[PATCH V2 2/5] ACPI/CPPC: acquire pcc_lock only while accessing PCC subspace

Prashanth Prakash
2016-07-26T19:46:03Z

We need to acquire pcc_lock only when we are accessing registers
that are in the PCC subspsace.

Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Signed-off-by: Prashanth Prakash <pprakash@codeaurora.org>
---
drivers/acpi/cppc_acpi.c | 30 ++++++++++++++++--------------
1 file changed, 16 insertions(+), 14 deletions(-)

diff --git a/drivers/acpi/cppc_acpi.c b/drivers/acpi/cppc_acpi.c
index fea58e2..93826c7 100644
--- a/drivers/acpi/cppc_acpi.c
+++ b/drivers/acpi/cppc_acpi.c
@@ -763,7 +763,7 @@ int cppc_get_perf_caps(int cpunum, struct cppc_perf_caps *perf_caps)
struct cpc_register_resource *highest_reg, *lowest_reg, *ref_perf,
*nom_perf;
u64 high, low, ref, nom;
- int ret = 0;
+ int ret = 0, regs_in_pcc = 0;

if (!cpc_desc) {
pr_debug("No CPC descriptor for CPU:%d\n", cpunum);
@@ -775,13 +775,13 @@ int cppc_get_perf_caps(int cpunum, struct cppc_perf_caps *perf_caps)
ref_perf = &cpc_desc->cpc_regs[REFERENCE_PERF];
nom_perf = &cpc_desc->cpc_regs[NOMINAL_PERF];

- spin_lock(&pcc_lock);
-
/* Are any of the regs PCC ?*/
if ((highest_reg->cpc_entry.reg.space_id == ACPI_ADR_SPACE_PLATFORM_COMM) ||
- (lowest_reg->cpc_entry.reg.space_id == ACPI_ADR_SPACE_PLATFORM_COMM) ||
- (ref_perf->cpc_entry.reg.space_id == ACPI_ADR_SPACE_PLATFORM_COMM) ||
- (nom_perf->cpc_entry.reg.space_id == ACPI_ADR_SPACE_PLATFORM_COMM)) {
+ (lowest_reg->cpc_entry.reg.space_id == ACPI_ADR_SPACE_PLATFORM_COMM) ||
+ (ref_perf->cpc_entry.reg.space_id == ACPI_ADR_SPACE_PLATFORM_COMM) ||
+ (nom_perf->cpc_entry.reg.space_id == ACPI_ADR_SPACE_PLATFORM_COMM)) {
+ spin_lock(&pcc_lock);
+ regs_in_pcc = 1;
/* Ring doorbell once to update PCC subspace */
if (send_pcc_cmd(CMD_READ) < 0) {
ret = -EIO;
@@ -808,7 +808,8 @@ int cppc_get_perf_caps(int cpunum, struct cppc_perf_caps *perf_caps)
ret = -EFAULT;

out_err:
- spin_unlock(&pcc_lock);
+ if (regs_in_pcc)
+ spin_unlock(&pcc_lock);
return ret;
}
EXPORT_SYMBOL_GPL(cppc_get_perf_caps);
@@ -825,7 +826,7 @@ int cppc_get_perf_ctrs(int cpunum, struct cppc_perf_fb_ctrs *perf_fb_ctrs)
struct cpc_desc *cpc_desc = per_cpu(cpc_desc_ptr, cpunum);
struct cpc_register_resource *delivered_reg, *reference_reg;
u64 delivered, reference;
- int ret = 0;
+ int ret = 0, regs_in_pcc = 0;

if (!cpc_desc) {
pr_debug("No CPC descriptor for CPU:%d\n", cpunum);
@@ -835,11 +836,11 @@ int cppc_get_perf_ctrs(int cpunum, struct cppc_perf_fb_ctrs *perf_fb_ctrs)
delivered_reg = &cpc_desc->cpc_regs[DELIVERED_CTR];
reference_reg = &cpc_desc->cpc_regs[REFERENCE_CTR];

- spin_lock(&pcc_lock);
-
/* Are any of the regs PCC ?*/
if ((delivered_reg->cpc_entry.reg.space_id == ACPI_ADR_SPACE_PLATFORM_COMM) ||
(reference_reg->cpc_entry.reg.space_id == ACPI_ADR_SPACE_PLATFORM_COMM)) {
+ spin_lock(&pcc_lock);
+ regs_in_pcc = 1;
/* Ring doorbell once to update PCC subspace */
if (send_pcc_cmd(CMD_READ) < 0) {
ret = -EIO;
@@ -865,7 +866,8 @@ int cppc_get_perf_ctrs(int cpunum, struct cppc_perf_fb_ctrs *perf_fb_ctrs)
perf_fb_ctrs->prev_reference = reference;

out_err:
- spin_unlock(&pcc_lock);
+ if (regs_in_pcc)
+ spin_unlock(&pcc_lock);
return ret;
}
EXPORT_SYMBOL_GPL(cppc_get_perf_ctrs);
@@ -890,10 +892,9 @@ int cppc_set_perf(int cpu, struct cppc_perf_ctrls *perf_ctrls)

desired_reg = &cpc_desc->cpc_regs[DESIRED_PERF];

- spin_lock(&pcc_lock);
-
/* If this is PCC reg, check if channel is free before writing */
if (desired_reg->cpc_entry.reg.space_id == ACPI_ADR_SPACE_PLATFORM_COMM) {
+ spin_lock(&pcc_lock);
ret = check_pcc_chan();
if (ret)
goto busy_channel;
@@ -912,7 +913,8 @@ int cppc_set_perf(int cpu, struct cppc_perf_ctrls *perf_ctrls)
ret = -EIO;
}
busy_channel:
- spin_unlock(&pcc_lock);
+ if (desired_reg->cpc_entry.reg.space_id == ACPI_ADR_SPACE_PLATFORM_COMM)
+ spin_unlock(&pcc_lock);
return ret;
}
EXPORT_SYMBOL_GPL(cppc_set_perf);
--
Qualcomm Datacenter Technologies on behalf of Qualcomm Technologies, Inc.
Qualcomm Technologies, Inc. is a member of the
Code Aurora Forum, a Linux Foundation Collaborative Project.