From: Jagan Teki <jagan@amarulasolutions.com>
To: Maxime Ripard <maxime.ripard@bootlin.com>
Cc: bbrezillon@kernel.org,
dri-devel <dri-devel@lists.freedesktop.org>,
Paul Kocialkowski <paul.kocialkowski@bootlin.com>,
Chen-Yu Tsai <wens@csie.org>, Sean Paul <seanpaul@chromium.org>,
Thomas Petazzoni <thomas.petazzoni@bootlin.com>,
Jagan Teki <jagan@openedev.com>,
linux-arm-kernel <linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH v2 3/9] drm/sun4i: dsi: Change the start delay calculation
Date: Thu, 7 Mar 2019 23:24:01 +0530 [thread overview]
Message-ID: <CAMty3ZD8+=7im113mBWDZaR7D=fCZSxeHnwfKoJ5ZjqYwS56dA@mail.gmail.com> (raw)
In-Reply-To: <6e5f72e68f47ca0223877464bf12f0c3f3978de8.1549619502.git-series.maxime.ripard@bootlin.com>
Hi Maxime,
On Fri, Feb 8, 2019 at 3:23 PM Maxime Ripard <maxime.ripard@bootlin.com> wrote:
>
> The current calculation for the video start delay in the current DSI driver
> is that it is the total vertical size, minus the front porch and sync length,
> plus 1. This equals to the active vertical size plus the back porch plus 1.
>
> That 1 is coming in the Allwinner BSP from an variable that is set to 1.
> However, if we look at the Allwinner BSP more closely, and especially in
> the "legacy" code for the display (in drivers/video/sunxi/legacy/), we can
> see that this variable is actually computed from the porches and the sync
> minus 10, clamped between 8 and 100.
>
> This fixes the start delay symptom we've seen on some panels (vblank
> timeouts with vertical white stripes at the bottom of the panel).
>
> Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>
> ---
> drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
> index 380fc527a707..9471fa695ec7 100644
> --- a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
> +++ b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
> @@ -357,7 +357,9 @@ static void sun6i_dsi_inst_init(struct sun6i_dsi *dsi,
> static u16 sun6i_dsi_get_video_start_delay(struct sun6i_dsi *dsi,
> struct drm_display_mode *mode)
> {
> - return mode->vtotal - (mode->vsync_end - mode->vdisplay) + 1;
> + u16 start = clamp(mode->vtotal - mode->vdisplay - 10, 8, 100);
> +
> + return mode->vtotal - (mode->vsync_end - mode->vdisplay) + start;
> }
As you stated in commit message about result as "active vertical size
+ Back porch" which indeed correct in reverse way of previous code.
but the change seems incorrect to me.
=> mode->vtotal - (mode->vsync_end - mode->vdisplay) + start
=> mode->vtotal - (mode->vsync_end - mode->vdisplay) + (mode->vtotal -
mode->vdisplay) # bypass 10 for now
=> mode->vtotal - mode->vsync_end + mode->vdisplay + mode->vtotal -
mode->vdisplay
=> (mode->vtotal - mode->vsync_end) + mode->vtotal
=> Back porch + mode->vtotal
but not
=> Back porch + mode->vdisplay
Let me know if I'm wrong?
_______________________________________________
dri-devel mailing list
dri-devel@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/dri-devel
next prev parent reply other threads:[~2019-03-07 17:54 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-02-08 9:53 [PATCH v2 0/9] drm/sun4i: dsi: Add burst mode support Maxime Ripard
2019-02-08 9:53 ` [PATCH v2 1/9] fixup! ARM: dts: sun8i-a33: bridgemate: Enable display support Maxime Ripard
2019-02-08 9:57 ` Maxime Ripard
2019-02-08 9:53 ` [PATCH v2 2/9] drm/sun4i: dsi: Restrict DSI tcon clock divider Maxime Ripard
2019-02-08 9:53 ` [PATCH v2 3/9] drm/sun4i: dsi: Change the start delay calculation Maxime Ripard
2019-03-07 17:54 ` Jagan Teki [this message]
2019-03-11 14:12 ` Maxime Ripard
2019-03-11 14:37 ` Jagan Teki
2019-03-19 10:18 ` Maxime Ripard
2019-02-08 9:53 ` [PATCH v2 4/9] drm/sun4i: dsi: Enforce boundaries on the start delay Maxime Ripard
2019-02-08 9:53 ` [PATCH v2 5/9] drm/sun4i: dsi: Fix front vs back porch calculation Maxime Ripard
2019-02-08 9:53 ` [PATCH v2 6/9] drm/sun4i: dsi: Fix DRQ calculation Maxime Ripard
2019-02-08 9:53 ` [PATCH v2 7/9] drm/sun4i: dsi: Rework a bit the hblk calculation Maxime Ripard
2019-02-08 9:53 ` [PATCH v2 8/9] drm/sun4i: dsi: Add burst support Maxime Ripard
2019-02-08 9:53 ` [PATCH v2 9/9] drm/panel: Add Ronbo RB070D30 panel Maxime Ripard
2019-02-08 12:24 ` Konstantin Sudakov
2019-02-11 14:40 ` Maxime Ripard
2019-02-08 18:21 ` Sam Ravnborg
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to='CAMty3ZD8+=7im113mBWDZaR7D=fCZSxeHnwfKoJ5ZjqYwS56dA@mail.gmail.com' \
--to=jagan@amarulasolutions.com \
--cc=bbrezillon@kernel.org \
--cc=dri-devel@lists.freedesktop.org \
--cc=jagan@openedev.com \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=maxime.ripard@bootlin.com \
--cc=paul.kocialkowski@bootlin.com \
--cc=seanpaul@chromium.org \
--cc=thomas.petazzoni@bootlin.com \
--cc=wens@csie.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).