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SubjectRe: [PATCH v1] scsi: ufs: change msleep to usleep_range
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Hi Bean,

On Mon, 2019-07-15 at 11:21 +0000, Bean Huo (beanhuo) wrote:
> From: Bean Huo <beanhuo@micron.com>
>
> This patch is to change msleep() to usleep_range() based on
> Documentation/timers/timers-howto.txt. It suggests using
> usleep_range() for small msec(1ms - 20ms) since msleep()
> will often sleep longer than desired value.
>
> After changing, booting time will be 5ms-10ms faster than before.
> I tested this change on two different platforms, one has 5ms faster,
> another one is about 10ms. I think this is different on different
> platform.
>
> Actually, from UFS host side, 1ms-5ms delay is already sufficient for
> its initialization of the local UIC layer.
>
> Fixes: 7a3e97b0dc4b ([SCSI] ufshcd: UFS Host controller driver)
> Signed-off-by: Bean Huo <beanhuo@micron.com>
> ---
> drivers/scsi/ufs/ufshcd.c | 10 ++--------
> 1 file changed, 2 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
> index a208589426b1..21f7b3b8026c 100644
> --- a/drivers/scsi/ufs/ufshcd.c
> +++ b/drivers/scsi/ufs/ufshcd.c
> @@ -4213,12 +4213,6 @@ static int ufshcd_hba_execute_hce(struct ufs_hba *hba)
> {
> int retry;
>
> - /*
> - * msleep of 1 and 5 used in this function might result in msleep(20),
> - * but it was necessary to send the UFS FPGA to reset mode during
> - * development and testing of this driver. msleep can be changed to
> - * mdelay and retry count can be reduced based on the controller.
> - */
> if (!ufshcd_is_hba_active(hba))
> /* change controller state to "reset state" */
> ufshcd_hba_stop(hba, true);
> @@ -4241,7 +4235,7 @@ static int ufshcd_hba_execute_hce(struct ufs_hba *hba)
> * instruction might be read back.
> * This delay can be changed based on the controller.
> */
> - msleep(1);
> + usleep_range(1000, 1100);
>
> /* wait for the host controller to complete initialization */
> retry = 10;
> @@ -4253,7 +4247,7 @@ static int ufshcd_hba_execute_hce(struct ufs_hba *hba)
> "Controller enable failed\n");
> return -EIO;
> }
> - msleep(5);
> + usleep_range(5000, 5100);
> }
>
> /* enable UIC related interrupts */

Acked-by: Stanley Chu <stanley.chu@mediatek.com>

Thanks,
Stanley



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