linux-kernel - Re: [PATCHv6 3/3] iommu: arm-smmu-impl: Add sdm845 implementation hook

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Date:   Thu, 19 Sep 2019 13:00:51 -0700
From:   Stephen Boyd <swboyd@...omium.org>
To:     Bjorn Andersson <bjorn.andersson@...aro.org>,
        Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org>
Cc:     Robin Murphy <robin.murphy@....com>, Will Deacon <will@...nel.org>,
        Joerg Roedel <joro@...tes.org>,
        iommu@...ts.linux-foundation.org,
        Vivek Gautam <vivek.gautam@...eaurora.org>,
        Andy Gross <agross@...nel.org>, linux-arm-msm@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Rajendra Nayak <rnayak@...eaurora.org>,
        linux-arm-msm-owner@...r.kernel.org
Subject: Re: [PATCHv6 3/3] iommu: arm-smmu-impl: Add sdm845 implementation hook

Quoting Sai Prakash Ranjan (2019-09-19 11:54:27)
> On 2019-09-19 08:48, Sai Prakash Ranjan wrote:
> > On 2019-09-19 05:55, Bjorn Andersson wrote:
> >> In the transition to this new design we lost the ability to
> >> enable/disable the safe toggle per board, which according to Vivek
> >> would result in some issue with Cheza.
> >> 
> >> Can you confirm that this is okay? (Or introduce the DT property for
> >> enabling the safe_toggle logic?)
> >> 
> > 
> > Hmm, I don't remember Vivek telling about any issue on Cheza because
> > of this logic.
> > But I will test this on Cheza and let you know.
> > 
> 
> I tested this on Cheza and no perf degradation nor any other issue is 
> seen
> atleast openly, although I see this below stack dump always with 
> cant_sleep change added.

The usage of cant_sleep() here is wrong then, and the comment should be
removed from the scm API as well because it looks like it's perfectly OK
to call the function from a context that can sleep.

> 
> [    5.048860] BUG: assuming atomic context at 
> /mnt/host/source/src/third_party/kernel/v5.3/drivers/firmware/qcom_scm-64.c:206
> [    5.060303] in_atomic(): 0, irqs_disabled(): 0, pid: 1, name: 
> swapper/0
> [    5.067118] CPU: 4 PID: 1 Comm: swapper/0 Not tainted 5.3.0 #102
> [    5.073299] Hardware name: Google Cheza (rev3+) (DT)
> [    5.078416] Call trace:
> [    5.080953]  dump_backtrace+0x0/0x16c
> [    5.084727]  show_stack+0x20/0x2c
> [    5.088156]  dump_stack+0x90/0xcc
> [    5.091585]  __cant_sleep+0xb4/0xc4
> [    5.095192]  __qcom_scm_qsmmu500_wait_safe_toggle+0x5c/0xa0
> [    5.100929]  qcom_scm_qsmmu500_wait_safe_toggle+0x28/0x34
> [    5.106491]  qcom_sdm845_smmu500_reset+0x24/0x50
> [    5.111249]  arm_smmu_device_reset+0x1a4/0x25c
> [    5.115827]  arm_smmu_device_probe+0x418/0x50c
> [    5.120406]  platform_drv_probe+0x90/0xb0