[PATCH v2] drm/sun4i: add lvds mode_valid function

[PATCH v2] drm/sun4i: add lvds mode_valid function

[Giulio Benetti]

mode_valid function is missing for lvds.

Add it making it pointed by encoder helper functions.

Signed-off-by: Giulio Benetti <giulio.benetti@micronovasrl.com>
---
 drivers/gpu/drm/sun4i/sun4i_lvds.c | 55 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 55 insertions(+)

diff --git a/drivers/gpu/drm/sun4i/sun4i_lvds.c b/drivers/gpu/drm/sun4i/sun4i_lvds.c
index be3f14d..bffff4c 100644
--- a/drivers/gpu/drm/sun4i/sun4i_lvds.c
+++ b/drivers/gpu/drm/sun4i/sun4i_lvds.c
@@ -94,9 +94,64 @@ static void sun4i_lvds_encoder_disable(struct drm_encoder *encoder)
 	}
 }
 
+static enum drm_mode_status sun4i_lvds_encoder_mode_valid(struct drm_encoder *crtc,
+							  const struct drm_display_mode *mode)
+{
+	struct sun4i_lvds *lvds = drm_encoder_to_sun4i_lvds(crtc);
+	struct sun4i_tcon *tcon = lvds->tcon;
+	u32 hsync = mode->hsync_end - mode->hsync_start;
+	u32 vsync = mode->vsync_end - mode->vsync_start;
+	unsigned long rate = mode->clock * 1000;
+	long rounded_rate;
+
+	DRM_DEBUG_DRIVER("Validating modes...\n");
+
+	if (hsync < 1)
+		return MODE_HSYNC_NARROW;
+
+	if (hsync > 0x3ff)
+		return MODE_HSYNC_WIDE;
+
+	if ((mode->hdisplay < 1) || (mode->htotal < 1))
+		return MODE_H_ILLEGAL;
+
+	if ((mode->hdisplay > 0x7ff) || (mode->htotal > 0xfff))
+		return MODE_BAD_HVALUE;
+
+	DRM_DEBUG_DRIVER("Horizontal parameters OK\n");
+
+	if (vsync < 1)
+		return MODE_VSYNC_NARROW;
+
+	if (vsync > 0x3ff)
+		return MODE_VSYNC_WIDE;
+
+	if ((mode->vdisplay < 1) || (mode->vtotal < 1))
+		return MODE_V_ILLEGAL;
+
+	if ((mode->vdisplay > 0x7ff) || (mode->vtotal > 0xfff))
+		return MODE_BAD_VVALUE;
+
+	DRM_DEBUG_DRIVER("Vertical parameters OK\n");
+
+	tcon->dclk_min_div = 7;
+	tcon->dclk_max_div = 7;
+	rounded_rate = clk_round_rate(tcon->dclk, rate);
+	if (rounded_rate < rate)
+		return MODE_CLOCK_LOW;
+
+	if (rounded_rate > rate)
+		return MODE_CLOCK_HIGH;
+
+	DRM_DEBUG_DRIVER("Clock rate OK\n");
+
+	return MODE_OK;
+}
+
 static const struct drm_encoder_helper_funcs sun4i_lvds_enc_helper_funcs = {
 	.disable	= sun4i_lvds_encoder_disable,
 	.enable		= sun4i_lvds_encoder_enable,
+	.mode_valid	= sun4i_lvds_encoder_mode_valid,
 };
 
 static const struct drm_encoder_funcs sun4i_lvds_enc_funcs = {
-- 
2.7.4

Re: [PATCH v2] drm/sun4i: add lvds mode_valid function

[Maxime Ripard]

[-- Attachment #1: Type: text/plain, Size: 386 bytes --]

On Tue, Mar 13, 2018 at 12:20:19PM +0100, Giulio Benetti wrote:
> mode_valid function is missing for lvds.
> 
> Add it making it pointed by encoder helper functions.
> 
> Signed-off-by: Giulio Benetti <giulio.benetti@micronovasrl.com>

Applied, thanks!
Maxime

-- 
Maxime Ripard, Bootlin (formerly Free Electrons)
Embedded Linux and Kernel engineering
https://bootlin.com

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 833 bytes --]

Re: [v2] drm/sun4i: add lvds mode_valid function

[Ondřej Jirman]

Hello Giulio,

this patch breaks LVDS output on A83T. Without it, modesetting works,
with it there's no output.

Some more info below...

On Tue, Mar 13, 2018 at 12:20:19PM +0100, Giulio Benetti wrote:
> mode_valid function is missing for lvds.
> 
> Add it making it pointed by encoder helper functions.
> 
> Signed-off-by: Giulio Benetti <giulio.benetti@micronovasrl.com>
> ---
>  drivers/gpu/drm/sun4i/sun4i_lvds.c | 55 ++++++++++++++++++++++++++++++++++++++
>  1 file changed, 55 insertions(+)
> 
> diff --git a/drivers/gpu/drm/sun4i/sun4i_lvds.c b/drivers/gpu/drm/sun4i/sun4i_lvds.c
> index be3f14d..bffff4c 100644
> --- a/drivers/gpu/drm/sun4i/sun4i_lvds.c
> +++ b/drivers/gpu/drm/sun4i/sun4i_lvds.c
> @@ -94,9 +94,64 @@ static void sun4i_lvds_encoder_disable(struct drm_encoder *encoder)
>  	}
>  }
>  
> +static enum drm_mode_status sun4i_lvds_encoder_mode_valid(struct drm_encoder *crtc,
> +							  const struct drm_display_mode *mode)
> +{
> +	struct sun4i_lvds *lvds = drm_encoder_to_sun4i_lvds(crtc);
> +	struct sun4i_tcon *tcon = lvds->tcon;
> +	u32 hsync = mode->hsync_end - mode->hsync_start;
> +	u32 vsync = mode->vsync_end - mode->vsync_start;
> +	unsigned long rate = mode->clock * 1000;
> +	long rounded_rate;
> +
> +	DRM_DEBUG_DRIVER("Validating modes...\n");
> +
> +	if (hsync < 1)
> +		return MODE_HSYNC_NARROW;
> +
> +	if (hsync > 0x3ff)
> +		return MODE_HSYNC_WIDE;
> +
> +	if ((mode->hdisplay < 1) || (mode->htotal < 1))
> +		return MODE_H_ILLEGAL;
> +
> +	if ((mode->hdisplay > 0x7ff) || (mode->htotal > 0xfff))
> +		return MODE_BAD_HVALUE;
> +
> +	DRM_DEBUG_DRIVER("Horizontal parameters OK\n");
> +
> +	if (vsync < 1)
> +		return MODE_VSYNC_NARROW;
> +
> +	if (vsync > 0x3ff)
> +		return MODE_VSYNC_WIDE;
> +
> +	if ((mode->vdisplay < 1) || (mode->vtotal < 1))
> +		return MODE_V_ILLEGAL;
> +
> +	if ((mode->vdisplay > 0x7ff) || (mode->vtotal > 0xfff))
> +		return MODE_BAD_VVALUE;
> +
> +	DRM_DEBUG_DRIVER("Vertical parameters OK\n");
> +
> +	tcon->dclk_min_div = 7;
> +	tcon->dclk_max_div = 7;

Why would validation function change any state anywhere?

> +	rounded_rate = clk_round_rate(tcon->dclk, rate);

The issue is here, on A83T TBS A711 tablet, I get...

sun4i-tcon 1c0c000.lcd-controller: XXX: hsync=20 hdisplay=1024 htotal=1384
  vsync=5 vdisplay=600 vtotal=640 rate=52000000 rounded_rate=51857142

> +	if (rounded_rate < rate)
> +		return MODE_CLOCK_LOW;
> +
> +	if (rounded_rate > rate)
> +		return MODE_CLOCK_HIGH;

... while the previous conditions require an exact match for some reason.

But HW works fine without an exact rate match. Why is exact match required here?

thank you,
  Ondrej

> +	DRM_DEBUG_DRIVER("Clock rate OK\n");
> +
> +	return MODE_OK;
> +}
> +
>  static const struct drm_encoder_helper_funcs sun4i_lvds_enc_helper_funcs = {
>  	.disable	= sun4i_lvds_encoder_disable,
>  	.enable		= sun4i_lvds_encoder_enable,
> +	.mode_valid	= sun4i_lvds_encoder_mode_valid,
>  };
>  
>  static const struct drm_encoder_funcs sun4i_lvds_enc_funcs = {

Re: [v2] drm/sun4i: add lvds mode_valid function

[Chen-Yu Tsai]

On Thu, Apr 19, 2018 at 9:34 PM, Ondřej Jirman
<doudahwezomiechahtah@xff.cz> wrote:
> Hello Giulio,
>
> this patch breaks LVDS output on A83T. Without it, modesetting works,
> with it there's no output.
>
> Some more info below...
>
> On Tue, Mar 13, 2018 at 12:20:19PM +0100, Giulio Benetti wrote:
>> mode_valid function is missing for lvds.
>>
>> Add it making it pointed by encoder helper functions.
>>
>> Signed-off-by: Giulio Benetti <giulio.benetti@micronovasrl.com>
>> ---
>>  drivers/gpu/drm/sun4i/sun4i_lvds.c | 55 ++++++++++++++++++++++++++++++++++++++
>>  1 file changed, 55 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/sun4i/sun4i_lvds.c b/drivers/gpu/drm/sun4i/sun4i_lvds.c
>> index be3f14d..bffff4c 100644
>> --- a/drivers/gpu/drm/sun4i/sun4i_lvds.c
>> +++ b/drivers/gpu/drm/sun4i/sun4i_lvds.c
>> @@ -94,9 +94,64 @@ static void sun4i_lvds_encoder_disable(struct drm_encoder *encoder)
>>       }
>>  }
>>
>> +static enum drm_mode_status sun4i_lvds_encoder_mode_valid(struct drm_encoder *crtc,
>> +                                                       const struct drm_display_mode *mode)
>> +{
>> +     struct sun4i_lvds *lvds = drm_encoder_to_sun4i_lvds(crtc);
>> +     struct sun4i_tcon *tcon = lvds->tcon;
>> +     u32 hsync = mode->hsync_end - mode->hsync_start;
>> +     u32 vsync = mode->vsync_end - mode->vsync_start;
>> +     unsigned long rate = mode->clock * 1000;
>> +     long rounded_rate;
>> +
>> +     DRM_DEBUG_DRIVER("Validating modes...\n");
>> +
>> +     if (hsync < 1)
>> +             return MODE_HSYNC_NARROW;
>> +
>> +     if (hsync > 0x3ff)
>> +             return MODE_HSYNC_WIDE;
>> +
>> +     if ((mode->hdisplay < 1) || (mode->htotal < 1))
>> +             return MODE_H_ILLEGAL;
>> +
>> +     if ((mode->hdisplay > 0x7ff) || (mode->htotal > 0xfff))
>> +             return MODE_BAD_HVALUE;
>> +
>> +     DRM_DEBUG_DRIVER("Horizontal parameters OK\n");
>> +
>> +     if (vsync < 1)
>> +             return MODE_VSYNC_NARROW;
>> +
>> +     if (vsync > 0x3ff)
>> +             return MODE_VSYNC_WIDE;
>> +
>> +     if ((mode->vdisplay < 1) || (mode->vtotal < 1))
>> +             return MODE_V_ILLEGAL;
>> +
>> +     if ((mode->vdisplay > 0x7ff) || (mode->vtotal > 0xfff))
>> +             return MODE_BAD_VVALUE;
>> +
>> +     DRM_DEBUG_DRIVER("Vertical parameters OK\n");
>> +
>> +     tcon->dclk_min_div = 7;
>> +     tcon->dclk_max_div = 7;
>
> Why would validation function change any state anywhere?
>
>> +     rounded_rate = clk_round_rate(tcon->dclk, rate);
>
> The issue is here, on A83T TBS A711 tablet, I get...
>
> sun4i-tcon 1c0c000.lcd-controller: XXX: hsync=20 hdisplay=1024 htotal=1384
>   vsync=5 vdisplay=600 vtotal=640 rate=52000000 rounded_rate=51857142
>
>> +     if (rounded_rate < rate)
>> +             return MODE_CLOCK_LOW;
>> +
>> +     if (rounded_rate > rate)
>> +             return MODE_CLOCK_HIGH;
>
> ... while the previous conditions require an exact match for some reason.
>
> But HW works fine without an exact rate match. Why is exact match required here?

This thread might provide some more info, though we could never get an
agreement.

https://patchwork.kernel.org/patch/9446385/

ChenYu

>
> thank you,
>   Ondrej
>
>> +     DRM_DEBUG_DRIVER("Clock rate OK\n");
>> +
>> +     return MODE_OK;
>> +}
>> +
>>  static const struct drm_encoder_helper_funcs sun4i_lvds_enc_helper_funcs = {
>>       .disable        = sun4i_lvds_encoder_disable,
>>       .enable         = sun4i_lvds_encoder_enable,
>> +     .mode_valid     = sun4i_lvds_encoder_mode_valid,
>>  };
>>
>>  static const struct drm_encoder_funcs sun4i_lvds_enc_funcs = {

Re: [v2] drm/sun4i: add lvds mode_valid function

[Giulio Benetti]

Hi everybody,

Il 19/04/2018 15:36, Chen-Yu Tsai ha scritto:
> On Thu, Apr 19, 2018 at 9:34 PM, Ondřej Jirman
> <doudahwezomiechahtah@xff.cz> wrote:
>> Hello Giulio,
>>
>> this patch breaks LVDS output on A83T. Without it, modesetting works,
>> with it there's no output.
>>
>> Some more info below...
>>
>> On Tue, Mar 13, 2018 at 12:20:19PM +0100, Giulio Benetti wrote:
>>> mode_valid function is missing for lvds.
>>>
>>> Add it making it pointed by encoder helper functions.
>>>
>>> Signed-off-by: Giulio Benetti <giulio.benetti@micronovasrl.com>
>>> ---
>>>   drivers/gpu/drm/sun4i/sun4i_lvds.c | 55 ++++++++++++++++++++++++++++++++++++++
>>>   1 file changed, 55 insertions(+)
>>>
>>> diff --git a/drivers/gpu/drm/sun4i/sun4i_lvds.c b/drivers/gpu/drm/sun4i/sun4i_lvds.c
>>> index be3f14d..bffff4c 100644
>>> --- a/drivers/gpu/drm/sun4i/sun4i_lvds.c
>>> +++ b/drivers/gpu/drm/sun4i/sun4i_lvds.c
>>> @@ -94,9 +94,64 @@ static void sun4i_lvds_encoder_disable(struct drm_encoder *encoder)
>>>        }
>>>   }
>>>
>>> +static enum drm_mode_status sun4i_lvds_encoder_mode_valid(struct drm_encoder *crtc,
>>> +                                                       const struct drm_display_mode *mode)
>>> +{
>>> +     struct sun4i_lvds *lvds = drm_encoder_to_sun4i_lvds(crtc);
>>> +     struct sun4i_tcon *tcon = lvds->tcon;
>>> +     u32 hsync = mode->hsync_end - mode->hsync_start;
>>> +     u32 vsync = mode->vsync_end - mode->vsync_start;
>>> +     unsigned long rate = mode->clock * 1000;
>>> +     long rounded_rate;
>>> +
>>> +     DRM_DEBUG_DRIVER("Validating modes...\n");
>>> +
>>> +     if (hsync < 1)
>>> +             return MODE_HSYNC_NARROW;
>>> +
>>> +     if (hsync > 0x3ff)
>>> +             return MODE_HSYNC_WIDE;
>>> +
>>> +     if ((mode->hdisplay < 1) || (mode->htotal < 1))
>>> +             return MODE_H_ILLEGAL;
>>> +
>>> +     if ((mode->hdisplay > 0x7ff) || (mode->htotal > 0xfff))
>>> +             return MODE_BAD_HVALUE;
>>> +
>>> +     DRM_DEBUG_DRIVER("Horizontal parameters OK\n");
>>> +
>>> +     if (vsync < 1)
>>> +             return MODE_VSYNC_NARROW;
>>> +
>>> +     if (vsync > 0x3ff)
>>> +             return MODE_VSYNC_WIDE;
>>> +
>>> +     if ((mode->vdisplay < 1) || (mode->vtotal < 1))
>>> +             return MODE_V_ILLEGAL;
>>> +
>>> +     if ((mode->vdisplay > 0x7ff) || (mode->vtotal > 0xfff))
>>> +             return MODE_BAD_VVALUE;
>>> +
>>> +     DRM_DEBUG_DRIVER("Vertical parameters OK\n");
>>> +
>>> +     tcon->dclk_min_div = 7;
>>> +     tcon->dclk_max_div = 7;
>>
>> Why would validation function change any state anywhere?
>>
>>> +     rounded_rate = clk_round_rate(tcon->dclk, rate);
>>
>> The issue is here, on A83T TBS A711 tablet, I get...
>>
>> sun4i-tcon 1c0c000.lcd-controller: XXX: hsync=20 hdisplay=1024 htotal=1384
>>    vsync=5 vdisplay=600 vtotal=640 rate=52000000 rounded_rate=51857142
>>
>>> +     if (rounded_rate < rate)
>>> +             return MODE_CLOCK_LOW;
>>> +
>>> +     if (rounded_rate > rate)
>>> +             return MODE_CLOCK_HIGH;
>>
>> ... while the previous conditions require an exact match for some reason.
>>
>> But HW works fine without an exact rate match. Why is exact match required here?
> 
> This thread might provide some more info, though we could never get an
> agreement.
> 
> https://patchwork.kernel.org/patch/9446385/

Thanks for pointing that Thread ChenYu.
So the only chance is to trim frequency according to encoder capabilities.
I agree to block when encoder can't provide frequency specified,
otherwise you could drive you panel at the near the lowest(highest)
frequency and get out of limits for a few without knowing it.

Best regards

-- 
Giulio Benetti
CTO

MICRONOVA SRL
Sede: Via A. Niedda 3 - 35010 Vigonza (PD)
Tel. 049/8931563 - Fax 049/8931346
Cod.Fiscale - P.IVA 02663420285
Capitale Sociale € 26.000 i.v.
Iscritta al Reg. Imprese di Padova N. 02663420285
Numero R.E.A. 258642

> 
> ChenYu
> 
>>
>> thank you,
>>    Ondrej
>>
>>> +     DRM_DEBUG_DRIVER("Clock rate OK\n");
>>> +
>>> +     return MODE_OK;
>>> +}
>>> +
>>>   static const struct drm_encoder_helper_funcs sun4i_lvds_enc_helper_funcs = {
>>>        .disable        = sun4i_lvds_encoder_disable,
>>>        .enable         = sun4i_lvds_encoder_enable,
>>> +     .mode_valid     = sun4i_lvds_encoder_mode_valid,
>>>   };
>>>
>>>   static const struct drm_encoder_funcs sun4i_lvds_enc_funcs = {
> _______________________________________________
> dri-devel mailing list
> dri-devel@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel
> 

Re: [v2] drm/sun4i: add lvds mode_valid function

[Ondřej Jirman]

Hello,

On Thu, Apr 19, 2018 at 04:02:08PM +0200, Giulio Benetti wrote:
> Hi everybody,
> 
> Il 19/04/2018 15:36, Chen-Yu Tsai ha scritto:
> > On Thu, Apr 19, 2018 at 9:34 PM, Ondřej Jirman
> > <doudahwezomiechahtah@xff.cz> wrote:
> > > Hello Giulio,
> > > 
> > > this patch breaks LVDS output on A83T. Without it, modesetting works,
> > > with it there's no output.
> > > 
> > > Some more info below...
> > > 
> > > On Tue, Mar 13, 2018 at 12:20:19PM +0100, Giulio Benetti wrote:
> > > > mode_valid function is missing for lvds.
> > > > 
> > > > Add it making it pointed by encoder helper functions.
> > > > 
> > > > Signed-off-by: Giulio Benetti <giulio.benetti@micronovasrl.com>
> > > > ---
> > > >   drivers/gpu/drm/sun4i/sun4i_lvds.c | 55 ++++++++++++++++++++++++++++++++++++++
> > > >   1 file changed, 55 insertions(+)
> > > > 
> > > > diff --git a/drivers/gpu/drm/sun4i/sun4i_lvds.c b/drivers/gpu/drm/sun4i/sun4i_lvds.c
> > > > index be3f14d..bffff4c 100644
> > > > --- a/drivers/gpu/drm/sun4i/sun4i_lvds.c
> > > > +++ b/drivers/gpu/drm/sun4i/sun4i_lvds.c
> > > > @@ -94,9 +94,64 @@ static void sun4i_lvds_encoder_disable(struct drm_encoder *encoder)
> > > >        }
> > > >   }
> > > > 
> > > > +static enum drm_mode_status sun4i_lvds_encoder_mode_valid(struct drm_encoder *crtc,
> > > > +                                                       const struct drm_display_mode *mode)
> > > > +{
> > > > +     struct sun4i_lvds *lvds = drm_encoder_to_sun4i_lvds(crtc);
> > > > +     struct sun4i_tcon *tcon = lvds->tcon;
> > > > +     u32 hsync = mode->hsync_end - mode->hsync_start;
> > > > +     u32 vsync = mode->vsync_end - mode->vsync_start;
> > > > +     unsigned long rate = mode->clock * 1000;
> > > > +     long rounded_rate;
> > > > +
> > > > +     DRM_DEBUG_DRIVER("Validating modes...\n");
> > > > +
> > > > +     if (hsync < 1)
> > > > +             return MODE_HSYNC_NARROW;
> > > > +
> > > > +     if (hsync > 0x3ff)
> > > > +             return MODE_HSYNC_WIDE;
> > > > +
> > > > +     if ((mode->hdisplay < 1) || (mode->htotal < 1))
> > > > +             return MODE_H_ILLEGAL;
> > > > +
> > > > +     if ((mode->hdisplay > 0x7ff) || (mode->htotal > 0xfff))
> > > > +             return MODE_BAD_HVALUE;
> > > > +
> > > > +     DRM_DEBUG_DRIVER("Horizontal parameters OK\n");
> > > > +
> > > > +     if (vsync < 1)
> > > > +             return MODE_VSYNC_NARROW;
> > > > +
> > > > +     if (vsync > 0x3ff)
> > > > +             return MODE_VSYNC_WIDE;
> > > > +
> > > > +     if ((mode->vdisplay < 1) || (mode->vtotal < 1))
> > > > +             return MODE_V_ILLEGAL;
> > > > +
> > > > +     if ((mode->vdisplay > 0x7ff) || (mode->vtotal > 0xfff))
> > > > +             return MODE_BAD_VVALUE;
> > > > +
> > > > +     DRM_DEBUG_DRIVER("Vertical parameters OK\n");
> > > > +
> > > > +     tcon->dclk_min_div = 7;
> > > > +     tcon->dclk_max_div = 7;
> > > 
> > > Why would validation function change any state anywhere?
> > > 
> > > > +     rounded_rate = clk_round_rate(tcon->dclk, rate);
> > > 
> > > The issue is here, on A83T TBS A711 tablet, I get...
> > > 
> > > sun4i-tcon 1c0c000.lcd-controller: XXX: hsync=20 hdisplay=1024 htotal=1384
> > >    vsync=5 vdisplay=600 vtotal=640 rate=52000000 rounded_rate=51857142
> > > 
> > > > +     if (rounded_rate < rate)
> > > > +             return MODE_CLOCK_LOW;
> > > > +
> > > > +     if (rounded_rate > rate)
> > > > +             return MODE_CLOCK_HIGH;
> > > 
> > > ... while the previous conditions require an exact match for some reason.
> > > 
> > > But HW works fine without an exact rate match. Why is exact match required here?
> > 
> > This thread might provide some more info, though we could never get an
> > agreement.
> > 
> > https://patchwork.kernel.org/patch/9446385/
> 
> Thanks for pointing that Thread ChenYu.
> So the only chance is to trim frequency according to encoder capabilities.
> I agree to block when encoder can't provide frequency specified,
> otherwise you could drive you panel at the near the lowest(highest)
> frequency and get out of limits for a few without knowing it.

When I set the range of pixel clock frequencies on simple-panel connected
to this encoder, the check still fails, so there's something not working
there as expected. This check is only called once with a typical frequency.

I guess drm doesn't implement clock-frequency range on panels. But I haven't
looked.

I can set the exact frequency that the SoC can provide on the simple-panel,
but that's a bit of a hack.

regards,
  o.

> Best regards
> 
> -- 
> Giulio Benetti

Re: [v2] drm/sun4i: add lvds mode_valid function

[Maxime Ripard]

On Fri, Apr 20, 2018 at 03:10:26PM +0200, Ondřej Jirman wrote:
> Hello,
> 
> On Thu, Apr 19, 2018 at 04:02:08PM +0200, Giulio Benetti wrote:
> > Hi everybody,
> > 
> > Il 19/04/2018 15:36, Chen-Yu Tsai ha scritto:
> > > On Thu, Apr 19, 2018 at 9:34 PM, Ondřej Jirman
> > > <doudahwezomiechahtah@xff.cz> wrote:
> > > > Hello Giulio,
> > > > 
> > > > this patch breaks LVDS output on A83T. Without it, modesetting works,
> > > > with it there's no output.
> > > > 
> > > > Some more info below...
> > > > 
> > > > On Tue, Mar 13, 2018 at 12:20:19PM +0100, Giulio Benetti wrote:
> > > > > mode_valid function is missing for lvds.
> > > > > 
> > > > > Add it making it pointed by encoder helper functions.
> > > > > 
> > > > > Signed-off-by: Giulio Benetti <giulio.benetti@micronovasrl.com>
> > > > > ---
> > > > >   drivers/gpu/drm/sun4i/sun4i_lvds.c | 55 ++++++++++++++++++++++++++++++++++++++
> > > > >   1 file changed, 55 insertions(+)
> > > > > 
> > > > > diff --git a/drivers/gpu/drm/sun4i/sun4i_lvds.c b/drivers/gpu/drm/sun4i/sun4i_lvds.c
> > > > > index be3f14d..bffff4c 100644
> > > > > --- a/drivers/gpu/drm/sun4i/sun4i_lvds.c
> > > > > +++ b/drivers/gpu/drm/sun4i/sun4i_lvds.c
> > > > > @@ -94,9 +94,64 @@ static void sun4i_lvds_encoder_disable(struct drm_encoder *encoder)
> > > > >        }
> > > > >   }
> > > > > 
> > > > > +static enum drm_mode_status sun4i_lvds_encoder_mode_valid(struct drm_encoder *crtc,
> > > > > +                                                       const struct drm_display_mode *mode)
> > > > > +{
> > > > > +     struct sun4i_lvds *lvds = drm_encoder_to_sun4i_lvds(crtc);
> > > > > +     struct sun4i_tcon *tcon = lvds->tcon;
> > > > > +     u32 hsync = mode->hsync_end - mode->hsync_start;
> > > > > +     u32 vsync = mode->vsync_end - mode->vsync_start;
> > > > > +     unsigned long rate = mode->clock * 1000;
> > > > > +     long rounded_rate;
> > > > > +
> > > > > +     DRM_DEBUG_DRIVER("Validating modes...\n");
> > > > > +
> > > > > +     if (hsync < 1)
> > > > > +             return MODE_HSYNC_NARROW;
> > > > > +
> > > > > +     if (hsync > 0x3ff)
> > > > > +             return MODE_HSYNC_WIDE;
> > > > > +
> > > > > +     if ((mode->hdisplay < 1) || (mode->htotal < 1))
> > > > > +             return MODE_H_ILLEGAL;
> > > > > +
> > > > > +     if ((mode->hdisplay > 0x7ff) || (mode->htotal > 0xfff))
> > > > > +             return MODE_BAD_HVALUE;
> > > > > +
> > > > > +     DRM_DEBUG_DRIVER("Horizontal parameters OK\n");
> > > > > +
> > > > > +     if (vsync < 1)
> > > > > +             return MODE_VSYNC_NARROW;
> > > > > +
> > > > > +     if (vsync > 0x3ff)
> > > > > +             return MODE_VSYNC_WIDE;
> > > > > +
> > > > > +     if ((mode->vdisplay < 1) || (mode->vtotal < 1))
> > > > > +             return MODE_V_ILLEGAL;
> > > > > +
> > > > > +     if ((mode->vdisplay > 0x7ff) || (mode->vtotal > 0xfff))
> > > > > +             return MODE_BAD_VVALUE;
> > > > > +
> > > > > +     DRM_DEBUG_DRIVER("Vertical parameters OK\n");
> > > > > +
> > > > > +     tcon->dclk_min_div = 7;
> > > > > +     tcon->dclk_max_div = 7;
> > > > 
> > > > Why would validation function change any state anywhere?
> > > > 
> > > > > +     rounded_rate = clk_round_rate(tcon->dclk, rate);
> > > > 
> > > > The issue is here, on A83T TBS A711 tablet, I get...
> > > > 
> > > > sun4i-tcon 1c0c000.lcd-controller: XXX: hsync=20 hdisplay=1024 htotal=1384
> > > >    vsync=5 vdisplay=600 vtotal=640 rate=52000000 rounded_rate=51857142
> > > > 
> > > > > +     if (rounded_rate < rate)
> > > > > +             return MODE_CLOCK_LOW;
> > > > > +
> > > > > +     if (rounded_rate > rate)
> > > > > +             return MODE_CLOCK_HIGH;
> > > > 
> > > > ... while the previous conditions require an exact match for some reason.
> > > > 
> > > > But HW works fine without an exact rate match. Why is exact match required here?
> > > 
> > > This thread might provide some more info, though we could never get an
> > > agreement.
> > > 
> > > https://patchwork.kernel.org/patch/9446385/
> > 
> > Thanks for pointing that Thread ChenYu.
> > So the only chance is to trim frequency according to encoder capabilities.
> > I agree to block when encoder can't provide frequency specified,
> > otherwise you could drive you panel at the near the lowest(highest)
> > frequency and get out of limits for a few without knowing it.
> 
> When I set the range of pixel clock frequencies on simple-panel connected
> to this encoder, the check still fails, so there's something not working
> there as expected. This check is only called once with a typical frequency.
> 
> I guess drm doesn't implement clock-frequency range on panels. But I haven't
> looked.

It does, but only omapdss is able to use it iirc. We could do it too,
but that would be way out of scope for a fix.

> I can set the exact frequency that the SoC can provide on the simple-panel,
> but that's a bit of a hack.

Yes. And if the only device using this thus far is broken, that's not
really great either.

Can you send a revert?

Thanks!
Maxime

-- 
Maxime Ripard, Bootlin (formerly Free Electrons)
Embedded Linux and Kernel engineering
https://bootlin.com