Re: [PATCH -next] irq-chip/gic-v3-its: Fixed an issue where the ITS executes the residual commands in the queue again when the ITS wakes up from sleep mode.

[xuqiang (M)]

在 2020/11/5 22:24, Marc Zyngier 写道:
> On 2020-11-05 14:06, xuqiang (M) wrote:
> > 在 2020/11/5 21:12, Marc Zyngier 写道:
> > > Please don't top-post.
> > >
> > > On 2020-11-05 11:54, xuqiang (M) wrote:
> > > > The kernel sends three commands in the following sequence:
> > > >
> > > > 1.mapd(deviceA, ITT_addr1, valid:1)
> > > >
> > > > 2.mapti(deviceA):ITS write ITT_addr1 memory;
> > > >
> > > > 3.mapd(deviceA, ITT_addr1, valid:0) and kfree(ITT_addr1);
> > > >
> > > > 4.mapd(deviceA, ITT_addr2, valid:1);
> > > >
> > > > 5.mapti(deviceA):ITS write ITT_addr2 memory;
> > > >
> > > > In this case, the processor enters the sleep mode. After the kernel
> > > > performs the suspend operation, the firmware performs the store
> > > > operation and saves GITS_CBASER and GITS_CWRITER registers.
> > > >
> > > > Then, the processor is woken up, and the firmware restores GITS_CBASER
> > > > and GITS_CWRITER registers. Because GITS_CWRITER register is not 0,
> > > > ITS will read the above command sequence execution from the command
> > > > queue, causing ITT_addr1 memory to be trampled.
> > >
> > > This cannot work. By doing a memset on the command queue, you are
> > > only feeding crap to the ITS (command 0 simply does not exist).
> > > Consider yourself lucky that it doesn't just lock-up.
> > >
> > > What needs to happen is the restore sequence that is already in the
> > > driver, so that the command queue is in a sane state before re-enabling
> > > the ITS.
> > >
> > >         M.
> >
> >
> > On my platform, ITS_FLAGS_SAVE_SUSPEND_STATE is not set, thus
> > the first if condition in its_save_disable under list_for_each_entry 
> > goes
> > to the continue, however, I want to set the GITS_CWRITER to 0 at the
> > end of list_for_each_entry.
> >
> > Do you have any suggestions about how to do this?
>
> That's pretty much dropping the checks for ITS_FLAGS_SAVE_SUSPEND_STATE,
> isn't it? But I assume your ITS is already enabled by the time you 
> reenter
> the kernel? If so, I bet your firmware is doing more than just writing
> to CBASER and CWRITER...
>
>         M.

Yes, you are right.My firmware stores GITS_CTRL,GITS_CBASER,GITS_CWRITER

and GITS_BASER<n> in the suspend, and restores these registers in the 
resume.

So I will drop the checks for ITS_FLAGS_SAVE_SUSPEND_STATE. In the case 
of ITS disabled,

set the GITS_CWRITER to 0.

Thanks

             Xu.