Messages in this thread | | | Date | Tue, 01 Dec 2020 11:29:29 +0800 | From | Can Guo <> | Subject | Re: [RFC PATCH v1] scsi: ufs: Remove pre-defined initial VCC voltage values |
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On 2020-12-01 11:19, Asutosh Das (asd) wrote: > On 11/30/2020 6:53 PM, Bjorn Andersson wrote: >> On Mon 30 Nov 17:54 CST 2020, 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? >>> >>> Am open to other ideas though. >>> >> >> But that means that for a board where we don't know (don't want to >> know) >> if we have a 2.x or 3.x device we need to set: >> >> regulator-min-microvolt = <2.4V> >> regulator-max-microvolt = <3.6V> >> >> And the 2.5V and the two ranges should be hard coded into the ufshcd >> (in >> particular if they come from the specification). >> >> For devices with only 2.x or 3.x devices, >> regulator-{min,max}-microvolt >> should be adjusted accordingly. >> >> Note that driving the regulators outside these ranges will either >> damage >> the hardware or cause it to misbehave, so these values should be >> defined >> in the board.dts anyways. >> >> Also note that regulator_set_voltage(2.4V, 3.6V) won't give you "a >> voltage between 2.4V and 3.6V, it will most likely give either 2.4V or >> any more specific voltage that we've specified in the board file >> because >> the regulator happens to be shared with some other consumer and >> changing >> it in runtime would be bad. >> >> Regards, >> Bjorn >> > > Understood. > I also understand that assumptions on the regulator limits in the > driver is a bad idea. I'm not sure how it's designed, but I should > think the power-grid design should take care of regulator sharing; if > it's being shared and the platform supports both 2.x and 3.x. Perhaps, > such platforms be identified using a dts flag - not sure if that's > such a good idea though. > > I like Stanley's proposal of a vops and let vendors handle it, until > specs or someone has a better suggestion.
Agree, vops is all we need as of now, please upload a change to add one properly.
Thanks,
Can Guo.
> > -asd
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