Re: [PATCH v8 8/9] mfd: smpro-mfd: Adds Ampere's Altra SMpro MFD driver

From: Quan Nguyen
Date: Wed Jun 29 2022 - 05:24:30 EST

Dear Lee Jones,

Thank you for the comment as on the link: https://lore.kernel.org/lkml/202204230554.4528TqPu-lkp@xxxxxxxxx/T/#m476dce286d806bb3713f689663fa631f5a1f0909

I'm not sure what happen (maybe due to my bad junk filter) but I could only see your email when checking the link mentioned above.

I will try to response on each of your comment inline.

Thank you very much for the comment.
- Quan

On 22/04/2022 09:46, Quan Nguyen wrote:
Adds Multi-function devices driver for SMpro co-processor found on the
[Lee] Please drop the term MFD and describe the device instead.

[Quan] Will replace MFD with "core" as your suggestion.

Mt.Jade hardware reference platform with Ampere's Altra processor family.

Signed-off-by: Quan Nguyen <quan@xxxxxxxxxxxxxxxxxxxxxx>
---
Changes in v8:
+ None

Changes in v7:
+ Smpro-mfd now significant changes in compare with simple-mfd-i2c
driver, remove the copyright note about simple-mfd-i2c [Quan]
+ Install bus->read/write() to handle multiple types of bus
access. [Quan]
+ Update license to MODULE_LICENSE("GPL") [Quan]
+ Add others minor refactor the code [Quan]

Changes in v6:
+ Update license part to reflect that this driver is clone from
simple-mfd-i2c driver [Quan]

Changes in v5:
+ Dropped the use of simple-mfd-i2c driver [Quan]
+ Introduced drivers/mfd/smpro-mfd.c driver to instantiate
sub-devices. This is to avoid DT nodes without resource issue [Quan]
+ Revised commit message [Quan]

Changes in v4:
+ Add "depends on I2C" to fix build issue found by kernel test
robot [Guenter]

Changes in v3:
+ None

Changes in v2:
+ Used 'struct of_device_id's .data attribute [Lee Jones]

drivers/mfd/Kconfig | 12 ++++
drivers/mfd/Makefile | 1 +
drivers/mfd/smpro-mfd.c | 134 ++++++++++++++++++++++++++++++++++++++++
[Lee] Please drop the 'mfd' part. Does 'core' work instead?

[Quan] Will drop the MFD thoroughly in next version.

3 files changed, 147 insertions(+)
create mode 100644 drivers/mfd/smpro-mfd.c

diff --git a/drivers/mfd/Kconfig b/drivers/mfd/Kconfig
index 3b59456f5545..383d0e6cfb91 100644
--- a/drivers/mfd/Kconfig
+++ b/drivers/mfd/Kconfig
@@ -77,6 +77,18 @@ config MFD_AS3711
help
Support for the AS3711 PMIC from AMS
+config MFD_SMPRO
+ tristate "Ampere Computing MFD SMpro core driver"
+ depends on I2C
+ select MFD_CORE
+ select REGMAP_I2C
+ help
+ Say yes here to enable SMpro driver support for Ampere's Altra
+ processor family.
+
+ Ampere's Altra SMpro exposes an I2C regmap interface that can
+ be accessed by child devices.
+
config MFD_AS3722
tristate "ams AS3722 Power Management IC"
select MFD_CORE
diff --git a/drivers/mfd/Makefile b/drivers/mfd/Makefile
index 858cacf659d6..36f8981cc4fd 100644
--- a/drivers/mfd/Makefile
+++ b/drivers/mfd/Makefile
@@ -266,6 +266,7 @@ obj-$(CONFIG_MFD_QCOM_PM8008) += qcom-pm8008.o
obj-$(CONFIG_SGI_MFD_IOC3) += ioc3.o
obj-$(CONFIG_MFD_SIMPLE_MFD_I2C) += simple-mfd-i2c.o
+obj-$(CONFIG_MFD_SMPRO) += smpro-mfd.o
obj-$(CONFIG_MFD_INTEL_M10_BMC) += intel-m10-bmc.o
obj-$(CONFIG_MFD_ATC260X) += atc260x-core.o
diff --git a/drivers/mfd/smpro-mfd.c b/drivers/mfd/smpro-mfd.c
new file mode 100644
index 000000000000..485c4f89ebd9
--- /dev/null
+++ b/drivers/mfd/smpro-mfd.c
@@ -0,0 +1,134 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Ampere Altra Family SMPro MFD - I2C
+ *
+ * Copyright (c) 2022, Ampere Computing LLC
+ * Author: Quan Nguyen <quan@xxxxxxxxxxxxxxxxxxxxxxx>
+ */
+
+#include <linux/i2c.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/of_platform.h>
+#include <linux/mfd/core.h>
+#include <linux/regmap.h>
+
[Lee] Alphabetical.

[Quan] Will sort the included files follow alphbetical order in next version.

+/* Identification Registers */
+#define MANUFACTURER_ID_REG 0x02
+#define AMPERE_MANUFACTURER_ID 0xCD3A
+
+static int smpro_mfd_write(void *context, const void *data, size_t count)
+{
+ struct device *dev = context;
+ struct i2c_client *i2c = to_i2c_client(dev);
+ int ret;
+
+ ret = i2c_master_send(i2c, data, count);
+ if (ret == count)
+ return 0;
+ else if (ret < 0)
+ return ret;
+ else
+ return -EIO;
+}
+
+static int smpro_mfd_read(void *context, const void *reg, size_t reg_size,
+ void *val, size_t val_size)
+{
+ struct device *dev = context;
+ struct i2c_client *i2c = to_i2c_client(dev);
+ struct i2c_msg xfer[2];
+ unsigned char buf[2];
+ int ret;
+
+ xfer[0].addr = i2c->addr;
+ xfer[0].flags = 0;
+
+ buf[0] = *(u8 *)reg;
+ buf[1] = val_size;
+ xfer[0].len = 2;
+ xfer[0].buf = buf;
+
+ xfer[1].addr = i2c->addr;
+ xfer[1].flags = I2C_M_RD;
+ xfer[1].len = val_size;
+ xfer[1].buf = val;
+
+ ret = i2c_transfer(i2c->adapter, xfer, 2);
+ if (ret == 2)
+ return 0;
+ else if (ret < 0)
+ return ret;
+ else
+ return -EIO;
+}
+
[Lee] This looks all too familiar.

I wonder how generic these i2c call-backs actually are.

[Quan] yes, this is similar with regmap_i2c_read() but with reg_size is force to 2.
We can reuse regmap_i2c_read() but it needs to be exported from drivers/base/regmap/regmap-i2c.c

+static const struct regmap_bus smpro_regmap_bus = {
+ .read = smpro_mfd_read,
+ .write = smpro_mfd_write,
+ .val_format_endian_default = REGMAP_ENDIAN_BIG,
+};
+
+static bool smpro_mfd_readable_noinc_reg(struct device *dev, unsigned int reg)
+{
+ return (reg == 0x82 || reg == 0x85 || reg == 0x92 || reg == 0x95 ||
+ reg == 0xC2 || reg == 0xC5 || reg == 0xD2 || reg == 0xDA);
+}
[Lee] No magic numbers. Please define these registers.

[Quan] Will fix this in next version.

+
+static const struct regmap_config smpro_regmap_config = {
+ .reg_bits = 8,
+ .val_bits = 16,
+ .readable_noinc_reg = smpro_mfd_readable_noinc_reg,
+};
+
+static const struct mfd_cell smpro_devs[] = {
+ MFD_CELL_NAME("smpro-hwmon"),
+ MFD_CELL_NAME("smpro-errmon"),
+ MFD_CELL_NAME("smpro-misc"),
+};
+
+static int smpro_mfd_probe(struct i2c_client *i2c)
+{
+ const struct regmap_config *config;
+ struct regmap *regmap;
+ unsigned int val;
+ int ret;
+
+ config = device_get_match_data(&i2c->dev);
+ if (!config)
+ config = &smpro_regmap_config;
+
[Lee] This use-case is not currently supported.

Please return an error instead.

[Quan] Will update in next version.

+ regmap = devm_regmap_init(&i2c->dev, &smpro_regmap_bus, &i2c->dev, config);
+ if (IS_ERR(regmap))
+ return PTR_ERR(regmap);
+
+ /* Check for valid ID */
[Lee] Decent #define nomenclature should render this comment superfluous.

[Quan] Thanks, will remove in next version.

+ ret = regmap_read(regmap, MANUFACTURER_ID_REG, &val);
+ if (ret)
+ return ret;
+
+ if (val != AMPERE_MANUFACTURER_ID)
+ return -ENODEV;
+
+ return devm_mfd_add_devices(&i2c->dev, PLATFORM_DEVID_AUTO,
+ smpro_devs, ARRAY_SIZE(smpro_devs), NULL, 0, NULL);
+}
+
+static const struct of_device_id smpro_mfd_of_match[] = {
+ { .compatible = "ampere,smpro", .data = &smpro_regmap_config },
+ {}
+};
+MODULE_DEVICE_TABLE(of, smpro_mfd_of_match);
+
+static struct i2c_driver smpro_mfd_driver = {
+ .probe_new = smpro_mfd_probe,
+ .driver = {
+ .name = "smpro-mfd-i2c",
[Lee] "smpro-core"

[Quan] Will change mfd to "core" thoroughly.
Thanks for the review.

+ .of_match_table = smpro_mfd_of_match,
+ },
+};
+module_i2c_driver(smpro_mfd_driver);
+
+MODULE_AUTHOR("Quan Nguyen <quan@xxxxxxxxxxxxxxxxxxxxxx>");
+MODULE_DESCRIPTION("SMPRO MFD - I2C driver");
+MODULE_LICENSE("GPL");