> By expanding the original formula, we can find that the const 10 is not
> substracted, instead it's added to the value (because 10 is negative
> when calculating hsa, and hsa itself is negative when calculating hblk).
> This breaks the similar pattern to other formulas, so restoring the
> original formula is more proper.
> Signed-off-by: Icenowy Zheng <icenowy at aosc.io>
> drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c | 9 ++-------
> 1 file changed, 2 insertions(+), 7 deletions(-)
> diff --git a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
> index 2d3e822a7739..cb5fd19c0d0d 100644
> --- a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
> +++ b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
> @@ -577,14 +577,9 @@ static void sun6i_dsi_setup_timings(struct sun6i_dsi *dsi,
> (mode->hsync_start - mode->hdisplay) * Bpp - HFP_PACKET_OVERHEAD);
> - * The blanking is set using a sync event (4 bytes)
> - * and a blanking packet (4 bytes + payload + 2
> - * bytes). Its minimal size is therefore 10 bytes.
> + * hblk seems to be the line + porches length.
> -#define HBLK_PACKET_OVERHEAD 10
> - hblk = max((unsigned int)HBLK_PACKET_OVERHEAD,
> - (mode->htotal - (mode->hsync_end - mode->hsync_start)) * Bpp -
> - HBLK_PACKET_OVERHEAD);
> + hblk = mode->htotal * Bpp - hsa;
The original formula is correct according to BSP  and work with my
panels which I have tested before. May be the horizontal timings on
panels you have leads to negative value.
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