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| author | Tamar Mashiah <tamar.mashiah@intel.com> | 2021-04-11 17:15:32 +0300 |
|---|---|---|
| committer | Hans de Goede <hdegoede@redhat.com> | 2021-04-13 10:26:40 +0300 |
| commit | ee7abc105e2b30378187e520be458a127d1d3762 (patch) | |
| tree | 70e57d2d1459c9190223079d91cbd9aed0bd07f1 /Documentation/ABI | |
| parent | 6759e18e5cd8745a5dfc5726e4a3db5281ec1639 (diff) | |
| download | linux-ee7abc105e2b30378187e520be458a127d1d3762.tar.xz | |
platform/x86: intel_pmc_core: export platform global reset bits via etr3 sysfs file
During PCH (platform/board) manufacturing process a global platform
reset has to be induced in order for the configuration changes take
the effect upon following platform reset. This is an internal platform
state and is not intended to be used in the regular platform resets.
The setting is exposed via ETR3 (Extended Test Mode Register 3).
After the manufacturing process is completed the register cannot be
written anymore and is hardware locked.
This setting was commonly done by accessing PMC registers via /dev/mem
but due to security concerns /dev/mem access is much more restricted,
hence the reason for exposing this setting via the dedicated sysfs
interface.
To prevent post manufacturing abuse the register is protected
by hardware locking and the file is set to read-only mode via is_visible
handler.
The register in MMIO space is defined for Cannon Lake and newer PCHs.
Cc: Hans de Goede <hdegoede@redhat.com>
Cc: David E Box <david.e.box@intel.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Tamar Mashiah <tamar.mashiah@intel.com>
Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Link: https://lore.kernel.org/r/20210411141532.3004893-1-tomas.winkler@intel.com
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Diffstat (limited to 'Documentation/ABI')
| -rw-r--r-- | Documentation/ABI/testing/sysfs-platform-intel-pmc | 20 |
1 files changed, 20 insertions, 0 deletions
diff --git a/Documentation/ABI/testing/sysfs-platform-intel-pmc b/Documentation/ABI/testing/sysfs-platform-intel-pmc new file mode 100644 index 000000000000..ef199af75ab0 --- /dev/null +++ b/Documentation/ABI/testing/sysfs-platform-intel-pmc @@ -0,0 +1,20 @@ +What: /sys/devices/platform/<platform>/etr3 +Date: Apr 2021 +KernelVersion: 5.13 +Contact: "Tomas Winkler" <tomas.winkler@intel.com> +Description: + The file exposes "Extended Test Mode Register 3" global + reset bits. The bits are used during an Intel platform + manufacturing process to indicate that consequent reset + of the platform is a "global reset". This type of reset + is required in order for manufacturing configurations + to take effect. + + Display global reset setting bits for PMC. + * bit 31 - global reset is locked + * bit 20 - global reset is set + Writing bit 20 value to the etr3 will induce + a platform "global reset" upon consequent platform reset, + in case the register is not locked. + The "global reset bit" should be locked on a production + system and the file is in read-only mode. |