* [PATCH] clocksource/fsl: Fix errata A-007728 for flextimer
@ 2016-09-08 2:04 Meng Yi
2016-09-08 6:22 ` Alexander Stein
0 siblings, 1 reply; 3+ messages in thread
From: Meng Yi @ 2016-09-08 2:04 UTC (permalink / raw)
To: daniel.lezcano, tglx, linux-kernel; +Cc: Meng Yi
If the FTM counter reaches the FTM_MOD value between the reading of the
TOF bit and the writing of 0 to the TOF bit, the process of clearing the
TOF bit does not work as expected when FTMx_CONF[NUMTOF] != 0 and the
current TOF count is less than FTMx_CONF[NUMTOF]. If the above condition
is met, the TOF bit remains set. If the TOF interrupt is enabled
(FTMx_SC[TOIE] = 1), the TOF interrupt also remains asserted.
Above is the errata discription
The workaround is clearing TOF bit until it is cleaned(FTM counter doesn't
always reache the FTM_MOD anyway),which may cost some cycles.
Signed-off-by: Meng Yi <meng.yi@nxp.com>
---
drivers/clocksource/fsl_ftm_timer.c | 9 ++++-----
1 file changed, 4 insertions(+), 5 deletions(-)
diff --git a/drivers/clocksource/fsl_ftm_timer.c b/drivers/clocksource/fsl_ftm_timer.c
index 738515b..ade26e5 100644
--- a/drivers/clocksource/fsl_ftm_timer.c
+++ b/drivers/clocksource/fsl_ftm_timer.c
@@ -83,11 +83,10 @@ static inline void ftm_counter_disable(void __iomem *base)
static inline void ftm_irq_acknowledge(void __iomem *base)
{
- u32 val;
-
- val = ftm_readl(base + FTM_SC);
- val &= ~FTM_SC_TOF;
- ftm_writel(val, base + FTM_SC);
+ /*read and clean the FTM_SC_TOF bit until its cleared*/
+ while (FTM_SC_TOF & ftm_readl(base + FTM_SC))
+ ftm_writel(ftm_readl(base + FTM_SC) & (~FTM_SC_TOF),
+ base + FTM_SC);
}
static inline void ftm_irq_enable(void __iomem *base)
--
2.1.0.27.g96db324
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] clocksource/fsl: Fix errata A-007728 for flextimer
2016-09-08 2:04 [PATCH] clocksource/fsl: Fix errata A-007728 for flextimer Meng Yi
@ 2016-09-08 6:22 ` Alexander Stein
2016-09-08 6:28 ` Meng Yi
0 siblings, 1 reply; 3+ messages in thread
From: Alexander Stein @ 2016-09-08 6:22 UTC (permalink / raw)
To: linux-kernel; +Cc: Meng Yi, daniel.lezcano, tglx
On Thursday 08 September 2016 10:04:55, Meng Yi wrote:
> If the FTM counter reaches the FTM_MOD value between the reading of the
> TOF bit and the writing of 0 to the TOF bit, the process of clearing the
> TOF bit does not work as expected when FTMx_CONF[NUMTOF] != 0 and the
> current TOF count is less than FTMx_CONF[NUMTOF]. If the above condition
> is met, the TOF bit remains set. If the TOF interrupt is enabled
> (FTMx_SC[TOIE] = 1), the TOF interrupt also remains asserted.
>
> Above is the errata discription
>
> The workaround is clearing TOF bit until it is cleaned(FTM counter doesn't
> always reache the FTM_MOD anyway),which may cost some cycles.
>
> Signed-off-by: Meng Yi <meng.yi@nxp.com>
> ---
> drivers/clocksource/fsl_ftm_timer.c | 9 ++++-----
> 1 file changed, 4 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/clocksource/fsl_ftm_timer.c
> b/drivers/clocksource/fsl_ftm_timer.c index 738515b..ade26e5 100644
> --- a/drivers/clocksource/fsl_ftm_timer.c
> +++ b/drivers/clocksource/fsl_ftm_timer.c
> @@ -83,11 +83,10 @@ static inline void ftm_counter_disable(void __iomem
> *base)
>
> static inline void ftm_irq_acknowledge(void __iomem *base)
> {
> - u32 val;
> -
> - val = ftm_readl(base + FTM_SC);
> - val &= ~FTM_SC_TOF;
> - ftm_writel(val, base + FTM_SC);
> + /*read and clean the FTM_SC_TOF bit until its cleared*/
> + while (FTM_SC_TOF & ftm_readl(base + FTM_SC))
> + ftm_writel(ftm_readl(base + FTM_SC) & (~FTM_SC_TOF),
> + base + FTM_SC);
> }
So you are essentially polling hardware in interrupt context. Please add a
sensible timeout to abort this loop in case of defective hardware, and maybe
disable the interrupt in that case.
Best regards,
Alexander
^ permalink raw reply [flat|nested] 3+ messages in thread
* RE: [PATCH] clocksource/fsl: Fix errata A-007728 for flextimer
2016-09-08 6:22 ` Alexander Stein
@ 2016-09-08 6:28 ` Meng Yi
0 siblings, 0 replies; 3+ messages in thread
From: Meng Yi @ 2016-09-08 6:28 UTC (permalink / raw)
To: Alexander Stein; +Cc: daniel.lezcano, tglx, linux-kernel
> > drivers/clocksource/fsl_ftm_timer.c | 9 ++++-----
> > 1 file changed, 4 insertions(+), 5 deletions(-)
> >
> > diff --git a/drivers/clocksource/fsl_ftm_timer.c
> > b/drivers/clocksource/fsl_ftm_timer.c index 738515b..ade26e5 100644
> > --- a/drivers/clocksource/fsl_ftm_timer.c
> > +++ b/drivers/clocksource/fsl_ftm_timer.c
> > @@ -83,11 +83,10 @@ static inline void ftm_counter_disable(void
> > __iomem
> > *base)
> >
> > static inline void ftm_irq_acknowledge(void __iomem *base) {
> > - u32 val;
> > -
> > - val = ftm_readl(base + FTM_SC);
> > - val &= ~FTM_SC_TOF;
> > - ftm_writel(val, base + FTM_SC);
> > + /*read and clean the FTM_SC_TOF bit until its cleared*/
> > + while (FTM_SC_TOF & ftm_readl(base + FTM_SC))
> > + ftm_writel(ftm_readl(base + FTM_SC) & (~FTM_SC_TOF),
> > + base + FTM_SC);
> > }
>
> So you are essentially polling hardware in interrupt context. Please add a
> sensible timeout to abort this loop in case of defective hardware, and maybe
> disable the interrupt in that case.
>
Oh, right. Thank for your comments. I will correct that in next version.
Best regards,
Meng
^ permalink raw reply [flat|nested] 3+ messages in thread
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2016-09-08 6:22 ` Alexander Stein
2016-09-08 6:28 ` Meng Yi
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