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Date: Fri, 25 Nov 2022 21:03:24 -0600
From: Samuel Holland <samuel@...lland.org>
To: Andre Przywara <andre.przywara@....com>
Cc: Liam Girdwood <lgirdwood@...il.com>,
Mark Brown <broonie@...nel.org>, Chen-Yu Tsai <wens@...e.org>,
Jernej Skrabec <jernej.skrabec@...il.com>,
Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
Rob Herring <robh+dt@...nel.org>, Andrew Lunn <andrew@...n.ch>,
Heiko Stuebner <heiko@...ech.de>,
Maxime Ripard <mripard@...nel.org>, devicetree@...r.kernel.org,
linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
linux-sunxi@...ts.linux.dev
Subject: Re: [PATCH v4 2/4] regulator: sun20i: Add Allwinner D1 LDOs driver
Hi Andre,
On 11/25/22 18:22, Andre Przywara wrote:
> On Thu, 24 Nov 2022 22:01:10 -0600
> Samuel Holland <samuel@...lland.org> wrote:
>
> Hi Samuel,
>
>> D1 contains two pairs of LDOs, "analog" LDOs and "system" LDOs. They are
>> similar and can share a driver, but only the system LDOs have a DT
>> binding defined so far.
>>
>> The system LDOs have a single linear range. The voltage step is not an
>> integer, so a custom .list_voltage is needed to get the rounding right.
>>
>> Signed-off-by: Samuel Holland <samuel@...lland.org>
>> ---
>>
>> Changes in v4:
>> - Drop the analog LDOs until the codec binding is ready
>>
>> Changes in v3:
>> - Adjust control flow in sun20i_regulator_get_regmap() for clarity
>>
>> Changes in v2:
>> - Use decimal numbers for .n_voltages instead of field widths
>> - Get the regmap from the parent device instead of a property/phandle
>>
>> drivers/regulator/Kconfig | 8 ++
>> drivers/regulator/Makefile | 1 +
>> drivers/regulator/sun20i-regulator.c | 150 +++++++++++++++++++++++++++
>> 3 files changed, 159 insertions(+)
>> create mode 100644 drivers/regulator/sun20i-regulator.c
>>
>> diff --git a/drivers/regulator/Kconfig b/drivers/regulator/Kconfig
>> index 070e4403c6c2..8480532114c1 100644
>> --- a/drivers/regulator/Kconfig
>> +++ b/drivers/regulator/Kconfig
>> @@ -1280,6 +1280,14 @@ config REGULATOR_STW481X_VMMC
>> This driver supports the internal VMMC regulator in the STw481x
>> PMIC chips.
>>
>> +config REGULATOR_SUN20I
>> + tristate "Allwinner D1 internal LDOs"
>> + depends on ARCH_SUNXI || COMPILE_TEST
>> + select MFD_SYSCON
>> + default ARCH_SUNXI
>> + help
>> + This driver supports the internal LDOs in the Allwinner D1 SoC.
>> +
>> config REGULATOR_SY7636A
>> tristate "Silergy SY7636A voltage regulator"
>> depends on MFD_SY7636A
>> diff --git a/drivers/regulator/Makefile b/drivers/regulator/Makefile
>> index 5962307e1130..8e9b5a21123d 100644
>> --- a/drivers/regulator/Makefile
>> +++ b/drivers/regulator/Makefile
>> @@ -150,6 +150,7 @@ obj-$(CONFIG_REGULATOR_STM32_VREFBUF) += stm32-vrefbuf.o
>> obj-$(CONFIG_REGULATOR_STM32_PWR) += stm32-pwr.o
>> obj-$(CONFIG_REGULATOR_STPMIC1) += stpmic1_regulator.o
>> obj-$(CONFIG_REGULATOR_STW481X_VMMC) += stw481x-vmmc.o
>> +obj-$(CONFIG_REGULATOR_SUN20I) += sun20i-regulator.o
>> obj-$(CONFIG_REGULATOR_SY7636A) += sy7636a-regulator.o
>> obj-$(CONFIG_REGULATOR_SY8106A) += sy8106a-regulator.o
>> obj-$(CONFIG_REGULATOR_SY8824X) += sy8824x.o
>> diff --git a/drivers/regulator/sun20i-regulator.c b/drivers/regulator/sun20i-regulator.c
>> new file mode 100644
>> index 000000000000..031bcc3dee50
>> --- /dev/null
>> +++ b/drivers/regulator/sun20i-regulator.c
>> @@ -0,0 +1,150 @@
>> +// SPDX-License-Identifier: GPL-2.0-only
>> +//
>> +// Copyright (c) 2021-2022 Samuel Holland <samuel@...lland.org>
>> +//
>> +
>> +#include <linux/mfd/syscon.h>
>> +#include <linux/module.h>
>> +#include <linux/of_device.h>
>> +#include <linux/platform_device.h>
>> +#include <linux/regmap.h>
>> +#include <linux/regulator/driver.h>
>> +
>> +#define SUN20I_SYS_LDO_CTRL_REG 0x150
>> +
>> +struct sun20i_regulator_data {
>> + const struct regulator_desc *descs;
>> + unsigned int ndescs;
>> +};
>> +
>> +/* regulator_list_voltage_linear() modified for the non-integral uV_step. */
>> +static int sun20i_d1_system_ldo_list_voltage(struct regulator_dev *rdev,
>> + unsigned int selector)
>> +{
>> + const struct regulator_desc *desc = rdev->desc;
>> + unsigned int uV;
>> +
>> + if (selector >= desc->n_voltages)
>> + return -EINVAL;
>> +
>> + uV = desc->min_uV + (desc->uV_step * selector);
>> +
>> + /* Produce correctly-rounded absolute voltages. */
>> + return uV + ((selector + 1 + (desc->min_uV % 4)) / 3);
>> +}
>> +
>> +static const struct regulator_ops sun20i_d1_system_ldo_ops = {
>> + .list_voltage = sun20i_d1_system_ldo_list_voltage,
>> + .map_voltage = regulator_map_voltage_ascend,
>> + .set_voltage_sel = regulator_set_voltage_sel_regmap,
>> + .get_voltage_sel = regulator_get_voltage_sel_regmap,
>> +};
>> +
>> +static const struct regulator_desc sun20i_d1_system_ldo_descs[] = {
>> + {
>> + .name = "ldoa",
>> + .supply_name = "ldo-in",
>> + .of_match = "ldoa",
>> + .ops = &sun20i_d1_system_ldo_ops,
>> + .type = REGULATOR_VOLTAGE,
>> + .owner = THIS_MODULE,
>> + .n_voltages = 32,
>> + .min_uV = 1600000,
>> + .uV_step = 13333, /* repeating */
>
> So while I see that those values are probably the closest we can with a
> simple linear algorithm, they first two values seem to be slightly off
> from those values in the manual:
> sel diff algor manual
> 0: 7 (1.600 - 1.593)
> 1: 6 (1.613 - 1.607)
> Oddly enough the rest of the values are spot on.
> I don't know if this really matters, or if the LDOs are actually
> accurate enough to that level of precision, or if it's a manual bug, or
> if we really care at all, but it might warrant some comment, I guess?
> I just got triggered by the min value not being the first value in the
> list.
Whoops, I did the math based on the default 1.8 V and after some spot
checks assumed the range was linear. I should have noticed this.
Conveniently, LDOB is unused on most boards, so I can measure the range
directly. The INA219 I'm using gives me a 4 mV LSB in its most precise
mode, which I'm averaging to get 2 mV precision.
reg measure manual diff
============================
0x00: 1.160 1.167 -7
0x08: 1.266 1.273 -7
0x09: 1.280 1.287 -7
0x0a: 1.292 1.300 -8
0x0b: 1.306 1.313 -7
0x0c: 1.320 1.327 -7
0x0d: 1.332 1.340 -8
0x0e: 1.346 1.353 -7
0x0f: 1.360 1.367 -7
0x10: 1.372 1.380 -8
0x18: 1.480 1.487 -7
0x1c: 1.532 1.540 -8
0x1d: 1.546 1.553 -7
0x1e: 1.560 1.567 -7
0x1f: 1.572 1.580 -8
0x20: 1.586 1.593 -7 <<
0x21: 1.600 1.607 -7 <<
0x22: 1.620 1.627 -7 <<
0x23: 1.632 1.640 -8 <<
0x24: 1.646 1.653 -7
0x25: 1.660 1.667 -7
0x26: 1.672 1.680 -8
0x27: 1.686 1.693 -7
0x28: 1.700 1.707 -7
0x30: 1.806 1.813 -7
0x38: 1.912 1.920 -8
0x3e: 1.992 2.000 -8
0x3f: 2.006 2.013 -7
So it looks like the LDOs are accurate, and the manual is quite correct.
I'm willing to blame the constant offset on my crude test setup.
>> + .vsel_reg = SUN20I_SYS_LDO_CTRL_REG,
>> + .vsel_mask = GENMASK(7, 0),
>> + },
>> + {
>> + .name = "ldob",
>> + .supply_name = "ldo-in",
>> + .of_match = "ldob",
>> + .ops = &sun20i_d1_system_ldo_ops,
>> + .type = REGULATOR_VOLTAGE,
>> + .owner = THIS_MODULE,
>> + .n_voltages = 64,
>> + .min_uV = 1166666,
>> + .uV_step = 13333, /* repeating */
>
> For LDOB it seems to be worse, as the second half is constantly off by
> what looks like 6.666mV:
> sel diff algor manual
> ...
> 32: 0 (1.593 - 1.593)
> 33: 0 (1.607 - 1.607)
> 34: -7 (1.620 - 1.627)
> 35: -7 (1.633 - 1.64)
> 36: -6 (1.647 - 1.653)
> ...
> 63: -6 (2.007 - 2.013)
> The first half is correct, though. Closer inspection reveals that
> everything with bit 5 set is exactly the same as LDOA. Maybe we can use
> that to our advantage?
Since I already have a custom .list_voltage implementation, I think the
simplest solution is:
if (uV >= 1620000)
uV += 7000;
or similar to get the rounding right.
Regards,
Samuel
> Cheers,
> Andre
>
>> + .vsel_reg = SUN20I_SYS_LDO_CTRL_REG,
>> + .vsel_mask = GENMASK(15, 8),
>> + },
>> +};
>> +
>> +static const struct sun20i_regulator_data sun20i_d1_system_ldos = {
>> + .descs = sun20i_d1_system_ldo_descs,
>> + .ndescs = ARRAY_SIZE(sun20i_d1_system_ldo_descs),
>> +};
>> +
>> +static struct regmap *sun20i_regulator_get_regmap(struct device *dev)
>> +{
>> + struct regmap *regmap;
>> +
>> + /*
>> + * First try the syscon interface. The system control device is not
>> + * compatible with "syscon", so fall back to getting the regmap from
>> + * its platform device. This is ugly, but required for devicetree
>> + * backward compatibility.
>> + */
>> + regmap = syscon_node_to_regmap(dev->parent->of_node);
>> + if (!IS_ERR(regmap))
>> + return regmap;
>> +
>> + regmap = dev_get_regmap(dev->parent, NULL);
>> + if (regmap)
>> + return regmap;
>> +
>> + return ERR_PTR(-EPROBE_DEFER);
>> +}
>> +
>> +static int sun20i_regulator_probe(struct platform_device *pdev)
>> +{
>> + const struct sun20i_regulator_data *data;
>> + struct device *dev = &pdev->dev;
>> + struct regulator_config config;
>> + struct regmap *regmap;
>> +
>> + data = of_device_get_match_data(dev);
>> + if (!data)
>> + return -EINVAL;
>> +
>> + regmap = sun20i_regulator_get_regmap(dev);
>> + if (IS_ERR(regmap))
>> + return dev_err_probe(dev, PTR_ERR(regmap), "Failed to get regmap\n");
>> +
>> + config = (struct regulator_config) {
>> + .dev = dev,
>> + .regmap = regmap,
>> + };
>> +
>> + for (unsigned int i = 0; i < data->ndescs; ++i) {
>> + const struct regulator_desc *desc = &data->descs[i];
>> + struct regulator_dev *rdev;
>> +
>> + rdev = devm_regulator_register(dev, desc, &config);
>> + if (IS_ERR(rdev))
>> + return PTR_ERR(rdev);
>> + }
>> +
>> + return 0;
>> +}
>> +
>> +static const struct of_device_id sun20i_regulator_of_match[] = {
>> + {
>> + .compatible = "allwinner,sun20i-d1-system-ldos",
>> + .data = &sun20i_d1_system_ldos,
>> + },
>> + { },
>> +};
>> +MODULE_DEVICE_TABLE(of, sun20i_regulator_of_match);
>> +
>> +static struct platform_driver sun20i_regulator_driver = {
>> + .probe = sun20i_regulator_probe,
>> + .driver = {
>> + .name = "sun20i-regulator",
>> + .of_match_table = sun20i_regulator_of_match,
>> + },
>> +};
>> +module_platform_driver(sun20i_regulator_driver);
>> +
>> +MODULE_AUTHOR("Samuel Holland <samuel@...lland.org>");
>> +MODULE_DESCRIPTION("Allwinner D1 internal LDO driver");
>> +MODULE_LICENSE("GPL");
>
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