On Thu, Sep 9, 2021 at 1:54 PM Rob Clark robdclark@gmail.com wrote:
On Thu, Sep 9, 2021 at 12:50 PM Akhil P Oommen akhilpo@codeaurora.org wrote:
On 9/9/2021 9:42 PM, Amit Pundir wrote:
On Thu, 9 Sept 2021 at 17:47, Amit Pundir amit.pundir@linaro.org wrote:
On Wed, 8 Sept 2021 at 07:50, Bjorn Andersson bjorn.andersson@linaro.org wrote:
On Mon 09 Aug 10:26 PDT 2021, Akhil P Oommen wrote:
On 8/9/2021 9:48 PM, Caleb Connolly wrote: > > > On 09/08/2021 17:12, Rob Clark wrote: >> On Mon, Aug 9, 2021 at 7:52 AM Akhil P Oommen >> akhilpo@codeaurora.org wrote:
[..]
>>> I am a bit confused. We don't define a power domain for gpu in dt, >>> correct? Then what exactly set_opp do here? Do you think this usleep is >>> what is helping here somehow to mask the issue? > The power domains (for cx and gx) are defined in the GMU DT, the OPPs in > the GPU DT. For the sake of simplicity I'll refer to the lowest > frequency (257000000) and OPP level (RPMH_REGULATOR_LEVEL_LOW_SVS) as > the "min" state, and the highest frequency (710000000) and OPP level > (RPMH_REGULATOR_LEVEL_TURBO_L1) as the "max" state. These are defined in > sdm845.dtsi under the gpu node. > > The new devfreq behaviour unmasks what I think is a driver bug, it > inadvertently puts much more strain on the GPU regulators than they > usually get. With the new behaviour the GPU jumps from it's min state to > the max state and back again extremely rapidly under workloads as small > as refreshing UI. Where previously the GPU would rarely if ever go above > 342MHz when interacting with the device, it now jumps between min and > max many times per second. > > If my understanding is correct, the current implementation of the GMU > set freq is the following: > - Get OPP for frequency to set > - Push the frequency to the GMU - immediately updating the core clock > - Call dev_pm_opp_set_opp() which triggers a notify chain, this winds > up somewhere in power management code and causes the gx regulator level > to be updated
Nope. dev_pm_opp_set_opp() sets the bandwidth for gpu and nothing else. We were using a different api earlier which got deprecated - dev_pm_opp_set_bw().
On the Lenovo Yoga C630 this is reproduced by starting alacritty and if I'm lucky I managed to hit a few keys before it crashes, so I spent a few hours looking into this as well...
As you say, the dev_pm_opp_set_opp() will only cast a interconnect vote. The opp-level is just there for show and isn't used by anything, at least not on 845.
Further more, I'm missing something in my tree, so the interconnect doesn't hit sync_state, and as such we're not actually scaling the buses. So the problem is not that Linux doesn't turn on the buses in time.
So I suspect that the "AHB bus error" isn't saying that we turned off the bus, but rather that the GPU becomes unstable or something of that sort.
Lastly, I reverted 9bc95570175a ("drm/msm: Devfreq tuning") and ran Aquarium for 20 minutes without a problem. I then switched the gpu devfreq governor to "userspace" and ran the following:
while true; do echo 257000000 > /sys/class/devfreq/5000000.gpu/userspace/set_freq echo 710000000 > /sys/class/devfreq/5000000.gpu/userspace/set_freq done
It took 19 iterations of this loop to crash the GPU.
Ack. With your above script, I can reproduce a crash too on db845c (A630) running v5.14. I didn't get any crash log though and device just rebooted to USB crash mode.
And same crash on RB5 (A650) too https://hastebin.com/raw/ejutetuwun
Are we sure this is the same issue? It could be, but I thought we were seeing a bunch of random gpu errors (which may eventually hit device crash).
In the sense that async-serror often seems to be a clk issue, it *could* be related.. but this would have to be triggered by CPU access. The symptom does seem very different.
The more I think about it, the more I think this is a different issue.. a650 is somewhat different wrt gmu (ie. hfi vs legacy code paths).
Amit, could you try the same experiment (with 9bc95570175a ("drm/msm: Devfreq tuning") revert) while running something like webgl aquarium to prevent the GPU from suspending? I'm kinda suspecting the issue you hit is more likely some suspend/resume issue.
BR, -R