[PATCH 5.15.y 1/3] Revert "Revert "ACPI: CPPC: Use access_width over bit_width for system memory accesses""

[Easwar Hariharan <eahariha@linux.microsoft.com>]

This reverts commit b54c4632946ae42f2b39ed38abd909bbf78cbcc2 which was a
revert of a backport of commit 2f4a4d63a193be6fd530d180bb13c3592052904c
upstream to 5.15.y.

The original commit[1] fixed a kernel panic on boot on the Microsoft
Azure Cobalt 100 platform, but as reported by Vanshidhar Konda [2],
caused a regression in AmpereOne systems. While testing [2], there was
an additional bug found in [1] which resulted in [3]

[1] commit 2f4a4d63a193 ("ACPI: CPPC: Use access_width over bit_width for system memory accesses")
[2] commit f489c948028b ("ACPI: CPPC: Fix access width used for PCC registers")
[3] commit 05d92ee782ee ("ACPI: CPPC: Fix bit_offset shift in MASK_VAL() macro").

Cc: Jarred White <jarredwhite@linux.microsoft.com>
Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Cc: Vanshidhar Konda <vanshikonda@os.amperecomputing.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Easwar Hariharan <eahariha@linux.microsoft.com>
---
 drivers/acpi/cppc_acpi.c | 27 ++++++++++++++++++++++++---
 1 file changed, 24 insertions(+), 3 deletions(-)

diff --git a/drivers/acpi/cppc_acpi.c b/drivers/acpi/cppc_acpi.c
index 7cc9183c8dc8..408b1fda5702 100644
--- a/drivers/acpi/cppc_acpi.c
+++ b/drivers/acpi/cppc_acpi.c
@@ -161,6 +161,13 @@ show_cppc_data(cppc_get_perf_caps, cppc_perf_caps, nominal_freq);
 show_cppc_data(cppc_get_perf_ctrs, cppc_perf_fb_ctrs, reference_perf);
 show_cppc_data(cppc_get_perf_ctrs, cppc_perf_fb_ctrs, wraparound_time);
 
+/* Check for valid access_width, otherwise, fallback to using bit_width */
+#define GET_BIT_WIDTH(reg) ((reg)->access_width ? (8 << ((reg)->access_width - 1)) : (reg)->bit_width)
+
+/* Shift and apply the mask for CPC reads/writes */
+#define MASK_VAL(reg, val) ((val) >> ((reg)->bit_offset & 			\
+					GENMASK(((reg)->bit_width), 0)))
+
 static ssize_t show_feedback_ctrs(struct kobject *kobj,
 		struct kobj_attribute *attr, char *buf)
 {
@@ -762,8 +769,10 @@ int acpi_cppc_processor_probe(struct acpi_processor *pr)
 			} else if (gas_t->space_id == ACPI_ADR_SPACE_SYSTEM_MEMORY) {
 				if (gas_t->address) {
 					void __iomem *addr;
+					size_t access_width;
 
-					addr = ioremap(gas_t->address, gas_t->bit_width/8);
+					access_width = GET_BIT_WIDTH(gas_t) / 8;
+					addr = ioremap(gas_t->address, access_width);
 					if (!addr)
 						goto out_free;
 					cpc_ptr->cpc_regs[i-2].sys_mem_vaddr = addr;
@@ -936,6 +945,7 @@ static int cpc_read(int cpu, struct cpc_register_resource *reg_res, u64 *val)
 {
 	int ret_val = 0;
 	void __iomem *vaddr = NULL;
+	int size;
 	int pcc_ss_id = per_cpu(cpu_pcc_subspace_idx, cpu);
 	struct cpc_reg *reg = &reg_res->cpc_entry.reg;
 
@@ -955,7 +965,9 @@ static int cpc_read(int cpu, struct cpc_register_resource *reg_res, u64 *val)
 		return acpi_os_read_memory((acpi_physical_address)reg->address,
 				val, reg->bit_width);
 
-	switch (reg->bit_width) {
+	size = GET_BIT_WIDTH(reg);
+
+	switch (size) {
 	case 8:
 		*val = readb_relaxed(vaddr);
 		break;
@@ -974,12 +986,16 @@ static int cpc_read(int cpu, struct cpc_register_resource *reg_res, u64 *val)
 		ret_val = -EFAULT;
 	}
 
+	if (reg->space_id == ACPI_ADR_SPACE_SYSTEM_MEMORY)
+		*val = MASK_VAL(reg, *val);
+
 	return ret_val;
 }
 
 static int cpc_write(int cpu, struct cpc_register_resource *reg_res, u64 val)
 {
 	int ret_val = 0;
+	int size;
 	void __iomem *vaddr = NULL;
 	int pcc_ss_id = per_cpu(cpu_pcc_subspace_idx, cpu);
 	struct cpc_reg *reg = &reg_res->cpc_entry.reg;
@@ -994,7 +1010,12 @@ static int cpc_write(int cpu, struct cpc_register_resource *reg_res, u64 val)
 		return acpi_os_write_memory((acpi_physical_address)reg->address,
 				val, reg->bit_width);
 
-	switch (reg->bit_width) {
+	size = GET_BIT_WIDTH(reg);
+
+	if (reg->space_id == ACPI_ADR_SPACE_SYSTEM_MEMORY)
+		val = MASK_VAL(reg, val);
+
+	switch (size) {
 	case 8:
 		writeb_relaxed(val, vaddr);
 		break;

base-commit: b925f60c6ee7ec871d2d48575d0fde3872129c20
-- 
2.34.1