Timothy Pearson (tpearson@raptorengineeringinc.com) just uploaded a new patch set to gerrit, which you can find at http://review.coreboot.org/11985
-gerrit
commit 994c2962087c1b42697b0c7cef61bc1fb8fb1587 Author: Timothy Pearson tpearson@raptorengineeringinc.com Date: Wed Jun 10 00:35:05 2015 -0500
northbridge/amd/amdfam10: Add ability to set maximum P-state limit
Under specific circumstances, for instance in low power or fanless machines, it may be useful to cap the maximum P-state of the CPU.
Allow the maximum CPU P-state to be set via an NVRAM option.
Change-Id: Ifdbb1ad11a856f855c59702ae0ee99e95b08520e Signed-off-by: Timothy Pearson tpearson@raptorengineeringinc.com --- src/northbridge/amd/amdfam10/misc_control.c | 24 ++++++++++++++++++++---- 1 file changed, 20 insertions(+), 4 deletions(-)
diff --git a/src/northbridge/amd/amdfam10/misc_control.c b/src/northbridge/amd/amdfam10/misc_control.c index 24c422d..847b599 100644 --- a/src/northbridge/amd/amdfam10/misc_control.c +++ b/src/northbridge/amd/amdfam10/misc_control.c @@ -120,16 +120,32 @@ static void mcf3_set_resources(device_t dev)
static void misc_control_init(struct device *dev) { - u32 cmd; + uint32_t dword; + uint8_t nvram; + uint8_t boost_limit; + uint8_t current_boost;
printk(BIOS_DEBUG, "NB: Function 3 Misc Control.. ");
/* Disable Machine checks from Invalid Locations. * This is needed for PC backwards compatibility. */ - cmd = pci_read_config32(dev, 0x44); - cmd |= (1<<6) | (1<<25); - pci_write_config32(dev, 0x44, cmd ); + dword = pci_read_config32(dev, 0x44); + dword |= (1<<6) | (1<<25); + pci_write_config32(dev, 0x44, dword); + + boost_limit = 0xf; + if (get_option(&nvram, "maximum_p_state_limit") == CB_SUCCESS) + boost_limit = nvram & 0xf; + + /* Set P-state maximum value */ + dword = pci_read_config32(dev, 0xdc); + current_boost = (dword >> 8) & 0x7; + if (boost_limit > current_boost) + boost_limit = current_boost; + dword &= ~(0x7 << 8); + dword |= (boost_limit & 0x7) << 8; + pci_write_config32(dev, 0xdc, dword);
printk(BIOS_DEBUG, "done.\n"); }