Re: [PATCH v4] drm/i2c: tda998x: fix sync generation and calculation

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On 06/20/2013 10:06 PM, Russell King - ARM Linux wrote:
On Thu, Jun 20, 2013 at 09:46:03PM +0200, Sebastian Hesselbarth wrote:
+	ref_pix      = 3 + mode->hsync_start - mode->hdisplay;
+	de_pix_s     = mode->htotal - mode->hdisplay;
+	de_pix_e     = de_pix_s + mode->hdisplay;
+	hs_pix_s     = mode->hsync_start - mode->hdisplay;
+	hs_pix_e     = hs_pix_s + mode->hsync_end - mode->hsync_start;

Correct, however, these can be simplified.
[...]
These calculations are the same as what was originally in the driver:

+       de_start   = mode->htotal - mode->hdisplay;
+       de_end     = mode->htotal;
+       hs_start   = mode->hsync_start - mode->hdisplay;
+       hs_end     = mode->hsync_end - mode->hdisplay;

when it was first committed.

This is otherwise exactly what I came up with which gets my TV working
again in HDMI mode.

Russell,

I am fine with any way to describe de/hs but you should notice that
I also modified refpix/refline and added interlaced sync. With the
original sync calculation, on some modes there was source blanking
captured by TDA998x which was also visible in the output image. I
chose the above description to make it more readable.

Also the patch takes care of input sync and output sync inversion
while the original driver always expected positive HS/VS.

I tested these sync settings on 4 DVI monitors and TV sets all
accepted each mode perfectly. Especially, not-so-cheap TV sets
are very picky about wrong sync.

Sebastian
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