linux-kernel - Re: [PATCH v2 1/3] scsi: ufshcd: Update the set frequency to devfreq

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Date:   Mon, 25 May 2020 16:19:51 -0600
From:   Jeffrey Hugo <jeffrey.l.hugo@...il.com>
To:     Asutosh Das <asutoshd@...eaurora.org>
Cc:     Avri Altman <Avri.Altman@....com>, Can Guo <cang@...eaurora.org>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        linux-scsi@...r.kernel.org, MSM <linux-arm-msm@...r.kernel.org>,
        Alim Akhtar <alim.akhtar@...sung.com>,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        Stanley Chu <stanley.chu@...iatek.com>,
        Bean Huo <beanhuo@...ron.com>,
        Bart Van Assche <bvanassche@....org>,
        Venkat Gopalakrishnan <venkatg@...eaurora.org>,
        Tomas Winkler <tomas.winkler@...el.com>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 1/3] scsi: ufshcd: Update the set frequency to devfreq

On Wed, Mar 25, 2020 at 12:29 PM Asutosh Das <asutoshd@...eaurora.org> wrote:
>
> Currently, the frequency that devfreq provides the
> driver to set always leads the clocks to be scaled up.
> Hence, round the clock-rate to the nearest frequency
> before deciding to scale.
>
> Also update the devfreq statistics of current frequency.
>
> Signed-off-by: Asutosh Das <asutoshd@...eaurora.org>

This change appears to cause issues for the Lenovo Miix 630, as
identified by git bisect.

On 5.6-final, My boot log looks normal.  On 5.7-rc7, the Lenovo Miix
630 rarely boots, usually stuck in some kind of infinite printk loop.

If I disable some of the UFS logging, I can capture this from the
logs, as soon as UFS inits -

[    4.353860] ufshcd-qcom 1da4000.ufshc: ufshcd_intr: Unhandled
interrupt 0x00000000
[    4.359605] ufshcd-qcom 1da4000.ufshc: ufshcd_intr: Unhandled
interrupt 0x00000000
[    4.365412] ufshcd-qcom 1da4000.ufshc: ufshcd_check_errors:
saved_err 0x4 saved_uic_err 0x2
[    4.371121] ufshcd-qcom 1da4000.ufshc: hba->ufs_version = 0x210,
hba->capabilities = 0x1587001f
[    4.376846] ufshcd-qcom 1da4000.ufshc: hba->outstanding_reqs =
0x100000, hba->outstanding_tasks = 0x0
[    4.382636] ufshcd-qcom 1da4000.ufshc: last_hibern8_exit_tstamp at
0 us, hibern8_exit_cnt = 0
[    4.388368] ufshcd-qcom 1da4000.ufshc: No record of pa_err
[    4.394001] ufshcd-qcom 1da4000.ufshc: dl_err[0] = 0x80000001 at 3873626 us
[    4.399577] ufshcd-qcom 1da4000.ufshc: No record of nl_err
[    4.405053] ufshcd-qcom 1da4000.ufshc: No record of tl_err
[    4.410464] ufshcd-qcom 1da4000.ufshc: No record of dme_err
[    4.415747] ufshcd-qcom 1da4000.ufshc: No record of auto_hibern8_err
[    4.420950] ufshcd-qcom 1da4000.ufshc: No record of fatal_err
[    4.426013] ufshcd-qcom 1da4000.ufshc: No record of link_startup_fail
[    4.430950] ufshcd-qcom 1da4000.ufshc: No record of resume_fail
[    4.435786] ufshcd-qcom 1da4000.ufshc: No record of suspend_fail
[    4.440538] ufshcd-qcom 1da4000.ufshc: dev_reset[0] = 0x0 at 3031009 us
[    4.445199] ufshcd-qcom 1da4000.ufshc: No record of host_reset
[    4.449750] ufshcd-qcom 1da4000.ufshc: No record of task_abort
[    4.454214] ufshcd-qcom 1da4000.ufshc: clk: core_clk, rate: 50000000
[    4.458590] ufshcd-qcom 1da4000.ufshc: clk: core_clk_unipro, rate: 37500000

I don't understand how this change is breaking things, but it clearly is for me.

What kind of additional data would be useful to get to the bottom of this?