linux-kernel - Re: [PATCH v4] bus: mhi: host: Skip MHI reset if device is in RDDM

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Message-ID: <113156cf-5770-c0c7-dea6-4ddca43b4438@quicinc.com>
Date:   Mon, 22 May 2023 15:01:53 +0800
From:   Qiang Yu <quic_qianyu@...cinc.com>
To:     Manivannan Sadhasivam <mani@...nel.org>
CC:     <quic_jhugo@...cinc.com>, <mhi@...ts.linux.dev>,
        <linux-arm-msm@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <quic_cang@...cinc.com>, <quic_mrana@...cinc.com>,
        <stable@...r.kernel.org>
Subject: Re: [PATCH v4] bus: mhi: host: Skip MHI reset if device is in RDDM


On 5/19/2023 9:51 PM, Manivannan Sadhasivam wrote:
> On Thu, May 18, 2023 at 02:22:39PM +0800, Qiang Yu wrote:
>> In RDDM EE, device can not process MHI reset issued by host. In case of MHI
>> power off, host is issuing MHI reset and polls for it to get cleared until
>> it times out. Since this timeout can not be avoided in case of RDDM, skip
>> the MHI reset in this scenarios.
>>
>> Cc: <stable@...r.kernel.org>
>> Fixes: a6e2e3522f29 ("bus: mhi: core: Add support for PM state transitions")
>> Signed-off-by: Qiang Yu <quic_qianyu@...cinc.com>
>> Reviewed-by: Jeffrey Hugo <quic_jhugo@...cinc.com>
>> ---
>> v1->v2: use ~75 columns in commit text, add Fixes tag
>> v2->v3: update Fixes tag
>> v3->v4: add review tag and CC stable
>>
>>   drivers/bus/mhi/host/pm.c | 5 +++++
>>   1 file changed, 5 insertions(+)
>>
>> diff --git a/drivers/bus/mhi/host/pm.c b/drivers/bus/mhi/host/pm.c
>> index 0834590..8a4362d 100644
>> --- a/drivers/bus/mhi/host/pm.c
>> +++ b/drivers/bus/mhi/host/pm.c
>> @@ -470,6 +470,10 @@ static void mhi_pm_disable_transition(struct mhi_controller *mhi_cntrl)
>>   
>>   	/* Trigger MHI RESET so that the device will not access host memory */
>>   	if (!MHI_PM_IN_FATAL_STATE(mhi_cntrl->pm_state)) {
>> +		/* Skip MHI RESET if in RDDM state */
>> +		if (mhi_cntrl->rddm_image && mhi_get_exec_env(mhi_cntrl) == MHI_EE_RDDM)
> Do we really need to check for rddm_image? Wouldn't the EE check sufficient
> enough?
>
> In that case, the check can be moved to the prior if condition.
>
> - Mani

If rddm_image is NULL, that means this device does not support RDDM. In this case, it is unnecessary to access MMIO register.

>> +			goto skip_mhi_reset;
>> +
>>   		dev_dbg(dev, "Triggering MHI Reset in device\n");
>>   		mhi_set_mhi_state(mhi_cntrl, MHI_STATE_RESET);
>>   
>> @@ -495,6 +499,7 @@ static void mhi_pm_disable_transition(struct mhi_controller *mhi_cntrl)
>>   		}
>>   	}
>>   
>> +skip_mhi_reset:
>>   	dev_dbg(dev,
>>   		 "Waiting for all pending event ring processing to complete\n");
>>   	mhi_event = mhi_cntrl->mhi_event;
>> -- 
>> 2.7.4
>>
>>