Hi, On 1/6/21 3:59 PM, Peter Zijlstra wrote: > On Wed, Jan 06, 2021 at 01:31:46PM +0100, Hans de Goede wrote: >> Hi All, >> >> I've 2 different kernel bugs where the fix requires differentiating between >> Cherry Trail vs Brasswell, just checking the CPU model does not allow to >> differentiate between these 2 since they are both using Airmont cores. >> >> I have the same issue with the Bay Trail laptop SoCs vs the >> Bay Trail-T tablet SoCs, but for now lets focus on >> Cherry Trail vs Brasswell since that is less confusing: >> >> https://ark.intel.com/content/www/us/en/ark/products/codename/46629/cherry-trail.html >> https://ark.intel.com/content/www/us/en/ark/products/codename/66094/braswell.html >> >> So I see a number of possible solutions here: >> >> 1) Do a (substring) check on the CPU model-name checking for "x5-Z8" and "x7-Z8" >> 2) Check for presence of some embedded peripheral which is present on one but not the >> other. E.g. The Braswell devices have HDA audio where as the Cherry Trail devices >> use the "Low Power Engine (LPE) Audio Controller" >> 3) Check for acpi_gbl_reduced_hardware, but I'm not sure if that is a reliable >> indicator of running on the tablet versions of the SoCs. >> >> 1 and 2 will work but neither is very pretty, I guess I could try to spend some >> more time investigating 3. But I only have limited access to the non tablet versions >> of the Bay Trail and I'm not sure if I have any Braswell devices at all. >> >> So I was wondering if anyone else has any better ideas here? > > Does MSR_PLATFORM_ID (0x17) bits 50-52 work to differentiate these? Thank you, that is (was) a good idea. So since you send this email I've added a debug print to the kernel for these bits and collected the output of that debug print on various devices. Unfortunately these bits always read 0 on all Bay Trail / Bay Trail-T / Cherry Trail devices which I've tested, so these bits do not help. Regards, Hans
