cpufreq / cppc: Work around for Hisilicon CPPC cpufreq

Hisilicon chips do not support delivered performance counter register
and reference performance counter register. But the platform can
calculate the real performance using its own method. We reuse the
desired performance register to store the real performance calculated by
the platform. After the platform finished the frequency adjust, it gets
the real performance and writes it into desired performance register. Os
can use it to calculate the real frequency.
Signed-off-by: Xiongfeng Wang <wangxiongfeng2@huawei.com>
[ rjw: Drop unnecessary braces ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/cpufreq/cppc_cpufreq.c

@@ -42,6 +42,66 @@
  */
 static struct cppc_cpudata **all_cpu_data;
 
+struct cppc_workaround_oem_info {
+	char oem_id[ACPI_OEM_ID_SIZE +1];
+	char oem_table_id[ACPI_OEM_TABLE_ID_SIZE + 1];
+	u32 oem_revision;
+};
+
+static bool apply_hisi_workaround;
+
+static struct cppc_workaround_oem_info wa_info[] = {
+	{
+		.oem_id		= "HISI  ",
+		.oem_table_id	= "HIP07   ",
+		.oem_revision	= 0,
+	}, {
+		.oem_id		= "HISI  ",
+		.oem_table_id	= "HIP08   ",
+		.oem_revision	= 0,
+	}
+};
+
+static unsigned int cppc_cpufreq_perf_to_khz(struct cppc_cpudata *cpu,
+					unsigned int perf);
+
+/*
+ * HISI platform does not support delivered performance counter and
+ * reference performance counter. It can calculate the performance using the
+ * platform specific mechanism. We reuse the desired performance register to
+ * store the real performance calculated by the platform.
+ */
+static unsigned int hisi_cppc_cpufreq_get_rate(unsigned int cpunum)
+{
+	struct cppc_cpudata *cpudata = all_cpu_data[cpunum];
+	u64 desired_perf;
+	int ret;
+
+	ret = cppc_get_desired_perf(cpunum, &desired_perf);
+	if (ret < 0)
+		return -EIO;
+
+	return cppc_cpufreq_perf_to_khz(cpudata, desired_perf);
+}
+
+static void cppc_check_hisi_workaround(void)
+{
+	struct acpi_table_header *tbl;
+	acpi_status status = AE_OK;
+	int i;
+
+	status = acpi_get_table(ACPI_SIG_PCCT, 0, &tbl);
+	if (ACPI_FAILURE(status) || !tbl)
+		return;
+
+	for (i = 0; i < ARRAY_SIZE(wa_info); i++) {
+		if (!memcmp(wa_info[i].oem_id, tbl->oem_id, ACPI_OEM_ID_SIZE) &&
+		    !memcmp(wa_info[i].oem_table_id, tbl->oem_table_id, ACPI_OEM_TABLE_ID_SIZE) &&
+		    wa_info[i].oem_revision == tbl->oem_revision)
+			apply_hisi_workaround = true;
+	}
+}
+
 /* Callback function used to retrieve the max frequency from DMI */
 static void cppc_find_dmi_mhz(const struct dmi_header *dm, void *private)
 {
@@ -334,6 +394,9 @@ static unsigned int cppc_cpufreq_get_rate(unsigned int cpunum)
 	struct cppc_cpudata *cpu = all_cpu_data[cpunum];
 	int ret;
 
+	if (apply_hisi_workaround)
+		return hisi_cppc_cpufreq_get_rate(cpunum);
+
 	ret = cppc_get_perf_ctrs(cpunum, &fb_ctrs_t0);
 	if (ret)
 		return ret;
@@ -386,6 +449,8 @@ static int __init cppc_cpufreq_init(void)
 		goto out;
 	}
 
+	cppc_check_hisi_workaround();
+
 	ret = cpufreq_register_driver(&cppc_cpufreq_driver);
 	if (ret)
 		goto out;