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 19:19:21 -0800 |
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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.
-asd
-- The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, Linux Foundation Collaborative Project
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