linux-kernel - Re: [PATCH] atyfb: fix distorted image on PowerMacs

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Message-Id: <1233286970.18767.19.camel@pasglop>
Date:	Fri, 30 Jan 2009 14:42:50 +1100
From:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
To:	Risto Suominen <risto.suominen@...il.com>
Cc:	Alex Kern <alex.kern@....de>, linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] atyfb: fix distorted image on PowerMacs

On Thu, 2009-01-22 at 20:22 +0200, Risto Suominen wrote:
> Since the complete re-write in 2.6.10, some PowerMacs (At least PowerMac 5500
> and PowerMac G3 Beige rev A) with ATI Mach64 chip have suffered from unstable
> columns in their framebuffer image. This seems to depend on a value (4) read
> from PLL_EXT_CNTL register, which leads to incorrect DSP config parameters to
> be written to the chip. This patch uses a value calculated by aty_init_pll_ct
> instead, as a starting point.
> 
> Signed-off-by: Risto Suominen <Risto.Suominen@...il.com>
> ---
> The testing is done on kernel version 2.6.18.

This also fixes my oooold wallstreet powerbook.

Andrew, do you mind if I include that in the powerpc tree ?

Cheers,
Ben.

> --- a/drivers/video/aty/mach64_ct.c.org	2006-09-20 06:42:06.000000000 +0300
> +++ b/drivers/video/aty/mach64_ct.c	2009-01-22 14:28:13.000000000 +0200
> @@ -7,6 +7,7 @@
>  #include <linux/delay.h>
>  #include <asm/io.h>
>  #include <video/mach64.h>
> +#include <asm/machdep.h>
>  #include "atyfb.h"
> 
>  #undef DEBUG
> @@ -536,6 +537,14 @@ static int __init aty_init_pll_ct(const
>  	pll->ct.xclk_post_div_real = postdividers[xpost_div];
>  	pll->ct.mclk_fb_div = q * pll->ct.xclk_post_div_real / 8;
> 
> +#ifdef CONFIG_PPC
> +	if (machine_is(powermac)) {
> +		/* Override PLL_EXT_CNTL & 0x07. */
> +		pll->ct.xclk_post_div = xpost_div;
> +		pll->ct.xclk_ref_div = 1;
> +	}
> +#endif
> +
>  #ifdef DEBUG
>  	pllmclk = (1000000 * pll->ct.mclk_fb_mult * pll->ct.mclk_fb_div) /
>  			(par->ref_clk_per * pll->ct.pll_ref_div);

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