linux-kernel - [PATCH] acpi: Use access_width over register

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Message-Id: <20230925180552.76071-1-jarredwhite@linux.microsoft.com>
Date:   Mon, 25 Sep 2023 11:05:52 -0700
From:   Jarred White <jarredwhite@...ux.microsoft.com>
To:     "Rafael J. Wysocki" <rafael@...nel.org>,
        Len Brown <lenb@...nel.org>,
        linux-acpi@...r.kernel.org (open list:ACPI),
        linux-kernel@...r.kernel.org (open list)
Subject: [PATCH] acpi: Use access_width over register_width for system memory accesses

To align with ACPI 6.3+, since bit_width can be any 8-bit value, we cannot
depend on it being always on a clean 8b boundary. Instead, use access_width
to determine the size and use the offset and width to shift and mask the
bit swe want to read/write out. Make sure to add a check for system memory
since pcc redefines the access_width to subspace id.

Signed-off-by: Jarred White <jarredwhite@...ux.microsoft.com>
---
 drivers/acpi/cppc_acpi.c | 24 +++++++++++++++++++++---
 1 file changed, 21 insertions(+), 3 deletions(-)

diff --git a/drivers/acpi/cppc_acpi.c b/drivers/acpi/cppc_acpi.c
index 7ff269a78c20..07619b36c056 100644
--- a/drivers/acpi/cppc_acpi.c
+++ b/drivers/acpi/cppc_acpi.c
@@ -777,6 +777,7 @@ 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;
 
 					if (!osc_cpc_flexible_adr_space_confirmed) {
 						pr_debug("Flexible address space capability not supported\n");
@@ -784,7 +785,8 @@ int acpi_cppc_processor_probe(struct acpi_processor *pr)
 							goto out_free;
 					}
 
-					addr = ioremap(gas_t->address, gas_t->bit_width/8);
+					access_width = ((8 << (gas_t->access_width - 1)) / 8);
+					addr = ioremap(gas_t->address, access_width);
 					if (!addr)
 						goto out_free;
 					cpc_ptr->cpc_regs[i-2].sys_mem_vaddr = addr;
@@ -980,6 +982,7 @@ int __weak cpc_write_ffh(int cpunum, struct cpc_reg *reg, u64 val)
 static int cpc_read(int cpu, struct cpc_register_resource *reg_res, u64 *val)
 {
 	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;
 
@@ -1015,7 +1018,12 @@ 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) {
+	if (reg->space_id == ACPI_ADR_SPACE_SYSTEM_MEMORY)
+		size = (8 << (reg->access_width - 1));
+	else
+		size = reg->bit_width;
+
+	switch (size) {
 	case 8:
 		*val = readb_relaxed(vaddr);
 		break;
@@ -1034,12 +1042,16 @@ static int cpc_read(int cpu, struct cpc_register_resource *reg_res, u64 *val)
 		return -EFAULT;
 	}
 
+	if (reg->space_id == ACPI_ADR_SPACE_SYSTEM_MEMORY)
+		*val = (*val >> reg->bit_offset) & GENMASK((reg->bit_width) - 1, 0);
+
 	return 0;
 }
 
 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;
@@ -1067,7 +1079,13 @@ 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) {
+	if (reg->space_id == ACPI_ADR_SPACE_SYSTEM_MEMORY) {
+		size = (8 << (reg->access_width - 1));
+		val = (val >> reg->bit_offset) & GENMASK((reg->bit_width) - 1, 0);
+	} else
+		size = reg->bit_width;
+
+	switch (size) {
 	case 8:
 		writeb_relaxed(val, vaddr);
 		break;
-- 
2.34.1