linux-kernel - [RESEND PATCH v2] acpi: Use access_width over register

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Message-Id: <20231216001312.1160-1-jarredwhite@linux.microsoft.com>
Date: Fri, 15 Dec 2023 16:13:12 -0800
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: [RESEND PATCH v2] 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
bits we 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>
---
Original thread
https://lore.kernel.org/all/20230925180552.76071-1-jarredwhite@linux.microsoft.com/
---
changelog:
v1-->v2:
	1. Fixed coding style errors
        2. Backwards compatibility with ioremapping of address still an
           open question. Suggestions are welcomed.

 drivers/acpi/cppc_acpi.c | 36 +++++++++++++++++++++++++++++++-----
 1 file changed, 31 insertions(+), 5 deletions(-)

diff --git a/drivers/acpi/cppc_acpi.c b/drivers/acpi/cppc_acpi.c
index 7ff269a78c20..fb37e1727bf8 100644
--- a/drivers/acpi/cppc_acpi.c
+++ b/drivers/acpi/cppc_acpi.c
@@ -163,6 +163,13 @@ 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);
 
+/* Use access_width to determine the total number of bits */
+#define ACCESS_WIDTH_TO_BITS(reg) 8 << ((reg)->access_width - 1)
+
+/* Shift and apply the mask for CPC reads/writes */
+#define MASK_VAL(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)
 {
@@ -777,6 +784,7 @@ 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 +792,8 @@ int acpi_cppc_processor_probe(struct acpi_processor *pr)
 							goto out_free;
 					}
 
-					addr = ioremap(gas_t->address, gas_t->bit_width/8);
+					access_width = ACCESS_WIDTH_TO_BITS(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;
@@ -980,6 +989,7 @@ 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;
 
@@ -991,7 +1001,7 @@ static int cpc_read(int cpu, struct cpc_register_resource *reg_res, u64 *val)
 	*val = 0;
 
 	if (reg->space_id == ACPI_ADR_SPACE_SYSTEM_IO) {
-		u32 width = 8 << (reg->access_width - 1);
+		u32 width = ACCESS_WIDTH_TO_BITS(reg);
 		u32 val_u32;
 		acpi_status status;
 
@@ -1015,7 +1025,12 @@ 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 = ACCESS_WIDTH_TO_BITS(reg);
+	else
+		size = reg->bit_width;
+
+	switch (size) {
 	case 8:
 		*val = readb_relaxed(vaddr);
 		break;
@@ -1034,18 +1049,22 @@ 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 = MASK_VAL(*val);
+
 	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;
 
 	if (reg->space_id == ACPI_ADR_SPACE_SYSTEM_IO) {
-		u32 width = 8 << (reg->access_width - 1);
+		u32 width = ACCESS_WIDTH_TO_BITS(reg);
 		acpi_status status;
 
 		status = acpi_os_write_port((acpi_io_address)reg->address,
@@ -1067,7 +1086,14 @@ 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 = ACCESS_WIDTH_TO_BITS(reg);
+		val = MASK_VAL(val);
+	} else {
+		size = reg->bit_width;
+	}
+
+	switch (size) {
 	case 8:
 		writeb_relaxed(val, vaddr);
 		break;
-- 
2.34.1