2020-07-14 02:31:02

by Can Guo

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

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 <[email protected]>
---
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);
+ }
}

/**
--
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project.

2020-07-14 03:49:57

by Bart Van Assche

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

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 <[email protected]>
> ---
> 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.

2020-07-14 04:19:39

by Can Guo

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

Hi Bart,

On 2020-07-14 11:47, Bart Van Assche wrote:
> 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 <[email protected]>
>> ---
>> 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.

Maybe you are right, but this is not the purpose of this change. I am
just
trying to make sure this func can be invoked from any contexts without
making troubles like schedule while atomic and/or race conditions.

Thanks,

Can Guo.