Re: [PATCH V2 3/8] drm/msm: Unconditionally call dev_pm_opp_of_remove_table()

[Viresh Kumar]

On 01-09-20, 15:15, Rajendra Nayak wrote:
> 
> On 9/1/2020 2:08 PM, Viresh Kumar wrote:
> > On 01-09-20, 13:01, Rajendra Nayak wrote:
> > > So FWIU, dpu_unbind() gets called even when dpu_bind() fails for some reason.
> > 
> > Ahh, I see.
> > 
> > > I tried to address that earlier [1] which I realized did not land.
> > 
> > I don't think that patch was required, as you can call
> > dev_pm_opp_put_clkname() multiple times and it will return without any
> > errors/crash.
> 
> We did see a crash (Sai had reported it), perhaps with dsi [1] and not this
> driver. But it was the same scenario that was possible here as well, which is
> dev_pm_opp_put_clkname() getting called without dev_pm_opp_set_clkname()
> being done. I think we ended up passing a NULL as opp_table in that case
> and the function tries de-referencing it.

Heh, yeah I did miss that stupid thing :(

> > 
> > > But with these changes
> > > it will be even more broken unless we identify if we failed dpu_bind() before
> > > adding the OPP table, while adding it, or all went well with opps and handle things
> > > accordingly in dpu_unbind.
> > 
> > Maybe not as dev_pm_opp_of_remove_table() can be called multiple times
> > as well without any errors or crash.
> 
> Can it be called without the driver ever doing a dev_pm_opp_of_add_table()?

Yes, as we will fail to find the OPP device in that case with -ENODEV
and so won't even print a warning.

Also if the OPP table was previously added as a response to
dev_pm_opp_set_clkname(), then we won't free it as well. So yes, it
should work just fine.

-- 
viresh