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

[Jeff Hugo <jeff.hugo@oss.qualcomm.com>]

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