Re: [PATCH v3 1/4] ACPI: CPPC: Add cppc_get_reg_val and cppc_set_reg_val function
From: Pierre Gondois
Date: Fri Jan 10 2025 - 05:17:07 EST
Hello Lifeng,
On 1/10/25 03:23, zhenglifeng (A) wrote:
Hello Pierre,
On 2025/1/8 0:54, Pierre Gondois wrote:
Hello Lifeng,
On 12/20/24 09:30, zhenglifeng (A) wrote:
On 2024/12/17 21:48, Pierre Gondois wrote:
Hello Lifeng,
On 12/16/24 10:16, Lifeng Zheng wrote:
Rename cppc_get_perf() to cppc_get_reg_val() as a generic function to read
cppc registers, with four changes:
1. Change the error kind to "no such device" when pcc_ss_id < 0, which
means that this cpu cannot get a valid pcc_ss_id.
2. Add a check to verify if the register is a cpc supported one before
using it.
3. Extract the operations if register is in pcc out as
cppc_get_reg_val_in_pcc().
4. Return the result of cpc_read() instead of 0.
Add cppc_set_reg_val_in_pcc() and cppc_set_reg_val() as generic functions
for setting cppc registers value. Unlike other set reg ABIs,
cppc_set_reg_val() checks CPC_SUPPORTED right after getting the register,
because the rest of the operations are meaningless if this register is not
a cpc supported one.
These functions can be used to reduce some existing code duplication.
Signed-off-by: Lifeng Zheng <zhenglifeng1@xxxxxxxxxx>
---
drivers/acpi/cppc_acpi.c | 111 +++++++++++++++++++++++++++++----------
1 file changed, 84 insertions(+), 27 deletions(-)
diff --git a/drivers/acpi/cppc_acpi.c b/drivers/acpi/cppc_acpi.c
index c1f3568d0c50..bb5333a503a2 100644
--- a/drivers/acpi/cppc_acpi.c
+++ b/drivers/acpi/cppc_acpi.c
@@ -1179,43 +1179,100 @@ static int cpc_write(int cpu, struct cpc_register_resource *reg_res, u64 val)
return ret_val;
}
-static int cppc_get_perf(int cpunum, enum cppc_regs reg_idx, u64 *perf)
+static int cppc_get_reg_val_in_pcc(int cpu, struct cpc_register_resource *reg, u64 *val)
{
- struct cpc_desc *cpc_desc = per_cpu(cpc_desc_ptr, cpunum);
+ int pcc_ss_id = per_cpu(cpu_pcc_subspace_idx, cpu);
+ struct cppc_pcc_data *pcc_ss_data = NULL;
+ int ret;
+
+ if (pcc_ss_id < 0) {
+ pr_debug("Invalid pcc_ss_id\n");
+ return -ENODEV;
+ }
+
+ pcc_ss_data = pcc_data[pcc_ss_id];
+
+ down_write(&pcc_ss_data->pcc_lock);
+
+ if (send_pcc_cmd(pcc_ss_id, CMD_READ) >= 0)
+ ret = cpc_read(cpu, reg, val);
+ else
+ ret = -EIO;
+
+ up_write(&pcc_ss_data->pcc_lock);
+
+ return ret;
+}
+
+static int cppc_get_reg_val(int cpu, enum cppc_regs reg_idx, u64 *val)
+{
+ struct cpc_desc *cpc_desc = per_cpu(cpc_desc_ptr, cpu);
struct cpc_register_resource *reg;
if (!cpc_desc) {
- pr_debug("No CPC descriptor for CPU:%d\n", cpunum);
+ pr_debug("No CPC descriptor for CPU:%d\n", cpu);
return -ENODEV;
}
reg = &cpc_desc->cpc_regs[reg_idx];
- if (CPC_IN_PCC(reg)) {
- int pcc_ss_id = per_cpu(cpu_pcc_subspace_idx, cpunum);
- struct cppc_pcc_data *pcc_ss_data = NULL;
- int ret = 0;
-
- if (pcc_ss_id < 0)
- return -EIO;
+ if (!CPC_SUPPORTED(reg)) {
+ pr_debug("CPC register (reg_idx=%d) is not supported\n", reg_idx);
+ return -EOPNOTSUPP;
+ }
I think this is only valid for optional fields. Meaning that:
- if the function is used one day for the mandatory 'Lowest Performance'
field, an integer value of 0 would be valid.
- if the function is used for a mandatory field containing a NULL Buffer,
it seems we would return -EFAULT currently, through cpc_read(). -EOPNOTSUPP
doesn't seem appropriate as the field would be mandatory.
Maybe the function needs an additional 'bool optional' input parameter
to do these check conditionally.
Indeed, I should have judged the type before doing this check. But adding a
input parameter is not a really nice way to me. How about adding a bool
list of length MAX_CPC_REG_ENT in cppc_acpi.h to indicate wheter it is
optional?
Actually all these functions:
- cppc_get_desired_perf
- cppc_get_highest_perf
- cppc_get_epp_perf
- cppc_set_epp
- cppc_get_auto_act_window
- cppc_set_auto_act_window
As you suggest in another patch, the logic should be placed in
cppc_get_auto_act_window() and some other functions. I'm afraid these
functions couldn't be implemented with the macros you suggest.
If you're referring to the [get|set]_auto_act_window() functions, I guess
it should be ok to have the getter/setter functions implemented as a macros,
and then have a wrapper to do the conversion of the value.
- cppc_get_auto_sel
- cppc_get_nominal_perf
and in general all the functions getting / setting one value at a time could
be implemented by macros similars to show_cppc_data(). From what I see the
input parameters required are:
- name of the field
- if the field is mandatory to have or not
If with this parameter, we should put all the cppc_get_reg_val() and
cppc_set_reg_val() in the macro. This wouldn't look really nice. I
prefer to use a macro to judge mandatory / optional. I'll show you in
v4.
If you prefer to have specific macro names to distinguish optional/mandatory
fields, it also seems a good solution.
- if the field is writeable
I think we can define a READ macro, a WRITE macro and a RW macro. For
the registers which are not writeable, only use the READ macro to
implement getting function.
Yes right, same comment as above.
- if the field is implemented as an integer, register, or can be both
I don't think this parameter is necessary. The field type can be got
from cpc_desc->cpc_regs[reg_idx].type.
Yes indeed.
This would avoid having numerous function definitions doing approximately the
same thing.
So from what I see the input parameters required are name of the field
and reg_idx. Thanks for your advice!