On 12/19/2017 02:10 PM, Jarkko Sakkinen wrote: > On Tue, Dec 19, 2017 at 12:34:46AM +0100, Javier Martinez Canillas wrote: >> Hello Jason, >> >> On 12/18/2017 09:19 PM, Jason Gunthorpe wrote: >>> On Mon, Dec 18, 2017 at 07:34:29PM +0000, Shaikh, Azhar wrote: >>> >>>>> IIUC, if CLKRUN_EN is enabled, then all the devices attached to the >>>>> LPC bus have to support the CLKRUN protocol. My guess is that on >>>>> some Braswell systems LPC power management is enabled but the TPM >>>>> device doesn't have CLKRUN support. >>>> >>>> I think this is what might be happening here. >>> >>> That makes it a BIOS bug, not a chipset bug, and we shouldn't be >>> trying to fix it like this in Linux. >>> >> >> Indeed, the system integrator should make sure that all peripherals that >> are connected through the LPC bus either support the CLKRUN protocol and >> CLKRUN_EN is enabled or CLKRUN_EN should be disabled. >> >>> Based on the original discussion I always thought this was an Intel >>> chipset bug and applies to all cases. >>> >> >> After thinking about this and with a better understanding of the issue, >> I think we have 2 options (please let me know if I got something wrong): >> >> 1) Leave the code as is and apply the patch I shared with James. In that >> case the CLKRUN protocol will be disabled only during TPM transactions >> and not enabled again after transactions if it wasn't enabled. >> >> This shouldn't affect other peripherals since even if they have CLKRUN >> support, they should work correctly while CLKRUN protocol is disabled. >> >> The disadvantage is that TPM devices that have CLKRUN support (do they >> exist?) will not take the advantage of the power management feature of >> stopping the LPC host LCLK clock during low-power states. > > CLKRUN is enabled after TPM has processed the command so how this could > make power mgmt worse? > I meant if there are Braswell systems with a TPM that _does_ support CLKRUN protocol. Since the current code disables ClKRUN_EN for all Braswell boards. > /Jarkko > Best regards, -- Javier Martinez Canillas Software Engineer - Desktop Hardware Enablement Red Hat
