mach64: detect the dot clock divider correctly on sparc

commit 76ebebd2464c5c8a4453c98b6dbf9c95a599e810 upstream.

On Sun Ultra 5, it happens that the dot clock is not set up properly for
some videomodes. For example, if we set the videomode "r1024x768x60" in
the firmware, Linux would incorrectly set a videomode with refresh rate
180Hz when booting (suprisingly, my LCD monitor can display it, although
display quality is very low).

The reason is this: Older mach64 cards set the divider in the register
VCLK_POST_DIV. The register has four 2-bit fields (the field that is
actually used is specified in the lowest two bits of the register
CLOCK_CNTL). The 2 bits select divider "1, 2, 4, 8". On newer mach64 cards,
there's another bit added - the top four bits of PLL_EXT_CNTL extend the
divider selection, so we have possible dividers "1, 2, 4, 8, 3, 5, 6, 12".
The Linux driver clears the top four bits of PLL_EXT_CNTL and never sets
them, so it can work regardless if the card supports them. However, the
sparc64 firmware may set these extended dividers during boot - and the
mach64 driver detects incorrect dot clock in this case.

This patch makes the driver read the additional divider bit from
PLL_EXT_CNTL and calculate the initial refresh rate properly.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Cc: stable@vger.kernel.org
Acked-by: David S. Miller <davem@davemloft.net>
Reviewed-by: Ville Syrjälä <syrjala@sci.fi>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 5 insertions, 5 deletions

diff --git a/drivers/video/fbdev/aty/mach64_ct.c b/drivers/video/fbdev/aty/mach64_ct.c
index 7d3bd723d3d5..d55f4bacb41c 100644
--- a/drivers/video/fbdev/aty/mach64_ct.c
+++ b/drivers/video/fbdev/aty/mach64_ct.c
@@ -115,7 +115,7 @@ static void aty_st_pll_ct(int offset, u8 val, const struct atyfb_par *par)
  */
 
 #define Maximum_DSP_PRECISION 7
-static u8 postdividers[] = {1,2,4,8,3};
+const u8 aty_postdividers[8] = {1,2,4,8,3,5,6,12};
 
 static int aty_dsp_gt(const struct fb_info *info, u32 bpp, struct pll_ct *pll)
 {
@@ -222,7 +222,7 @@ static int aty_valid_pll_ct(const struct fb_info *info, u32 vclk_per, struct pll
 		pll->vclk_post_div += (q <  64*8);
 		pll->vclk_post_div += (q <  32*8);
 	}
-	pll->vclk_post_div_real = postdividers[pll->vclk_post_div];
+	pll->vclk_post_div_real = aty_postdividers[pll->vclk_post_div];
 	//    pll->vclk_post_div <<= 6;
 	pll->vclk_fb_div = q * pll->vclk_post_div_real / 8;
 	pllvclk = (1000000 * 2 * pll->vclk_fb_div) /
@@ -513,7 +513,7 @@ static int aty_init_pll_ct(const struct fb_info *info, union aty_pll *pll)
 		u8 mclk_fb_div, pll_ext_cntl;
 		pll->ct.pll_ref_div = aty_ld_pll_ct(PLL_REF_DIV, par);
 		pll_ext_cntl = aty_ld_pll_ct(PLL_EXT_CNTL, par);
-		pll->ct.xclk_post_div_real = postdividers[pll_ext_cntl & 0x07];
+		pll->ct.xclk_post_div_real = aty_postdividers[pll_ext_cntl & 0x07];
 		mclk_fb_div = aty_ld_pll_ct(MCLK_FB_DIV, par);
 		if (pll_ext_cntl & PLL_MFB_TIMES_4_2B)
 			mclk_fb_div <<= 1;
@@ -535,7 +535,7 @@ static int aty_init_pll_ct(const struct fb_info *info, union aty_pll *pll)
 		xpost_div += (q <  64*8);
 		xpost_div += (q <  32*8);
 	}
-	pll->ct.xclk_post_div_real = postdividers[xpost_div];
+	pll->ct.xclk_post_div_real = aty_postdividers[xpost_div];
 	pll->ct.mclk_fb_div = q * pll->ct.xclk_post_div_real / 8;
 
 #ifdef CONFIG_PPC
@@ -584,7 +584,7 @@ static int aty_init_pll_ct(const struct fb_info *info, union aty_pll *pll)
 			mpost_div += (q <  64*8);
 			mpost_div += (q <  32*8);
 		}
-		sclk_post_div_real = postdividers[mpost_div];
+		sclk_post_div_real = aty_postdividers[mpost_div];
 		pll->ct.sclk_fb_div = q * sclk_post_div_real / 8;
 		pll->ct.spll_cntl2 = mpost_div << 4;
 #ifdef DEBUG