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Message-ID: <53BF41C8.4080304@collabora.co.uk>
Date: Fri, 11 Jul 2014 03:45:44 +0200
From: Javier Martinez Canillas <javier.martinez@...labora.co.uk>
To: amit daniel kachhap <amit.daniel@...sung.com>
CC: Lee Jones <lee.jones@...aro.org>,
Alessandro Zummo <a.zummo@...ertech.it>,
Krzysztof Kozlowski <k.kozlowski@...sung.com>,
Kukjin Kim <kgene.kim@...sung.com>,
Mike Turquette <mturquette@...aro.org>,
Tomeu Vizoso <tomeu.vizoso@...labora.com>,
devicetree@...r.kernel.org,
Yadwinder Singh Brar <yadi.brar01@...il.com>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
Liam Girdwood <lgirdwood@...il.com>,
Doug Anderson <dianders@...omium.org>,
Tushar Behera <trblinux@...il.com>,
Mark Brown <broonie@...nel.org>,
"linux-samsung-soc@...r.kernel.org"
<linux-samsung-soc@...r.kernel.org>,
Olof Johansson <olof@...om.net>,
Andreas Farber <afaerber@...e.de>,
LAK <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v7 08/24] mfd: max77686: Add Dynamic Voltage Scaling (DVS)
support
Hello Amit,
On 07/10/2014 11:59 AM, amit daniel kachhap wrote:
> On Sat, Jul 5, 2014 at 1:54 AM, Javier Martinez Canillas
> <javier.martinez@...labora.co.uk> wrote:
>> Some regulators on the MAX77686 PMIC have Dynamic Voltage Scaling
>> (DVS) support that allows output voltage to change dynamically.
>>
>> For MAX77686, these regulators are Buck regulators 2, 3 and 4.
>>
>> Each Buck output voltage is selected using a set of external
>> inputs: DVS1-3 and SELB2-4.
>>
>> DVS registers can be used to configure the output voltages for each
>> Buck regulator and which one is active is controled by DVSx lines.
>>
>> SELBx lines are used to control if individual Buck lines are ON or OFF.
>>
>> This patch adds support to configure the DVSx and SELBx lines
>> from DT and to setup and read the GPIO lines connected to them.
>
> The entire series looks nice. Few minor comments from my side. I guess
> still one more version in needed as per other ppls comment.
> You may add,
> Reviewed-by: Amit Daniel Kachhap <amit.daniel@...sung.com>
>
Thanks.
>>
>> Signed-off-by: Javier Martinez Canillas <javier.martinez@...labora.co.uk>
>> Reviewed-by: Krzysztof Kozlowski <k.kozlowski@...sung.com>
>> ---
>>
>> Changes since v6:
>> - Add a comment that max77686_read_gpios() function can sleep.
>> Sugggested by Krzysztof Kozlowski
>> ---
>> drivers/mfd/max77686.c | 119 +++++++++++++++++++++++++++++++++++++++++++
>> include/linux/mfd/max77686.h | 18 ++++---
>> 2 files changed, 129 insertions(+), 8 deletions(-)
>>
>> diff --git a/drivers/mfd/max77686.c b/drivers/mfd/max77686.c
>> index 8650832..d193873 100644
>> --- a/drivers/mfd/max77686.c
>> +++ b/drivers/mfd/max77686.c
>> @@ -32,8 +32,10 @@
>> #include <linux/mfd/core.h>
>> #include <linux/mfd/max77686.h>
>> #include <linux/mfd/max77686-private.h>
>> +#include <linux/gpio/consumer.h>
>> #include <linux/err.h>
>> #include <linux/of.h>
>> +#include <linux/export.h>
>>
>> #define I2C_ADDR_RTC (0x0C >> 1)
>>
>> @@ -101,9 +103,119 @@ static const struct of_device_id max77686_pmic_dt_match[] = {
>> {},
>> };
>>
>> +static void max77686_dt_parse_dvs_gpio(struct device *dev)
>> +{
>> + struct max77686_platform_data *pd = dev_get_platdata(dev);
>> + int i;
>> +
>> + /*
>> + * NOTE: we don't consider GPIO errors fatal; board may have some lines
>> + * directly pulled high or low and thus doesn't specify them.
>> + */
>> + for (i = 0; i < ARRAY_SIZE(pd->buck_gpio_dvs); i++)
>> + pd->buck_gpio_dvs[i] =
>> + devm_gpiod_get_index(dev, "max77686,pmic-buck-dvs", i);
>> +
>> + for (i = 0; i < ARRAY_SIZE(pd->buck_gpio_selb); i++)
>> + pd->buck_gpio_selb[i] =
>> + devm_gpiod_get_index(dev, "max77686,pmic-buck-selb", i);
>> +}
>> +
>> +/**
>> + * max77686_setup_gpios() - init DVS-related GPIOs
>> + * @dev: device whose platform data contains the dvs GPIOs information
>> + *
>> + * This function claims / initalizations GPIOs related to DVS if they are
>> + * defined. This may have the effect of switching voltages if the
>> + * pdata->buck_default_idx does not match the boot time state of pins.
>> + */
>> +int max77686_setup_gpios(struct device *dev)
>> +{
>> + struct max77686_platform_data *pd = dev_get_platdata(dev);
>> + int buck_default_idx = pd->buck_default_idx;
>> + int ret;
>> + int i;
>> +
>> + /* Set all SELB high to avoid glitching while DVS is changing */
>> + for (i = 0; i < ARRAY_SIZE(pd->buck_gpio_selb); i++) {
>> + struct gpio_desc *gpio = pd->buck_gpio_selb[i];
>> +
>> + /* OK if some GPIOs aren't defined */
>> + if (IS_ERR(gpio))
>> + continue;
>> +
>> + ret = gpiod_direction_output_raw(gpio, 1);
>> + if (ret) {
>> + dev_err(dev, "can't set gpio[%d] dir: %d\n", i, ret);
>> + return ret;
>> + }
>> + }
>> +
>> + /* Set our initial setting */
>> + for (i = 0; i < ARRAY_SIZE(pd->buck_gpio_dvs); i++) {
>> + struct gpio_desc *gpio = pd->buck_gpio_dvs[i];
>> +
>> + /* OK if some GPIOs aren't defined */
>> + if (IS_ERR(gpio))
>> + continue;
>> +
>> + /* If a GPIO is valid, set it */
>> + gpiod_direction_output(gpio, (buck_default_idx >> i) & 1);
>> + if (ret) {
>> + dev_err(dev, "can't set gpio[%d]: dir %d\n", i, ret);
>> + return ret;
>> + }
>> + }
>> +
>> + /* Now set SELB low to take effect */
>> + for (i = 0; i < ARRAY_SIZE(pd->buck_gpio_selb); i++) {
>> + struct gpio_desc *gpio = pd->buck_gpio_selb[i];
>> +
>> + if (!IS_ERR(gpio))
>> + gpiod_set_value(gpio, 0);
>> + }
>> +
>> + return 0;
>> +}
>> +EXPORT_SYMBOL_GPL(max77686_setup_gpios);
>> +
>> +/**
>> + * max77686_read_gpios() - read the current state of the dvs GPIOs
>> + * @pdata: platform data that contains the dvs GPIOs information
>> + *
>> + * We call this function at bootup to detect what slot the firmware was
>> + * using for the DVS GPIOs. That way we can properly preserve the firmware's
>> + * voltage settings
>> + *
>> + * This function can sleep so must not be called from atomic context.
>> + */
>> +int max77686_read_gpios(struct max77686_platform_data *pdata)
>> +{
>> + int buck_default_idx = pdata->buck_default_idx;
>> + int result = 0;
>> + int i;
>> +
>> + for (i = 0; i < ARRAY_SIZE(pdata->buck_gpio_dvs); i++) {
>> + struct gpio_desc *gpio = pdata->buck_gpio_dvs[i];
>> +
>> + /* OK if some GPIOs aren't defined; we'll use default */
>> + if (IS_ERR(gpio)) {
>> + result |= buck_default_idx & (1 << i);
>> + continue;
>> + }
>> +
>> + if (gpiod_get_value_cansleep(gpio))
>> + result |= 1 << i;
>> + }
>> +
>> + return result;
>> +}
>> +EXPORT_SYMBOL_GPL(max77686_read_gpios);
>> +
>> static struct max77686_platform_data *max77686_i2c_parse_dt_pdata(struct device
>> *dev)
>> {
>> + struct device_node *np = dev->of_node;
>> struct max77686_platform_data *pd;
>>
>> pd = devm_kzalloc(dev, sizeof(*pd), GFP_KERNEL);
>> @@ -111,6 +223,13 @@ static struct max77686_platform_data *max77686_i2c_parse_dt_pdata(struct device
>> return NULL;
>>
>> dev->platform_data = pd;
>> +
>> + /* Read default index and ignore errors, since default is 0 */
>> + of_property_read_u32(np, "max77686,pmic-buck-default-dvs-idx",
>> + &pd->buck_default_idx);
> Any error checking code here. Say if pmic-buck-default-dvs-idx exceed 8?
I'm not a DT expert but AFAIK the kernel should expect the data in a FDT to be
correct and should not validate it on runtime. There is work-in-progress to add
a proper schema checking for DTS to the dtc so on build time it can be validated
that a DTS is valid.
AFAIU the only thing that the kernel should check is if a required property does
not exist.
>> +
>> + max77686_dt_parse_dvs_gpio(dev);
>> +
>> return pd;
>> }
>>
>> diff --git a/include/linux/mfd/max77686.h b/include/linux/mfd/max77686.h
>> index 4cbcc13..46a736b 100644
>> --- a/include/linux/mfd/max77686.h
>> +++ b/include/linux/mfd/max77686.h
>> @@ -99,15 +99,17 @@ struct max77686_platform_data {
>> struct max77686_opmode_data *opmode_data;
>>
>> /*
>> - * GPIO-DVS feature is not enabled with the current version of
>> - * MAX77686 driver. Buck2/3/4_voltages[0] is used as the default
>> - * voltage at probe. DVS/SELB gpios are set as OUTPUT-LOW.
>> + * GPIO-DVS feature is not fully enabled with the current version of
>> + * MAX77686 driver, but the driver does support using a DVS index other
>> + * than the default of 0.
>> */
>> - int buck234_gpio_dvs[3]; /* GPIO of [0]DVS1, [1]DVS2, [2]DVS3 */
>> - int buck234_gpio_selb[3]; /* [0]SELB2, [1]SELB3, [2]SELB4 */
>> - unsigned int buck2_voltage[8]; /* buckx_voltage in uV */
>> - unsigned int buck3_voltage[8];
>> - unsigned int buck4_voltage[8];
> I think when DVS gpio is used all the 8 voltage levels are fetched
> from DT during booting and the registers are programmed accordingly.
> Any further set/get_voltage just changes the GPIO lines.
> Any reason why this method is not used?
What are you describing is how the DT binding works for other Maxim PMICs that
also have DVS support right? (e.g: max8997).
The DVS binding in max77686/802 is actually a subset of the one in max8997 so it
let's you only choose which single DVS index is going to be used. The GPIOs in
"max77686,pmic-buck-dvs-gpios" should match "pmic-buck-default-dvs-idx".
To be honest I just took the DT binding that was used in the max77xxx driver
from the Chrome OS 3.8 kernel and didn't compare it with other Maxim PMICs DT
bingings.
I wonder if I should just take the DVS patches out from this initial version to
avoid blocking the max77802 support and then we can discuss this in more detail.
>> + struct gpio_desc *buck_gpio_dvs[3]; /* GPIO of [0]DVS1, [1]DVS2, [2]DVS3 */
>> + int buck_default_idx; /* Default value of DVS1, 2, 3 */
>> +
>> + struct gpio_desc *buck_gpio_selb[3]; /* Buck regulators 2, 3, 4 */
>> };
>>
>> +extern int max77686_setup_gpios(struct device *dev);
>> +extern int max77686_read_gpios(struct max77686_platform_data *pdata);
>> +
>> #endif /* __LINUX_MFD_MAX77686_H */
>> --
>> 2.0.0.rc2
>>
Best regards,
Javier
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