[PATCH 5.19 191/717] ACPI: PCC: replace wait_for_completion()

Greg Kroah-Hartman
2022-10-22T07:47:04Z

From: Huisong Li <lihuisong@huawei.com>

[ Upstream commit 91cefefb699120efd0a5ba345d12626b688f86ce ]

Currently, the function waiting for completion of mailbox operation is
'wait_for_completion()'. The PCC method will be permanently blocked if
this mailbox message fails to execute. So this patch replaces it with
'wait_for_completion_timeout()'. And set the timeout interval to an
arbitrary retries on top of nominal to prevent the remote processor is
slow to respond to PCC commands.

Fixes: 77e2a04745ff ("ACPI: PCC: Implement OperationRegion handler for the PCC Type 3 subtype")
Signed-off-by: Huisong Li <lihuisong@huawei.com>
Reviewed-by: Sudeep Holla <sudeep.holla@arm.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/acpi/acpi_pcc.c | 23 +++++++++++++++++++++--
1 file changed, 21 insertions(+), 2 deletions(-)

diff --git a/drivers/acpi/acpi_pcc.c b/drivers/acpi/acpi_pcc.c
index 84f1ac416b57..16ba875e3293 100644
--- a/drivers/acpi/acpi_pcc.c
+++ b/drivers/acpi/acpi_pcc.c
@@ -23,6 +23,12 @@

#include <acpi/pcc.h>

+/*
+ * Arbitrary retries in case the remote processor is slow to respond
+ * to PCC commands
+ */
+#define PCC_CMD_WAIT_RETRIES_NUM 500
+
struct pcc_data {
struct pcc_mbox_chan *pcc_chan;
void __iomem *pcc_comm_addr;
@@ -89,6 +95,7 @@ acpi_pcc_address_space_handler(u32 function, acpi_physical_address addr,
{
int ret;
struct pcc_data *data = region_context;
+ u64 usecs_lat;

reinit_completion(&data->done);

@@ -99,8 +106,20 @@ acpi_pcc_address_space_handler(u32 function, acpi_physical_address addr,
if (ret < 0)
return AE_ERROR;

- if (data->pcc_chan->mchan->mbox->txdone_irq)
- wait_for_completion(&data->done);
+ if (data->pcc_chan->mchan->mbox->txdone_irq) {
+ /*
+ * pcc_chan->latency is just a Nominal value. In reality the remote
+ * processor could be much slower to reply. So add an arbitrary
+ * amount of wait on top of Nominal.
+ */
+ usecs_lat = PCC_CMD_WAIT_RETRIES_NUM * data->pcc_chan->latency;
+ ret = wait_for_completion_timeout(&data->done,
+ usecs_to_jiffies(usecs_lat));
+ if (ret == 0) {
+ pr_err("PCC command executed timeout!\n");
+ return AE_TIME;
+ }
+ }

mbox_client_txdone(data->pcc_chan->mchan, ret);

--
2.35.1