Date:   Fri, 04 Jun 2021 02:01:33 +0530
From:   nitirawa@...eaurora.org
To:     Bjorn Andersson <bjorn.andersson@...aro.org>
Cc:     asutoshd@...eaurora.org, cang@...eaurora.org,
        stummala@...eaurora.org, vbadigan@...eaurora.org,
        alim.akhtar@...sung.com, avri.altman@....com, jejb@...ux.ibm.com,
        martin.petersen@...cle.com, stanley.chu@...iatek.com,
        beanhuo@...ron.com, adrian.hunter@...el.com, bvanassche@....org,
        linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org,
        nitirawa=codeaurora.org@...eaurora.org
Subject: Re: [PATCH V2 3/3] scsi: ufs-qcom: configure VCC voltage level in
 vendor file

On 2021-05-26 12:53, nitirawa@...eaurora.org wrote:
> On 2021-04-01 20:42, Bjorn Andersson wrote:
>> On Thu 01 Apr 09:58 CDT 2021, nitirawa@...eaurora.org wrote:
>> 
>>> On 2021-03-31 23:49, Bjorn Andersson wrote:
>>> > On Wed 24 Mar 16:55 CDT 2021, nitirawa@...eaurora.org wrote:
>>> >
>>> > > On 2021-03-23 20:58, Bjorn Andersson wrote:
>>> > > > On Sun 21 Mar 16:57 CDT 2021, Nitin Rawat wrote:
>>> > > >
>>> > > > > As a part of vops handler, VCC voltage is updated
>>> > > > > as per the ufs device probed after reading the device
>>> > > > > descriptor. We follow below steps to configure voltage
>>> > > > > level.
>>> > > > >
>>> > > > > 1. Set the device to SLEEP state.
>>> > > > > 2. Disable the Vcc Regulator.
>>> > > > > 3. Set the vcc voltage according to the device type and reenable
>>> > > > >    the regulator.
>>> > > > > 4. Set the device mode back to ACTIVE.
>>> > > > >
>>> > > >
>>> > > > When we discussed this a while back this was described as a requirement
>>> > > > from the device specification, you only operate on objects "owned" by
>>> > > > ufshcd and you invoke ufshcd operations to perform the actions.
>>> > > >
>>> > > > So why is this a ufs-qcom patch and not something in ufshcd?
>>> > > >
>>> > > > Regards,
>>> > > > Bjorn
>>> > > >
>>> > > > > Signed-off-by: Nitin Rawat <nitirawa@...eaurora.org>
>>> > > > > Signed-off-by: Veerabhadrarao Badiganti <vbadigan@...eaurora.org>
>>> > > > > ---
>>> > > > >  drivers/scsi/ufs/ufs-qcom.c | 51
>>> > > > > +++++++++++++++++++++++++++++++++++++++++++++
>>> > > > >  1 file changed, 51 insertions(+)
>>> > > > >
>>> > > > > diff --git a/drivers/scsi/ufs/ufs-qcom.c b/drivers/scsi/ufs/ufs-qcom.c
>>> > > > > index f97d7b0..ca35f5c 100644
>>> > > > > --- a/drivers/scsi/ufs/ufs-qcom.c
>>> > > > > +++ b/drivers/scsi/ufs/ufs-qcom.c
>>> > > > > @@ -21,6 +21,17 @@
>>> > > > >  #define UFS_QCOM_DEFAULT_DBG_PRINT_EN	\
>>> > > > >  	(UFS_QCOM_DBG_PRINT_REGS_EN | UFS_QCOM_DBG_PRINT_TEST_BUS_EN)
>>> > > > >
>>> > > > > +#define	ANDROID_BOOT_DEV_MAX	30
>>> > > > > +static char android_boot_dev[ANDROID_BOOT_DEV_MAX];
>>> > > > > +
>>> > > > > +/* Min and Max VCC voltage values for ufs 2.x and
>>> > > > > + * ufs 3.x devices
>>> > > > > + */
>>> > > > > +#define UFS_3X_VREG_VCC_MIN_UV	2540000 /* uV */
>>> > > > > +#define UFS_3X_VREG_VCC_MAX_UV	2700000 /* uV */
>>> > > > > +#define UFS_2X_VREG_VCC_MIN_UV	2950000 /* uV */
>>> > > > > +#define UFS_2X_VREG_VCC_MAX_UV	2960000 /* uV */
>>> > > > > +
>>> > > > >  enum {
>>> > > > >  	TSTBUS_UAWM,
>>> > > > >  	TSTBUS_UARM,
>>> > > > > @@ -1293,6 +1304,45 @@ static void
>>> > > > > ufs_qcom_print_hw_debug_reg_all(struct ufs_hba *hba,
>>> > > > >  	print_fn(hba, reg, 9, "UFS_DBG_RD_REG_TMRLUT ", priv);
>>> > > > >  }
>>> > > > >
>>> > > > > +  /**
>>> > > > > +   * ufs_qcom_setup_vcc_regulators - Update VCC voltage
>>> > > > > +   * @hba: host controller instance
>>> > > > > +   * Update VCC voltage based on UFS device(ufs 2.x or
>>> > > > > +   * ufs 3.x probed)
>>> > > > > +   */
>>> > > > > +static int ufs_qcom_setup_vcc_regulators(struct ufs_hba *hba)
>>> > > > > +{
>>> > > > > +	struct ufs_dev_info *dev_info = &hba->dev_info;
>>> > > > > +	struct ufs_vreg *vreg = hba->vreg_info.vcc;
>>> > > > > +	int ret;
>>> > > > > +
>>> > > > > +	/* Put the device in sleep before lowering VCC level */
>>> > > > > +	ret = ufshcd_set_dev_pwr_mode(hba, UFS_SLEEP_PWR_MODE);
>>> > > > > +
>>> > > > > +	/* Switch off VCC before switching it ON at 2.5v or 2.96v */
>>> > > > > +	ret = ufshcd_disable_vreg(hba->dev, vreg);
>>> > > > > +
>>> > > > > +	/* add ~2ms delay before renabling VCC at lower voltage */
>>> > > > > +	usleep_range(2000, 2100);
>>> > > > > +
>>> > > > > +	/* set VCC min and max voltage according to ufs device type */
>>> > > > > +	if (dev_info->wspecversion >= 0x300) {
>>> > > > > +		vreg->min_uV = UFS_3X_VREG_VCC_MIN_UV;
>>> > > > > +		vreg->max_uV = UFS_3X_VREG_VCC_MAX_UV;
>>> > > > > +	}
>>> > > > > +
>>> > > > > +	else {
>>> > > > > +		vreg->min_uV = UFS_2X_VREG_VCC_MIN_UV;
>>> > > > > +		vreg->max_uV = UFS_2X_VREG_VCC_MAX_UV;
>>> > > > > +	}
>>> > > > > +
>>> > > > > +	ret = ufshcd_enable_vreg(hba->dev, vreg);
>>> > > > > +
>>> > > > > +	/* Bring the device in active now */
>>> > > > > +	ret = ufshcd_set_dev_pwr_mode(hba, UFS_ACTIVE_PWR_MODE);
>>> > > > > +	return ret;
>>> > > > > +}
>>> > > > > +
>>> > > > >  static void ufs_qcom_enable_test_bus(struct ufs_qcom_host *host)
>>> > > > >  {
>>> > > > >  	if (host->dbg_print_en & UFS_QCOM_DBG_PRINT_TEST_BUS_EN) {
>>> > > > > @@ -1490,6 +1540,7 @@ static const struct ufs_hba_variant_ops
>>> > > > > ufs_hba_qcom_vops = {
>>> > > > >  	.device_reset		= ufs_qcom_device_reset,
>>> > > > >  	.config_scaling_param = ufs_qcom_config_scaling_param,
>>> > > > >  	.program_key		= ufs_qcom_ice_program_key,
>>> > > > > +	.setup_vcc_regulators	= ufs_qcom_setup_vcc_regulators,
>>> > > > >  };
>>> > > > >
>>> > > > >  /**
>>> > > > > --
>>> > > > > 2.7.4
>>> > > > >
>>> > >
>>> > > Hi Bjorn,
>>> > > Thanks for your review.
>>> > > But As per the earlier discussion regarding handling of vcc voltage
>>> > > for platform supporting both ufs 2.x and ufs 3.x , it was finally
>>> > > concluded
>>> > > to
>>> > > use "vops and let vendors handle it, until specs or someone
>>> > > has a better suggestion". Please correct me in case i am wrong.
>>> > >
>>> >
>>> > I was under the impression that this would result in something custom
>>> > per platform, but what I'm objecting to now that I see the code is that
>>> > this is completely generic.
>>> >
>>> > And the concerns we discussed regarding these regulators being shared
>>> > with other devices is not considered in this implementation. But in
>>> > practice I don't see how you could support 2.x, 3.x and rail sharing at
>>> > the same time.
>>> >
>>> > Regards,
>>> > Bjorn
>>> >
>>> > > https://www.mail-archive.com/linux-kernel@vger.kernel.org/msg2399116.html
>>> > >
>>> > > Regards,
>>> > > Nitin
>>> 
>>> Hi Bjorn,
>>> Thanks for your feedback.
>>> Regarding your query for regulator being shared with other device,
>>> Imho, the soc/pmic designer should share only those device
>>> with ufs regulator which has the same voltage range (2.4-3.6v).
>>> If that is not considered by the pmic designer,
>>> wouldn't that would be a board design issue ???
>>> 
>> 
>> It's not only that the rail needs to stay within 2.4-3.6V, depending 
>> on
>> operating mode of this device it either need to be at 2.54-2.7V or
>> 2.95-2.96V depending on wspecversion for this instance.
>> 
>> So either that other device need to be completely flexible in that 
>> range
>> and support the voltage jumping between them without notice, or such
>> design isn't possible.
>> 
>> And as you say, that would be something that the hardware designers
>> would need to handle for us.
>> 
>>> And I agree with you that - the code looks generic but
>>> since the below steps is not part of the specs,
>>> I had to keep it in vendor specific file for which I
>>> had to export few api from ufshcd.c to use in vendor
>>> specific files.
>>> 
>>> 1. Set the device to SLEEP state.
>>> 2. Disable the Vcc Regulator.
>>> 3. Set the vcc voltage according to the device type and reenable
>>>    the regulator.
>>> 4. Set the device mode back to ACTIVE.
>>> 
>>> Please correct me if my understanding is not correct.
>>> 
>> 
>> Are you saying that steps 1 to 4 here are not defined in the
>> specification and therefor Qualcomm specific? Do we expect other 
>> vendors
>> to not follow this sequence, or do they simply not have these voltage
>> constraints?
>> 
>> And again, isn't this the voltage for the attached UFS device? (Rather
>> than a Qualcomm thing)
>> 
>> Regards,
>> Bjorn
> 
> 
> Hi Bjorn,
> Sorry for quite late reply.
> Yes Bjorn above steps(1-4) are not mentioned in the specs. But 
> definitely other
> vendor can follow the same steps . If no vendor have any concerns,
> I can put these steps as generic in ufshcd.c file.
> Let me know what's you opinion on this ??
> 
> Thanks,
> Nitin


Hi Bjorn/Stanley,
Please could you let me know your views/suggestion on my last comment.

Regards,
Nitin

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