linux-kernel - [RFC v1 1/1] imx-drm: match ipu_di_signal_cfg's clk

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Message-Id: <20181025161711.13727-2-TheSven73@googlemail.com>
Date:   Thu, 25 Oct 2018 12:17:11 -0400
From:   thesven73@...il.com
To:     svendev@...x.com, p.zabel@...gutronix.de, denis@...rea.com,
        rmk+kernel@....linux.org.uk
Cc:     linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org
Subject: [RFC v1 1/1] imx-drm: match ipu_di_signal_cfg's clk_pol with its observed behaviour.

From: Sven Van Asbroeck <svendev@...x.com>

We used an oscilloscope to observe the actual polarity of the
DI's pixel clock, and saw the following:

DI_GENERAL bit 17 is SET:
	pixel data is stable on the pixel clock's FALLING edge
DI_GENERAL bit 17 is CLEAR:
	pixel data is stable on the pixel clock's RISING  edge

However, the current driver configures the exact opposite of the
behaviour documented in video/imx-ipu-v3.h:
  unsigned clk_pol:1;     /* true = rising edge */

Fixes: 85de9d17c485c4196f74 ("imx-drm: match ipu_di_signal_cfg's clk_pol with its description.")
Signed-off-by: Sven Van Asbroeck <svendev@...x.com>
---
 drivers/gpu/ipu-v3/ipu-di.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/ipu-v3/ipu-di.c b/drivers/gpu/ipu-v3/ipu-di.c
index d2f1bd9d3deb..f296fa461875 100644
--- a/drivers/gpu/ipu-v3/ipu-di.c
+++ b/drivers/gpu/ipu-v3/ipu-di.c
@@ -619,7 +619,7 @@ int ipu_di_init_sync_panel(struct ipu_di *di, struct ipu_di_signal_cfg *sig)
 	if (sig->mode.flags & DISPLAY_FLAGS_VSYNC_HIGH)
 		di_gen |= ipu_di_gen_polarity(sig->vsync_pin);
 
-	if (sig->clk_pol)
+	if (!sig->clk_pol)
 		di_gen |= DI_GEN_POLARITY_DISP_CLK;
 
 	ipu_di_write(di, di_gen, DI_GENERAL);
-- 
2.17.1