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Message-ID: <32306c0d-58cf-b1df-2794-5b1f17e3d062@quicinc.com>
Date:   Thu, 7 Jul 2022 11:50:15 +0530
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Subject: Re: [PATCHv2] iommu/arm-smmu-qcom: Add debug support for TLB sync
 timeouts
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To:     Will Deacon <will@kernel.org>
CC:     Robin Murphy <robin.murphy@arm.com>,
        Joerg Roedel <joro@8bytes.org>,
        <iommu@lists.linux-foundation.org>,
        <linux-arm-kernel@lists.infradead.org>,
        <linux-kernel@vger.kernel.org>, <linux-arm-msm@vger.kernel.org>,
        <quic_guptap@quicinc.com>, Rob Clark <robdclark@chromium.org>,
        "Bjorn Andersson" <bjorn.andersson@linaro.org>
References: <20220526041403.9984-1-quic_saipraka@quicinc.com>
 <20220706115638.GD2403@willie-the-truck>
From:   Sai Prakash Ranjan <quic_saipraka@quicinc.com>
In-Reply-To: <20220706115638.GD2403@willie-the-truck>
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On 7/6/2022 5:26 PM, Will Deacon wrote:
> On Thu, May 26, 2022 at 09:44:03AM +0530, Sai Prakash Ranjan wrote:
>> TLB sync timeouts can be due to various reasons such as TBU power down
>> or pending TCU/TBU invalidation/sync and so on. Debugging these often
>> require dumping of some implementation defined registers to know the
>> status of TBU/TCU operations and some of these registers are not
>> accessible in non-secure world such as from kernel and requires SMC
>> calls to read them in the secure world. So, add this debug support
>> to dump implementation defined registers for TLB sync timeout issues.
>>
>> Signed-off-by: Sai Prakash Ranjan <quic_saipraka@quicinc.com>
>> ---
>>
>> Changes in v2:
>>   * Use scm call consistently so that it works on older chipsets where
>>     some of these regs are secure registers.
>>   * Add device specific data to get the implementation defined register
>>     offsets.
>>
>> ---
>>   drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c | 161 ++++++++++++++++++---
>>   drivers/iommu/arm/arm-smmu/arm-smmu.c      |   2 +
>>   drivers/iommu/arm/arm-smmu/arm-smmu.h      |   1 +
>>   3 files changed, 146 insertions(+), 18 deletions(-)
> If this is useful to you, then I suppose it's something we could support,
> however I'm pretty worried about our ability to maintain/scale this stuff
> as it is extended to support additional SoCs and other custom debugging
> features.
>
> Perhaps you could stick it all in arm-smmu-qcom-debug.c and have a new
> config option for that, so at least it's even further out of the way?
>
> Will

Sounds good to me, will do that.

Thanks,
Sai