Patchwork SB700: enable PrefetchEnSPIFromHost to improve boot time from SPI flash

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@notabs.org>

On 10/17/10 6:49 PM, Scott Duplichan wrote:
> 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@notabs.org>

Acked-by: Stefan Reinauer <stepan@coreboot.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) */
>
>
>

On 18.10.2010 03:49, Scott Duplichan wrote:
> 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@notabs.org>
>   

(Speaking with my flashrom hat on)
Looks good to me.

I think we want the same setting for SB600 if it is available there.

Acked-by: Carl-Daniel Hailfinger <c-d.hailfinger.devel.2006@gmx.net>

Can you commit or should I do it?

Regards,
Carl-Daniel

]> 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@notabs.org>
]>   
]
](Speaking with my flashrom hat on)
]Looks good to me.
]
]I think we want the same setting for SB600 if it is available there.
]
]Acked-by: Carl-Daniel Hailfinger <c-d.hailfinger.devel.2006@gmx.net>
]
]Can you commit or should I do it?
]
]Regards,
]Carl-Daniel
]
]-- 
]http://www.hailfinger.org/

Thanks Carl-Daniel,

I managed to do the commit. Unfortunately, SB600 does not support
this option. Starting with SB800, the fast mode SPI writes can be
used in addition to PrefetchEnSPIFromHost. SB900 has even more 
SPI improvement.

Thanks,
Scott

On 18.10.2010 06:10, Scott Duplichan wrote:
> I managed to do the commit. Unfortunately, SB600 does not support
> this option.

Right, I remembered something like that, but I didn't have the datasheet
handy to check.


> Starting with SB800, the fast mode SPI writes can be
> used in addition to PrefetchEnSPIFromHost. SB900 has even more 
> SPI improvement.
>   

Thanks for the info. I really hope the RS880 and SB800 datasheets will
become public (or are they and I just missed the announcement)?

Regards,
Carl-Daniel