Re: [PATCH 2/2] gpio: modepin: Add driver support for modepin GPIO controller

Hi Piyush!

thanks for your patch!

On Tue, Jun 15, 2021 at 10:06 AM Piyush Mehta [off-list ref] wrote:

This patch adds support for the mode pin GPIO controller. GPIO Modepin
driver set and get the value and status of the PS_MODE pin, based on
device-tree pin configuration. These 4-bits boot-mode pins are dedicated
configurable as input/output. After the stabilization of the system,
these mode pins are sampled.

Signed-off-by: Piyush Mehta <redacted>

OK, sounds interesting!

+#include <linux/slab.h>

I think I saw somewhere that this is not needed anymore, check if you need it.

+#define GET_OUTEN_PIN(pin)             (1U << (pin))

Delete this macro and just use BIT(pin) inline.
#include <linux/bits.h>

+static int modepin_gpio_get_value(struct gpio_chip *chip, unsigned int pin)
+{
+       u32 out_en;
+       u32 regval = 0;
+       int ret;
+
+       out_en = GET_OUTEN_PIN(pin);

Drop this and out_en

+       ret = zynqmp_pm_bootmode_read(&regval);
+       if (ret) {
+               pr_err("modepin: get value err %d\n", ret);
+               return ret;
+       }
+
+       return (out_en & (regval >> 8U)) ? 1 : 0;

return !!(regval & BIT(pin + 8));

should work and is easier to read IMO. We just check the right
bit immediately.

+static void modepin_gpio_set_value(struct gpio_chip *chip, unsigned int pin,
+                                  int state)
+{
+       u32 out_en;
+       u32 bootpin_val = 0;
+       int ret;
+
+       out_en = GET_OUTEN_PIN(pin);

Skip this helper variable.

+       state = state != 0 ? out_en : 0;

Uh that is really hard to read and modified a parameter. Skip that too.

+       bootpin_val = (state << (8U)) | out_en;

What you want is mask and set.

bootpin_val = BIT(pin + 8);

+       /* Configure bootpin value */
+       ret = zynqmp_pm_bootmode_write(bootpin_val);

This just looks weird.

Why are you not reading the value first since you are using
read/modify/write?

I *think* you want to do this:

ret = zynqmp_pm_bootmode_read(&val);
if (ret)
   /* error handling */
if (state)
    val |= BIT(pin + 8);
else
    val &= ~BIT(pin + 8);
ret = zynqmp_pm_bootmode_write(val);
if (ret)
   /* error handling */

+/*
+ * modepin_gpio_dir_in - Set the direction of the specified GPIO pin as input
+ * @chip:      gpio_chip instance to be worked on
+ * @pin:       gpio pin number within the device
+ *
+ * Return: 0 always
+ */
+static int modepin_gpio_dir_in(struct gpio_chip *chip, unsigned int pin)
+{
+       return 0;
+}

I think you said this was configurable in the commit message.

Use the define GPIO_LINE_DIRECTION_OUT rather than 0.

+static int modepin_gpio_dir_out(struct gpio_chip *chip, unsigned int pin,
+                               int state)
+{
+       return 0;
+}

Configurable?

+       status = devm_gpiochip_add_data(&pdev->dev, chip, chip);
+       if (status)
+               dev_err_probe(&pdev->dev, status,
+                             "Failed to add GPIO chip\n");

just return dev_err_probe(...)

Yours,
Linus Walleij