[coreboot] [PATCH] v3: rework Geode LX RAMinit DIMM size formula

[Carl-Daniel Hailfinger]

Rework Geode LX RAMinit DIMM size formula to be more
understandable. Added benefit is complaining loudly for
unsupported 2 GB DIMM size.

Signed-off-by: Carl-Daniel Hailfinger <c-d.hailfinger.devel.2006 at gmx.net>

Index: LinuxBIOSv3-stuff/northbridge/amd/geodelx/raminit.c
===================================================================
--- LinuxBIOSv3-stuff/northbridge/amd/geodelx/raminit.c	(Revision 659)
+++ LinuxBIOSv3-stuff/northbridge/amd/geodelx/raminit.c	(Arbeitskopie)
@@ -151,16 +151,12 @@
 	banner(BIOS_DEBUG, "SPDBANKDENSITY");
 	dimm_size = spd_read_byte(dimm, SPD_BANK_DENSITY);
 
-	/* Align so 1 GB (bit 0) is bit 8. This is a little weird to get gcc
-	 * to not optimize this out.
+	/* Bits 0-1 have been redefined by JEDEC to contain what would have
+	 * been in non-existing bits 8 (1GB) and 9 (2GB). Move bits 0-1 to
+	 * bits 8-9 and mask bits 0-1 off.
 	 */
-	dimm_size |= (dimm_size << 8);
+	dimm_size = ((dimm_size & 0x3) << 8) | (dimm_size & ~0x3);
 
-	/* And off 2 GB DIMM size: not supported and the 1 GB size we just
-	 * moved up to bit 8 as well as all the extra on top.
-	 */
-	dimm_size &= 0x01FC;
-
 	/* Module Density * Module Banks */
 	/* Shift to multiply by the number of DIMM banks. */
 	dimm_size <<= (dimm_setting >> CF07_UPPER_D0_MB_SHIFT) & 1;


-- 
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