On Mon, Sep 25, 2023 at 8:06 PM Jarred White
<jarredwhite@xxxxxxxxxxxxxxxxxxx> wrote:
>
> 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.
This is fine, but what if there are systems in the field where
bit_width is invalid, but they just happen to work because of the way
it is currently handled?
> Signed-off-by: Jarred White <jarredwhite@xxxxxxxxxxxxxxxxxxx>
> ---
> 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);
The 8 << (gas_t->access_width - 1) is duplicated twice below. There
could be an inline function doing that computation.
And the outer parens above are not needed AFAICS.
> + 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 = ®_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));
Code duplication, outer perens not needed.
> + 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);
The formula on the right-hand side of this is duplicated below.
Again, there could be an inline function doing this.
> +
> 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 = ®_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;
Missing braces (as per the kernel coding style).
> +
> + switch (size) {
> case 8:
> writeb_relaxed(val, vaddr);
> break;
> --
> 2.34.1
>
