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Message-ID: <87c8d5cb-d5b5-ab6c-00d9-bae7f972d777@quicinc.com>
Date: Fri, 21 Jun 2024 19:05:14 -0700
From: Abhinav Kumar <quic_abhinavk@...cinc.com>
To: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
CC: <freedreno@...ts.freedesktop.org>, Rob Clark <robdclark@...il.com>,
"Sean
Paul" <sean@...rly.run>,
Marijn Suijten <marijn.suijten@...ainline.org>,
"David Airlie" <airlied@...il.com>, Daniel Vetter <daniel@...ll.ch>,
<dri-devel@...ts.freedesktop.org>, <seanpaul@...omium.org>,
<swboyd@...omium.org>, <dianders@...omium.org>,
<quic_jesszhan@...cinc.com>, <linux-arm-msm@...r.kernel.org>,
<linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH 1/4] drm/msm: register a fault handler for display mmu
faults
On 6/21/2024 4:35 PM, Abhinav Kumar wrote:
>
>
> On 5/19/2024 1:38 AM, Dmitry Baryshkov wrote:
>> On Fri, May 17, 2024 at 04:37:56PM -0700, Abhinav Kumar wrote:
>>> In preparation to register a iommu fault handler for display
>>> related modules, register a fault handler for the backing
>>> mmu object of msm_kms.
>>>
>>> Currently, the fault handler only captures the display snapshot
>>> but we can expand this later if more information needs to be
>>> added to debug display mmu faults.
>>>
>>> Signed-off-by: Abhinav Kumar <quic_abhinavk@...cinc.com>
>>> ---
>>> drivers/gpu/drm/msm/msm_kms.c | 25 +++++++++++++++++++++++++
>>> 1 file changed, 25 insertions(+)
>>>
>>> diff --git a/drivers/gpu/drm/msm/msm_kms.c
>>> b/drivers/gpu/drm/msm/msm_kms.c
>>> index af6a6fcb1173..62c8e6163e81 100644
>>> --- a/drivers/gpu/drm/msm/msm_kms.c
>>> +++ b/drivers/gpu/drm/msm/msm_kms.c
>>> @@ -200,6 +200,28 @@ struct msm_gem_address_space
>>> *msm_kms_init_aspace(struct drm_device *dev)
>>> return aspace;
>>> }
>>> +static int msm_kms_fault_handler(void *arg, unsigned long iova, int
>>> flags, void *data)
>>> +{
>>> + struct msm_kms *kms = arg;
>>> + struct msm_disp_state *state;
>>> + int ret;
>>> +
>>> + ret = mutex_lock_interruptible(&kms->dump_mutex);
>>> + if (ret)
>>> + return ret;
>>> +
>>> + state = msm_disp_snapshot_state_sync(kms);
>>> +
>>> + mutex_unlock(&kms->dump_mutex);
>>> +
>>> + if (IS_ERR(state)) {
>>> + DRM_DEV_ERROR(kms->dev->dev, "failed to capture snapshot\n");
>>> + return PTR_ERR(state);
>>> + }
>>> +
>>> + return 0;
>>
>> Hmm, after reading the rest of the code, this means that we won't get
>> the error on the console. Could you please change this to -ENOSYS?
>>
>
> I am perhaps missing something here. Are you referring to this
> documentation?
>
> * Specifically, -ENOSYS is returned if a fault handler isn't installed
> * (though fault handlers can also return -ENOSYS, in case they want to
> * elicit the default behavior of the IOMMU drivers).
> */
> int report_iommu_fault(struct iommu_domain *domain, struct device *dev,
> unsigned long iova, int flags)
>
> Doesnt this mean ENOSYS is when fault handler is not installed?
>
> Because the console print will come if we return 0?
>
> if (!report_iommu_fault(ctx->domain, ctx->dev, iova, 0)) {
> dev_err_ratelimited(ctx->dev,
> "Unhandled context fault: fsr=0x%x, "
> "iova=0x%016llx, fsynr=0x%x, cb=%d\n",
> fsr, iova, fsynr, ctx->asid);
> }
>
I was checking the wrong place, you are correct.
I will return ENOSYS here.
Thanks.
>>> +}
>>> +
>>> void msm_drm_kms_uninit(struct device *dev)
>>> {
>>> struct platform_device *pdev = to_platform_device(dev);
>>> @@ -261,6 +283,9 @@ int msm_drm_kms_init(struct device *dev, const
>>> struct drm_driver *drv)
>>> goto err_msm_uninit;
>>> }
>>> + if (kms->aspace)
>>> + msm_mmu_set_fault_handler(kms->aspace->mmu, kms,
>>> msm_kms_fault_handler);
>>> +
>>> drm_helper_move_panel_connectors_to_head(ddev);
>>> drm_for_each_crtc(crtc, ddev) {
>>> --
>>> 2.44.0
>>>
>>
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