diff mbox series

[v5] drm/sun4i: tcon: fix inverted DCLK polarity

Message ID 20210113160526.928766-1-giulio.benetti@benettiengineering.com (mailing list archive)
State New, archived
Headers show
Series [v5] drm/sun4i: tcon: fix inverted DCLK polarity | expand

Commit Message

Giulio Benetti Jan. 13, 2021, 4:05 p.m. UTC
From: Giulio Benetti <giulio.benetti@micronovasrl.com>

During commit 88bc4178568b ("drm: Use new
DRM_BUS_FLAG_*_(DRIVE|SAMPLE)_(POS|NEG)EDGE flags") DRM_BUS_FLAG_*
macros have been changed to avoid ambiguity but just because of this
ambiguity previous DRM_BUS_FLAG_PIXDATA_(POS/NEG)EDGE were used meaning
_SAMPLE_ not _DRIVE_. This leads to DLCK inversion and need to fix but
instead of swapping phase values, let's adopt an easier approach Maxime
suggested:
It turned out that bit 26 of SUN4I_TCON0_IO_POL_REG is dedicated to
invert DCLK polarity and this makes things really easier than before. So
let's handle DCLK polarity by adding SUN4I_TCON0_IO_POL_DCLK_DRIVE_NEGEDGE
as bit 26 and activating according to bus_flags the same way it is done
for all the other signals polarity.

Fixes: 88bc4178568b ("drm: Use new DRM_BUS_FLAG_*_(DRIVE|SAMPLE)_(POS|NEG)EDGE flags")
Suggested-by: Maxime Ripard <maxime@cerno.tech>
Signed-off-by: Giulio Benetti <giulio.benetti@micronovasrl.com>
---
V2->V3:
- squash 2 patches into 1
V3->V4:
- add SUN4I_TCON0_IO_POL_DCLK_POSITIVE to regmap_update_bits()
V4->V5:
polarity is still wrong so:
- let's use SUN4I_TCON0_IO_POL_DCLK_DRIVE_NEGEDGE macro
  instead of _DCLK_POSITIVE(that would make sense only in realtion with DCLK)
- invert condition using _NEGEDGE instead of _POSEDGE and then matching with
  register bit SUN4I_TCON0_IO_POL_DCLK_DRIVE_NEGEDGE
- correct commit log according to V4->V5 changes
---
 drivers/gpu/drm/sun4i/sun4i_tcon.c | 21 ++-------------------
 drivers/gpu/drm/sun4i/sun4i_tcon.h |  1 +
 2 files changed, 3 insertions(+), 19 deletions(-)

Comments

Marjan Pascolo Jan. 14, 2021, 7:58 a.m. UTC | #1
Hi Giulio,

You did a typo

Il 13/01/2021 17:05, Giulio Benetti ha scritto:
> From: Giulio Benetti <giulio.benetti@micronovasrl.com>
>
> During commit 88bc4178568b ("drm: Use new
> DRM_BUS_FLAG_*_(DRIVE|SAMPLE)_(POS|NEG)EDGE flags") DRM_BUS_FLAG_*
> macros have been changed to avoid ambiguity but just because of this
> ambiguity previous DRM_BUS_FLAG_PIXDATA_(POS/NEG)EDGE were used meaning
> _SAMPLE_ not _DRIVE_. This leads to DLCK inversion and need to fix but
> instead of swapping phase values, let's adopt an easier approach Maxime
> suggested:
> It turned out that bit 26 of SUN4I_TCON0_IO_POL_REG is dedicated to
> invert DCLK polarity and this makes things really easier than before. So
> let's handle DCLK polarity by adding SUN4I_TCON0_IO_POL_DCLK_DRIVE_NEGEDGE
> as bit 26 and activating according to bus_flags the same way it is done
> for all the other signals polarity.
>
> Fixes: 88bc4178568b ("drm: Use new DRM_BUS_FLAG_*_(DRIVE|SAMPLE)_(POS|NEG)EDGE flags")
> Suggested-by: Maxime Ripard <maxime@cerno.tech>
> Signed-off-by: Giulio Benetti <giulio.benetti@micronovasrl.com>
> ---
> V2->V3:
> - squash 2 patches into 1
> V3->V4:
> - add SUN4I_TCON0_IO_POL_DCLK_POSITIVE to regmap_update_bits()
> V4->V5:
> polarity is still wrong so:
> - let's use SUN4I_TCON0_IO_POL_DCLK_DRIVE_NEGEDGE macro
>    instead of _DCLK_POSITIVE(that would make sense only in realtion with DCLK)
> - invert condition using _NEGEDGE instead of _POSEDGE and then matching with
>    register bit SUN4I_TCON0_IO_POL_DCLK_DRIVE_NEGEDGE
> - correct commit log according to V4->V5 changes
> ---
>   drivers/gpu/drm/sun4i/sun4i_tcon.c | 21 ++-------------------
>   drivers/gpu/drm/sun4i/sun4i_tcon.h |  1 +
>   2 files changed, 3 insertions(+), 19 deletions(-)
>
> diff --git a/drivers/gpu/drm/sun4i/sun4i_tcon.c b/drivers/gpu/drm/sun4i/sun4i_tcon.c
> index eaaf5d70e352..c172ccfff7e5 100644
> --- a/drivers/gpu/drm/sun4i/sun4i_tcon.c
> +++ b/drivers/gpu/drm/sun4i/sun4i_tcon.c
> @@ -569,30 +569,13 @@ static void sun4i_tcon0_mode_set_rgb(struct sun4i_tcon *tcon,
>   	if (info->bus_flags & DRM_BUS_FLAG_DE_LOW)
>   		val |= SUN4I_TCON0_IO_POL_DE_NEGATIVE;
>   
> -	/*
> -	 * On A20 and similar SoCs, the only way to achieve Positive Edge
> -	 * (Rising Edge), is setting dclk clock phase to 2/3(240°).
> -	 * By default TCON works in Negative Edge(Falling Edge),
> -	 * this is why phase is set to 0 in that case.
> -	 * Unfortunately there's no way to logically invert dclk through
> -	 * IO_POL register.
> -	 * The only acceptable way to work, triple checked with scope,
> -	 * is using clock phase set to 0° for Negative Edge and set to 240°
> -	 * for Positive Edge.
> -	 * On A33 and similar SoCs there would be a 90° phase option,
> -	 * but it divides also dclk by 2.
> -	 * Following code is a way to avoid quirks all around TCON
> -	 * and DOTCLOCK drivers.
> -	 */
> -	if (info->bus_flags & DRM_BUS_FLAG_PIXDATA_DRIVE_POSEDGE)
> -		clk_set_phase(tcon->dclk, 240);
> -
>   	if (info->bus_flags & DRM_BUS_FLAG_PIXDATA_DRIVE_NEGEDGE)
> -		clk_set_phase(tcon->dclk, 0);
> +		val |= SUN4I_TCON0_IO_POL_DCLK_DRIVE_NEGEDGE;
>   
>   	regmap_update_bits(tcon->regs, SUN4I_TCON0_IO_POL_REG,
>   			   SUN4I_TCON0_IO_POL_HSYNC_POSITIVE |
>   			   SUN4I_TCON0_IO_POL_VSYNC_POSITIVE |
Here Below you missed an 'E'
> +			   SUN4I_TCON0_IO_POL_DCLK_DRIVE_NEGDGE |
>   			   SUN4I_TCON0_IO_POL_DE_NEGATIVE,
>   			   val);
>   
> diff --git a/drivers/gpu/drm/sun4i/sun4i_tcon.h b/drivers/gpu/drm/sun4i/sun4i_tcon.h
> index cfbf4e6c1679..c5ac1b02482c 100644
> --- a/drivers/gpu/drm/sun4i/sun4i_tcon.h
> +++ b/drivers/gpu/drm/sun4i/sun4i_tcon.h
> @@ -113,6 +113,7 @@
>   #define SUN4I_TCON0_IO_POL_REG			0x88
>   #define SUN4I_TCON0_IO_POL_DCLK_PHASE(phase)		((phase & 3) << 28)
>   #define SUN4I_TCON0_IO_POL_DE_NEGATIVE			BIT(27)
> +#define SUN4I_TCON0_IO_POL_DCLK_DRIVE_NEGEDGE		BIT(26)
>   #define SUN4I_TCON0_IO_POL_HSYNC_POSITIVE		BIT(25)
>   #define SUN4I_TCON0_IO_POL_VSYNC_POSITIVE		BIT(24)
>
Giulio Benetti Jan. 14, 2021, 8:12 a.m. UTC | #2
Hi Marjan,

On 1/14/21 8:58 AM, Marjan Pascolo wrote:
> Hi Giulio,
> 
> You did a typo
> 
> Il 13/01/2021 17:05, Giulio Benetti ha scritto:
>> From: Giulio Benetti <giulio.benetti@micronovasrl.com>
>>
>> During commit 88bc4178568b ("drm: Use new
>> DRM_BUS_FLAG_*_(DRIVE|SAMPLE)_(POS|NEG)EDGE flags") DRM_BUS_FLAG_*
>> macros have been changed to avoid ambiguity but just because of this
>> ambiguity previous DRM_BUS_FLAG_PIXDATA_(POS/NEG)EDGE were used meaning
>> _SAMPLE_ not _DRIVE_. This leads to DLCK inversion and need to fix but
>> instead of swapping phase values, let's adopt an easier approach Maxime
>> suggested:
>> It turned out that bit 26 of SUN4I_TCON0_IO_POL_REG is dedicated to
>> invert DCLK polarity and this makes things really easier than before. So
>> let's handle DCLK polarity by adding SUN4I_TCON0_IO_POL_DCLK_DRIVE_NEGEDGE
>> as bit 26 and activating according to bus_flags the same way it is done
>> for all the other signals polarity.
>>
>> Fixes: 88bc4178568b ("drm: Use new DRM_BUS_FLAG_*_(DRIVE|SAMPLE)_(POS|NEG)EDGE flags")
>> Suggested-by: Maxime Ripard <maxime@cerno.tech>
>> Signed-off-by: Giulio Benetti <giulio.benetti@micronovasrl.com>
>> ---
>> V2->V3:
>> - squash 2 patches into 1
>> V3->V4:
>> - add SUN4I_TCON0_IO_POL_DCLK_POSITIVE to regmap_update_bits()
>> V4->V5:
>> polarity is still wrong so:
>> - let's use SUN4I_TCON0_IO_POL_DCLK_DRIVE_NEGEDGE macro
>>     instead of _DCLK_POSITIVE(that would make sense only in realtion with DCLK)
>> - invert condition using _NEGEDGE instead of _POSEDGE and then matching with
>>     register bit SUN4I_TCON0_IO_POL_DCLK_DRIVE_NEGEDGE
>> - correct commit log according to V4->V5 changes
>> ---
>>    drivers/gpu/drm/sun4i/sun4i_tcon.c | 21 ++-------------------
>>    drivers/gpu/drm/sun4i/sun4i_tcon.h |  1 +
>>    2 files changed, 3 insertions(+), 19 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/sun4i/sun4i_tcon.c b/drivers/gpu/drm/sun4i/sun4i_tcon.c
>> index eaaf5d70e352..c172ccfff7e5 100644
>> --- a/drivers/gpu/drm/sun4i/sun4i_tcon.c
>> +++ b/drivers/gpu/drm/sun4i/sun4i_tcon.c
>> @@ -569,30 +569,13 @@ static void sun4i_tcon0_mode_set_rgb(struct sun4i_tcon *tcon,
>>    	if (info->bus_flags & DRM_BUS_FLAG_DE_LOW)
>>    		val |= SUN4I_TCON0_IO_POL_DE_NEGATIVE;
>>    
>> -	/*
>> -	 * On A20 and similar SoCs, the only way to achieve Positive Edge
>> -	 * (Rising Edge), is setting dclk clock phase to 2/3(240°).
>> -	 * By default TCON works in Negative Edge(Falling Edge),
>> -	 * this is why phase is set to 0 in that case.
>> -	 * Unfortunately there's no way to logically invert dclk through
>> -	 * IO_POL register.
>> -	 * The only acceptable way to work, triple checked with scope,
>> -	 * is using clock phase set to 0° for Negative Edge and set to 240°
>> -	 * for Positive Edge.
>> -	 * On A33 and similar SoCs there would be a 90° phase option,
>> -	 * but it divides also dclk by 2.
>> -	 * Following code is a way to avoid quirks all around TCON
>> -	 * and DOTCLOCK drivers.
>> -	 */
>> -	if (info->bus_flags & DRM_BUS_FLAG_PIXDATA_DRIVE_POSEDGE)
>> -		clk_set_phase(tcon->dclk, 240);
>> -
>>    	if (info->bus_flags & DRM_BUS_FLAG_PIXDATA_DRIVE_NEGEDGE)
>> -		clk_set_phase(tcon->dclk, 0);
>> +		val |= SUN4I_TCON0_IO_POL_DCLK_DRIVE_NEGEDGE;
>>    
>>    	regmap_update_bits(tcon->regs, SUN4I_TCON0_IO_POL_REG,
>>    			   SUN4I_TCON0_IO_POL_HSYNC_POSITIVE |
>>    			   SUN4I_TCON0_IO_POL_VSYNC_POSITIVE |
> Here Below you missed an 'E'

yes, thank you, going to send v6.

Best regards
diff mbox series

Patch

diff --git a/drivers/gpu/drm/sun4i/sun4i_tcon.c b/drivers/gpu/drm/sun4i/sun4i_tcon.c
index eaaf5d70e352..c172ccfff7e5 100644
--- a/drivers/gpu/drm/sun4i/sun4i_tcon.c
+++ b/drivers/gpu/drm/sun4i/sun4i_tcon.c
@@ -569,30 +569,13 @@  static void sun4i_tcon0_mode_set_rgb(struct sun4i_tcon *tcon,
 	if (info->bus_flags & DRM_BUS_FLAG_DE_LOW)
 		val |= SUN4I_TCON0_IO_POL_DE_NEGATIVE;
 
-	/*
-	 * On A20 and similar SoCs, the only way to achieve Positive Edge
-	 * (Rising Edge), is setting dclk clock phase to 2/3(240°).
-	 * By default TCON works in Negative Edge(Falling Edge),
-	 * this is why phase is set to 0 in that case.
-	 * Unfortunately there's no way to logically invert dclk through
-	 * IO_POL register.
-	 * The only acceptable way to work, triple checked with scope,
-	 * is using clock phase set to 0° for Negative Edge and set to 240°
-	 * for Positive Edge.
-	 * On A33 and similar SoCs there would be a 90° phase option,
-	 * but it divides also dclk by 2.
-	 * Following code is a way to avoid quirks all around TCON
-	 * and DOTCLOCK drivers.
-	 */
-	if (info->bus_flags & DRM_BUS_FLAG_PIXDATA_DRIVE_POSEDGE)
-		clk_set_phase(tcon->dclk, 240);
-
 	if (info->bus_flags & DRM_BUS_FLAG_PIXDATA_DRIVE_NEGEDGE)
-		clk_set_phase(tcon->dclk, 0);
+		val |= SUN4I_TCON0_IO_POL_DCLK_DRIVE_NEGEDGE;
 
 	regmap_update_bits(tcon->regs, SUN4I_TCON0_IO_POL_REG,
 			   SUN4I_TCON0_IO_POL_HSYNC_POSITIVE |
 			   SUN4I_TCON0_IO_POL_VSYNC_POSITIVE |
+			   SUN4I_TCON0_IO_POL_DCLK_DRIVE_NEGDGE |
 			   SUN4I_TCON0_IO_POL_DE_NEGATIVE,
 			   val);
 
diff --git a/drivers/gpu/drm/sun4i/sun4i_tcon.h b/drivers/gpu/drm/sun4i/sun4i_tcon.h
index cfbf4e6c1679..c5ac1b02482c 100644
--- a/drivers/gpu/drm/sun4i/sun4i_tcon.h
+++ b/drivers/gpu/drm/sun4i/sun4i_tcon.h
@@ -113,6 +113,7 @@ 
 #define SUN4I_TCON0_IO_POL_REG			0x88
 #define SUN4I_TCON0_IO_POL_DCLK_PHASE(phase)		((phase & 3) << 28)
 #define SUN4I_TCON0_IO_POL_DE_NEGATIVE			BIT(27)
+#define SUN4I_TCON0_IO_POL_DCLK_DRIVE_NEGEDGE		BIT(26)
 #define SUN4I_TCON0_IO_POL_HSYNC_POSITIVE		BIT(25)
 #define SUN4I_TCON0_IO_POL_VSYNC_POSITIVE		BIT(24)