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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <49b331dc-37eb-6e26-f701-c83187a30788@quicinc.com>
Date:   Wed, 8 Nov 2023 16:21:52 +0800
From:   Can Guo <quic_cang@...cinc.com>
To:     Manivannan Sadhasivam <mani@...nel.org>,
        Can Guo <cang@....qualcomm.com>
CC:     <bvanassche@....org>, <stanley.chu@...iatek.com>,
        <adrian.hunter@...el.com>, <beanhuo@...ron.com>,
        <avri.altman@....com>, <junwoo80.lee@...sung.com>,
        <martin.petersen@...cle.com>, <linux-scsi@...r.kernel.org>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        "open list:ARM/QUALCOMM SUPPORT" <linux-arm-msm@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 3/7] scsi: ufs: ufs-qcom: Allow the first init start
 with the maximum supported gear

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@...cinc.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.
> 
> 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.