linux-kernel - Re: [PATCH 3/3] bus: mhi: keep device context through suspend cycles

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Message-ID: <c40f13e8-7420-4046-880d-7c72620fc021@collabora.com>
Date: Thu, 10 Jul 2025 20:07:25 +0500
From: Muhammad Usama Anjum <usama.anjum@...labora.com>
To: Krishna Chaitanya Chundru <krishna.chundru@....qualcomm.com>,
 Manivannan Sadhasivam <mani@...nel.org>, Jeff Johnson <jjohnson@...nel.org>,
 Jeff Hugo <jeff.hugo@....qualcomm.com>,
 Youssef Samir <quic_yabdulra@...cinc.com>,
 Matthew Leung <quic_mattleun@...cinc.com>, Yan Zhen <yanzhen@...o.com>,
 Alexander Wilhelm <alexander.wilhelm@...termo.com>,
 Alex Elder <elder@...nel.org>, Kunwu Chan <chentao@...inos.cn>,
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
 Siddartha Mohanadoss <smohanad@...eaurora.org>,
 Sujeev Dias <sdias@...eaurora.org>, Julia Lawall <julia.lawall@...6.fr>,
 John Crispin <john@...ozen.org>, Muna Sinada <quic_msinada@...cinc.com>,
 Venkateswara Naralasetty <quic_vnaralas@...cinc.com>,
 Maharaja Kennadyrajan <quic_mkenna@...cinc.com>, mhi@...ts.linux.dev,
 linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-wireless@...r.kernel.org, ath11k@...ts.infradead.org
Cc: kernel@...labora.com
Subject: Re: [PATCH 3/3] bus: mhi: keep device context through suspend cycles

On 7/8/25 3:15 PM, Krishna Chaitanya Chundru wrote:
> 
> 
> On 6/30/2025 1:13 PM, Muhammad Usama Anjum wrote:
>> Don't deinitialize the device context while going into suspend or
>> hibernation cycles. Otherwise the resume may fail if at resume time, the
>> memory pressure is high and no dma memory is available.
>>
>> Tested-on: WCN6855 WLAN.HSP.1.1-03926.13-QCAHSPSWPL_V2_SILICONZ_CE-2.52297.6
>>
>> Fixes: 3000f85b8f47 ("bus: mhi: core: Add support for basic PM operations")
>> Signed-off-by: Muhammad Usama Anjum <usama.anjum@...labora.com>
>> ---
>>   drivers/bus/mhi/host/init.c | 11 ++++++-----
>>   1 file changed, 6 insertions(+), 5 deletions(-)
>>
>> diff --git a/drivers/bus/mhi/host/init.c b/drivers/bus/mhi/host/init.c
>> index 2e0f18c939e68..8f56e73fdc42e 100644
>> --- a/drivers/bus/mhi/host/init.c
>> +++ b/drivers/bus/mhi/host/init.c
>> @@ -1133,9 +1133,11 @@ int mhi_prepare_for_power_up(struct mhi_controller *mhi_cntrl)
>>         mutex_lock(&mhi_cntrl->pm_mutex);
>>   -    ret = mhi_init_dev_ctxt(mhi_cntrl);
> mhi init dev ctxt also initializes the ring pointers to base value,
> I think we should take care of them also ?
Are you referring to mhi_rings? They are getting initialized inside
mhi_init_dev_ctxt() and de-initialized in __mhi_deinit_dev_ctxt(). That's
why I've not handled them separately.

> 
> - Krishna Chaitanya.
>> -    if (ret)
>> -        goto error_dev_ctxt;
>> +    if (!mhi_cntrl->mhi_ctxt) {
>> +        ret = mhi_init_dev_ctxt(mhi_cntrl);
>> +        if (ret)
>> +            goto error_dev_ctxt;
>> +    }
>>         ret = mhi_read_reg(mhi_cntrl, mhi_cntrl->regs, BHIOFF, &bhi_off);
>>       if (ret) {
>> @@ -1212,8 +1214,6 @@ void mhi_deinit_dev_ctxt(struct mhi_controller *mhi_cntrl)
>>   {
>>       mhi_cntrl->bhi = NULL;
>>       mhi_cntrl->bhie = NULL;
>> -
>> -    __mhi_deinit_dev_ctxt(mhi_cntrl);
>>   }
>>     void mhi_unprepare_after_power_down(struct mhi_controller *mhi_cntrl)
>> @@ -1234,6 +1234,7 @@ void mhi_unprepare_after_power_down(struct mhi_controller *mhi_cntrl)
>>       }
>>         mhi_deinit_dev_ctxt(mhi_cntrl);
>> +    __mhi_deinit_dev_ctxt(mhi_cntrl);
>>   }
>>   EXPORT_SYMBOL_GPL(mhi_unprepare_after_power_down);
>>