[2/2] drivers: qcom: rpmh-rsc: fix read back of trigger register
diff mbox series

Message ID 20190701152907.16407-2-ilina@codeaurora.org
State Superseded
Headers show
Series
  • [1/2] drivers: qcom: rpmh-rsc: simplify TCS locking
Related show

Commit Message

Lina Iyer July 1, 2019, 3:29 p.m. UTC
When triggering a TCS to send its contents, reading back the trigger
value may return an incorrect value. That is because, writing the
trigger may raise an interrupt which could be handled immediately and
the trigger value could be reset in the interrupt handler. By doing a
read back we may end up spinning waiting for the value we wrote.

Fixes: 658628 ("drivers: qcom: rpmh-rsc: add RPMH controller for QCOM
SoCs")
Signed-off-by: Lina Iyer <ilina@codeaurora.org>
---
 drivers/soc/qcom/rpmh-rsc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Comments

Lina Iyer July 1, 2019, 3:53 p.m. UTC | #1
Switching Andy's email address.

On Mon, Jul 01 2019 at 09:32 -0600, Lina Iyer wrote:
>When triggering a TCS to send its contents, reading back the trigger
>value may return an incorrect value. That is because, writing the
>trigger may raise an interrupt which could be handled immediately and
>the trigger value could be reset in the interrupt handler. By doing a
>read back we may end up spinning waiting for the value we wrote.
>
>Fixes: 658628 ("drivers: qcom: rpmh-rsc: add RPMH controller for QCOM
>SoCs")
>Signed-off-by: Lina Iyer <ilina@codeaurora.org>
>---
> drivers/soc/qcom/rpmh-rsc.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
>diff --git a/drivers/soc/qcom/rpmh-rsc.c b/drivers/soc/qcom/rpmh-rsc.c
>index 92461311aef3..2fc2fa879480 100644
>--- a/drivers/soc/qcom/rpmh-rsc.c
>+++ b/drivers/soc/qcom/rpmh-rsc.c
>@@ -300,7 +300,7 @@ static void __tcs_trigger(struct rsc_drv *drv, int tcs_id)
> 	enable = TCS_AMC_MODE_ENABLE;
> 	write_tcs_reg_sync(drv, RSC_DRV_CONTROL, tcs_id, enable);
> 	enable |= TCS_AMC_MODE_TRIGGER;
>-	write_tcs_reg_sync(drv, RSC_DRV_CONTROL, tcs_id, enable);
>+	write_tcs_reg(drv, RSC_DRV_CONTROL, tcs_id, enable);
> }
>
> static int check_for_req_inflight(struct rsc_drv *drv, struct tcs_group *tcs,
>--
>The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
>a Linux Foundation Collaborative Project
>
Stephen Boyd July 19, 2019, 6:22 p.m. UTC | #2
Quoting Lina Iyer (2019-07-01 08:29:07)
> When triggering a TCS to send its contents, reading back the trigger
> value may return an incorrect value. That is because, writing the
> trigger may raise an interrupt which could be handled immediately and
> the trigger value could be reset in the interrupt handler. By doing a
> read back we may end up spinning waiting for the value we wrote.

Doesn't this need to be squashed into the patch that gets rid of the
irqs disabled state of this code? It sounds an awful lot like this
problem only happens now because the previous patch removed the
irqsave/irqrestore code around this function.
Lina Iyer July 22, 2019, 3:51 p.m. UTC | #3
On Fri, Jul 19 2019 at 12:22 -0600, Stephen Boyd wrote:
>Quoting Lina Iyer (2019-07-01 08:29:07)
>> When triggering a TCS to send its contents, reading back the trigger
>> value may return an incorrect value. That is because, writing the
>> trigger may raise an interrupt which could be handled immediately and
>> the trigger value could be reset in the interrupt handler. By doing a
>> read back we may end up spinning waiting for the value we wrote.
>
>Doesn't this need to be squashed into the patch that gets rid of the
>irqs disabled state of this code? It sounds an awful lot like this
>problem only happens now because the previous patch removed the
>irqsave/irqrestore code around this function.
>

True. Could be rolled into that fix.

--Lina

Patch
diff mbox series

diff --git a/drivers/soc/qcom/rpmh-rsc.c b/drivers/soc/qcom/rpmh-rsc.c
index 92461311aef3..2fc2fa879480 100644
--- a/drivers/soc/qcom/rpmh-rsc.c
+++ b/drivers/soc/qcom/rpmh-rsc.c
@@ -300,7 +300,7 @@  static void __tcs_trigger(struct rsc_drv *drv, int tcs_id)
 	enable = TCS_AMC_MODE_ENABLE;
 	write_tcs_reg_sync(drv, RSC_DRV_CONTROL, tcs_id, enable);
 	enable |= TCS_AMC_MODE_TRIGGER;
-	write_tcs_reg_sync(drv, RSC_DRV_CONTROL, tcs_id, enable);
+	write_tcs_reg(drv, RSC_DRV_CONTROL, tcs_id, enable);
 }
 
 static int check_for_req_inflight(struct rsc_drv *drv, struct tcs_group *tcs,