linux-kernel - Re: [PATCH v4 2/7] scsi: ufs-qcom: Add reset control support for host controller

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Message-ID: <c52906ce2d8b97aa394d347955dfd8d0@codeaurora.org>
Date:   Fri, 15 Nov 2019 09:25:22 +0800
From:   Can Guo <cang@...eaurora.org>
To:     Avri Altman <Avri.Altman@....com>
Cc:     asutoshd@...eaurora.org, nguyenb@...eaurora.org,
        rnayak@...eaurora.org, linux-scsi@...r.kernel.org,
        kernel-team@...roid.com, saravanak@...gle.com, salyzyn@...gle.com,
        Andy Gross <agross@...nel.org>,
        Alim Akhtar <alim.akhtar@...sung.com>,
        Pedro Sousa <pedrom.sousa@...opsys.com>,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        "open list:ARM/QUALCOMM SUPPORT" <linux-arm-msm@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 2/7] scsi: ufs-qcom: Add reset control support for host
 controller

On 2019-11-14 17:03, Avri Altman wrote:
> Hi,
> 
>> 
>> 
>> Add reset control for host controller so that host controller can be 
>> reset as
>> required in its power up sequence.
>> 
>> Signed-off-by: Can Guo <cang@...eaurora.org>
>> +       ret = reset_control_assert(host->core_reset);
>> +       if (ret) {
>> +               dev_err(hba->dev, "%s: core_reset assert failed, err = 
>> %d\n",
>> +                                __func__, ret);
>> +               goto out;
>> +       }
>> +
>> +       /*
>> +        * The hardware requirement for delay between assert/deassert
>> +        * is at least 3-4 sleep clock (32.7KHz) cycles, which comes 
>> to
>> +        * ~125us (4/32768). To be on the safe side add 200us delay.
>> +        */
>> +       usleep_range(200, 210);
> Aren't you sleeping anyway in your reset_control_ops?
> 

For our cases, reset_control_assert uses the reset_control_ops->assert() 
we registered for
node &clock_gcc. There is no sleep or delay in Q's 
reset_control_ops->assert() func.

>> +
>> +       ret = reset_control_deassert(host->core_reset);
>> +       if (ret)
>> +               dev_err(hba->dev, "%s: core_reset deassert failed, err 
>> = %d\n",
>> +                                __func__, ret);
>> +
>> +       usleep_range(1000, 1100);
> ditto

Same as above.

Best Regards,
Can Guo.