Re: [PATCH v2 1/4] reset: gpio: Add GPIO-based reset controller

On 05/01/2024 17:39, Biju Das wrote:

Hi Krzysztof Kozlowski,

Thanks for the patch.

...

-----Original Message----- From: Krzysztof Kozlowski krzysztof.kozlowski@linaro.org Sent: Friday, January 5, 2024 3:59 PM Subject: [PATCH v2 1/4] reset: gpio: Add GPIO-based reset controller

Add a simple driver to control GPIO-based resets using the reset controller API for the cases when the GPIOs are shared and reset should be coordinated. The driver is expected to be used by reset core framework for ad-hoc reset controllers.

Cc: Bartosz Golaszewski brgl@bgdev.pl Cc: Sean Anderson sean.anderson@seco.com Signed-off-by: Krzysztof Kozlowski krzysztof.kozlowski@linaro.org

---

MAINTAINERS | 5 ++ drivers/reset/Kconfig | 9 +++ drivers/reset/Makefile | 1 + drivers/reset/reset-gpio.c | 121 +++++++++++++++++++++++++++++++++++++ 4 files changed, 136 insertions(+) create mode 100644 drivers/reset/reset-gpio.c

diff --git a/MAINTAINERS b/MAINTAINERS index 7fe27cd60e1b..a0fbd4814bc7 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -8866,6 +8866,11 @@ F: Documentation/i2c/muxes/i2c-mux-gpio.rst F: drivers/i2c/muxes/i2c-mux-gpio.c F: include/linux/platform_data/i2c-mux-gpio.h

+GENERIC GPIO RESET DRIVER +M: Krzysztof Kozlowski krzysztof.kozlowski@linaro.org +S: Maintained +F: drivers/reset/reset-gpio.c

GENERIC HDLC (WAN) DRIVERS M: Krzysztof Halasa khc@pm.waw.pl S: Maintained diff --git a/drivers/reset/Kconfig b/drivers/reset/Kconfig index ccd59ddd7610..bb1b5a326eb7 100644 --- a/drivers/reset/Kconfig +++ b/drivers/reset/Kconfig @@ -66,6 +66,15 @@ config RESET_BRCMSTB_RESCAL This enables the RESCAL reset controller for SATA, PCIe0, or PCIe1 on BCM7216.

+config RESET_GPIO

• tristate "GPIO reset controller"
• help

•  This enables a generic reset controller for resets attached via
  

•  GPIOs.  Typically for OF platforms this driver expects "reset-
  

gpios"

•  property.
  

•  If compiled as module, it will be called reset-gpio.
  

config RESET_HSDK bool "Synopsys HSDK Reset Driver" depends on HAS_IOMEM diff --git a/drivers/reset/Makefile b/drivers/reset/Makefile index 8270da8a4baa..fd8b49fa46fc 100644 --- a/drivers/reset/Makefile +++ b/drivers/reset/Makefile @@ -11,6 +11,7 @@ obj-$(CONFIG_RESET_BCM6345) += reset-bcm6345.o obj-$(CONFIG_RESET_BERLIN) += reset-berlin.o obj-$(CONFIG_RESET_BRCMSTB) += reset-brcmstb.o obj-$(CONFIG_RESET_BRCMSTB_RESCAL) += reset-brcmstb-rescal.o +obj-$(CONFIG_RESET_GPIO) += reset-gpio.o obj-$(CONFIG_RESET_HSDK) += reset-hsdk.o obj-$(CONFIG_RESET_IMX7) += reset-imx7.o obj-$(CONFIG_RESET_INTEL_GW) += reset-intel-gw.o diff --git a/drivers/reset/reset-gpio.c b/drivers/reset/reset-gpio.c new file mode 100644 index 000000000000..cf0a867cbc5f --- /dev/null +++ b/drivers/reset/reset-gpio.c @@ -0,0 +1,121 @@ +// SPDX-License-Identifier: GPL-2.0

+#include <linux/gpio/consumer.h> +#include <linux/mod_devicetable.h> +#include <linux/module.h> +#include <linux/of.h> +#include <linux/platform_device.h> +#include <linux/reset-controller.h>

+struct reset_gpio_priv {

• struct reset_controller_dev rc;
• struct gpio_desc *reset;

+};

+static inline struct reset_gpio_priv +*rc_to_reset_gpio(struct reset_controller_dev *rc) {

• return container_of(rc, struct reset_gpio_priv, rc); }

+static int reset_gpio_assert(struct reset_controller_dev *rc, unsigned +long id) {

• struct reset_gpio_priv *priv = rc_to_reset_gpio(rc);
• gpiod_set_value_cansleep(priv->reset, 1);
• return 0;

+}

+static int reset_gpio_deassert(struct reset_controller_dev *rc,

• 	       unsigned long id)
  

+{

• struct reset_gpio_priv *priv = rc_to_reset_gpio(rc);
• gpiod_set_value_cansleep(priv->reset, 0);
• return 0;

+}

+static int reset_gpio_status(struct reset_controller_dev *rc, unsigned +long id) {

• struct reset_gpio_priv *priv = rc_to_reset_gpio(rc);
• return gpiod_get_value_cansleep(priv->reset);

+}

+static const struct reset_control_ops reset_gpio_ops = {

• .assert = reset_gpio_assert,
• .deassert = reset_gpio_deassert,
• .status = reset_gpio_status,

+};

+static void reset_gpio_of_args_put(void *data) {

• of_node_put(data);

+}

+static int reset_gpio_probe(struct platform_device *pdev) {

• struct device *dev = &pdev->dev;
• struct device_node **platdata = dev_get_platdata(dev);
• struct of_phandle_args gpio_args;
• struct reset_gpio_priv *priv;
• int ret;
• if (!platdata || !*platdata)

Maybe, if (!(platdata && *platdata)) which reduces 1 inversion operation.

I would not call it easier to understand... To me !A and !*A are quite obvious and easy to read instantly because !A is obvious: check if it is not NULL. Therefore original check is obvious: is NULL or points to NULL? Then exit.

Now your check is a bit more complicated. It is not even frequent code pattern which my brain used to see. You want to check if both are not NULL and then negate it, wait, no, opposite, check if they are something and then negate? To me it is really opposite of readable code.

Best regards, Krzysztof