diff mbox series

[08/12] drm/sun4i: sun6i_mipi_dsi: Refactor vertical video start delay

Message ID 20180927114850.24565-9-jagan@amarulasolutions.com
State Superseded, archived
Headers show
Series drm/sun4i: Allwinner A64 MIPI-DSI support | expand

Commit Message

Jagan Teki Sept. 27, 2018, 11:48 a.m. UTC
Accordingly to BPI-M64-bsp DE DSI code Video start delay
can be computed by subtracting total vertical timing with
front porch timing and with adding 1 delay line for TCON.

This patch simply add the start_delay logic from BPI-M64-bsp,
w/o this new computation, the DSI on A64 encounter vblank time out.

[CRTC:36:crtc-0] vblank wait timed out

Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>
---
 drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

Comments

Maxime Ripard Sept. 27, 2018, 5:14 p.m. UTC | #1
On Thu, Sep 27, 2018 at 05:18:46PM +0530, Jagan Teki wrote:
> Accordingly to BPI-M64-bsp DE DSI code Video start delay
> can be computed by subtracting total vertical timing with
> front porch timing and with adding 1 delay line for TCON.

This is what the current code is doing as well.

> This patch simply add the start_delay logic from BPI-M64-bsp,
> w/o this new computation, the DSI on A64 encounter vblank time out.
> 
> [CRTC:36:crtc-0] vblank wait timed out
>
> Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>
> ---
>  drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c | 12 +++++++++++-
>  1 file changed, 11 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
> index 9918fdb990ff..217db74c6dc3 100644
> --- a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
> +++ b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
> @@ -358,7 +358,17 @@ 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;
> +	u32 vfp = mode->vsync_start - mode->vdisplay;

Again, this is wrong and contrary to what your commit log is saying.

The Allwinner code has:

u32 vfp = panel->lcd_vt - panel->lcd_y - panel->lcd_vbp;
u32 dsi_start_delay = panel->lcd_vt - vfp + 1;

So, essentially:

vtotal - (vtotal - vdisplay - back porch) + 1

The backporch is hsync_total - hsync_end, so we end up, removing the
addition / removal of vtotal, with:

vdisplay - (vsync_total - vsync_end) + 1

The formula used there looks indeed different, but unlike what you
were saying.

> +	u32 start_delay;
> +
> +	start_delay = mode->vtotal - vfp + 1;
> +	if (start_delay > mode->vtotal)
> +		start_delay -= mode->vtotal;
> +
> +	if (!start_delay)
> +		start_delay = 1;
> +

I guess that it's actually the clamping that fixes thing. It should be
mentionned in your commit log.

Maxime
Jagan Teki Sept. 27, 2018, 5:33 p.m. UTC | #2
On Thu, Sep 27, 2018 at 10:44 PM Maxime Ripard
<maxime.ripard@bootlin.com> wrote:
>
> On Thu, Sep 27, 2018 at 05:18:46PM +0530, Jagan Teki wrote:
> > Accordingly to BPI-M64-bsp DE DSI code Video start delay
> > can be computed by subtracting total vertical timing with
> > front porch timing and with adding 1 delay line for TCON.
>
> This is what the current code is doing as well.

The current code
return mode->vtotal - (mode->vsync_end - mode->vdisplay) + 1;

(mode->vsync_end - mode->vdisplay) = front porch + sync

but I'm updating here only front porch.

>
> > This patch simply add the start_delay logic from BPI-M64-bsp,
> > w/o this new computation, the DSI on A64 encounter vblank time out.
> >
> > [CRTC:36:crtc-0] vblank wait timed out
> >
> > Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>
> > ---
> >  drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c | 12 +++++++++++-
> >  1 file changed, 11 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
> > index 9918fdb990ff..217db74c6dc3 100644
> > --- a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
> > +++ b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
> > @@ -358,7 +358,17 @@ 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;
> > +     u32 vfp = mode->vsync_start - mode->vdisplay;

let me explain this.

Actual code from Allwinner
u32 vfp = panel->lcd_vt - panel->lcd_y - panel->lcd_vbp;

So,

=> (panel->lcd_vt - panel->lcd_y) - (panel->lcd_vbp)
=> (front porch + sync + back porch) - (back porch + sync)
=> front porch + sync + back porch - back porch - sync
=> front porch
=> mode->vsync_start - mode->vdisplay

Hope it clear.
Maxime Ripard Sept. 29, 2018, 3:27 p.m. UTC | #3
On Thu, Sep 27, 2018 at 11:03:19PM +0530, Jagan Teki wrote:
> On Thu, Sep 27, 2018 at 10:44 PM Maxime Ripard
> <maxime.ripard@bootlin.com> wrote:
> >
> > On Thu, Sep 27, 2018 at 05:18:46PM +0530, Jagan Teki wrote:
> > > Accordingly to BPI-M64-bsp DE DSI code Video start delay
> > > can be computed by subtracting total vertical timing with
> > > front porch timing and with adding 1 delay line for TCON.
> >
> > This is what the current code is doing as well.
> 
> The current code
> return mode->vtotal - (mode->vsync_end - mode->vdisplay) + 1;
> 
> (mode->vsync_end - mode->vdisplay) = front porch + sync
> 
> but I'm updating here only front porch.
> 
> >
> > > This patch simply add the start_delay logic from BPI-M64-bsp,
> > > w/o this new computation, the DSI on A64 encounter vblank time out.
> > >
> > > [CRTC:36:crtc-0] vblank wait timed out
> > >
> > > Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>
> > > ---
> > >  drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c | 12 +++++++++++-
> > >  1 file changed, 11 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
> > > index 9918fdb990ff..217db74c6dc3 100644
> > > --- a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
> > > +++ b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
> > > @@ -358,7 +358,17 @@ 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;
> > > +     u32 vfp = mode->vsync_start - mode->vdisplay;
> 
> let me explain this.
> 
> Actual code from Allwinner
> u32 vfp = panel->lcd_vt - panel->lcd_y - panel->lcd_vbp;
> 
> So,
> 
> => (panel->lcd_vt - panel->lcd_y) - (panel->lcd_vbp)
> => (front porch + sync + back porch) - (back porch + sync)

Unless Allwinner is doing something fishy, in which case that should
be mentionned, the back porch doesn't contain the sync pulse.

Maxime
Jagan Teki Oct. 1, 2018, 7:55 a.m. UTC | #4
On Saturday 29 September 2018 08:57 PM, Maxime Ripard wrote:
> On Thu, Sep 27, 2018 at 11:03:19PM +0530, Jagan Teki wrote:
>> On Thu, Sep 27, 2018 at 10:44 PM Maxime Ripard
>> <maxime.ripard@bootlin.com> wrote:
>>>
>>> On Thu, Sep 27, 2018 at 05:18:46PM +0530, Jagan Teki wrote:
>>>> Accordingly to BPI-M64-bsp DE DSI code Video start delay
>>>> can be computed by subtracting total vertical timing with
>>>> front porch timing and with adding 1 delay line for TCON.
>>>
>>> This is what the current code is doing as well.
>>
>> The current code
>> return mode->vtotal - (mode->vsync_end - mode->vdisplay) + 1;
>>
>> (mode->vsync_end - mode->vdisplay) = front porch + sync
>>
>> but I'm updating here only front porch.
>>
>>>
>>>> This patch simply add the start_delay logic from BPI-M64-bsp,
>>>> w/o this new computation, the DSI on A64 encounter vblank time out.
>>>>
>>>> [CRTC:36:crtc-0] vblank wait timed out
>>>>
>>>> Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>
>>>> ---
>>>>   drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c | 12 +++++++++++-
>>>>   1 file changed, 11 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
>>>> index 9918fdb990ff..217db74c6dc3 100644
>>>> --- a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
>>>> +++ b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
>>>> @@ -358,7 +358,17 @@ 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;
>>>> +     u32 vfp = mode->vsync_start - mode->vdisplay;
>>
>> let me explain this.
>>
>> Actual code from Allwinner
>> u32 vfp = panel->lcd_vt - panel->lcd_y - panel->lcd_vbp;
>>
>> So,
>>
>> => (panel->lcd_vt - panel->lcd_y) - (panel->lcd_vbp)
>> => (front porch + sync + back porch) - (back porch + sync)
> 
> Unless Allwinner is doing something fishy, in which case that should
> be mentionned, the back porch doesn't contain the sync pulse.

As per as I understand panel->lcd_vbp is not back porch timings value 
which i used by drm. It is BSP DTS property value and actual back porch 
is calculated as "panel->lcd_vbp - panel->sync"

timmings->ver_sync_time= panel_info->lcd_vspw;
timmings->ver_back_porch= panel_info->lcd_vbp-panel_info->lcd_vspw;
Maxime Ripard Oct. 2, 2018, 1:29 p.m. UTC | #5
On Mon, Oct 01, 2018 at 01:25:59PM +0530, Jagan Teki wrote:
> On Saturday 29 September 2018 08:57 PM, Maxime Ripard wrote:
> > On Thu, Sep 27, 2018 at 11:03:19PM +0530, Jagan Teki wrote:
> > > On Thu, Sep 27, 2018 at 10:44 PM Maxime Ripard
> > > <maxime.ripard@bootlin.com> wrote:
> > > > 
> > > > On Thu, Sep 27, 2018 at 05:18:46PM +0530, Jagan Teki wrote:
> > > > > Accordingly to BPI-M64-bsp DE DSI code Video start delay
> > > > > can be computed by subtracting total vertical timing with
> > > > > front porch timing and with adding 1 delay line for TCON.
> > > > 
> > > > This is what the current code is doing as well.
> > > 
> > > The current code
> > > return mode->vtotal - (mode->vsync_end - mode->vdisplay) + 1;
> > > 
> > > (mode->vsync_end - mode->vdisplay) = front porch + sync
> > > 
> > > but I'm updating here only front porch.
> > > 
> > > > 
> > > > > This patch simply add the start_delay logic from BPI-M64-bsp,
> > > > > w/o this new computation, the DSI on A64 encounter vblank time out.
> > > > > 
> > > > > [CRTC:36:crtc-0] vblank wait timed out
> > > > > 
> > > > > Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>
> > > > > ---
> > > > >   drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c | 12 +++++++++++-
> > > > >   1 file changed, 11 insertions(+), 1 deletion(-)
> > > > > 
> > > > > diff --git a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
> > > > > index 9918fdb990ff..217db74c6dc3 100644
> > > > > --- a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
> > > > > +++ b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
> > > > > @@ -358,7 +358,17 @@ 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;
> > > > > +     u32 vfp = mode->vsync_start - mode->vdisplay;
> > > 
> > > let me explain this.
> > > 
> > > Actual code from Allwinner
> > > u32 vfp = panel->lcd_vt - panel->lcd_y - panel->lcd_vbp;
> > > 
> > > So,
> > > 
> > > => (panel->lcd_vt - panel->lcd_y) - (panel->lcd_vbp)
> > > => (front porch + sync + back porch) - (back porch + sync)
> > 
> > Unless Allwinner is doing something fishy, in which case that should
> > be mentionned, the back porch doesn't contain the sync pulse.
> 
> As per as I understand panel->lcd_vbp is not back porch timings value which
> i used by drm. It is BSP DTS property value and actual back porch is
> calculated as "panel->lcd_vbp - panel->sync"
> 
> timmings->ver_sync_time= panel_info->lcd_vspw;
> timmings->ver_back_porch= panel_info->lcd_vbp-panel_info->lcd_vspw;

Then this is what you should have started with in your commit
log. Where is that code coming from? Have you been able to confirm
that with an oscilloscope?

Maxime
diff mbox series

Patch

diff --git a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
index 9918fdb990ff..217db74c6dc3 100644
--- a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
+++ b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
@@ -358,7 +358,17 @@  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;
+	u32 vfp = mode->vsync_start - mode->vdisplay;
+	u32 start_delay;
+
+	start_delay = mode->vtotal - vfp + 1;
+	if (start_delay > mode->vtotal)
+		start_delay -= mode->vtotal;
+
+	if (!start_delay)
+		start_delay = 1;
+
+	return start_delay;
 }
 
 static void sun6i_dsi_setup_burst(struct sun6i_dsi *dsi,