Messages in this thread | | | Date | Thu, 19 Oct 2023 14:41:55 +0800 | Subject | Re: [PATCH] coresight: etm4x: Enable ETE device accessed via MMIO | From | Ruidong Tian <> |
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Hi Suzuki
You are right, I review armv9 Spec again, and find that ETE only support system instructions access. This patch is meaningless and need to drop it.
Ruidong
在 2023/10/18 17:36, Suzuki K Poulose 写道: > Hi > > On 18/10/2023 10:30, Ruidong Tian wrote: >> Hi Suzuki, >> >> Now ETM4X driver use MMIO or system instruction depends on this check >> in function etm4_init_csdev_access: >> >> if (drvdata->base) >> return etm4_init_iomem_access(drvdata, csa); >> >> This check always true if firmware provides a address range in ACPI >> table of ETE, and as a result, the ETE device in this case cannot be >> successfully probed. >> >> I think OS should be compatible with this situation, no matter firmware >> how to organize ETE information in ACPI table. How do you feel about >> it? > > My question is not about "What the patch does". But, why can't we use > system instructions on your system, when ETE was designed to be used > with that in the first place and get rid of the MMIO. > > Suzuki > >> >> Thank you >> >> Ruidong Tian >> 在 2023/10/18 16:28, Suzuki K Poulose 写道: >>> On 18/10/2023 08:05, Ruidong Tian wrote: >>>> The ETM4X driver now assume that all ETE as CPU system instructions >>>> accessed device, in fact the ETE device on some machines also accessed >>>> via MMIO. >>>> >>>> Signed-off-by: Ruidong Tian <tianruidong@linux.alibaba.com> >>> >>> Why are we going backwards to MMIO from system instructions ? Is it >>> because of an "unfriendly" hypervisor preventing access ? >>> >>> As such, without a sufficiently acceptable explanation, I am reluctant >>> to make this change >>> >>> Suzuki >>> >>>> --- >>>> drivers/hwtracing/coresight/coresight-etm4x-core.c | 5 +++-- >>>> 1 file changed, 3 insertions(+), 2 deletions(-) >>>> >>>> diff --git a/drivers/hwtracing/coresight/coresight-etm4x-core.c >>>> b/drivers/hwtracing/coresight/coresight-etm4x-core.c >>>> index 285539104bcc..ad298c9cc87e 100644 >>>> --- a/drivers/hwtracing/coresight/coresight-etm4x-core.c >>>> +++ b/drivers/hwtracing/coresight/coresight-etm4x-core.c >>>> @@ -1103,8 +1103,9 @@ static bool etm4_init_iomem_access(struct >>>> etmv4_drvdata *drvdata, >>>> * with MMIO. But we cannot touch the OSLK until we are >>>> * sure this is an ETM. So rely only on the TRCDEVARCH. >>>> */ >>>> - if ((devarch & ETM_DEVARCH_ID_MASK) != ETM_DEVARCH_ETMv4x_ARCH) { >>>> - pr_warn_once("TRCDEVARCH doesn't match ETMv4 >>>> architecture\n"); >>>> + if ((devarch & ETM_DEVARCH_ID_MASK) != ETM_DEVARCH_ETMv4x_ARCH && >>>> + (devarch & ETM_DEVARCH_ID_MASK) != ETM_DEVARCH_ETE_ARCH) { >>>> + pr_warn_once("TRCDEVARCH doesn't match ETMv4/ETE >>>> architecture\n"); >>>> return false; >>>> }
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