From: Can Guo <cang@codeaurora.org>
To: Adrian Hunter <adrian.hunter@intel.com>
Cc: Bjorn Andersson <bjorn.andersson@linaro.org>,
Ziqi Chen <ziqichen@codeaurora.org>,
asutoshd@codeaurora.org, nguyenb@codeaurora.org,
hongwus@codeaurora.org, rnayak@codeaurora.org,
vinholikatti@gmail.com, jejb@linux.vnet.ibm.com,
martin.petersen@oracle.com, linux-scsi@vger.kernel.org,
kernel-team@android.com, saravanak@google.com,
salyzyn@google.com, kwmad.kim@samsung.com,
stanley.chu@mediatek.com, Alim Akhtar <alim.akhtar@samsung.com>,
Avri Altman <avri.altman@wdc.com>,
"James E.J. Bottomley" <jejb@linux.ibm.com>,
Andy Gross <agross@kernel.org>,
Matthias Brugger <matthias.bgg@gmail.com>,
Bean Huo <beanhuo@micron.com>,
Bart Van Assche <bvanassche@acm.org>,
Satya Tangirala <satyat@google.com>,
"moderated list:UNIVERSAL FLASH STORAGE HOST CONTROLLER
DRIVER..." <linux-mediatek@lists.infradead.org>,
open list <linux-kernel@vger.kernel.org>,
"open list:ARM/QUALCOMM SUPPORT" <linux-arm-msm@vger.kernel.org>,
"moderated list:ARM/Mediatek SoC support"
<linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH RFC v4 1/1] scsi: ufs: Fix ufs power down/on specs violation
Date: Tue, 05 Jan 2021 18:06:12 +0800 [thread overview]
Message-ID: <bb0a37d5825eec1ec03a1ba1104fec86@codeaurora.org> (raw)
In-Reply-To: <a509d1ad-617d-8160-1dae-da0dbf19652c@intel.com>
On 2021-01-05 15:33, Adrian Hunter wrote:
> On 5/01/21 9:28 am, Can Guo wrote:
>> On 2021-01-05 15:16, Adrian Hunter wrote:
>>> On 4/01/21 8:55 pm, Bjorn Andersson wrote:
>>>> On Mon 04 Jan 03:15 CST 2021, Adrian Hunter wrote:
>>>>
>>>>> On 22/12/20 3:49 pm, Ziqi Chen wrote:
>>>>>> As per specs, e.g, JESD220E chapter 7.2, while powering
>>>>>> off/on the ufs device, RST_N signal and REF_CLK signal
>>>>>> should be between VSS(Ground) and VCCQ/VCCQ2.
>>>>>>
>>>>>> To flexibly control device reset line, refactor the function
>>>>>> ufschd_vops_device_reset(sturct ufs_hba *hba) to ufshcd_
>>>>>> vops_device_reset(sturct ufs_hba *hba, bool asserted). The
>>>>>> new parameter "bool asserted" is used to separate device reset
>>>>>> line pulling down from pulling up.
>>>>>
>>>>> This patch assumes the power is controlled by voltage regulators,
>>>>> but
>>>>> for us
>>>>> it is controlled by firmware (ACPI), so it is not correct to change
>>>>> RST_n
>>>>> for all host controllers as you are doing.
>>>>>
>>>>> Also we might need to use a firmware interface for device reset, in
>>>>> which
>>>>> case the 'asserted' value doe not make sense.
>>>>>
>>>>
>>>> Are you saying that the entire flip-flop-the-reset is a single
>>>> firmware
>>>> operation in your case?
>>>
>>> Yes
>>>
>>>> If you look at the Mediatek driver, the
>>>> implementation of ufs_mtk_device_reset_ctrl() is a jump to firmware.
>>>>
>>>>
>>>> But perhaps "asserted" isn't the appropriate English word for saying
>>>> "the reset is in the resetting state"?
>>>>
>>>> I just wanted to avoid the use of "high"/"lo" as if you look at the
>>>> Mediatek code they pass the expected line-level to the firmware,
>>>> while
>>>> in the Qualcomm code we pass the logical state to the GPIO code
>>>> which is
>>>> setup up as "active low" and thereby flip the meaning before hitting
>>>> the
>>>> pad.
>>>>
>>>>> Can we leave the device reset callback alone, and instead introduce
>>>>> a new
>>>>> variant operation for setting RST_n to match voltage regulator
>>>>> power
>>>>> changes?
>>>>
>>>> Wouldn't this new function just have to look like the proposed
>>>> patches?
>>>> In which case for existing platforms we'd have both?
>>>>
>>>> How would you implement this, or would you simply skip implementing
>>>> this?
>>>
>>> Functionally, doing a device reset is not the same as adjusting
>>> signal
>>> levels to meet power up/off ramp requirements. However, the issue is
>>> that
>>> we do not use regulators, so the power is not necessarily being
>>> changed at
>>> those points, and we definitely do not want to reset instead of
>>> entering
>>> DeepSleep for example.
>>>
>>> Off the top of my head, I imagine something like a callback called
>>> ufshcd_vops_prepare_power_ramp(hba, bool on) which is called only if
>>> hba->vreg_info->vcc is not NULL.
>>
>> Hi Adrian,
>>
>> I don't see you have the vops device_reset() implemented anywhere in
>> current code base, how is this change impacting you? Do I miss
>> anything
>> or are you planning to push a change which implements device_reset()
>> soon?
>
> At some point, yes.
OK, then we don't even have to add a new vops, just go back to version
#1 to
use ufshcd_vops_suspend() to control the device_reset. We took the hard
way
because we wanted to fix it for all users.
prev parent reply other threads:[~2021-01-05 10:07 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-22 13:49 [PATCH RFC v4 1/1] scsi: ufs: Fix ufs power down/on specs violation Ziqi Chen
2020-12-23 9:33 ` Stanley Chu
2020-12-23 12:17 ` Can Guo
2020-12-23 20:45 ` Avri Altman
2020-12-24 15:35 ` ziqichen
2020-12-28 17:55 ` Bjorn Andersson
2020-12-29 1:18 ` Can Guo
2020-12-29 1:48 ` Can Guo
2021-01-04 18:59 ` Bjorn Andersson
2021-01-04 18:57 ` Bjorn Andersson
2021-01-05 1:39 ` Can Guo
2021-01-04 9:15 ` Adrian Hunter
2021-01-04 18:55 ` Bjorn Andersson
2021-01-05 7:16 ` Adrian Hunter
2021-01-05 7:28 ` Can Guo
2021-01-05 7:33 ` Adrian Hunter
2021-01-05 10:06 ` Can Guo [this message]
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