platform/x86:intel/pmc: Use SSRAM to discover pwrm base address of primary PMC

On older platforms, the base address for PMC was hardcoded in the
driver. Newer platforms can now retrieve the base address from SSRAM.
Use SSRAM to discover pwrm base address on Meteor Lake platform. If
this method fails, it will fall back to the hardcoded value.
Signed-off-by: Xi Pardee <xi.pardee@intel.com>
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Link: https://lore.kernel.org/r/20230613225347.2720665-7-rajvi.jingar@linux.intel.comSigned-off-by: Hans de Goede <hdegoede@redhat.com>

drivers/platform/x86/intel/pmc/mtl.c

@@ -467,7 +467,12 @@ const struct pmc_reg_map mtl_socm_reg_map = {
 	.lpm_live_status_offset = MTL_LPM_LIVE_STATUS_OFFSET,
 };
 
+#define PMC_DEVID_SOCM	0x7e7f
 static struct pmc_info mtl_pmc_info_list[] = {
+	{
+		.devid = PMC_DEVID_SOCM,
+		.map = &mtl_socm_reg_map,
+	},
 	{}
 };
 
@@ -513,9 +518,7 @@ static int mtl_resume(struct pmc_dev *pmcdev)
 int mtl_core_init(struct pmc_dev *pmcdev)
 {
 	struct pmc *pmc = pmcdev->pmcs[PMC_IDX_SOC];
-	int ret;
-
-	pmc->map = &mtl_socm_reg_map;
+	int ret = 0;
 
 	mtl_d3_fixup();
 
@@ -524,9 +527,13 @@ int mtl_core_init(struct pmc_dev *pmcdev)
 	pmcdev->regmap_list = mtl_pmc_info_list;
 	pmc_core_ssram_init(pmcdev);
 
-	ret = get_primary_reg_base(pmc);
-	if (ret)
-		return ret;
+	/* If regbase not assigned, set map and discover using legacy method */
+	if (!pmc->regbase) {
+		pmc->map = &mtl_socm_reg_map;
+		ret = get_primary_reg_base(pmc);
+		if (ret)
+			return ret;
+	}
 
 	/* Due to a hardware limitation, the GBE LTR blocks PC10
 	 * when a cable is attached. Tell the PMC to ignore it.