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SubjectRe: [RFC PATCH RESEND 1/3] mfd: upboard: Add UP2 platform controller driver
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Date
On Sat, 2018-04-21 at 09:50 +0100, Javier Arteaga wrote:
> UP Squared (UP2) is a x86 SBC from AAEON based on Intel Apollo Lake.

> +config MFD_UPBOARD
> + tristate "UP Squared"
> + depends on ACPI
> + depends on GPIOLIB
> + select MFD_CORE
> + select REGMAP
> + help
> + If you say yes here you get support for the platform
> controller
> + of the UP Squared single-board computer.
> +
> + This driver provides common support for accessing the
> device,
> + additional drivers must be enabled in order to use the
> + functionality of the device.
> +
> + This driver can also be built as a module. If so, the
> module
> + will be called upboard.

"upboard"

>
> +static int upboard_read(void *context, unsigned int reg, unsigned int
> *val)
> +{
> + const struct upboard * const upboard = context;
> + int i;
> +
> + gpiod_set_value(upboard->clear_gpio, 0);
> + gpiod_set_value(upboard->clear_gpio, 1);
> +
> + reg |= UPBOARD_READ_FLAG;
> +
> + for (i = UPBOARD_ADDRESS_SIZE; i >= 0; i--) {
> + gpiod_set_value(upboard->strobe_gpio, 0);
> + gpiod_set_value(upboard->datain_gpio, (reg >> i) &
> 0x1);
> + gpiod_set_value(upboard->strobe_gpio, 1);
> + }
> +

> + gpiod_set_value(upboard->strobe_gpio, 0);
> + *val = 0;
> +
> + for (i = UPBOARD_REGISTER_SIZE - 1; i >= 0; i--) {
> + gpiod_set_value(upboard->strobe_gpio, 1);
> + gpiod_set_value(upboard->strobe_gpio, 0);
> + *val |= gpiod_get_value(upboard->dataout_gpio) << i;
> + }
> +
> + gpiod_set_value(upboard->strobe_gpio, 1);

Can't you rewrite this like

for (addr) {
strobe(0)
data(x)
strobe(1)
}

for (register) {
strobe(0)
val = data(x)
strobe(1)
}

val &= BIT(register_size);
strobe(0)

?

> +
> + return 0;
> +};
> +
> +static int upboard_write(void *context, unsigned int reg, unsigned
> int val)
> +{
> + const struct upboard * const upboard = context;
> + int i;
> +
> + gpiod_set_value(upboard->clear_gpio, 0);
> + gpiod_set_value(upboard->clear_gpio, 1);
> +
> + for (i = UPBOARD_ADDRESS_SIZE; i >= 0; i--) {
> + gpiod_set_value(upboard->strobe_gpio, 0);
> + gpiod_set_value(upboard->datain_gpio, (reg >> i) &
> 0x1);
> + gpiod_set_value(upboard->strobe_gpio, 1);
> + }
> +
> + gpiod_set_value(upboard->strobe_gpio, 0);
> +
> + for (i = UPBOARD_REGISTER_SIZE - 1; i >= 0; i--) {
> + gpiod_set_value(upboard->datain_gpio, (val >> i) &
> 0x1);
> + gpiod_set_value(upboard->strobe_gpio, 1);
> + gpiod_set_value(upboard->strobe_gpio, 0);
> + }
> +
> + gpiod_set_value(upboard->strobe_gpio, 1);

Similar here:

for (addr) {
strobe(0)
data(x)
strobe(1)
}

for (register) {
strobe(0)
data(x)
strobe(1)
}

strobe(0)
strobe(1)

?

> +
> + return 0;
> +};

Moreover these two functions have duplications, i.e.

static ... upboard_clear()
{
clear(0)
clear(1)
}

static ... upboard_set_address()
{
for (addr) {
...
}
}


Additional question is about spi-bitbang and i2c-gpio. Can one of them
be utilized here? Why not?

> +struct upboard_data {
> + const struct regmap_config *regmapconf;
> + const struct mfd_cell *cells;
> + size_t ncells;
> +};

> +static int upboard_init_gpio(struct upboard *upboard)
> +{
> + struct gpio_desc *enable_gpio;
> +
> + enable_gpio = devm_gpiod_get(upboard->dev, "enable",
> GPIOD_OUT_LOW);
> + if (IS_ERR(enable_gpio))
> + return PTR_ERR(enable_gpio);

> + gpiod_set_value(enable_gpio, 1);

When do you disable it? Why not?

> + return 0;
> +}

> +
> +static int upboard_check_supported(struct upboard *upboard)
> +{

> + const unsigned int AAEON_MANUFACTURER_ID = 0x01;
> + const unsigned int SUPPORTED_FW_MAJOR = 0x0;

Why to hide here instead of putting at the top of file as defined
constants?

> + unsigned int platform_id, manufacturer_id;
> + unsigned int firmware_id, build, major, minor, patch;
> + int ret;

> + build = (firmware_id >> 12) & 0xf;
> + major = (firmware_id >> 8) & 0xf;
> + minor = (firmware_id >> 4) & 0xf;

> + patch = firmware_id & 0xf;

For style purposes you can use
(firmware >> 0) & 0xf here

> +static int upboard_probe(struct platform_device *pdev)
> +{
> + struct upboard *upboard;
> + const struct acpi_device_id *id;
> + const struct upboard_data *upboard_data;
> + int ret;

> + id = acpi_match_device(upboard_acpi_match, &pdev->dev);
> + if (!id)
> + return -ENODEV;
> +
> + upboard_data = (const struct upboard_data *) id->driver_data;

Use new API for that.

> +MODULE_LICENSE("GPL");

License mismatch.

> +#define UPBOARD_ADDRESS_SIZE 7
> +#define UPBOARD_REGISTER_SIZE 16

> +#define UPBOARD_READ_FLAG BIT(UPBOARD_ADDRESS_SIZE)

It's not clear why this one is defined in this way.
Comment is needed.

--
Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Intel Finland Oy

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