On Mon, 04 May 2020, Lubomir Rintel wrote:

Hi,

thanks for your review. There are some inline responses below. Where I'm not
responding it means that I'll be just fixing what you've pointed out.

On Wed, Apr 29, 2020 at 07:00:37AM +0100, Lee Jones wrote:

quoted

On Sat, 25 Apr 2020, Lubomir Rintel wrote:

quoted

This driver provides access to the EC RAM of said embedded controller
attached to the I2C bus as well as optionally supporting its slightly weird
power-off/restart protocol.

A particular implementation of the EC firmware can be identified by a
model byte. If this driver identifies the Dell Ariel platform, it
registers the appropriate cells.

Signed-off-by: Lubomir Rintel <lkundrak@v3.sk>
---
 drivers/mfd/Kconfig      |  10 ++
 drivers/mfd/Makefile     |   1 +
 drivers/mfd/ene-kb3930.c | 209 +++++++++++++++++++++++++++++++++++++++
 3 files changed, 220 insertions(+)
 create mode 100644 drivers/mfd/ene-kb3930.c

diff --git a/drivers/mfd/Kconfig b/drivers/mfd/Kconfig
index 0a59249198d3..dae18a2beab5 100644
--- a/drivers/mfd/Kconfig
+++ b/drivers/mfd/Kconfig

@@ -398,6 +398,16 @@ config MFD_DLN2
 	  etc. must be enabled in order to use the functionality of
 	  the device.
 
+config MFD_ENE_KB3930
+	tristate "ENE KB3930 Embedded Controller support"
+	depends on I2C
+	depends on MACH_MMP3_DT || COMPILE_TEST
+	select MFD_CORE
+	help
+	  This adds support for accessing the registers on ENE KB3930, Embedded
+	  Controller. Additional drivers such as LEDS_ARIEL must be enabled in
+	  order to use the functionality of the device.
+
 config MFD_EXYNOS_LPASS
 	tristate "Samsung Exynos SoC Low Power Audio Subsystem"
 	depends on ARCH_EXYNOS || COMPILE_TEST

diff --git a/drivers/mfd/Makefile b/drivers/mfd/Makefile
index f935d10cbf0f..2d2f5bc12841 100644
--- a/drivers/mfd/Makefile
+++ b/drivers/mfd/Makefile

@@ -14,6 +14,7 @@ obj-$(CONFIG_ARCH_BCM2835)	+= bcm2835-pm.o
 obj-$(CONFIG_MFD_BCM590XX)	+= bcm590xx.o
 obj-$(CONFIG_MFD_BD9571MWV)	+= bd9571mwv.o
 obj-$(CONFIG_MFD_CROS_EC_DEV)	+= cros_ec_dev.o
+obj-$(CONFIG_MFD_ENE_KB3930)	+= ene-kb3930.o
 obj-$(CONFIG_MFD_EXYNOS_LPASS)	+= exynos-lpass.o
 
 obj-$(CONFIG_HTC_PASIC3)	+= htc-pasic3.o

diff --git a/drivers/mfd/ene-kb3930.c b/drivers/mfd/ene-kb3930.c
new file mode 100644
index 000000000000..1123f3a1c816
--- /dev/null
+++ b/drivers/mfd/ene-kb3930.c

@@ -0,0 +1,209 @@
+// SPDX-License-Identifier: BSD-2-Clause OR GPL-2.0-or-later
+/*
+ * ENE KB3930 Embedded Controller Driver
+ *
+ * Copyright (C) 2020 Lubomir Rintel
+ */
+
+#include <linux/module.h>
+#include <linux/i2c.h>
+#include <linux/gpio/consumer.h>
+#include <linux/delay.h>
+#include <linux/reboot.h>
+#include <linux/regmap.h>
+#include <linux/mfd/core.h>

Alphabetical.

quoted

+enum {
+	EC_DATA_IN	= 0x00,
+	EC_RAM_OUT	= 0x80,
+	EC_RAM_IN	= 0x81,
+};

Are these registers?

These are I2C registers that are multiplexing access to the EC RAM.
Should I add a comment or make it clearer in some other way?

A comment sounds good.

quoted

quoted

+enum {
+	EC_MODEL_ID	= 0x30,
+	EC_VERSION_MAJ	= 0x31,
+	EC_VERSION_MIN	= 0x32,
+};

As above?

These are the locations in EC RAM, multiplexed via EC_DATA_IN and
EC_RAM_IN/OUT.

As above.

quoted

quoted

+struct kb3930 {
+	struct i2c_client *client;
+	struct regmap *ec_ram;

This is usually called 'regmap'.

Yes. But the device has a set of registers directly on the I2C bus as
well as another set of registers in the RAM access to which is
multiplexed via a pair of I2C registers.

This regmap is for the latter register block which is the only one
exposed currently. I believe it still makes sense to make it obvious
this is not the I2C registers in case the driver is extended to expose
those in future.

ram_regmap or similar.

quoted

quoted

+	struct gpio_descs *off_gpios; 
+};
+
+struct kb3930 *global_kb3930;

Globals are massively frowned upon.  Please move it.

This is necessary for the pm_power_off hook that takes no argument. All
other MFD drivers that implement power off use a global:

Ah, it's one of those:

  static struct kb3920_power_off

  ab8500-sysctrl.c: static struct device *sysctrl_dev;
  axp20x.c:         static struct axp20x_dev *axp20x_pm_power_off;
  dm355evm_msp.c:   static struct i2c_client *msp430;
  max77620.c:       static struct max77620_chip *max77620_scratch;
  max8907.c:        static struct max8907 *max8907_pm_off;
  palmas.c:         static struct palmas *palmas_dev;
  retu-mfd.c:       static struct retu_dev *retu_pm_power_off;
  rk808.c:          static struct i2c_client *rk808_i2c_client;
  rn5t618.c:        static struct rn5t618 *rn5t618_pm_power_off;
  tps6586x.c:       static struct device *tps6586x_dev;
  tps65910.c:       static struct i2c_client *tps65910_i2c_client;
  tps80031.c:       static struct tps80031 *tps80031_power_off_dev;
  twl-core.c:       static struct twl_private *twl_priv;

[...]

quoted

quoted

+					   ariel_ec_cells,
+					   ARRAY_SIZE(ariel_ec_cells),
+					   NULL, 0, NULL);
+		if (ret < 0)
+			return ret;
+	} else {
+		dev_err(dev, "unknown board model: %02x\n", model_id);
+		return -ENODEV;

If you reverse the logic here, you can put this in the if() and omit
the else.

It is intentionally structured this way.

Though the driver currently only supports the 'J' version of the EC
firmware, other versions are possible, with different cells exposed via
the EC RAM registers.

It's difficult to review based on whatifs.

I think it's worth doing it right for the current situation and adapt
it *if* things change in the future.

-- 
Lee Jones [李琼斯]
Linaro Services Technical Lead
Linaro.org │ Open source software for ARM SoCs
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