Re: [Linux-fbdev-users] atyfb: brokenness on PowerMac 5500 and Beige G3

[Gil B. <co...@ba...>]

Hello,

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I suspect I have found the reason for the breakage I reported earlier in =
the
driver - but I'd be very happy if someone was confirming that my attempt
wouldn't mess up my hardware before I set off to test it.

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This addition:

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+   /* according to ATI, we should use clock 3 for acelerated mode */
+   par->clk_wr_offset =3D 3;

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comes up right after a nice piece of code that actually tries to mask
clk_wr_offset:

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+   if (!(aty_ld_le32(CRTC_GEN_CNTL, par) & CRTC_EXT_DISP_EN))
+      par->clk_wr_offset =3D (inb(R_GENMO) & 0x0CU) >> 2;
+   else
+      par->clk_wr_offset =3D aty_ld_8(CLOCK_CNTL, par) & 0x03U;

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and so makes this code redundant with a static value that "seems" to =
come
out of nowhere.

Furthermore, looking at atyfb.h, this particular register has overloaded
meaning (by its comment) so it may cause the unexpected results I'm =
seeing.

But. these 4 lines of code replace an even bigger PLL calculation =
routine,
and I do not know if they are correct or are just an attempt to read the
value that got "commented out" because it was not complete.

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So I ripped out the first two lines and count on the next 4 lines to
initialize clk_wr_offset.

I already compiled the appropriate kernel, but since my understanding of =
all
the hidden subtleties of the mach64 registers is far from complete, and =
my
only mac is an all-in-one machine where damage to the crt by wrong =
clocking
will render the entire box useless, I would appreciate it if you tell me =
at
least what you think and if I am putting my hardware at any risk.

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Thanks,

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Gil Bahat,

System Administrator.