[RESEND PATCH v2] acpi: Use access_width over register_width for system memory accesses

Jarred White
2023-12-16T00:13:43Z

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@linux.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