Revert "drm/sun4i: Handle DRM_BUS_FLAG_PIXDATA_*EDGE"

Message ID 20180613081647.31183-1-paul.kocialkowski@bootlin.com
State New
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Series
  • Revert "drm/sun4i: Handle DRM_BUS_FLAG_PIXDATA_*EDGE"
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Commit Message

Paul Kocialkowski June 13, 2018, 8:16 a.m.
This reverts commit 2c17a4368aad2b88b68e4390c819e226cf320f70.

The offending commit triggers a run-time fault when accessing the panel
element of the sun4i_tcon structure when no such panel is attached.

It was apparently assumed in said commit that a panel is always used with
the TCON. Although it is often the case, this is not always true.
For instance a bridge might be used instead of a panel.

This issue was discovered using an A13-OLinuXino, that uses the TCON
in RGB mode for a simple DAC-based VGA bridge.

Cc: stable@vger.kernel.org
Signed-off-by: Paul Kocialkowski <paul.kocialkowski@bootlin.com>
---
 drivers/gpu/drm/sun4i/sun4i_tcon.c | 25 -------------------------
 1 file changed, 25 deletions(-)

Comments

Giulio Benetti June 13, 2018, 9:52 p.m. | #1
Hello,

sorry for my ignorance.
I don't know the right patch workflow in the case of "revert commit".
When I fix this bug, should I have to re-submit the previous patch 
entire plus bug-fix?
Or do I have to submit patch with bug-fix only?

Thanks in advance to everybody
Paul Kocialkowski June 14, 2018, 7:26 a.m. | #2
Hi,

On Wed, 2018-06-13 at 23:52 +0200, Giulio Benetti wrote:
> Hello,
> 
> sorry for my ignorance.
> I don't know the right patch workflow in the case of "revert commit".
> When I fix this bug, should I have to re-submit the previous patch 
> entire plus bug-fix?
>
> Or do I have to submit patch with bug-fix only?

Yes, that is usually how it works! The revert patch will be picked up by
the maintainer (Maxime), integrated in his tree and eventually merged
into Linus' tree (along with stable trees).

Fixup patches for this will need to take into account the revert patch,
so it becomes equivalent to submitting the same patch with that issue
resolved.

> Thanks in advance to everybody

Cheers !
Giulio Benetti June 15, 2018, 8:54 p.m. | #3
Hi Paul,

Il 14/06/2018 09:26, Paul Kocialkowski ha scritto:
> Hi,
> 
> On Wed, 2018-06-13 at 23:52 +0200, Giulio Benetti wrote:
>> Hello,
>>
>> sorry for my ignorance.
>> I don't know the right patch workflow in the case of "revert commit".
>> When I fix this bug, should I have to re-submit the previous patch
>> entire plus bug-fix?
>>
>> Or do I have to submit patch with bug-fix only?
> 
> Yes, that is usually how it works! The revert patch will be picked up by
> the maintainer (Maxime), integrated in his tree and eventually merged
> into Linus' tree (along with stable trees).
> 
> Fixup patches for this will need to take into account the revert patch,
> so it becomes equivalent to submitting the same patch with that issue
> resolved.

Thanks for explaining me.
I'm going to submit new patch asap.

Giulio
Maxime Ripard June 18, 2018, 8:27 a.m. | #4
On Wed, Jun 13, 2018 at 10:16:47AM +0200, Paul Kocialkowski wrote:
> This reverts commit 2c17a4368aad2b88b68e4390c819e226cf320f70.
> 
> The offending commit triggers a run-time fault when accessing the panel
> element of the sun4i_tcon structure when no such panel is attached.
> 
> It was apparently assumed in said commit that a panel is always used with
> the TCON. Although it is often the case, this is not always true.
> For instance a bridge might be used instead of a panel.
> 
> This issue was discovered using an A13-OLinuXino, that uses the TCON
> in RGB mode for a simple DAC-based VGA bridge.
> 
> Cc: stable@vger.kernel.org
> Signed-off-by: Paul Kocialkowski <paul.kocialkowski@bootlin.com>

Applied, thanks

Maxime

Patch

diff --git a/drivers/gpu/drm/sun4i/sun4i_tcon.c b/drivers/gpu/drm/sun4i/sun4i_tcon.c
index c3d92d537240..8045871335b5 100644
--- a/drivers/gpu/drm/sun4i/sun4i_tcon.c
+++ b/drivers/gpu/drm/sun4i/sun4i_tcon.c
@@ -17,7 +17,6 @@ 
 #include <drm/drm_encoder.h>
 #include <drm/drm_modes.h>
 #include <drm/drm_of.h>
-#include <drm/drm_panel.h>
 
 #include <uapi/drm/drm_mode.h>
 
@@ -350,9 +349,6 @@  static void sun4i_tcon0_mode_set_lvds(struct sun4i_tcon *tcon,
 static void sun4i_tcon0_mode_set_rgb(struct sun4i_tcon *tcon,
 				     const struct drm_display_mode *mode)
 {
-	struct drm_panel *panel = tcon->panel;
-	struct drm_connector *connector = panel->connector;
-	struct drm_display_info display_info = connector->display_info;
 	unsigned int bp, hsync, vsync;
 	u8 clk_delay;
 	u32 val = 0;
@@ -410,27 +406,6 @@  static void sun4i_tcon0_mode_set_rgb(struct sun4i_tcon *tcon,
 	if (mode->flags & DRM_MODE_FLAG_PVSYNC)
 		val |= SUN4I_TCON0_IO_POL_VSYNC_POSITIVE;
 
-	/*
-	 * 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 (display_info.bus_flags & DRM_BUS_FLAG_PIXDATA_POSEDGE)
-		clk_set_phase(tcon->dclk, 240);
-
-	if (display_info.bus_flags & DRM_BUS_FLAG_PIXDATA_NEGEDGE)
-		clk_set_phase(tcon->dclk, 0);
-
 	regmap_update_bits(tcon->regs, SUN4I_TCON0_IO_POL_REG,
 			   SUN4I_TCON0_IO_POL_HSYNC_POSITIVE | SUN4I_TCON0_IO_POL_VSYNC_POSITIVE,
 			   val);