On Wed, Apr 13, 2022 at 12:52:26PM -0600, Jeffrey Hugo wrote:
> From: Jeffrey Hugo <jhugo@xxxxxxxxxxxxxx>
>
> 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>
> Signed-off-by: Jeffrey Hugo <quic_jhugo@xxxxxxxxxxx>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@xxxxxxxxxx>
Thanks,
Mani
> ---
>
> v3:
> Rebase and use dev_err over dev_warn
>
> v2:
> Fix subject and remove use of cur_state
>
> drivers/bus/mhi/host/pm.c | 9 +++++++++
> 1 file changed, 9 insertions(+)
>
> diff --git a/drivers/bus/mhi/host/pm.c b/drivers/bus/mhi/host/pm.c
> index a0e91bd..f46158e 100644
> --- a/drivers/bus/mhi/host/pm.c
> +++ b/drivers/bus/mhi/host/pm.c
> @@ -483,6 +483,15 @@ static void mhi_pm_disable_transition(struct mhi_controller *mhi_cntrl)
> * hence re-program it
> */
> mhi_write_reg(mhi_cntrl, mhi_cntrl->bhi, BHI_INTVEC, 0);
> +
> + if (!MHI_IN_PBL(mhi_get_exec_env(mhi_cntrl))) {
> + /* wait for ready to be set */
> + ret = mhi_poll_reg_field(mhi_cntrl, mhi_cntrl->regs,
> + MHISTATUS,
> + MHISTATUS_READY_MASK, 1, 25000);
> + if (ret)
> + dev_err(dev, "Device failed to enter READY state\n");
> + }
> }
>
> dev_dbg(dev,
> --
> 2.7.4
>
>
