Re: [PATCH 2/2] scsi: ufs: core: Fix the code for entering hibernation

["Bao D. Nguyen" <quic_nguyenb@quicinc.com>]

On 8/21/2024 5:14 PM, Bart Van Assche wrote:
> On 8/21/24 4:26 PM, Bao D. Nguyen wrote:
>> On 8/21/2024 11:29 AM, Bart Van Assche wrote:
>>> Accessing a host controller register after the host controller has
>>> entered the hibernation state may cause the host controller to exit the
>>> hibernation state. Hence rework the hibernation entry code such that it
>>> does not modify the interrupt enabled status. Bart,
>  >
>> I am not clear on the offending condition, particularly the term 
>> "hibernation" used in this context. In the function 
>> ufshcd_uic_pwr_ctrl() where you are making the change, the host 
>> controller is fully active at this point, right?
>> Please help me clarify the issue.
> 
> Hi Bao,
> 
> Isn't "hibernation" terminology that comes from the M-PHY standard?
> See also the DME_HIBERNATE_ENTER and DME_HIBERNATE_EXIT constants in
> the UFSHCI driver source code. Please let me know if you need more
> information.

I see. Thanks Bart.
If I understand correctly, the link is hibernated because we had a 
successful ufshcd_uic_hibern8_enter() earlier. Then the 
ufshcd_uic_pwr_ctrl() is invoked probably from a power mode change 
command? (a callstack would be helpful in this case).
Anyway, accessing the UFSHCI host controller registers space somehow 
affected the M-PHY link state? If my understanding is correct, it seems 
like a hardware issue that we are trying to work around?

Thanks, Bao