From: Manivannan Sadhasivam <mani@kernel.org>
To: Jeffrey Hugo <quic_jhugo@quicinc.com>
Cc: quic_hemantk@quicinc.com, quic_bbhatt@quicinc.com,
mhi@lists.linux.dev, linux-arm-msm@vger.kernel.org,
linux-kernel@vger.kernel.org, Jeffrey Hugo <jhugo@codeaurora.org>
Subject: Re: [PATCH v3] bus: mhi: host: Wait for ready state after reset
Date: Mon, 18 Apr 2022 11:29:00 +0530 [thread overview]
Message-ID: <20220418055900.GD7431@thinkpad> (raw)
In-Reply-To: <1649875946-32516-1-git-send-email-quic_jhugo@quicinc.com>
On Wed, Apr 13, 2022 at 12:52:26PM -0600, Jeffrey Hugo wrote:
> From: Jeffrey Hugo <jhugo@codeaurora.org>
>
> 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@codeaurora.org>
> Reviewed-by: Hemant Kumar <hemantk@codeaurora.org>
> Signed-off-by: Jeffrey Hugo <quic_jhugo@quicinc.com>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
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
>
>
next prev parent reply other threads:[~2022-04-18 5:59 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-04-13 18:52 [PATCH v3] bus: mhi: host: Wait for ready state after reset Jeffrey Hugo
2022-04-18 5:59 ` Manivannan Sadhasivam [this message]
2022-04-18 6:26 ` Manivannan Sadhasivam
2022-04-18 13:53 ` Jeffrey Hugo
2022-04-18 14:12 ` Manivannan Sadhasivam
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