[coreboot] [PATCH] SB700: enable PrefetchEnSPIFromHost to improve boot time from SPI flash

Scott Duplichan scott at notabs.org
Mon Oct 18 03:49:45 CEST 2010


This patch enables SB700 option PrefetchEnSPIFromHost in early setup.
It affects only systems booting from SPI flash, not those booting from
LPC flash. By default, the SB700 reads dwords from the SPI flash chip.
Setting PrefetchEnSPIFromHost causes the SB700 to read entire cache
lines from the flash chip. 

Thanks,
Scott

Signed-off-by: Scott Duplichan <scott at notabs.org>

Index: src/southbridge/amd/sb700/sb700_early_setup.c
===================================================================
--- src/southbridge/amd/sb700/sb700_early_setup.c       (revision 5964)
+++ src/southbridge/amd/sb700/sb700_early_setup.c       (working copy)
@@ -129,6 +129,11 @@
        reg8 |= (1 << 5) | (1 << 6);
        pci_write_config8(dev, 0x47, reg8);

+       /* Enable PrefetchEnSPIFromHost to speed up SPI flash read (does not affect LPC) */
+       reg8 = pci_read_config8(dev, 0xbb);
+       reg8 |= 1 << 0;
+       pci_write_config8(dev, 0xbb, reg8);
+
        /* SuperIO, LPC ROM */
        reg8 = pci_read_config8(dev, 0x48);
        /* Decode ports 0x2e-0x2f, 0x4e-0x4f (SuperI/O configuration) */






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