Re: [PATCH] drm/sun4i: fix HSYNC and VSYNC polarity
From: Giulio Benetti
Date: Thu Dec 13 2018 - 06:58:58 EST
Il 13/12/2018 04:08, Jonathan Liu ha scritto:
Hi Giulio,
On Wed, 12 Dec 2018 at 04:20, Giulio Benetti
<giulio.benetti@xxxxxxxxxxxxxxxx> wrote:
Hi Jonathan,
Il 11/12/2018 11:49, Jonathan Liu ha scritto:
Hi Giulio,
On Thu, 6 Dec 2018 at 22:00, Giulio Benetti
<giulio.benetti@xxxxxxxxxxxxxxxx> wrote:
Hi Jonathan,
Il 06/12/2018 08:29, Jonathan Liu ha scritto:
Hi Giulio,
On Thu, 15 Feb 2018 at 17:54, Giulio Benetti
<giulio.benetti@xxxxxxxxxxxxxxxx> wrote:
Differently from other Lcd signals, HSYNC and VSYNC signals
result inverted if their bits are cleared to 0.
Invert their settings of IO_POL register.
Signed-off-by: Giulio Benetti <giulio.benetti@xxxxxxxxxxxxxxxx>
---
drivers/gpu/drm/sun4i/sun4i_tcon.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/sun4i/sun4i_tcon.c b/drivers/gpu/drm/sun4i/sun4i_tcon.c
index 3c15cf2..aaf911a 100644
--- a/drivers/gpu/drm/sun4i/sun4i_tcon.c
+++ b/drivers/gpu/drm/sun4i/sun4i_tcon.c
@@ -389,10 +389,10 @@ static void sun4i_tcon0_mode_set_rgb(struct sun4i_tcon *tcon,
SUN4I_TCON0_BASIC3_H_SYNC(hsync));
/* Setup the polarity of the various signals */
- if (!(mode->flags & DRM_MODE_FLAG_PHSYNC))
+ if (mode->flags & DRM_MODE_FLAG_PHSYNC)
val |= SUN4I_TCON0_IO_POL_HSYNC_POSITIVE;
- if (!(mode->flags & DRM_MODE_FLAG_PVSYNC))
+ if (mode->flags & DRM_MODE_FLAG_PVSYNC)
val |= SUN4I_TCON0_IO_POL_VSYNC_POSITIVE;
regmap_update_bits(tcon->regs, SUN4I_TCON0_IO_POL_REG,
I am running Linux 4.19.6 and noticed with Olimex LCD-OLinuXino-7TS 7"
LCD touchscreen (Innolux AT070TN92) connected to Olimex
A20-OLinuXino-MICRO that the image does not display correctly after
this change.
The image is shifted to the right.
Reverting the change results in the image being displayed correctly on
the screen.
I have in the device tree a "panel" node with compatible =
"innolux,at070tn92" which uses the timings in
drivers/gpu/drm/panel/panel-simple.c.
Any ideas?
Checking Display Datasheet:
https://www.olimex.com/Products/Retired/A13-LCD7-TS/resources/S700-AT070TN92.pdf
Page 13 section 3.3.2 you can see it needs active low VS and HS.
You can refer to this Thread and check scope captures about VS and HS
versus TCON0_IOPOL register:
https://lists.freedesktop.org/archives/dri-devel/2018-January/163874.html
There should be something that wrongly sets one of these or both:
mode->flags |= DRM_MODE_FLAG_PHSYNC;
and/or
mode->flags |= DRM_MODE_FLAG_PVSYNC;
Checked in panel-simple.c but it's not there.
flags is 0 because it is not assigned in the struct definition for the panel.
I don't think it is 0, because otherwise IO_POL_REG wouldn't be set to
0x03000000 but to 0.
What is checked is exactly mode->flags, so the problem seems to be upstream.
This is my doubt, it seems mode->flags is not initialized or overriden
at a certain point, this is why I want to debug it with Jtag tomorrow.
mode->flags is correct, just checked with debugger.
If you look at the change made by your patch:
--- a/drivers/gpu/drm/sun4i/sun4i_tcon.c
+++ b/drivers/gpu/drm/sun4i/sun4i_tcon.c
@@ -389,10 +389,10 @@ static void sun4i_tcon0_mode_set_rgb(struct
sun4i_tcon *tcon,
SUN4I_TCON0_BASIC3_H_SYNC(hsync));
/* Setup the polarity of the various signals */
- if (!(mode->flags & DRM_MODE_FLAG_PHSYNC))
+ if (mode->flags & DRM_MODE_FLAG_PHSYNC)
val |= SUN4I_TCON0_IO_POL_HSYNC_POSITIVE;
- if (!(mode->flags & DRM_MODE_FLAG_PVSYNC))
+ if (mode->flags & DRM_MODE_FLAG_PVSYNC)
val |= SUN4I_TCON0_IO_POL_VSYNC_POSITIVE;
regmap_update_bits(tcon->regs, SUN4I_TCON0_IO_POL_REG,
If mode->flags is 0,
mode->flags is 0xa(DRM_MODE_FLAG_NHSYNC | DRM_MODE_FLAG_NVSYNC) by
default if not specified different in panel-simple.c so the signals must
be active LOW(IO_POL_REG = 0x00000000).
then before your change it would set
SUN4I_TCON0_IO_POL_HSYNC_POSITIVE and
SUN4I_TCON0_IO_POL_VSYNC_POSITIVE bits to 1 (resulting in 0x03000000).
And it was wrong, because as I've pointed you above, especially in the
Thread with all the scope captures, 0x03000000 means active HIGH
H/Vsync, while 0x00000000 means active LOW H/Vsync.
If mode->flags is not 0, then after your change it would not set
SUN4I_TCON0_IO_POL_HSYNC_POSITIVE and
SUN4I_TCON0_IO_POL_VSYNC_POSITIVE bits to 1 (resulting in 0x00000000).
If mode->flags is 0x5(DRM_MODE_FLAG_PHSYNC | DRM_MODE_FLAG_PVSYNC) i.e.
specified in panel-simple.c the signals must be active HIGH(IO_POL_REG =
0x03000000).
IO_POL_REG = 0x03000000 is active HIGH
IO_POL_REG = 0x00000000 is active LOW
as I've checked many times and rechecked today lot of times too.
Before this change, TCON0_IO_POL_REG would be 0x03000000 (both bits
set to 1) and image displays correctly > After this change, TCON0_IO_POL_REG is 0x00000000 (both bits set to 0)
and image doesn't display correctly.
Checked using "devmem2 0x01c0c088" on A20-OLinuXino-MICRO Rev J.
0x03000000 as I've triple checked with scope means Positive H/Vsync,
and 0x00000000 Negative H/VSync.
Please check on the Thread I've pointed you above where there are all
the links to the scope captures.
Are you completely sure you're using the correct panel?
Yes, I am sure I am using the correct panel. It has the following
marking on sticker:
AT070TN92V.X 89A070ZZ-0K1
At this point the only way to make it working is to specify
DRM_MODE_FLAG_NHSYNC | DRM_MODE_FLAG_NVSYNC in panel-simple.c and check.
Can you do a check and tell me if this solves the problem?
Also, it's not sufficient to submit a patch for that display in
panel-simple.c (IMHO) because I would check with scope if it is the way
wou're describing.
I don't know how to describe it better than this and IMHO the scope can
give us the final answer.
Hope I've been helpful.
Best regards
--
Giulio Benetti
CTO
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