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SubjectRe: [Freedreno] [PATCH] drm/msm: Switch ordering of runpm put vs devfreq_idle
Hi,

On Thu, Jun 9, 2022 at 7:16 AM Akhil P Oommen <quic_akhilpo@quicinc.com> wrote:
>
> On 6/9/2022 2:17 AM, Rob Clark wrote:
> > On Wed, Jun 8, 2022 at 12:36 PM Akhil P Oommen <quic_akhilpo@quicinc.com> wrote:
> >> On 6/8/2022 3:00 AM, Rob Clark wrote:
> >>> On Tue, Sep 28, 2021 at 7:52 AM Akhil P Oommen <akhilpo@codeaurora.org> wrote:
> >>>> On 9/27/2021 8:59 PM, Rob Clark wrote:
> >>>>> From: Rob Clark <robdclark@chromium.org>
> >>>>>
> >>>>> I've seen a few crashes like:
> >>>>>
> >>>>> Internal error: synchronous external abort: 96000010 [#1] PREEMPT SMP
> >>>>> Modules linked in: snd_seq_dummy snd_seq snd_seq_device bridge stp llc tun nf_nat_tftp nf_conntrack_tftp nf_nat_ftp nf_conntrack_ftp esp6 ah6 ip6t_REJECT ip6t_ipv6header vhost_vsock vhost vmw_vsock_virtio_transport_common vsock rfcomm algif_hash algif_skcipher af_alg uinput veth xt_cgroup xt_MASQUERADE venus_enc venus_dec videobuf2_dma_contig qcom_spmi_adc5 qcom_spmi_adc_tm5 hci_uart qcom_vadc_common cros_ec_typec qcom_spmi_temp_alarm typec btqca snd_soc_rt5682_i2c snd_soc_rt5682 snd_soc_sc7180 bluetooth snd_soc_qcom_common snd_soc_rl6231 ecdh_generic ecc venus_core v4l2_mem2mem snd_soc_lpass_sc7180 snd_soc_lpass_hdmi snd_soc_lpass_cpu snd_soc_lpass_platform snd_soc_max98357a ip6table_nat fuse iio_trig_sysfs cros_ec_lid_angle cros_ec_sensors cros_ec_sensors_core industrialio_triggered_buffer kfifo_buf cros_ec_sensorhub lzo_rle ath10k_snoc lzo_compress ath10k_core ath zram mac80211 cfg80211 ax88179_178a usbnet mii uvcvideo videobuf2_vmalloc joydev
> >>>>> CPU: 3 PID: 212 Comm: A618-worker Tainted: G W 5.4.139-16300-g88d8e1285982 #1
> >>>>> Hardware name: Google Pompom (rev1) with LTE (DT)
> >>>>> pstate: 60c00009 (nZCv daif +PAN +UAO)
> >>>>> pc : a6xx_gmu_set_oob+0x114/0x200
> >>>>> lr : a6xx_gmu_set_oob+0x10c/0x200
> >>>>> sp : ffffffc011b7bc20
> >>>>> x29: ffffffc011b7bc20 x28: ffffffdad27c5000
> >>>>> x27: 0000000000000001 x26: ffffffdad1521044
> >>>>> x25: ffffffbef7498338 x24: 0000000000000018
> >>>>> x23: 0000000000000002 x22: 0000000000014648
> >>>>> x21: 0000033732fe638b x20: 0000000080000000
> >>>>> x19: ffffffbef7433bc8 x18: 0000000040000000
> >>>>> x17: 000000243508d982 x16: 000000000000b67e
> >>>>> x15: 00000000000090d4 x14: 0000000000000024
> >>>>> x13: 0000000000000024 x12: 0000000000017521
> >>>>> x11: 0000000000000b48 x10: 0000000000326a48
> >>>>> x9 : 1a130d33f6371600 x8 : ffffffc011e54648
> >>>>> x7 : 614948e00005003c x6 : ffffffbe3cd17e60
> >>>>> x5 : 0000000000000040 x4 : 0000000000000004
> >>>>> x3 : 0000000000000000 x2 : ffffffbef7488000
> >>>>> x1 : ffffffbef7488000 x0 : 0000000000000000
> >>>>> Call trace:
> >>>>> a6xx_gmu_set_oob+0x114/0x200
> >>>>> a6xx_gmu_set_freq+0xe0/0x1fc
> >>>>> msm_devfreq_target+0x80/0x13c
> >>>>> msm_devfreq_idle+0x54/0x94
> >>>>> retire_submit+0x170/0x254
> >>>>> retire_submits+0xa4/0xdc
> >>>>> retire_worker+0x1c/0x28
> >>>>> kthread_worker_fn+0xf4/0x1bc
> >>>>> kthread+0x140/0x158
> >>>>> ret_from_fork+0x10/0x18
> >>>>> Code: 52800c81 9415bbe5 f9400a68 8b160108 (b9400108)
> >>>>> ---[ end trace 16b871df2482cd61 ]---
> >>>>> Kernel panic - not syncing: Fatal exception
> >>>>> SMP: stopping secondary CPUs
> >>>>> Kernel Offset: 0x1ac1400000 from 0xffffffc010000000
> >>>>> PHYS_OFFSET: 0xffffffc280000000
> >>>>> CPU features: 0x88102e,2a80aa38
> >>>>> Memory Limit: none
> >>>>>
> >>>>> Which smells a lot like touching hw after power collapse. I'm not
> >>>>> *entirely* sure how it could have taken 66ms (the autosuspend delay)
> >>>>> before we get to a6xx_gmu_set_oob(), but to be safe we should move
> >>>>> the pm_runtime_put_autosuspend() after msm_devfreq_idle().
> >>>> https://elixir.bootlin.com/linux/v5.15-rc1/source/drivers/gpu/drm/msm/adreno/a6xx_gmu.c#L132
> >>>> We have this check in the gmu freq set path which should avoid this
> >>>> scenario. I might be a bit pedantic here, but I feel that the original
> >>>> code is more accurate. We should immediately mark last busy and put
> >>>> runtime_pm refcount.
> >>> So, I've been doing some experiments, changing the _put_autosuspend()
> >>> to _put_sync(), in the course of tracking down some remaining "GMU
> >>> OOB" timeout type issues and related badness, and discovered things
> >>> very quickly die with SError splats like below. Possibly the issue is
> >>> that runpm has some race conditions, but I'm not sure we can trust
> >>> pm_runtime_get_if_in_use() quite as much as one would like..
> >>>
> >>> -----------
> >>> [ 33.225332] CPU: 0 PID: 216 Comm: A618-worker Tainted: G W
> >>> 5.4.196 #7
> >>> [ 33.225337] Hardware name: Google Wormdingler rev1+ INX panel board (DT)
> >>> [ 33.225343] pstate: 20c00009 (nzCv daif +PAN +UAO)
> >>> [ 33.225353] pc : msm_readl+0x14/0x34
> >>> [ 33.225361] lr : a6xx_gpu_busy+0x40/0x80
> >>> [ 33.225365] sp : ffffffc011b93ad0
> >>> [ 33.225371] x29: ffffffc011b93ad0 x28: ffffffe77cba3000
> >>> [ 33.225377] x27: 0000000000000001 x26: ffffffe77bb4c4ac
> >>> [ 33.225384] x25: ffffffa2f227dfa0 x24: ffffffa2f22aab28
> >>> [ 33.225390] x23: 0000000000000000 x22: ffffffa2f22bf020
> >>> [ 33.225397] x21: ffffffa2f22bf000 x20: ffffffc011b93b10
> >>> [ 33.225404] x19: ffffffc011bd4110 x18: 000000000000000e
> >>> [ 33.225410] x17: 0000000000000004 x16: 000000000000000c
> >>> [ 33.225416] x15: 000001be3a969450 x14: 0000000000000400
> >>> [ 33.225423] x13: 00000000000101d6 x12: 0000000034155555
> >>> [ 33.225429] x11: 0000000000000001 x10: 0000000000000000
> >>> [ 33.225436] x9 : 0000000100000000 x8 : ffffffc011bd4000
> >>> [ 33.225443] x7 : 0000000000000000 x6 : 0000000000000007
> >>> [ 33.225450] x5 : ffffffc01d8b38f0 x4 : 0000000000000000
> >>> [ 33.225457] x3 : 00000000ffffffff x2 : 0000000000000002
> >>> [ 33.225463] x1 : 0000000000000000 x0 : ffffffc011bd4110
> >>> [ 33.225471] Call trace:
> >>> [ 33.225478] msm_readl+0x14/0x34
> >>> [ 33.225484] a6xx_gpu_busy+0x40/0x80
> >>> [ 33.225490] msm_devfreq_get_dev_status+0x70/0x1d0
> >>> [ 33.225500] devfreq_simple_ondemand_func+0x34/0x100
> >>> [ 33.225510] update_devfreq+0x50/0xe8
> >>> [ 33.225517] qos_notifier_call+0x2c/0x64
> >>> [ 33.225523] qos_max_notifier_call+0x1c/0x2c
> >>> [ 33.225532] notifier_call_chain+0x58/0x98
> >>> [ 33.225539] __blocking_notifier_call_chain+0x74/0x84
> >>> [ 33.225545] blocking_notifier_call_chain+0x38/0x48
> >>> [ 33.225554] pm_qos_update_target+0xf8/0x19c
> >>> [ 33.225560] freq_qos_apply+0x54/0x6c
> >>> [ 33.225566] apply_constraint+0x60/0x104
> >>> [ 33.225572] __dev_pm_qos_update_request+0xb4/0x184
> >>> [ 33.225578] dev_pm_qos_update_request+0x38/0x58
> >>> [ 33.225584] msm_devfreq_idle_work+0x34/0x40
> >>> [ 33.225591] kthread_worker_fn+0x144/0x1c8
> >>> [ 33.225597] kthread+0x140/0x284
> >>> [ 33.225604] ret_from_fork+0x10/0x18
> >>> [ 33.225617] Code: f9000bf3 910003fd aa0003f3 d503201f (b9400260)
> >>> [ 33.225623] ---[ end trace f6309767a42d0831 ]---
> >>> [ 33.236185] SMP: stopping secondary CPUs
> >>> [ 33.236186] Kernel Offset: 0x276b600000 from 0xffffffc010000000
> >>> [ 33.236186] PHYS_OFFSET: 0xffffffdf80000000
> >>> [ 33.236187] CPU features: 0x088102e,2a80aa38
> >>> -----------
> >> Any chance we are racing with system suspend here? Because, when
> >> "dev->power.disable_depth > 0", pm_runtime_get_if_in_use() returns
> >> -EINVAL. Then I guess we should look for a positive return value from
> >> pm_runtime_get_if_in_use() before proceeding.
> > I think that is possible.. although I can still still SErrors in
> > a6xx_gpu_busy() with:
> >
> > ----------
> > diff --git a/drivers/gpu/drm/msm/adreno/a6xx_gmu.c
> > b/drivers/gpu/drm/msm/adreno/a6xx_gmu.c
> > index 1ec90a9ca56c..61e1e33f355a 100644
> > --- a/drivers/gpu/drm/msm/adreno/a6xx_gmu.c
> > +++ b/drivers/gpu/drm/msm/adreno/a6xx_gmu.c
> > @@ -129,7 +129,7 @@ void a6xx_gmu_set_freq(struct msm_gpu *gpu, struct
> > dev_pm_opp *opp)
> > * This can get called from devfreq while the hardware is idle. Don't
> > * bring up the power if it isn't already active
> > */
> > - if (pm_runtime_get_if_in_use(gmu->dev) == 0)
> > + if (pm_runtime_get_if_in_use(gmu->dev) <= 0)
> > return;
> >
> > if (!gmu->legacy) {
> > diff --git a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
> > b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
> > index 95a6c3361a1e..b17a95f7b85c 100644
> > --- a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
> > +++ b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
> > @@ -1456,7 +1456,7 @@ static u64 a6xx_gpu_busy(struct msm_gpu *gpu,
> > unsigned long *out_sample_rate)
> > *out_sample_rate = 19200000;
> >
> > /* Only read the gpu busy if the hardware is already active */
> > - if (pm_runtime_get_if_in_use(a6xx_gpu->gmu.dev) == 0)
> > + if (pm_runtime_get_if_in_use(a6xx_gpu->gmu.dev) <= 0)
> > return 0;
> >
> > busy_cycles = gmu_read64(&a6xx_gpu->gmu,
> > ----------
> >
> > So I don't think this completely explains it
> >
> > I am starting to think it might not be a bad idea to drain the gpu's
> > kthread working in the suspend path
> If it helps, draining kthread sounds like a better solution compared to
> the current patch. Because msm_devfreq_idle() is queuing a work which
> can still race with autosuspend + system-suspend under enough system
> pressure.

So I think I've tracked down the crashes that we were seeing and that
they are fixed by:

https://lore.kernel.org/r/20220609073317.1.Ie846c5352bc307ee4248d7cab998ab3016b85d06@changeid

That being said, I'm still a fan of landing Rob's patch because it
gets rid of the potential WARN_ON in adreno_runtime_suspend() and
seems more correct.


> -Akhil.
> >
> > BR,
> > -R
> >
> >> -Akhil.
> >>>> -Akhil.
> >>>>
> >>>>> Fixes: 9bc95570175a ("drm/msm: Devfreq tuning")
> >>>>> Signed-off-by: Rob Clark <robdclark@chromium.org>
> >>>>> ---
> >>>>> drivers/gpu/drm/msm/msm_gpu.c | 6 +++---
> >>>>> 1 file changed, 3 insertions(+), 3 deletions(-)
> >>>>>
> >>>>> diff --git a/drivers/gpu/drm/msm/msm_gpu.c b/drivers/gpu/drm/msm/msm_gpu.c
> >>>>> index d1a16642ecd5..2b2bbe7499e6 100644
> >>>>> --- a/drivers/gpu/drm/msm/msm_gpu.c
> >>>>> +++ b/drivers/gpu/drm/msm/msm_gpu.c
> >>>>> @@ -667,9 +667,6 @@ static void retire_submit(struct msm_gpu *gpu, struct msm_ringbuffer *ring,
> >>>>>
> >>>>> msm_submit_retire(submit);
> >>>>>
> >>>>> - pm_runtime_mark_last_busy(&gpu->pdev->dev);
> >>>>> - pm_runtime_put_autosuspend(&gpu->pdev->dev);
> >>>>> -
> >>>>> spin_lock_irqsave(&ring->submit_lock, flags);
> >>>>> list_del(&submit->node);
> >>>>> spin_unlock_irqrestore(&ring->submit_lock, flags);
> >>>>> @@ -683,6 +680,9 @@ static void retire_submit(struct msm_gpu *gpu, struct msm_ringbuffer *ring,
> >>>>> mutex_unlock(&gpu->active_lock);
> >>>>>
> >>>>> msm_gem_submit_put(submit);
> >>>>> +
> >>>>> + pm_runtime_mark_last_busy(&gpu->pdev->dev);
> >>>>> + pm_runtime_put_autosuspend(&gpu->pdev->dev);
> >>>>> }
> >>>>>
> >>>>> static void retire_submits(struct msm_gpu *gpu)
> >>>>>
>

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