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 --- 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.
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 > --- > 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.
[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 --- 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.