On Fri, Oct 30, 2020 at 6:59 AM Viswas G <Viswas.G@xxxxxxxxxxxxxxxxx> wrote:
>
> From: akshatzen <akshatzen@xxxxxxxxxx>
>
> Today in function check_fw_ready we do busy wait using udelay. Due to
> which CPU is not released and we see CPU need_resched failures.
>
> Here busy waiting is not necessary since we are in process context and
> we should sleep instead. So to avoid busy waiting we are replacing
> udelay with msleep of 20 ms intervals to check for FW to become ready.
>
> It's verified that check_fw_ready today is not being used in interrupt
> context anywhere, hence it is safe to make this change.
>
> Tested:
> Installed the kernel and looked at dmesg for failures pertaining to
> need_resched and did not find them.
>
> Signed-off-by: akshatzen <akshatzen@xxxxxxxxxx>
> Signed-off-by: Viswas G <Viswas.G@xxxxxxxxxxxxx>
> Signed-off-by: Ruksar Devadi <Ruksar.devadi@xxxxxxxxxxxxx>
> Signed-off-by: Radha Ramachandran <radha@xxxxxxxxxx>
Acked-by: Jack Wang <jinpu.wang@xxxxxxxxxxxxxxx>
> ---
> drivers/scsi/pm8001/pm80xx_hwi.c | 21 +++++++++++----------
> drivers/scsi/pm8001/pm80xx_hwi.h | 6 ++++++
> 2 files changed, 17 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/scsi/pm8001/pm80xx_hwi.c b/drivers/scsi/pm8001/pm80xx_hwi.c
> index 1ba93fb76093..24a4f6b9e79d 100644
> --- a/drivers/scsi/pm8001/pm80xx_hwi.c
> +++ b/drivers/scsi/pm8001/pm80xx_hwi.c
> @@ -1042,6 +1042,7 @@ static int mpi_init_check(struct pm8001_hba_info *pm8001_ha)
>
> /**
> * check_fw_ready - The LLDD check if the FW is ready, if not, return error.
> + * This function sleeps hence it must not be used in atomic context.
> * @pm8001_ha: our hba card information
> */
> static int check_fw_ready(struct pm8001_hba_info *pm8001_ha)
> @@ -1052,16 +1053,16 @@ static int check_fw_ready(struct pm8001_hba_info *pm8001_ha)
> int ret = 0;
>
> /* reset / PCIe ready */
> - max_wait_time = max_wait_count = 100 * 1000; /* 100 milli sec */
> + max_wait_time = max_wait_count = 5; /* 100 milli sec */
> do {
> - udelay(1);
> + msleep(FW_READY_INTERVAL);
> value = pm8001_cr32(pm8001_ha, 0, MSGU_SCRATCH_PAD_1);
> } while ((value == 0xFFFFFFFF) && (--max_wait_count));
>
> /* check ila status */
> - max_wait_time = max_wait_count = 1000 * 1000; /* 1000 milli sec */
> + max_wait_time = max_wait_count = 50; /* 1000 milli sec */
> do {
> - udelay(1);
> + msleep(FW_READY_INTERVAL);
> value = pm8001_cr32(pm8001_ha, 0, MSGU_SCRATCH_PAD_1);
> } while (((value & SCRATCH_PAD_ILA_READY) !=
> SCRATCH_PAD_ILA_READY) && (--max_wait_count));
> @@ -1074,9 +1075,9 @@ static int check_fw_ready(struct pm8001_hba_info *pm8001_ha)
> }
>
> /* check RAAE status */
> - max_wait_time = max_wait_count = 1800 * 1000; /* 1800 milli sec */
> + max_wait_time = max_wait_count = 90; /* 1800 milli sec */
> do {
> - udelay(1);
> + msleep(FW_READY_INTERVAL);
> value = pm8001_cr32(pm8001_ha, 0, MSGU_SCRATCH_PAD_1);
> } while (((value & SCRATCH_PAD_RAAE_READY) !=
> SCRATCH_PAD_RAAE_READY) && (--max_wait_count));
> @@ -1089,9 +1090,9 @@ static int check_fw_ready(struct pm8001_hba_info *pm8001_ha)
> }
>
> /* check iop0 status */
> - max_wait_time = max_wait_count = 600 * 1000; /* 600 milli sec */
> + max_wait_time = max_wait_count = 30; /* 600 milli sec */
> do {
> - udelay(1);
> + msleep(FW_READY_INTERVAL);
> value = pm8001_cr32(pm8001_ha, 0, MSGU_SCRATCH_PAD_1);
> } while (((value & SCRATCH_PAD_IOP0_READY) != SCRATCH_PAD_IOP0_READY) &&
> (--max_wait_count));
> @@ -1107,9 +1108,9 @@ static int check_fw_ready(struct pm8001_hba_info *pm8001_ha)
> if ((pm8001_ha->chip_id != chip_8008) &&
> (pm8001_ha->chip_id != chip_8009)) {
> /* 200 milli sec */
> - max_wait_time = max_wait_count = 200 * 1000;
> + max_wait_time = max_wait_count = 10;
> do {
> - udelay(1);
> + msleep(FW_READY_INTERVAL);
> value = pm8001_cr32(pm8001_ha, 0, MSGU_SCRATCH_PAD_1);
> } while (((value & SCRATCH_PAD_IOP1_READY) !=
> SCRATCH_PAD_IOP1_READY) && (--max_wait_count));
> diff --git a/drivers/scsi/pm8001/pm80xx_hwi.h b/drivers/scsi/pm8001/pm80xx_hwi.h
> index 701951a0f715..ec48bc276de6 100644
> --- a/drivers/scsi/pm8001/pm80xx_hwi.h
> +++ b/drivers/scsi/pm8001/pm80xx_hwi.h
> @@ -1639,3 +1639,9 @@ typedef struct SASProtocolTimerConfig SASProtocolTimerConfig_t;
>
> #define MEMBASE_II_SHIFT_REGISTER 0x1010
> #endif
> +
> +/**
> + * As we know sleep (1~20) ms may result in sleep longer than ~20 ms, hence we
> + * choose 20 ms interval.
> + */
> +#define FW_READY_INTERVAL 20
> --
> 2.16.3
>
