Re: [PATCH v2 3/7] scsi: ufs: ufs-qcom: Allow the first init start with the maximum supported gear

Can Guo
2023-11-08T08:24:26Z

Hi Mani,

On 11/8/2023 4:21 PM, Can Guo wrote:
> Hi Mani,
>
> On 11/8/2023 1:23 PM, Manivannan Sadhasivam wrote:
>> On Mon, Nov 06, 2023 at 08:46:09PM -0800, Can Guo wrote:
>>> From: Can Guo <quic_cang@quicinc.com>
>>>
>>> During host driver init, the phy_gear is set to the minimum supported
>>> gear
>>> (HS_G2). Then, during the first power mode change, the negotiated
>>> gear, say
>>> HS-G4, is updated to the phy_gear variable so that in the second init
>>> the
>>> updated phy_gear can be used to program the PHY.
>>>
>>> But the current code only allows update the phy_gear to a higher
>>> value. If
>>> one wants to start the first init with the maximum support gear, say
>>> HS-G4,
>>> the phy_gear is not updated to HS-G3 if the device only supports HS-G3.
>>>
>>
>> Can you elaborate when this can happen? AFAICS, there are 3
>> possibilities of
>> initial phy gear with this series:
>>
>> 1. If ufshc is < 5.0, then G2 will be used.
>> 2. If ufshc is >= 5.0 and if the version is populated in register,
>> then that
>> gear will be used. Most likely that gear can be G4/G5 depending on the
>> device
>> connected.
>> 3. If ufshc is >=5.0 and version is not populated, then G4 will be used.
I think this made you confused, in case #3, HS-G5 is used as initial PHY
gear, not G4 (in the last patch in this series).

Thanks,
Can Guo.
>>
>> In all the above cases, I do not see any necessity to switch the phy gear
>> setting to lower one while scaling. Since the gears are backwards
>> compatible,
>> we always use one phy gear sequence. Moreover, we only have 2 init
>> sequences.
>>
>> Please correct me if I'm missing anything.
>>
>> - Mani
> In the next patch, I am setting the initial PHY gear to max HS gear read
> from UFS host cap register, so that we don't need to keep updating the
> initial value for host->phy_gear for different HW versions in future.
> FYI, for HW ver 5 and 6, it is HS-G5. In future, the max gear might
> become HS-G6 or higher on newer HW verions.
>
> I the case #3, if HS-G5 is set to host->phy_gear, the first init uses
> HS-G5, then after negotiation if the agreed gear is HS-G4, we need to
> update host->phy_gear to HS-G4 (a lower value) such that we use a power
> saving PHY gear settings during the 2nd init.
>
> If the commit message is making you confused, I can update it in next
> version. Please let me if I made any mistakes here.
>
> Thanks,
> Can Guo.