Make ASUS P3B-F RAM init actually work by enabling SPD access.

On this board all reads from SPD return 0xff by default, there's a custom
GPIO fiddling needed to enable access to the SPD SMBus offsets at
0x50-0x53. While coreboot actually sort of booted sometimes before r5193,
that was just sheer luck as the RAM init was hardcoded in certain ways.
Since the proper, more heavily SPD-based RAM init the brokenness of the
ASUS P3B-F RAM init was becoming visible.

This patch uses GPIOs to enable access to the SPD SMBus offsets,
and resets the GPIOs again after RAM init (this is needed to allow for
lm-sensors to work, for example).

Tested successfully on hardware.

Signed-off-by: Uwe Hermann <uwe@hermann-uwe.de>
Acked-by: Idwer Vollering <vidwer@gmail.com>



git-svn-id: svn://svn.coreboot.org/coreboot/trunk@5819 2b7e53f0-3cfb-0310-b3e9-8179ed1497e1

1 files changed, 38 insertions, 0 deletions

diff --git a/src/mainboard/asus/p3b-f/romstage.c b/src/mainboard/asus/p3b-f/romstage.c
index 0867886fa0..cde5400ff4 100644
--- a/src/mainboard/asus/p3b-f/romstage.c
+++ b/src/mainboard/asus/p3b-f/romstage.c
@@ -29,6 +29,7 @@
 #include "lib/ramtest.c"
 #include "southbridge/intel/i82371eb/i82371eb_enable_rom.c"
 #include "southbridge/intel/i82371eb/i82371eb_early_smbus.c"
+#include "southbridge/intel/i82371eb/i82371eb_early_pm.c"
 #include "northbridge/intel/i440bx/raminit.h"
 #include "lib/debug.c"
 #include "pc80/udelay_io.c"
@@ -49,6 +50,37 @@ static inline int spd_read_byte(unsigned int device, unsigned int address)
 #include "northbridge/intel/i440bx/raminit.c"
 #include "northbridge/intel/i440bx/debug.c"
 
+/*
+ * ASUS P3B-F specific SPD enable magic.
+ *
+ * Setting the byte at offset 0x37 in the PM I/O space to 0x6f will make the
+ * board DIMMs accessible at SMBus/SPD offsets 0x50-0x53. Per default the SPD
+ * offsets 0x50-0x53 are _not_ readable (all SPD reads will return 0xff) which
+ * will make RAM init fail.
+ *
+ * Tested values for PM I/O offset 0x37:
+ * 0x67: 11 00 111: Only SMBus/I2C offsets 0x48/0x49/0x2d accessible
+ * 0x6f: 11 01 111: Only SMBus/I2C offsets 0x50-0x53 (SPD) accessible
+ * 0x77: 11 10 111: Only SMBus/I2C offset 0x69 accessible
+ *
+ * PM I/O space offset 0x37 is GPOREG[31:24], i.e. it controls the GPIOs
+ * 24-30 of the PIIX4E (bit 31 is reserved). Thus, GPIOs 27 and 28
+ * control which SMBus/I2C offsets can be accessed.
+ */
+static void enable_spd(void)
+{
+	outb(0x6f, PM_IO_BASE + 0x37);
+}
+
+/*
+ * Disable SPD access after RAM init to allow access to SMBus/I2C offsets
+ * 0x48/0x49/0x2d, which is required e.g. by lm-sensors.
+ */
+static void disable_spd(void)
+{
+	outb(0x67, PM_IO_BASE + 0x37);
+}
+
 static void main(unsigned long bist)
 {
 	if (bist == 0)
@@ -64,10 +96,16 @@ static void main(unsigned long bist)
 	i82371eb_enable_rom(PCI_DEV(0, 4, 0)); /* ISA bridge is 00:04.0. */
 
 	enable_smbus();
+	enable_pm();
+
+	enable_spd();
+
 	/* dump_spd_registers(); */
 	sdram_set_registers();
 	sdram_set_spd_registers();
 	sdram_enable();
 	/* ram_check(0, 640 * 1024); */
+
+	disable_spd();
 }