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    Subject[PATCH 6.0 218/862] ACPI: PCC: replace wait_for_completion()
    Date
    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


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