linux-kernel - RE: [EXT] [PATCH 2/3] scsi: ufs: Allow resetting the UFS device

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Date:   Wed, 5 Jun 2019 21:17:48 +0000
From:   "Bean Huo (beanhuo)" <beanhuo@...ron.com>
To:     Bjorn Andersson <bjorn.andersson@...aro.org>
CC:     Pedro Sousa <pedrom.sousa@...opsys.com>,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        Andy Gross <agross@...nel.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        "linux-arm-msm@...r.kernel.org" <linux-arm-msm@...r.kernel.org>,
        "linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>
Subject: RE: [EXT] [PATCH 2/3] scsi: ufs: Allow resetting the UFS device

Hi, Bjorn
I think I should give up my preview suggestion DME_ENDPOINTRESET.req software reset,  go back to your HW reset.
Although SW reset can cover most of the requirement, and compatible with different vendor UFS device, for some device
fatal error cases, UFS internal stuck and would not accept SW Reset. An HW reset is expected.  
Please go on your reset way.

Thanks,
//Bean

>Andy Gross <agross@...nel.org>; Linus Walleij <linus.walleij@...aro.org>;
>Rob Herring <robh+dt@...nel.org>; Mark Rutland <mark.rutland@....com>;
>linux-arm-msm@...r.kernel.org; linux-gpio@...r.kernel.org;
>devicetree@...r.kernel.org; linux-kernel@...r.kernel.org; linux-
>scsi@...r.kernel.org
>Subject: Re: [EXT] [PATCH 2/3] scsi: ufs: Allow resetting the UFS device
>
>On Tue 04 Jun 01:13 PDT 2019, Bean Huo (beanhuo) wrote:
>> >@@ -6159,6 +6179,9 @@ static int ufshcd_reset_and_restore(struct
>> >ufs_hba
>> >*hba)
>> > 	int retries = MAX_HOST_RESET_RETRIES;
>> >
>> > 	do {
>> >+		/* Reset the attached device */
>> >+		ufshcd_device_reset(hba);
>> >+
>>
>> what's problem you met, and you should reset UFS device here? could you
>give more info?
>>
>> It is true that we don't reset UFS device in case of device fatal
>> error. According to UFS host spec, Host should be device reset except
>> that in addition to resetting UIC. But as so far, We didn't experience any
>problems result from this missing reset.
>>
>> We have three UFS device reset ways.  Comparing to this hardware
>> reset, I prefer to use DME_ENDPOINTRESET.req software reset.
>>
>
>Hi Bean,
>
>Thanks for your questions. With some memories we see issues establishing
>the link during bootup, so that's the purpose of issuing this reset.
>
>Unfortunately the downstream Qualcomm patch [1] (which I should have
>remembered to attribute), does not mention why the reset during host
>controller reset is needed - but I'm fairly certain that this scenario would be
>similar to the handover from bootloader to kernel that we do see an issue
>with.
>
>
>[1]
>https://nam01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fsource
>.codeaurora.org%2Fquic%2Fla%2Fkernel%2Fmsm-
>4.4%2Fcommit%2F%3Fh%3Dmsm-
>4.4%26id%3D0c82737188e2d63a08196e078e411032dbbc3b89&amp;data=02%
>7C01%7Cbeanhuo%40micron.com%7Cf72404eb906440e1f9c408d6e93c401d%7
>Cf38a5ecd28134862b11bac1d563c806f%7C0%7C0%7C636952842324926509&a
>mp;sdata=I%2FH7km6b34jyoUa1RVEPApfYt5uSFtHqL3%2BvV1bvryM%3D&amp
>;reserved=0
>
>Regards,
>Bjorn