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Date: Sat, 26 Nov 2022 00:22:43 +0000
From: Andre Przywara <andre.przywara@....com>
To: Samuel Holland <samuel@...lland.org>
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
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.
> + .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?
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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