Re: [PATCH 07/11] acpi: cppc: Add support for function fixed hardware address

[Rafael J. Wysocki]

On Thursday, August 18, 2016 03:36:48 PM Srinivas Pandruvada wrote:
> The CPPC registers can also be accessed via function fixed hardware
> addresses in X86. Add support by modifying cpc_read and cpc_write
> to be able to read/write MSRs on x86 platform. Also with this change,
> acpi_cppc_processor_probe doesn't bail out if space id is not equal to
> PCC or memory address space.
> 
> Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@xxxxxxxxxxxxxxx>
> ---
>  drivers/acpi/cppc_acpi.c | 77 +++++++++++++++++++++++++++++++++++++++++-------
>  1 file changed, 66 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/acpi/cppc_acpi.c b/drivers/acpi/cppc_acpi.c
> index 34209f5..939fb5c 100644
> --- a/drivers/acpi/cppc_acpi.c
> +++ b/drivers/acpi/cppc_acpi.c
> @@ -42,6 +42,10 @@
>  #include <linux/ktime.h>
>  
>  #include <acpi/cppc_acpi.h>
> +#ifdef CONFIG_X86
> +#include <asm/msr.h>
> +#endif

Please figure out how to avoid this.

> +
>  /*
>   * Lock to provide mutually exclusive access to the PCC
>   * channel. e.g. When the remote updates the shared region
> @@ -585,8 +589,9 @@ int acpi_cppc_processor_probe(struct acpi_processor *pr)
>  					pr_debug("Mismatched PCC ids.\n");
>  					goto out_free;
>  				}
> -			} else if (gas_t->space_id != ACPI_ADR_SPACE_SYSTEM_MEMORY) {
> -				/* Support only PCC and SYS MEM type regs */
> +			} else if (gas_t->space_id != ACPI_ADR_SPACE_SYSTEM_MEMORY &&
> +				   gas_t->space_id != ACPI_ADR_SPACE_FIXED_HARDWARE) {
> +				/* Support only PCC, FFH and SYS MEM type regs */
>  				pr_debug("Unsupported register type: %d\n", gas_t->space_id);
>  				goto out_free;
>  			}
> @@ -645,13 +650,59 @@ void acpi_cppc_processor_exit(struct acpi_processor *pr)
>  }
>  EXPORT_SYMBOL_GPL(acpi_cppc_processor_exit);
>  
> +#ifdef CONFIG_X86
> +static int cpc_read_ffh(int cpunum, struct cpc_reg *reg, u64 *val)
> +{
> +	int err;
> +
> +	err = rdmsrl_on_cpu(cpunum, reg->address, val);
> +	if (!err) {
> +		u64 mask = GENMASK_ULL(reg->bit_offset + reg->bit_width - 1,
> +				       reg->bit_offset);
> +
> +		*val &= mask;
> +		*val >>= reg->bit_offset;
> +	}
> +	return err;
> +}
> +
> +static int cpc_write_ffh(int cpunum, struct cpc_reg *reg, u64 val)
> +{
> +	u64 rd_val;
> +	int err;
> +
> +	err = rdmsrl_on_cpu(cpunum, reg->address, &rd_val);
> +	if (!err) {
> +		u64 mask = GENMASK_ULL(reg->bit_offset + reg->bit_width - 1,
> +				       reg->bit_offset);
> +
> +		val <<= reg->bit_offset;
> +		val &= mask;
> +		rd_val &= ~mask;
> +		rd_val |= val;
> +		err = wrmsrl_on_cpu(cpunum, reg->address, rd_val);
> +	}
> +	return err;
> +}

The above really should go somewhere under arch/x86/.

> +#else
> +static int cpc_read_ffh(int cpunum, struct cpc_reg *reg, u64 *val)
> +{
> +	return -EINVAL;
> +}
> +static int cpc_write_ffh(int cpunum, struct cpc_reg *reg, u64 val)
> +{
> +	return -EINVAL;
> +
> +}

And I would defined these as __weak functions.

Also another return value like -ENOTSUPP for example would better IMO.

> +#endif
> +
>  /*
>   * Since cpc_read and cpc_write are called while holding pcc_lock, it should be
>   * as fast as possible. We have already mapped the PCC subspace during init, so
>   * we can directly write to it.
>   */
>  
> -static int cpc_read(struct cpc_register_resource *res, u64 *val)
> +static int cpc_read(int cpunum, struct cpc_register_resource *res, u64 *val)
>  {
>  	struct cpc_reg *reg = &res->cpc_entry.reg;
>  	int ret_val = 0;
> @@ -684,13 +735,15 @@ static int cpc_read(struct cpc_register_resource *res, u64 *val)
>  				reg->bit_width);
>  			ret_val = -EFAULT;
>  		}
> +	} else if (reg->space_id == ACPI_ADR_SPACE_FIXED_HARDWARE) {
> +		ret_val = cpc_read_ffh(cpunum, reg, val);
>  	} else
>  		ret_val = acpi_os_read_memory((acpi_physical_address)reg->address,
>  					val, reg->bit_width);
>  	return ret_val;
>  }
>  
> -static int cpc_write(struct cpc_reg *reg, u64 val)
> +static int cpc_write(int cpunum, struct cpc_reg *reg, u64 val)
>  {
>  	int ret_val = 0;
>  
> @@ -716,6 +769,8 @@ static int cpc_write(struct cpc_reg *reg, u64 val)
>  			ret_val = -EFAULT;
>  			break;
>  		}
> +	} else if (reg->space_id == ACPI_ADR_SPACE_FIXED_HARDWARE) {
> +		ret_val = cpc_write_ffh(cpunum, reg, val);
>  	} else
>  		ret_val = acpi_os_write_memory((acpi_physical_address)reg->address,
>  				val, reg->bit_width);
> @@ -761,16 +816,16 @@ int cppc_get_perf_caps(int cpunum, struct cppc_perf_caps *perf_caps)
>  		}
>  	}
>  
> -	cpc_read(highest_reg, &high);
> +	cpc_read(cpunum, highest_reg, &high);
>  	perf_caps->highest_perf = high;
>  
> -	cpc_read(lowest_reg, &low);
> +	cpc_read(cpunum, lowest_reg, &low);
>  	perf_caps->lowest_perf = low;
>  
> -	cpc_read(ref_perf, &ref);
> +	cpc_read(cpunum, ref_perf, &ref);
>  	perf_caps->reference_perf = ref;
>  
> -	cpc_read(nom_perf, &nom);
> +	cpc_read(cpunum, nom_perf, &nom);
>  	perf_caps->nominal_perf = nom;
>  
>  	if (!ref)
> @@ -819,8 +874,8 @@ int cppc_get_perf_ctrs(int cpunum, struct cppc_perf_fb_ctrs *perf_fb_ctrs)
>  		}
>  	}
>  
> -	cpc_read(delivered_reg, &delivered);
> -	cpc_read(reference_reg, &reference);
> +	cpc_read(cpunum, delivered_reg, &delivered);
> +	cpc_read(cpunum, reference_reg, &reference);
>  
>  	if (!delivered || !reference) {
>  		ret = -EFAULT;
> @@ -875,7 +930,7 @@ int cppc_set_perf(int cpu, struct cppc_perf_ctrls *perf_ctrls)
>  	 * Skip writing MIN/MAX until Linux knows how to come up with
>  	 * useful values.
>  	 */
> -	cpc_write(&desired_reg->cpc_entry.reg, perf_ctrls->desired_perf);
> +	cpc_write(cpu, &desired_reg->cpc_entry.reg, perf_ctrls->desired_perf);
>  
>  	/* Is this a PCC reg ?*/
>  	if (desired_reg->cpc_entry.reg.space_id == ACPI_ADR_SPACE_PLATFORM_COMM) {
> 

Thanks,
Rafael