linux-kernel - Re: [PATCH v2] bus: mhi: host: don't free bhie tables during suspend/hibernation

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Message-ID: <ad5e99e8-3ff1-4727-aed6-528ac747f409@oss.qualcomm.com>
Date: Mon, 14 Apr 2025 08:14:54 -0600
From: Jeff Hugo <jeff.hugo@....qualcomm.com>
To: Muhammad Usama Anjum <usama.anjum@...labora.com>,
        Krishna Chaitanya Chundru <quic_krichai@...cinc.com>,
        Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
        Johannes Berg <johannes@...solutions.net>,
        Jeff Johnson
 <jjohnson@...nel.org>,
        Jeffrey Hugo <quic_jhugo@...cinc.com>, Yan Zhen <yanzhen@...o.com>,
        Youssef Samir <quic_yabdulra@...cinc.com>,
        Qiang Yu <quic_qianyu@...cinc.com>, Alex Elder <elder@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Kunwu Chan <chentao@...inos.cn>
Cc: kernel@...labora.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
Subject: Re: [PATCH v2] bus: mhi: host: don't free bhie tables during
 suspend/hibernation

On 4/14/2025 1:32 AM, Muhammad Usama Anjum wrote:
> On 4/12/25 6:22 AM, Krishna Chaitanya Chundru wrote:
>>
>> On 4/12/2025 12:02 AM, Muhammad Usama Anjum wrote:
>>> On 4/11/25 1:39 PM, Krishna Chaitanya Chundru wrote:
>>>>
>>>>
>>>> On 4/11/2025 12:32 PM, Muhammad Usama Anjum wrote:
>>>>> On 4/11/25 8:37 AM, Krishna Chaitanya Chundru wrote:
>>>>>>
>>>>>>
>>>>>> On 4/10/2025 8:26 PM, Muhammad Usama Anjum wrote:
>>>>>>> Fix dma_direct_alloc() failure at resume time during bhie_table
>>>>>>> allocation. There is a crash report where at resume time, the memory
>>>>>>> from the dma doesn't get allocated and MHI fails to re-initialize.
>>>>>>> There may be fragmentation of some kind which fails the allocation
>>>>>>> call.
>>>>>>>
>>>>>>> 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
>>>>>> If firmware image will change between suspend and resume ?
>>>>> Yes, correct.
>>>>>
>>>> why the firmware image size will change between suspend & resume?
>>>> who will update the firmware image after bootup?
>>>> It is not expected behaviour.
>>> I was trying to research if the firmware can change or not. I've not
>>> found any documentation on it.
>>>
>>> If the firmare is updated in filesystem before suspend/hibernate, would
>>> the new firwmare be loaded the next time kernel resumes as the older
>>> firmware is no where to be found?
>>>
>>> What do you think about this?
>>>
>> I don't think firmware can be updated before suspend/hibernate. I don't
>> see any reason why it can be updated. If you think it can be updated
>> please quote relevant doc.
> I've not found any documentation on it. Let's wait for others to review
> and it it cannot be updated, I'll remove this part.
> 

Wouldn't this be trivial to test?  Boot the device, go modify the 
firmware on the filesystem, then go through a suspend cycle.

-Jeff