platform/x86/amd: pmc: Clear metrics table at start of cycle

JIRA: https://issues.redhat.com/browse/RHEL-103121

commit 4dbd117
Author: Mario Limonciello <mario.limonciello@amd.com>
Date:   Tue Jun 3 08:24:08 2025 -0500

    platform/x86/amd: pmc: Clear metrics table at start of cycle

    The area of memory that contains the metrics table may contain garbage
    when the cycle starts.  This normally doesn't matter because the cycle
    itself will populate it with valid data, however commit 9f5595d
    ("platform/x86/amd: pmc: Require at least 2.5 seconds between HW sleep
    cycles") started to use it during the check() phase.  Depending upon
    what garbage is in the table it's possible that the system will wait
    2.5 seconds for even the first cycle, which will be visible to a user.

    To prevent this from happening explicitly clear the table when logging
    is started.

    Fixes: 9f5595d ("platform/x86/amd: pmc: Require at least 2.5 seconds between HW sleep cycles")
    Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
    Link: https://lore.kernel.org/r/20250603132412.3555302-1-superm1@kernel.org
    Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
    Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>

Signed-off-by: Steve Best <sbest@redhat.com>

Author: sfbest

drivers/platform/x86/amd/pmc/pmc.c

@@ -157,6 +157,8 @@ static int amd_pmc_setup_smu_logging(struct amd_pmc_dev *dev)
 			return -ENOMEM;
 	}
 
+	memset_io(dev->smu_virt_addr, 0, sizeof(struct smu_metrics));
+
 	/* Start the logging */
 	amd_pmc_send_cmd(dev, 0, NULL, SMU_MSG_LOG_RESET, false);
 	amd_pmc_send_cmd(dev, 0, NULL, SMU_MSG_LOG_START, false);