Re: [PATCH v2 3/4] ufs: ufs-qcom: Fix a few BUGs in func ufs_qcom_dump_dbg_regs()

Bart Van Assche
2020-07-14T03:47:22Z

On 2020-07-13 19:28, Can Guo wrote:
> Dumping testbus registers needs to sleep a bit intermittently as there are
> too many of them. Skip them for those contexts where sleep is not allowed.
>
> Meanwhile, if ufs_qcom_dump_dbg_regs() calls ufs_qcom_testbus_config() from
> ufshcd_suspend/resume and/or clk gate/ungate context, pm_runtime_get_sync()
> and ufshcd_hold() will cause racing problems. Fix it by removing the
> unnecessary calls of pm_runtime_get_sync() and ufshcd_hold().
>
> Signed-off-by: Can Guo <cang@codeaurora.org>
> ---
> drivers/scsi/ufs/ufs-qcom.c | 17 +++++++----------
> 1 file changed, 7 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/scsi/ufs/ufs-qcom.c b/drivers/scsi/ufs/ufs-qcom.c
> index 2e6ddb5..3743c17 100644
> --- a/drivers/scsi/ufs/ufs-qcom.c
> +++ b/drivers/scsi/ufs/ufs-qcom.c
> @@ -1604,9 +1604,6 @@ int ufs_qcom_testbus_config(struct ufs_qcom_host *host)
> */
> }
> mask <<= offset;
> -
> - pm_runtime_get_sync(host->hba->dev);
> - ufshcd_hold(host->hba, false);
> ufshcd_rmwl(host->hba, TEST_BUS_SEL,
> (u32)host->testbus.select_major << 19,
> REG_UFS_CFG1);
> @@ -1619,8 +1616,6 @@ int ufs_qcom_testbus_config(struct ufs_qcom_host *host)
> * committed before returning.
> */
> mb();
> - ufshcd_release(host->hba);
> - pm_runtime_put_sync(host->hba->dev);
>
> return 0;
> }
> @@ -1658,11 +1653,13 @@ static void ufs_qcom_dump_dbg_regs(struct ufs_hba *hba)
>
> /* sleep a bit intermittently as we are dumping too much data */
> ufs_qcom_print_hw_debug_reg_all(hba, NULL, ufs_qcom_dump_regs_wrapper);
> - udelay(1000);
> - ufs_qcom_testbus_read(hba);
> - udelay(1000);
> - ufs_qcom_print_unipro_testbus(hba);
> - udelay(1000);
> + if (in_task()) {
> + udelay(1000);
> + ufs_qcom_testbus_read(hba);
> + udelay(1000);
> + ufs_qcom_print_unipro_testbus(hba);
> + udelay(1000);
> + }
> }

It is not clear to me how udelay() calls can help in code that takes long
since these functions use busy-waiting? Should the udelay() calls perhaps
be changed into cond_resched() calls?

Thanks,

Bart.