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

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Date:   Fri, 20 Sep 2019 00:24:27 +0530
From:   Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org>
To:     Bjorn Andersson <bjorn.andersson@...aro.org>,
        Stephen Boyd <swboyd@...omium.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

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.

[    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
[    5.124542]  really_probe+0x14c/0x3b8
[    5.128327]  driver_probe_device+0x70/0x140
[    5.132643]  device_driver_attach+0x4c/0x6c
[    5.136960]  __driver_attach+0xc8/0x150
[    5.140917]  bus_for_each_dev+0x84/0xcc
[    5.144873]  driver_attach+0x2c/0x38
[    5.148555]  bus_add_driver+0x108/0x1fc
[    5.152512]  driver_register+0x64/0xf8
[    5.156375]  __platform_driver_register+0x4c/0x58
[    5.161226]  arm_smmu_driver_init+0x1c/0x24
[    5.165545]  do_one_initcall+0x11c/0x2dc
[    5.169595]  do_initcall_level+0x14c/0x174
[    5.173822]  do_basic_setup+0x30/0x48
[    5.177595]  kernel_init_freeable+0xc4/0x144
[    5.181990]  kernel_init+0x14/0x100
[    5.185584]  ret_from_fork+0x10/0x18