linux-kernel - Re: [PATCH v4] bus: mhi: host: don't free bhie tables during suspend/hibernation

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Message-ID: <5521efad-1ca8-41e3-b820-5527d634c539@collabora.com>
Date: Tue, 13 May 2025 11:44:34 +0500
From: Muhammad Usama Anjum <usama.anjum@...labora.com>
To: Jeff Hugo <jeff.hugo@....qualcomm.com>,
 Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
 Jeff Johnson <jjohnson@...nel.org>, Youssef Samir
 <quic_yabdulra@...cinc.com>, Matthew Leung <quic_mattleun@...cinc.com>,
 Yan Zhen <yanzhen@...o.com>, Greg Kroah-Hartman
 <gregkh@...uxfoundation.org>,
 Jacek Lawrynowicz <jacek.lawrynowicz@...ux.intel.com>,
 Kunwu Chan <chentao@...inos.cn>, Troy Hanson <quic_thanson@...cinc.com>,
 "Dr. David Alan Gilbert" <linux@...blig.org>
Cc: usama.anjum@...labora.com, kernel@...labora.com,
 sebastian.reichel@...labora.com, Carl Vanderlip <quic_carlv@...cinc.com>,
 Alex Elder <elder@...nel.org>, mhi@...ts.linux.dev,
 linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-wireless@...r.kernel.org, ath11k@...ts.infradead.org,
 ath12k@...ts.infradead.org
Subject: Re: [PATCH v4] bus: mhi: host: don't free bhie tables during
 suspend/hibernation

On 5/12/25 11:46 PM, Jeff Hugo wrote:
> On 5/6/2025 8:49 AM, Muhammad Usama Anjum wrote:
>> Fix dma_direct_alloc() failure at resume time during bhie_table
>> allocation because of memory pressure. There is a report where at
>> resume time, the memory from the dma doesn't get allocated and MHI
>> fails to re-initialize.
>>
>> To fix it, don't free the memory at power down during suspend /
>> hibernation. Instead, use the same allocated memory again after every
>> resume / hibernation. This patch has been tested with resume and
>> hibernation both.
>>
>> The rddm is of constant size for a given hardware. While the fbc_image
>> size depends on the firmware. If the firmware changes, we'll free and
>> allocate new memory for it.
> 
> Why is it valid to load new firmware as a result of suspend?  I don't
> users would expect that.
I'm not sure its valid or not. Like other users, I also don't expect
that firmware would get changed. It doesn't seem to be tested and hence
supported case.

But other drivers have code which have implementation like this. I'd
mentioned previously that this patch was motivated from the ath12k [1]
and ath11k [2] patches. They don't free the memory and reuse the same
memory if new size is same.


> 
>> diff --git a/drivers/bus/mhi/host/boot.c b/drivers/bus/mhi/host/boot.c
>> index efa3b6dddf4d2..bc8459798bbee 100644
>> --- a/drivers/bus/mhi/host/boot.c
>> +++ b/drivers/bus/mhi/host/boot.c
>> @@ -584,10 +584,17 @@ void mhi_fw_load_handler(struct mhi_controller
>> *mhi_cntrl)
>>        * device transitioning into MHI READY state
>>        */
>>       if (fw_load_type == MHI_FW_LOAD_FBC) {
> 
> Why is this FBC specific?
It seems we allocate fbc_image only when firmware load type is
FW_LOAD_FBC. I'm just optimizing the buffer allocation here.

> 
>> -        ret = mhi_alloc_bhie_table(mhi_cntrl, &mhi_cntrl->fbc_image,
>> fw_sz);
>> -        if (ret) {
>> -            release_firmware(firmware);
>> -            goto error_fw_load;
>> +        if (mhi_cntrl->fbc_image && fw_sz != mhi_cntrl->prev_fw_sz) {
>> +            mhi_free_bhie_table(mhi_cntrl, mhi_cntrl->fbc_image);
>> +            mhi_cntrl->fbc_image = NULL;
>> +        }
>> +        if (!mhi_cntrl->fbc_image) {
>> +            ret = mhi_alloc_bhie_table(mhi_cntrl, &mhi_cntrl-
>> >fbc_image, fw_sz);
>> +            if (ret) {
>> +                release_firmware(firmware);
>> +                goto error_fw_load;
>> +            }
>> +            mhi_cntrl->prev_fw_sz = fw_sz;
>>           }
>>             /* Load the firmware into BHIE vec table */
>> diff --git a/drivers/bus/mhi/host/pm.c b/drivers/bus/mhi/host/pm.c
>> index e6c3ff62bab1d..107d71b4cc51a 100644
>> --- a/drivers/bus/mhi/host/pm.c
>> +++ b/drivers/bus/mhi/host/pm.c
>> @@ -1259,10 +1259,19 @@ void mhi_power_down(struct mhi_controller
>> *mhi_cntrl, bool graceful)
>>   }
>>   EXPORT_SYMBOL_GPL(mhi_power_down);
>>   +static void __mhi_power_down_unprepare_keep_dev(struct
>> mhi_controller *mhi_cntrl)
>> +{
>> +    mhi_cntrl->bhi = NULL;
>> +    mhi_cntrl->bhie = NULL;
> 
> Why?
This function is shorter version of mhi_unprepare_after_power_down(). As
we need different code path in case of suspend/hibernation case, I was
adding a new API which Mani asked me remove and consolidate into
mhi_power_down_keep_dev() instead. So this static function has been
added. [3]



> 
>> +
>> +    mhi_deinit_dev_ctxt(mhi_cntrl);
>> +}

[1]
https://lore.kernel.org/all/20240419034034.2842-1-quic_bqiang@quicinc.com/
[2]
https://lore.kernel.org/all/20220506141448.10340-1-quic_akolli@quicinc.com/
[3]
https://lore.kernel.org/all/y5odcxzms6mwpz5bdxhbjxo7p6whsdgwm772usmmzqobhf6nam@p4ul7vn7d3an


-- 
Regards,
Usama