Re: [PATCH v2 11/13] regulator: hi6421v600-regulator: move it from staging

[Mauro Carvalho Chehab <mchehab+huawei@kernel.org>]

Em Mon, 18 Jan 2021 13:54:40 +0000
Mark Brown <broonie@kernel.org> escreveu:

> On Mon, Jan 18, 2021 at 02:28:12PM +0100, Mauro Carvalho Chehab wrote:
> 
> > index f385146d2bd1..3b23ad56b31a 100644
> > --- a/Documentation/devicetree/bindings/mfd/hisilicon,hi6421-spmi-pmic.yaml
> > +++ b/Documentation/devicetree/bindings/mfd/hisilicon,hi6421-spmi-pmic.yaml
> > @@ -60,6 +60,8 @@ required:
> >    - reg
> >    - regulators
> >  
> > +additionalProperties: false
> > +
> >  examples:
> >    - |
> >      /* pmic properties */  
> 
> Why is this part of this patch?

I'll place on a separate one.

> 
> > +// SPDX-License-Identifier: GPL-2.0
> > +//
> > +// Device driver for regulators in Hisi IC
> > +//
> > +// Copyright (c) 2013 Linaro Ltd.
> > +// Copyright (c) 2011 Hisilicon.
> > +//  
> 
> This looks like it needs an update.

Ok.

> 
> > +// This program is free software; you can redistribute it and/or modify
> > +// it under the terms of the GNU General Public License version 2 as
> > +// published by the Free Software Foundation.
> > +//
> > +// This program is distributed in the hope that it will be useful,
> > +// but WITHOUT ANY WARRANTY; without even the implied warranty of
> > +// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> > +// GNU General Public License for more details.  
> 
> This boilerplate can be removed.

Ok.

> 
> > +static int hi6421_spmi_regulator_enable(struct regulator_dev *rdev)
> > +{
> > +	struct hi6421_spmi_reg_info *sreg = rdev_get_drvdata(rdev);
> > +	struct hi6421_spmi_pmic *pmic = sreg->pmic;
> > +	int ret;
> > +
> > +	/* cannot enable more than one regulator at one time */
> > +	mutex_lock(&sreg->enable_mutex);
> > +	usleep_range(HISI_REGS_ENA_PROTECT_TIME,
> > +		     HISI_REGS_ENA_PROTECT_TIME + 1000);
> > +
> > +	/* set enable register */
> > +	ret = hi6421_spmi_pmic_rmw(pmic, rdev->desc->enable_reg,
> > +				   rdev->desc->enable_mask,
> > +				   rdev->desc->enable_mask);  
> 
> If for some reason the PMIC is sufficiently fragile to need a delay
> between enables it's not clear why the driver is doing it before
> enabling rather than after, presumably there's issues with the regulator
> ramping up and stabalising its output 

I don't have any datasheets or documentation from this device, except for 
the Linaro's official driver for Kernel 4.9 (from where this driver
was originally ported), and a high-level documentation for this 
hardware at 96boards site, which doesn't cover any details.

-

My understanding is that the issue here seems to be different.

This is the original code (which can be seen on changeset 42f24d9d446a,
already upstream):

	struct timeval last_enabled;

	static void ensured_time_after(struct timeval since, u32 delay_us)
	{
	       struct timeval now;
	       u64 elapsed_ns64, delay_ns64;
	       u32 actual_us32;

	       delay_ns64 = delay_us * NSEC_PER_USEC;
	       do_gettimeofday(&now);
	       elapsed_ns64 = timeval_to_ns(&now) - timeval_to_ns(&since);
	       if (delay_ns64 > elapsed_ns64) {
	               actual_us32 = ((u32)(delay_ns64 - elapsed_ns64) /
	                                                       NSEC_PER_USEC);
	               if (actual_us32 >= 1000) {
	                       mdelay(actual_us32 / 1000); /*lint !e647 */
	                       udelay(actual_us32 % 1000);
	               } else if (actual_us32 > 0) {
	                       udelay(actual_us32);
	               }
	       }
	       return;
	}

	static int hisi_regulator_enable(struct regulator_dev *dev)
	{
	       struct hisi_regulator *sreg = rdev_get_drvdata(dev);
	       struct hisi_pmic *pmic = rdev_to_pmic(dev);

	       /* keep a distance of off_on_delay from last time disabled */
	       ensured_time_after(sreg->last_off_time, sreg->off_on_delay);

	       BRAND_DEBUG("<[%s]: off_on_delay=%dus>\n", __func__, sreg->off_on_delay);

	       /* cannot enable more than one regulator at one time */
	       mutex_lock(&enable_mutex);
	       ensured_time_after(last_enabled, HISI_REGS_ENA_PROTECT_TIME);

	       /* set enable register */
	       hisi_pmic_rmw(pmic, sreg->register_info.ctrl_reg,
                               sreg->register_info.enable_mask,
                               sreg->register_info.enable_mask);
	       BRAND_DEBUG("<[%s]: ctrl_reg=0x%x,enable_mask=0x%x>\n", __func__, sreg->register_info.ctrl_reg,\
        	               sreg->register_info.enable_mask);

	       do_gettimeofday(&last_enabled);
	       mutex_unlock(&enable_mutex);

	       return 0;
	}

What I did here was to play safe. So, I removed the static var and the 
call to gettimeofday() and replaced by just a delay.

As, on this device, the power lines don't change too often: only
the USB power supply changes over time during its reset sequence.

The other power lines are powered during the boot and remain powered
if the hardware is detected.

> > +	/* set enable register to 0 */
> > +	return hi6421_spmi_pmic_rmw(pmic, rdev->desc->enable_reg,
> > +				    rdev->desc->enable_mask, 0);  
> 
> I'm not sure all these comments are adding anything.

I'll drop on a next version.
> 
> > +	if (unlikely(selector >= rdev->desc->n_voltages))
> > +		return -EINVAL;  
> 
> This should not be a hot path that needs an unlikely() annotation.

I'll drop unlikely().

> > +static unsigned int
> > +hi6421_spmi_regulator_get_optimum_mode(struct regulator_dev *rdev,
> > +				       int input_uV, int output_uV,
> > +				       int load_uA)
> > +{
> > +	struct hi6421_spmi_reg_info *sreg = rdev_get_drvdata(rdev);
> > +
> > +	if (load_uA || ((unsigned int)load_uA > sreg->eco_uA))
> > +		return REGULATOR_MODE_NORMAL;  
> 
> This means that for *any* load at all we select NORMAL - I'm not
> convinced this is intentional?

Indeed this seems to be a bug. Thanks for noticing it!

I'll fix that.

Thanks,
Mauro