Messages in this thread | | | Subject | Re: [RFC PATCH v2] coresight: etm4x: Modify core-commit of cpu to avoid the overflow of HiSilicon ETM | From | Qi Liu <> | Date | Fri, 13 Nov 2020 18:18:32 +0800 |
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On 2020/11/12 22:03, Suzuki K Poulose wrote: > On 11/12/20 1:09 PM, Qi Liu wrote: >> >> >> On 2020/11/12 1:03, Mathieu Poirier wrote: >>> On Wed, Nov 11, 2020 at 04:58:23PM +0800, Qi Liu wrote: >>>> Hi Mathieu, >>>> >>>> On 2020/9/10 0:26, Mathieu Poirier wrote: >>>>> On Wed, Sep 09, 2020 at 12:30:02PM +0100, Mike Leach wrote: >>>>>> Hi, >>>>>> >>>>>> On Wed, 2 Sep 2020 at 11:36, Suzuki K Poulose <suzuki.poulose@arm.com> wrote: >>>>>>> On 08/27/2020 09:44 PM, Mathieu Poirier wrote: >>>>>>>> Hi Liu, >>>>>>>> >>>>>>>> On Wed, Aug 19, 2020 at 04:06:37PM +0800, Qi Liu wrote: >>>>>>>>> When too much trace information is generated on-chip, the ETM will >>>>>>>>> overflow, and cause data loss. This is a common phenomenon on ETM >>>>>>>>> devices. >>>>>>>>> >>>>>>>>> But sometimes we do not want to lose performance trace data, so we >>>>>>>>> suppress the speed of instructions sent from CPU core to ETM to >>>>>>>>> avoid the overflow of ETM. >>>>>>>>> >>>>>>>>> Signed-off-by: Qi Liu <liuqi115@huawei.com> >>>>>>>>> --- >>>>>>>>> >>>>>>>>> Changes since v1: >>>>>>>>> - ETM on HiSilicon Hip09 platform supports backpressure, so does >>>>>>>>> not need to modify core commit. >>>>>>>>> >>>>>>>>> drivers/hwtracing/coresight/coresight-etm4x.c | 43 +++++++++++++++++++++++++++ >>>>>>>>> 1 file changed, 43 insertions(+) >>>>>>>>> >>>>>>>>> diff --git a/drivers/hwtracing/coresight/coresight-etm4x.c b/drivers/hwtracing/coresight/coresight-etm4x.c >>>>>>>>> index 7797a57..7641f89 100644 >>>>>>>>> --- a/drivers/hwtracing/coresight/coresight-etm4x.c >>>>>>>>> +++ b/drivers/hwtracing/coresight/coresight-etm4x.c >>>>>>>>> @@ -43,6 +43,10 @@ MODULE_PARM_DESC(boot_enable, "Enable tracing on boot"); >>>>>>>>> #define PARAM_PM_SAVE_NEVER 1 /* never save any state */ >>>>>>>>> #define PARAM_PM_SAVE_SELF_HOSTED 2 /* save self-hosted state only */ >>>>>>>>> >>>>>>>>> +#define CORE_COMMIT_CLEAR 0x3000 >>>>>>>>> +#define CORE_COMMIT_SHIFT 12 >>>>>>>>> +#define HISI_ETM_AMBA_ID_V1 0x000b6d01 >>>>>>>>> + >>>>>>>>> static int pm_save_enable = PARAM_PM_SAVE_FIRMWARE; >>>>>>>>> module_param(pm_save_enable, int, 0444); >>>>>>>>> MODULE_PARM_DESC(pm_save_enable, >>>>>>>>> @@ -104,11 +108,40 @@ struct etm4_enable_arg { >>>>>>>>> int rc; >>>>>>>>> }; >>>>>>>>> >>>>>>>>> +static void etm4_cpu_actlr1_cfg(void *info) >>>>>>>>> +{ >>>>>>>>> + struct etm4_enable_arg *arg = (struct etm4_enable_arg *)info; >>>>>>>>> + u64 val; >>>>>>>>> + >>>>>>>>> + asm volatile("mrs %0,s3_1_c15_c2_5" : "=r"(val)); >>>>>>> >>>>>>> The ID register (S3_1_C15_c2_5) falls into implementation defined space. >>>>>>> See Arm ARM DDI 0487F.a, section "D12.3.2 Reserved encodings for >>>>>>> IMPLEMENTATION DEFINED registers". >>>>>>> >>>>>>> So, please stop calling this "etm4_cpu_actlr1_cfg". Since, >>>>>>> 1) actlr1 is not an architected name for the said encoding >>>>>>> 2) The id register could mean something else on another CPU. >>>>>>> >>>>>>> Rather this should indicate platform/CPU specific. e.g, >>>>>>> >>>>>>> etm4_cpu_hisilicon_config_core_commit() >>>>>>> >>>>>>> >>>>>>>>> + val &= ~CORE_COMMIT_CLEAR; >>>>>>>>> + val |= arg->rc << CORE_COMMIT_SHIFT; >>>>>>>>> + asm volatile("msr s3_1_c15_c2_5,%0" : : "r"(val)); >>>>>>>>> +} >>>>>>>>> + >>>>>>>>> +static void etm4_config_core_commit(int cpu, int val) >>>>>>>>> +{ >>>>>>>>> + struct etm4_enable_arg arg = {0}; >>>>>>>>> + >>>>>>>>> + arg.rc = val; >>>>>>>>> + smp_call_function_single(cpu, etm4_cpu_actlr1_cfg, &arg, 1); >>>>>>>> Function etm4_enable/disable_hw() are already running on the CPU they are >>>>>>>> supposed to so no need to call smp_call_function_single(). >>>>>>>> >>>>>>>>> +} >>>>>>>>> + >>>>>>>>> static int etm4_enable_hw(struct etmv4_drvdata *drvdata) >>>>>>>>> { >>>>>>>>> int i, rc; >>>>>>>>> + struct amba_device *adev; >>>>>>>>> struct etmv4_config *config = &drvdata->config; >>>>>>>>> struct device *etm_dev = &drvdata->csdev->dev; >>>>>>>>> + struct device *dev = drvdata->csdev->dev.parent; >>>>>>>>> + >>>>>>>>> + adev = container_of(dev, struct amba_device, dev); >>>>>>>>> + /* >>>>>>>>> + * If ETM device is HiSilicon ETM device, reduce the >>>>>>>>> + * core-commit to avoid ETM overflow. >>>>>>>>> + */ >>>>>>>>> + if (adev->periphid == HISI_ETM_AMBA_ID_V1) >>>>>>> Please could you move this check to the function above ? >>>>>>> Ideally, it would be good to have something like : >>>>>>> >>>>>>> etm4_config_impdef_features(); >>>>>>> >>>>>>> And : >>>>>>> >>>>>>> etm4_config_impdef_features(struct etm4_drvdata *drvdata) >>>>>>> { >>>>>>> etm4_cpu_hisilicon_config_core_commit(drvdata); >>>>>>> } >>>>>>> >>>>>> In addition to the above, Is it worth having this implementation >>>>>> defined code gated in the kernel configuration - like we do for core >>>>>> features sometimes? >>>>>> i,.e. >>>>>> CONFIG_ETM4X_IMPDEF_FEATURE (controls overall impdef support in the driver) >>>>>> and >>>>>> CONFIG_ETM4X_IMPDEF_HISILICON (depends on CONFIG_ETM4X_IMPDEF_FEATURE ) >>>>>> >>>>>> This way we keep non ETM architectural code off platforms that cannot >>>>>> use it / test it. >>>>>> >>>>> That's a good idea - they do the same for CPU erratas. >>>>> >>>> Considering that users sometimes use the same set of code on different platforms, how about >>>> using both CONFIG andperiphid to keep core-commit code off the platforms that do not >>>> need it? >>>> i, .e. >>>> CONFIG_ETM4X_IMPDEF_FEATURE ( controls overall impdef support in the driver ) >>>> periphid ( match impdef code with the target platform ) >>>> >>>> This way we could keep the same set of code working on different platforms, and it could help to >>>> ensure compatibility. >>> >>> I'm not 100% sure of what you mean by "same set of code working on different >>> platforms"... Up to know the way we have been handling peripheral IDs has >>> worked quite well and I don't intend on changing it unless there is a really >>> good reason. >>> >> Hi Mathieu, >> >> Perhaps I didn't make it clear and here is the code to express what I mean: >> >> #ifdef CONFIG_ETM4X_IMPDEF_FEATURE >> >> #define HISI_HIP08_AMBA_ID 0x000b6d01 >> #define HISI_HIP08_AMBA_MASK 0xfffff >> static void etm4_enable_arch_specific(struct etmv4_drvdata *drvdata) >> { >> struct device *dev = drvdata->csdev->dev.parent; >> struct amba_device *adev = container_of(dev, struct amba_device, dev); > > There is no guarantee that this is always an "AMBA" device, with this > patchset (which is still under review). Also, doing this check at > every time we enable/disable the ETM is not idea.. > > May be we should add a concept of "features" and use a bit mask instead, > which can be set at probe time, where we do have this information. > > #define ETM4x_IMPDEF_HISILICON_CORE_COMMIT 0 > #define ETM4x_IMPDEF_ARCH_N_FEATS 1 > > struct etmv4_drvdata { > > ... > DECALRE_BITMAP(arch_features, ETM4x_IMPDEF_ARCH_FEAT_MAX); > } > > struct etm4x_arch_feature { > void (*callback)(struct etmv4_drdvata *, bool enable); > }; > > static struct etm4x_arch_features[] = { > [ETM4x_IMPDEF_HISILICON_CORE_COMMIT] = { > .callback = etm4x_hisilicon_core_commit, > }, > {} > }; > > static void etm4_enable_arch_specific(struct etmv4_drvdata *drvdata) > { > for_each_set_bit(i, &drvdata->arch_features) { > struct etm4x_arch_feature *ftr = &etm4x_arch_features[i]; > > if (ftr->callback) > ftr->callback(drvdata, true); > } > } > > etm4x_check_arch_features() { > if (hisilicon_etm4x_match_pid) > set_bit(drvdata->arch_features, ETM4x_IMPDEF_HISILICON_CORE_COMMIT); > } > > etm4x_probe() { > > etm4x_check_arch_features(); > } > > Suzuki
Hi Suzuki,
Add a check in probe is a good idea, and perhaps we could also add CONFIG_ETM4X_IMPDEF_FEATURE here, like: etm4x_probe() { ... #ifdef CONFIG_ETM4X_IMPDEF_FEATURE etm4x_check_arch_features(); #endif }
Thanks Qi > > . >
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