linux-kernel - Re: [PATCH v8 1/2] scsi: ufs: Enable power management for wlun

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Message-ID: <3b085cd7-529f-51b8-6a2f-6aa397e1acd3@intel.com>
Date:   Mon, 1 Mar 2021 21:12:55 +0200
From:   Adrian Hunter <adrian.hunter@...el.com>
To:     Asutosh Das <asutoshd@...eaurora.org>
Cc:     cang@...eaurora.org, martin.petersen@...cle.com,
        linux-scsi@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        Alim Akhtar <alim.akhtar@...sung.com>,
        Avri Altman <avri.altman@....com>,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        Pedro Sousa <pedrom.sousa@...opsys.com>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Stanley Chu <stanley.chu@...iatek.com>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ingo Molnar <mingo@...hat.com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Kiwoong Kim <kwmad.kim@...sung.com>,
        Bean Huo <beanhuo@...ron.com>,
        Lee Jones <lee.jones@...aro.org>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        Wei Yongjun <weiyongjun1@...wei.com>,
        Jaegeuk Kim <jaegeuk@...nel.org>,
        Satya Tangirala <satyat@...gle.com>,
        open list <linux-kernel@...r.kernel.org>,
        "moderated list:ARM/SAMSUNG S3C, S5P AND EXYNOS ARM ARCHITECTURES" 
        <linux-arm-kernel@...ts.infradead.org>,
        "open list:ARM/SAMSUNG S3C, S5P AND EXYNOS ARM ARCHITECTURES" 
        <linux-samsung-soc@...r.kernel.org>,
        "moderated list:UNIVERSAL FLASH STORAGE HOST CONTROLLER DRIVER..." 
        <linux-mediatek@...ts.infradead.org>
Subject: Re: [PATCH v8 1/2] scsi: ufs: Enable power management for wlun

On 1/03/21 8:10 pm, Asutosh Das wrote:
> On Mon, Mar 01 2021 at 05:23 -0800, Adrian Hunter wrote:
>> On 26/02/21 1:37 am, Asutosh Das wrote:
>>> @@ -8901,43 +9125,14 @@ static int ufshcd_resume(struct ufs_hba *hba, enum ufs_pm_op pm_op)
>>>              goto vendor_suspend;
>>>      }
>>
>> The ufshcd_reset_and_restore() in ufshcd_resume() will also change the power
>> mode of the UFS device to active.  Until the UFS device is also resumed and
>> then suspended, it will not return to a low power mode.
>>
>>
> Umm, sorry, I didn't understand this comment.
> Say, the UFS device was reset in ufshcd_reset_and_restore() it'd be a hardware
> reset and the UFS device would move to Powered On mode and then to Active power
> mode, when it is ready to begin initialization. And from this state it should
> move to all other legal states.
> Before entering system suspend ufshcd_system_suspend(), the ufs device is
> runtime resumed in ufshcd_suspend_prepare().
> 
> Please can you explain a bit more on this issue that you see?

Say you runtime resume the host controller, and
ufshcd_reset_and_restore() makes the UFS device active,
but the UFS device is still runtime suspended.


Example:

Add a debugfs file to show the current power mode:

diff --git a/drivers/scsi/ufs/ufs-debugfs.c b/drivers/scsi/ufs/ufs-debugfs.c
index dee98dc72d29..700b88df0866 100644
--- a/drivers/scsi/ufs/ufs-debugfs.c
+++ b/drivers/scsi/ufs/ufs-debugfs.c
@@ -48,6 +48,7 @@ void ufs_debugfs_hba_init(struct ufs_hba *hba)
 {
        hba->debugfs_root = debugfs_create_dir(dev_name(hba->dev), ufs_debugfs_root);
        debugfs_create_file("stats", 0400, hba->debugfs_root, hba, &ufs_debugfs_stats_fops);
+       debugfs_create_u32("curr_dev_pwr_mode", 0400, hba->debugfs_root, (u32 *)&hba->curr_dev_pwr_mode);
 }

 void ufs_debugfs_hba_exit(struct ufs_hba *hba)


# grep -H . /sys/bus/pci/drivers/ufshcd/0000\:00\:12.5/rpm*
/sys/bus/pci/drivers/ufshcd/0000:00:12.5/rpm_lvl:6
/sys/bus/pci/drivers/ufshcd/0000:00:12.5/rpm_target_dev_state:DEEPSLEEP
/sys/bus/pci/drivers/ufshcd/0000:00:12.5/rpm_target_link_state:OFF
# cat /sys/kernel/debug/ufshcd/0000\:00\:12.5/curr_dev_pwr_mode
4
# echo on > /sys/devices/pci0000:00/0000:00:12.5/power/control
# cat /sys/kernel/debug/ufshcd/0000\:00\:12.5/curr_dev_pwr_mode
1
# grep -H . /sys/bus/pci/drivers/ufshcd/0000\:00\:12.5/host*/target*/*/power/runtime_status
/sys/bus/pci/drivers/ufshcd/0000:00:12.5/host1/target1:0:0/1:0:0:0/power/runtime_status:suspended
/sys/bus/pci/drivers/ufshcd/0000:00:12.5/host1/target1:0:0/1:0:0:49456/power/runtime_status:suspended
/sys/bus/pci/drivers/ufshcd/0000:00:12.5/host1/target1:0:0/1:0:0:49476/power/runtime_status:suspended
/sys/bus/pci/drivers/ufshcd/0000:00:12.5/host1/target1:0:0/1:0:0:49488/power/runtime_status:suspended

So UFS devices is runtime suspended and should in DeepSleep, but it is active.