Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII;
 format=flowed
Content-Transfer-Encoding: 7bit
Date:   Fri, 07 Feb 2020 13:10:35 +0800
From:   Can Guo <cang@codeaurora.org>
To:     Avri Altman <Avri.Altman@wdc.com>
Cc:     asutoshd@codeaurora.org, nguyenb@codeaurora.org,
        hongwus@codeaurora.org, rnayak@codeaurora.org,
        linux-scsi@vger.kernel.org, kernel-team@android.com,
        saravanak@google.com, salyzyn@google.com,
        Alim Akhtar <alim.akhtar@samsung.com>,
        "James E.J. Bottomley" <jejb@linux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@oracle.com>,
        Bean Huo <beanhuo@micron.com>,
        Stanley Chu <stanley.chu@mediatek.com>,
        Bart Van Assche <bvanassche@acm.org>,
        Venkat Gopalakrishnan <venkatg@codeaurora.org>,
        Tomas Winkler <tomas.winkler@intel.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Pedro Sousa <sousa@synopsys.com>,
        open list <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v7 8/8] scsi: ufs: Select INITIAL adapt for HS Gear4
In-Reply-To: <08101e2924d6262579beec488fcbd93f@codeaurora.org>
References: <1580978008-9327-1-git-send-email-cang@codeaurora.org>
 <1580978008-9327-9-git-send-email-cang@codeaurora.org>
 <MN2PR04MB6991EA027BB31FA58EEBDA81FC1D0@MN2PR04MB6991.namprd04.prod.outlook.com>
 <08101e2924d6262579beec488fcbd93f@codeaurora.org>
Message-ID: <ebbaf825f4a78b1a21da347e8c6d5531@codeaurora.org>
User-Agent: Roundcube Webmail/1.3.9
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On 2020-02-07 10:56, Can Guo wrote:
> On 2020-02-06 21:20, Avri Altman wrote:
>> Hi Can,
>> 
>> 
>>> ADAPT is added specifically for HS Gear4 mode only, select INITIAL 
>>> adapt
>>> before do power mode change to G4 and select no adapt before switch 
>>> to
>>> non-G4 modes.
>> 
>> UFSHCI 3.0 says:
>> 7.4.1 Adapt
>> The use of Adapt isn't mandatory but the specification provides some
>> guidelines on its use.
>> The HCI should perform an Initial Adapt in the following cases if the
>> link is running at HS-G4
>> speed:
>>  - If DME_RESET is initiated.
>>  - If an unused line is activated for HS-G4.
>>  - If UECDME.EC is triggered with bit 3 set to '1'.
>>  - If a change between Rate A and Rate B in HS-G4 is performed.
>> 
>> If it's not mandatory - why are we setting this for all vendors on all
>> platforms?
>> Or am I miss-reading the spec?
>> 
>> Thanks,
>> Avri
> 
> Hi Avri,
> 
> Yes, it is not mandatory, but I don't know a flash vendor that
> refuses to use ADAPT so far, it is even recommended by flash vendors.
> So there is no meaning of adding a specific quirk for it, as all flash
> vendors need this quirk. Otherwise, we would need to add another vops
> to allow platform vendors to control it before send PMC.
> 
> Any other suggestions?
> 
> FYI, ADAPT sequence is used to train an M-RX equalizer. It gives both
> sides better signal integrity against the influence caused by
> temperature and voltage variations. ADAPT is also used by Quality of
> Service Monitoring for HS-G4.
> 
> As for the usage of it, here is just setting the type of it before
> PMC to HS-G4, HW will use ADAPT, only if both sides support ADAPT,
> when it is required as what the spec is saying.
> 
> Thanks,
> 
> Can Guo.

Hi Avri,

I will drop this one for now as it may take some time to nail down it.
I will come back with a separate patch series for it later.

Thanks for the review.

Can Guo.