Re: [PATCH v2 RESEND] bus: mhi: core: Wait for ready state after reset

[Hemant Kumar]

On 3/10/21 12:41 PM, Jeffrey Hugo wrote:
> After the device has signaled the end of reset by clearing the reset bit,
> it will automatically reinit MHI and the internal device structures.  Once
> That is done, the device will signal it has entered the ready state.
>
> Signaling the ready state involves sending an interrupt (MSI) to the host
> which might cause IOMMU faults if it occurs at the wrong time.
>
> If the controller is being powered down, and possibly removed, then the
> reset flow would only wait for the end of reset.  At which point, the host
> and device would start a race.  The host may complete its reset work, and
> remove the interrupt handler, which would cause the interrupt to be
> disabled in the IOMMU.  If that occurs before the device signals the ready
> state, then the IOMMU will fault since it blocked an interrupt.  While
> harmless, the fault would appear like a serious issue has occurred so let's
> silence it by making sure the device hits the ready state before the host
> completes its reset processing.
>
> Signed-off-by: Jeffrey Hugo <jhugo@xxxxxxxxxxxxxx>

Reviewed-by: Hemant Kumar <hemantk@xxxxxxxxxxxxxx>

--
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project