Quoting Andy Shevchenko (2023-09-06 13:13:27) > On Wed, Sep 06, 2023 at 11:09:43AM -0700, Stephen Boyd wrote: > > It's possible for interrupts to get significantly delayed to the point > > that callers of intel_scu_ipc_dev_command() and friends can call the > > function once, hit a timeout, and call it again while the interrupt > > still hasn't been processed. This driver will get seriously confused if > > the interrupt is finally processed after the second IPC has been sent > > with ipc_command(). It won't know which IPC has been completed. This > > could be quite disastrous if calling code assumes something has happened > > upon return from intel_scu_ipc_dev_simple_command() when it actually > > hasn't. > > > > Let's avoid this scenario by simply returning -EBUSY in this case. > > Hopefully higher layers will know to back off or fail gracefully when > > this happens. It's all highly unlikely anyway, but it's better to be > > correct here as we have no way to know which IPC the status register is > > telling us about if we send a second IPC while the previous IPC is still > > processing. > > Reviewed-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx> > > Also see below. > > ... > > > @@ -450,6 +468,12 @@ int intel_scu_ipc_dev_simple_command(struct intel_scu_ipc_dev *scu, int cmd, > > return -ENODEV; > > } > > > scu = ipcdev; > > Side observation: Isn't this a bug? We should not override the supplied parameter. If it is a bug that would be great to know. I wanted to make an API that got the scu if it wasn't busy but then I ran across this code that replaced the scu with ipcdev.
