Messages in this thread | | | Subject | Re: [RFC PATCH v1] scsi: ufs: Remove pre-defined initial VCC voltage values | From | "Asutosh Das (asd)" <> | Date | Mon, 30 Nov 2020 19:07:53 -0800 |
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On 11/30/2020 5:25 PM, Stanley Chu wrote: > On Mon, 2020-11-30 at 15:54 -0800, Asutosh Das (asd) wrote: >> On 11/30/2020 3:14 PM, Bjorn Andersson wrote: >>> On Mon 30 Nov 16:51 CST 2020, Asutosh Das (asd) wrote: >>> >>>> On 11/30/2020 1:16 AM, Stanley Chu wrote: >>>>> UFS specficication allows different VCC configurations for UFS devices, >>>>> for example, >>>>> (1). 2.70V - 3.60V (By default) >>>>> (2). 1.70V - 1.95V (Activated if "vcc-supply-1p8" is declared in >>>>> device tree) >>>>> (3). 2.40V - 2.70V (Supported since UFS 3.x) >>>>> >>>>> With the introduction of UFS 3.x products, an issue is happening that >>>>> UFS driver will use wrong "min_uV/max_uV" configuration to toggle VCC >>>>> regulator on UFU 3.x products with VCC configuration (3) used. >>>>> >>>>> To solve this issue, we simply remove pre-defined initial VCC voltage >>>>> values in UFS driver with below reasons, >>>>> >>>>> 1. UFS specifications do not define how to detect the VCC configuration >>>>> supported by attached device. >>>>> >>>>> 2. Device tree already supports standard regulator properties. >>>>> >>>>> Therefore VCC voltage shall be defined correctly in device tree, and >>>>> shall not be changed by UFS driver. What UFS driver needs to do is simply >>>>> enabling or disabling the VCC regulator only. >>>>> >>>>> This is a RFC conceptional patch. Please help review this and feel >>>>> free to feedback any ideas. Once this concept is accepted, and then >>>>> I would post a more completed patch series to fix this issue. >>>>> >>>>> Signed-off-by: Stanley Chu <stanley.chu@mediatek.com> >>>>> --- >>>>> drivers/scsi/ufs/ufshcd-pltfrm.c | 10 +--------- >>>>> 1 file changed, 1 insertion(+), 9 deletions(-) >>>>> >>>>> diff --git a/drivers/scsi/ufs/ufshcd-pltfrm.c b/drivers/scsi/ufs/ufshcd-pltfrm.c >>>>> index a6f76399b3ae..3965be03c136 100644 >>>>> --- a/drivers/scsi/ufs/ufshcd-pltfrm.c >>>>> +++ b/drivers/scsi/ufs/ufshcd-pltfrm.c >>>>> @@ -133,15 +133,7 @@ static int ufshcd_populate_vreg(struct device *dev, const char *name, >>>>> vreg->max_uA = 0; >>>>> } >>>>> - if (!strcmp(name, "vcc")) { >>>>> - if (of_property_read_bool(np, "vcc-supply-1p8")) { >>>>> - vreg->min_uV = UFS_VREG_VCC_1P8_MIN_UV; >>>>> - vreg->max_uV = UFS_VREG_VCC_1P8_MAX_UV; >>>>> - } else { >>>>> - vreg->min_uV = UFS_VREG_VCC_MIN_UV; >>>>> - vreg->max_uV = UFS_VREG_VCC_MAX_UV; >>>>> - } >>>>> - } else if (!strcmp(name, "vccq")) { >>>>> + if (!strcmp(name, "vccq")) { >>>>> vreg->min_uV = UFS_VREG_VCCQ_MIN_UV; >>>>> vreg->max_uV = UFS_VREG_VCCQ_MAX_UV; >>>>> } else if (!strcmp(name, "vccq2")) { >>>>> >>>> >>>> Hi Stanley >>>> >>>> Thanks for the patch. Bao (nguyenb) was also working towards something >>>> similar. >>>> Would it be possible for you to take into account the scenario in which the >>>> same platform supports both 2.x and 3.x UFS devices? >>>> >>>> These've different voltage requirements, 2.4v-3.6v. >>>> I'm not sure if standard dts regulator properties can support this. >>>> >>> >>> What is the actual voltage requirement for these devices and how does >>> the software know what voltage to pick in this range? >>> >>> Regards, >>> Bjorn >>> >>>> -asd >>>> >>>> >>>> -- >>>> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, >>>> Linux Foundation Collaborative Project >> >> For platforms that support both 2.x (2.7v-3.6v) and 3.x (2.4v-2.7v), the >> voltage requirements (Vcc) are 2.4v-3.6v. The software initializes the >> ufs device at 2.95v & reads the version and if the device is 3.x, it may >> do the following: >> - Set the device power mode to SLEEP >> - Disable the Vcc >> - Enable the Vcc and set it to 2.5v >> - Set the device power mode to ACTIVE >> >> All of the above may be done at HS-G1 & moved to max supported gear >> based on the device version, perhaps? > > Hi Asutosh, > > Thanks for sharing this idea. > > 1. I did not see above flow defined in UFS specifications, please > correct me if I was wrong. > > 2. For above flow, the concern is that I am not sure if all devices > supporting VCC (2.4v - 2.7v) can accept higher voltage, say 2.95v, for > version detection. > > 3. For version detection, another concern is that I am not sure if all > 3.x devices support VCC (2.4v - 2.7v) only, or in other words, I am not > sure if all 2.x devices support VCC (2.7v - 3.6v) only. The above rule > will break any devices not obeying this "conventions". > > For platforms that support both 2.x (2.7v-3.6v) and 3.x (2.4v-2.7v), > > It would be good for UFS drivers detecting the correct voltage if the > protocol is well-defined in specifications. Until that day, any > "non-standard" way may be better implemented in vendor's ops? > > If the vop concept works on your platform, we could still keep struct > ufs_vreg and allow vendors to configure proper min_uV and max_uV to make > regulator_set_voltage() works during VCC toggling flow. Without specific > vendor configurations, min_uV and max_uV would be NULL by default and > UFS core driver will only enable/disasble VCC regulator only without > adjusting its voltage. >
I think this would work. Do you plan to implement this? If not, I can take this up. Please let me know.
> Maybe one possible another idea is to decide the correct voltage and > configure regulator properly before kernel? > > Thanks, > Stanley Chu > >> >> Am open to other ideas though. >> >> -asd >> >
-asd
-- The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, Linux Foundation Collaborative Project
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