Messages in this thread | ![/](/images/icornerl.gif) | | Date | Wed, 25 Jan 2023 10:27:50 +0000 | Subject | Re: [PATCH] coresight: tmc-etr: Don't enable ETR when it's not ready | From | Suzuki K Poulose <> |
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Folks,
On 24/01/2023 20:09, Yabin Cui wrote: > Ping for review. And I still can't reproduce it, even if I reduced the > timeout to 2us and tried different workloads. Any suggestions for how > to reproduce it? >
I think we should go ahead and fix this in the driver to handle flaky hardware cases. But I would like this to be addressed for all the TMC types, not just ETRs, as Mike pointed out.
Thanks Suzuki
> Thanks, > Yabin > > On Tue, Jan 10, 2023 at 1:06 PM Yabin Cui <yabinc@google.com> wrote: >> >>> Do you have a reproducer for this or some more info? >>> For example is it a regression or has it always been there? And on which >>> platform. >> >> It happens on Pixel 6 and 7. We collect ETM data periodically from some >> internal dogfood devices. The problem has happened several times on >> dogfood devices. But I am still trying to reproduce it locally. >> >> We use the scatter-gather mode of ETR, and allocate a 4M buffer. In userspace, >> we use simpleperf in Android to collect system wide ETM data. What is special >> is, simpleperf disables and reenables perf events every 100ms to flush ETM >> data to perf aux buffer. >> >> Pixel 6 and 7 have hardware monitoring AXI traffic. The hardware finds ETR is >> trying to read from or write to a low invalid address (like 0x2E0000). The >> problem always happens right after the "tmc_etr: timeout while waiting for TMC >> to be Ready" message. And in almost all cases, I can find a "timeout while >> waiting for completion of Manual Flush" message from the previous session. >> >> One log history is below: >> [11484.610008][ C0] coresight tmc_etr0: timeout while waiting for >> completion of Manual Flush >> [11484.610177][ C0] coresight tmc_etr0: timeout while waiting for >> TMC to be Ready >> [11484.615367][ C0] coresight tmc_etr0: timeout while waiting for >> completion of Manual Flush >> [11484.615534][ C0] coresight tmc_etr0: timeout while waiting for >> TMC to be Ready >> [12089.486044][ C0] coresight tmc_etr0: timeout while waiting for >> TMC to be Ready >> AXI error report reading from invalid address >> >> Another log history is below: >> [76709.382650][ C5] coresight tmc_etf1: timeout while waiting for >> TMC to be Ready >> [76709.382852][ C7] coresight tmc_etr0: timeout while waiting for >> completion of Manual Flush >> [76709.382995][ C7] coresight tmc_etr0: timeout while waiting for >> TMC to be Ready >> [76709.384510][ C7] coresight tmc_etr0: timeout while waiting for >> completion of Manual Flush >> [76709.384649][ C7] coresight tmc_etr0: timeout while waiting for >> TMC to be Ready >> [76709.384838][ C0] coresight tmc_etr0: timeout while waiting for >> TMC to be Ready >> AIX error report writing to invalid address >> >> It seems if the previous manual flush doesn't finish gracefully, ETR may not be >> ready for the next enable (even after 10min as in the first log). And if we >> continue to enable ETR, an invalid AXI IO may happen. >> >> Thanks, >> Yabin >> >> On Tue, Jan 10, 2023 at 10:04 AM Suzuki K Poulose >> <suzuki.poulose@arm.com> wrote: >>> >>> On 10/01/2023 17:48, Mike Leach wrote: >>>> Hi, >>>> >>>> On Tue, 10 Jan 2023 at 09:30, James Clark <james.clark@arm.com> wrote: >>>>> >>>>> >>>>> >>>>> On 09/01/2023 23:43, Yabin Cui wrote: >>>>>> Otherwise, it may cause error in AXI bus and result in a kernel panic. >>>>> >>>>> Hi Yabin, >>>>> >>>>> Thanks for the fix. Do you have a reproducer for this or some more info? >>>>> For example is it a regression or has it always been there? And on which >>>>> platform. >>>>> >>>>> Thanks >>>>> James >>>>> >>>>>> >>>>>> Signed-off-by: Yabin Cui <yabinc@google.com> >>>>>> --- >>>>>> .../hwtracing/coresight/coresight-tmc-core.c | 4 +++- >>>>>> .../hwtracing/coresight/coresight-tmc-etr.c | 18 +++++++++++++++--- >>>>>> drivers/hwtracing/coresight/coresight-tmc.h | 2 +- >>>>>> 3 files changed, 19 insertions(+), 5 deletions(-) >>>>>> >>>>>> diff --git a/drivers/hwtracing/coresight/coresight-tmc-core.c b/drivers/hwtracing/coresight/coresight-tmc-core.c >>>>>> index 07abf28ad725..c106d142e632 100644 >>>>>> --- a/drivers/hwtracing/coresight/coresight-tmc-core.c >>>>>> +++ b/drivers/hwtracing/coresight/coresight-tmc-core.c >>>>>> @@ -31,7 +31,7 @@ DEFINE_CORESIGHT_DEVLIST(etb_devs, "tmc_etb"); >>>>>> DEFINE_CORESIGHT_DEVLIST(etf_devs, "tmc_etf"); >>>>>> DEFINE_CORESIGHT_DEVLIST(etr_devs, "tmc_etr"); >>>>>> >>>>>> -void tmc_wait_for_tmcready(struct tmc_drvdata *drvdata) >>>>>> +int tmc_wait_for_tmcready(struct tmc_drvdata *drvdata) >>>>>> { >>>>>> struct coresight_device *csdev = drvdata->csdev; >>>>>> struct csdev_access *csa = &csdev->access; >>>>>> @@ -40,7 +40,9 @@ void tmc_wait_for_tmcready(struct tmc_drvdata *drvdata) >>>>>> if (coresight_timeout(csa, TMC_STS, TMC_STS_TMCREADY_BIT, 1)) { >>>>>> dev_err(&csdev->dev, >>>>>> "timeout while waiting for TMC to be Ready\n"); >>>>>> + return -EBUSY; >>>>>> } >>>>>> + return 0; >>>>>> } >>>>>> >>>>>> void tmc_flush_and_stop(struct tmc_drvdata *drvdata) >>>>>> diff --git a/drivers/hwtracing/coresight/coresight-tmc-etr.c b/drivers/hwtracing/coresight/coresight-tmc-etr.c >>>>>> index 867ad8bb9b0c..2da99dd41ed6 100644 >>>>>> --- a/drivers/hwtracing/coresight/coresight-tmc-etr.c >>>>>> +++ b/drivers/hwtracing/coresight/coresight-tmc-etr.c >>>>>> @@ -983,15 +983,21 @@ static void tmc_sync_etr_buf(struct tmc_drvdata *drvdata) >>>>>> etr_buf->ops->sync(etr_buf, rrp, rwp); >>>>>> } >>>>>> >>>>>> -static void __tmc_etr_enable_hw(struct tmc_drvdata *drvdata) >>>>>> +static int __tmc_etr_enable_hw(struct tmc_drvdata *drvdata) >>>>>> { >>>>>> u32 axictl, sts; >>>>>> struct etr_buf *etr_buf = drvdata->etr_buf; >>>>>> + int rc = 0; >>>>>> >>>>>> CS_UNLOCK(drvdata->base); >>>>>> >>>>>> /* Wait for TMCSReady bit to be set */ >>>>>> - tmc_wait_for_tmcready(drvdata); >>>>>> + rc = tmc_wait_for_tmcready(drvdata); >>>>>> + if (rc) { >>>>>> + dev_err(&drvdata->csdev->dev, "not ready ETR isn't enabled\n"); >>>>>> + CS_LOCK(drvdata->base); >>>>>> + return rc; >>>>>> + } >>>>>> >>>>>> writel_relaxed(etr_buf->size / 4, drvdata->base + TMC_RSZ); >>>>>> writel_relaxed(TMC_MODE_CIRCULAR_BUFFER, drvdata->base + TMC_MODE); >>>>>> @@ -1032,6 +1038,7 @@ static void __tmc_etr_enable_hw(struct tmc_drvdata *drvdata) >>>>>> tmc_enable_hw(drvdata); >>>>>> >>>>>> CS_LOCK(drvdata->base); >>>>>> + return rc; >>>>>> } >>>>>> >>>>>> static int tmc_etr_enable_hw(struct tmc_drvdata *drvdata, >>>>>> @@ -1060,7 +1067,12 @@ static int tmc_etr_enable_hw(struct tmc_drvdata *drvdata, >>>>>> rc = coresight_claim_device(drvdata->csdev); >>>>>> if (!rc) { >>>>>> drvdata->etr_buf = etr_buf; >>>>>> - __tmc_etr_enable_hw(drvdata); >>>>>> + rc = __tmc_etr_enable_hw(drvdata); >>>>>> + if (rc) { >>>>>> + drvdata->etr_buf = NULL; >>>>>> + coresight_disclaim_device(drvdata->csdev); >>>>>> + tmc_etr_disable_catu(drvdata); >>>>>> + } >>>>>> } >>>>>> >>>>>> return rc; >>>>>> diff --git a/drivers/hwtracing/coresight/coresight-tmc.h b/drivers/hwtracing/coresight/coresight-tmc.h >>>>>> index 66959557cf39..01c0382a29c0 100644 >>>>>> --- a/drivers/hwtracing/coresight/coresight-tmc.h >>>>>> +++ b/drivers/hwtracing/coresight/coresight-tmc.h >>>>>> @@ -255,7 +255,7 @@ struct tmc_sg_table { >>>>>> }; >>>>>> >>>>>> /* Generic functions */ >>>>>> -void tmc_wait_for_tmcready(struct tmc_drvdata *drvdata); >>>>>> +int tmc_wait_for_tmcready(struct tmc_drvdata *drvdata); >>>>>> void tmc_flush_and_stop(struct tmc_drvdata *drvdata); >>>>>> void tmc_enable_hw(struct tmc_drvdata *drvdata); >>>>>> void tmc_disable_hw(struct tmc_drvdata *drvdata); >>>> >>>> There is no point in waiting for a timeout, and then carrying on even >>>> when it is exceeded. As such this patch seems reasonable. >>>> We should also apply the same principle to the ETF and ETB devices >>>> which use the same tmc_wait_for_tmcready() function. >>> >>> +1 >>> >>> I am fine with pushing this change, as it is doing the right thing. >>> >>>> >>>> However - the concern is that this appears to be happening on starting >>>> the ETR - there should be no outstanding AXI operations that cause the >>>> system to not be ready - as we will either be using this the first >>>> time after reset, or we should have successfully stopped and flushed >>>> the ETR from the previous operation. This warrants further >>>> investigation - should we be extending the timeout - which is already >>>> at a rather generous 100uS, and do we also need to check the MemErr >>>> bit in the status register? >>> >>> It would be good to dump the value of TMC_STATUS to see what is going >>> on. >>> >>>> >>>> As James says, we need details of when and how the problem occurs - >>>> as far as I know it has not been seen on any systems we currently use >>>> (though could have been missed given the current code) >>> >>> +1 >>> >>> Kind regards >>> Suzuki >>> >>> >>>> >>>> Regards >>>> >>>> Mike >>>> >>>> >>>> -- >>>> Mike Leach >>>> Principal Engineer, ARM Ltd. >>>> Manchester Design Centre. UK >>>
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