On 4/11/2024 2:23 PM, Vanshidhar Konda wrote:
commit 2f4a4d63a193be6fd530d180bb13c3592052904c modified cpc_read/cpc_write to use access_width to read CPC registers. For PCC registers the access width field in the ACPI register macro specifies the PCC subspace id. For non-zero PCC subspace id the access width is incorrectly treated as access width. This causes errors when reading from PCC registers in the CPPC driver.
For PCC registers base the size of read/write on the bit width field. The debug message in cpc_read/cpc_write is updated to print relevant information for the address space type used to read the register.
Signed-off-by: Vanshidhar Konda vanshikonda@os.amperecomputing.com Tested-by: Jarred White jarredwhite@linux.microsoft.com Reviewed-by: Jarred White jarredwhite@linux.microsoft.com Cc: 5.15+ stable@vger.kernel.org # 5.15+
When testing v6.9-rc1 kernel on AmpereOne system dmesg showed that cpufreq policy had failed to initialize on some cores during boot because cpufreq->get() always returned 0. On this system CPPC registers are in PCC subspace index 2 that are 32 bits wide. With this patch the CPPC driver interpreted the access width field as 16 bits, causing the register read to roll over too quickly to provide valid values during frequency computation.
v2:
- Use size variable in debug print message
- Use size instead of reg->bit_width for acpi_os_read_memory and acpi_os_write_memory
drivers/acpi/cppc_acpi.c | 53 ++++++++++++++++++++++++++++------------ 1 file changed, 37 insertions(+), 16 deletions(-)
Thanks for adding the CC: stable tag. Couple of nits, assuming those are fixed:
Reviewed-by: Easwar Hariharan eahariha@linux.microsoft.com
diff --git a/drivers/acpi/cppc_acpi.c b/drivers/acpi/cppc_acpi.c index 4bfbe55553f4..a037e9d15f48 100644 --- a/drivers/acpi/cppc_acpi.c +++ b/drivers/acpi/cppc_acpi.c @@ -1002,14 +1002,14 @@ static int cpc_read(int cpu, struct cpc_register_resource *reg_res, u64 *val) } *val = 0;
- size = GET_BIT_WIDTH(reg);
if (reg->space_id == ACPI_ADR_SPACE_SYSTEM_IO) {
u32 width = GET_BIT_WIDTH(reg);status = acpi_os_read_port((acpi_io_address)reg->address,
&val_u32, width);
&val_u32, size);@@ -1018,17 +1018,22 @@ static int cpc_read(int cpu, struct cpc_register_resource *reg_res, u64 *val) *val = val_u32; return 0;
- } else if (reg->space_id == ACPI_ADR_SPACE_PLATFORM_COMM && pcc_ss_id >= 0)
- } else if (reg->space_id == ACPI_ADR_SPACE_PLATFORM_COMM && pcc_ss_id >= 0) {
/** For registers in PCC space, the register size is determined* by the bit width field; the access size is used to indicate* the PCC subspace id.*/size = reg->bit_width;- } else if (reg->space_id == ACPI_ADR_SPACE_SYSTEM_MEMORY) vaddr = reg_res->sys_mem_vaddr; else if (reg->space_id == ACPI_ADR_SPACE_FIXED_HARDWARE) return cpc_read_ffh(cpu, reg, val); else return acpi_os_read_memory((acpi_physical_address)reg->address,
val, reg->bit_width);- size = GET_BIT_WIDTH(reg);
val, size);switch (size) { case 8: @@ -1044,8 +1049,13 @@ static int cpc_read(int cpu, struct cpc_register_resource *reg_res, u64 *val) *val = readq_relaxed(vaddr); break; default:
pr_debug("Error: Cannot read %u bit width from PCC for ss: %d\n",reg->bit_width, pcc_ss_id);
if (reg->space_id == ACPI_ADR_SPACE_SYSTEM_MEMORY) {pr_debug("Error: Cannot read %u width from for system memory: 0x%llx\n",size, reg->address);
Nit: from for? There might be a missing word there, or just an extra. Ditto for cpc_write() below.
} else if (reg->space_id == ACPI_ADR_SPACE_PLATFORM_COMM) {pr_debug("Error: Cannot read %u bit width to PCC for ss: %d\n",size, pcc_ss_id);}@@ -1063,12 +1073,13 @@ static int cpc_write(int cpu, struct cpc_register_resource *reg_res, u64 val) int pcc_ss_id = per_cpu(cpu_pcc_subspace_idx, cpu); struct cpc_reg *reg = ®_res->cpc_entry.reg;
- size = GET_BIT_WIDTH(reg);
- if (reg->space_id == ACPI_ADR_SPACE_SYSTEM_IO) {
u32 width = GET_BIT_WIDTH(reg);status = acpi_os_write_port((acpi_io_address)reg->address,
(u32)val, width);
(u32)val, size);@@ -1076,17 +1087,22 @@ static int cpc_write(int cpu, struct cpc_register_resource *reg_res, u64 val) } return 0;
- } else if (reg->space_id == ACPI_ADR_SPACE_PLATFORM_COMM && pcc_ss_id >= 0)
- } else if (reg->space_id == ACPI_ADR_SPACE_PLATFORM_COMM && pcc_ss_id >= 0) {
/** For registers in PCC space, the register size is determined* by the bit width field; the access size is used to indicate* the PCC subspace id.*/size = reg->bit_width;- } else if (reg->space_id == ACPI_ADR_SPACE_SYSTEM_MEMORY) vaddr = reg_res->sys_mem_vaddr; else if (reg->space_id == ACPI_ADR_SPACE_FIXED_HARDWARE) return cpc_write_ffh(cpu, reg, val); else return acpi_os_write_memory((acpi_physical_address)reg->address,
val, reg->bit_width);- size = GET_BIT_WIDTH(reg);
val, size);if (reg->space_id == ACPI_ADR_SPACE_SYSTEM_MEMORY) val = MASK_VAL(reg, val); @@ -1105,8 +1121,13 @@ static int cpc_write(int cpu, struct cpc_register_resource *reg_res, u64 val) writeq_relaxed(val, vaddr); break; default:
pr_debug("Error: Cannot write %u bit width to PCC for ss: %d\n",reg->bit_width, pcc_ss_id);
if (reg->space_id == ACPI_ADR_SPACE_SYSTEM_MEMORY) {pr_debug("Error: Cannot write %u width from for system memory: 0x%llx\n",size, reg->address);} else if (reg->space_id == ACPI_ADR_SPACE_PLATFORM_COMM) {pr_debug("Error: Cannot write %u bit width to PCC for ss: %d\n",size, pcc_ss_id);}