Hi, All
This is the patch set to add the CVT/GTF algorithm in kernel space.
They are based on
the CVT/GTF function in xserver. But the CVT/GTF algorithm in xserver is
realized by using float-point
calculation. And the float-point calculation had better be avoided in kernel
space. I translate them
by using 32-bit integer calculation.
Patch 1/2. Add the CVT algorithm .
The CVT function can be called to generate the required modeline based
on the input parameters
Patch 2/2. Add the GTF algorithm
The GTF function can be called to generate the required modeline based
on the input parameters.
With the help of CVT/GFT function we can complete the standard timing
modeline contained in EDID
in case of KMS mode. At the same time we can also use them to add the default
modelines for some
output devices(for example: LVDS).
But there exists the inconsistent issue when the default modeline is
generated by using CVT/GTF(
the cvt/gtf utility tool in user space is used).
For example: For the modeline of 800*...@75hz
The parameter defined in xserver/hw/xfree86/common/xf86DefModeSet.c is :
hdisplay= 800, hsync_start=816, hsync_end=896, htotal=1056
vdisplay= 600, vsync_start=601, vsync_end=604, vtotal=625
Dotclk=49500KHz
The parameter generated by CVT is :
hdisplay= 800, hsyc_start=840, hsync_end=1020, htotal=1040
vdisplay= 600, vsync_start=603, vsync_end=607, vtotal=627
Dotclk=49000KHz
The parameter generate by GTF is :
hdisplay= 800, hsyc_start=840, hsync_end=1020, htotal=1040
vdisplay= 600, vsync_start=601, vsync_end=604, vtotal=627
Dotclk=48910KHz
At the same time there exists another issue when GTF is realized by
integer calculation. The modeline
parameter generated by the GTF function in patch 2 is different with that
generated by GTF utility tool in user space.
For example: For 1024*...@75hz
the parameter generated by user space GTF utility tool is :
hdisplay= 1024, hsyc_start=1080, hsync_end=1192, htotal=1360
vdisplay= 768, vsync_start=769, vsync_end=772, vtotal=802
Dotclk=81800KHz
But the parameter generated by the GTF algorithm in patch 2 is :
hdisplay= 1024, hsyc_start=1080, hsync_end=1192, htotal=1360
vdisplay= 768, vsync_start=769, vsync_end=772, vtotal=802
Dotclk=81833KHz
Can the above difference be ignored?
Welcome the comments.
Best regards.
Yakui
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