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

Stephen Boyd
2019-09-19T20:00:56Z

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