Date:   Thu, 9 Jun 2022 21:20:46 +0530
From:   Akhil P Oommen <quic_akhilpo@...cinc.com>
To:     Doug Anderson <dianders@...omium.org>
CC:     Rob Clark <robdclark@...il.com>,
        Rob Clark <robdclark@...omium.org>,
        freedreno <freedreno@...ts.freedesktop.org>,
        David Airlie <airlied@...ux.ie>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        Sean Paul <sean@...rly.run>
Subject: Re: [Freedreno] [PATCH] drm/msm: Switch ordering of runpm put vs
 devfreq_idle

On 6/9/2022 8:27 PM, Doug Anderson wrote:
> Hi,
>
> On Thu, Jun 9, 2022 at 7:16 AM Akhil P Oommen <quic_akhilpo@...cinc.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@...cinc.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@...eaurora.org> wrote:
>>>>>> On 9/27/2021 8:59 PM, Rob Clark wrote:
>>>>>>> From: Rob Clark <robdclark@...omium.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.
I missed that. Agree

-Akhil.
>> -Akhil.
>>> BR,
>>> -R
>>>
>>>> -Akhil.
>>>>>> -Akhil.
>>>>>>
>>>>>>> Fixes: 9bc95570175a ("drm/msm: Devfreq tuning")
>>>>>>> Signed-off-by: Rob Clark <robdclark@...omium.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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