Re: [PATCH] extcon: add MAX3355 driver

From: Sergei Shtylyov
Date: Tue Oct 20 2015 - 14:20:45 EST

Hello.

On 12/18/2014 12:58 AM, Sergei Shtylyov wrote:

MAX3355E chip integrates a charge pump and comparators to enable a system with
an integrated USB OTG dual-role transceiver to function as a USB OTG dual-role
device. In addition to sensing/controlling Vbus, the chip also passes thru the
ID signal from the USB OTG connector. On some Renesas boards, this signal is
just fed into the SoC thru a GPIO pin -- there's no real OTG controller, only
host and gadget USB controllers sharing the same USB bus; however, we'd like
to allow host or gadget drivers to be loaded depending on the cable type,
hence
the need for the MAX3355 extcon driver. The Vbus status signals are also wired
to GPIOs (however, we're not currently intested in them), the OFFVBUS# signal
is controlled by the host controllers, there's also the SHDN# signal wired to
GPIO, which should be high for normal operation.

Signed-off-by: Sergei Shtylyov <sergei.shtylyov@xxxxxxxxxxxxxxxxxx>

---
The patch is against the 'extcon-next' branch of the 'extcon.git' repo.

Documentation/devicetree/bindings/extcon/extcon-max3355.txt | 21 ++
drivers/extcon/Kconfig | 6
drivers/extcon/Makefile | 1
drivers/extcon/extcon-max3355.c | 122
++++++++++++
4 files changed, 150 insertions(+)

Index: extcon/Documentation/devicetree/bindings/extcon/extcon-max3355.txt
===================================================================
--- /dev/null
+++ extcon/Documentation/devicetree/bindings/extcon/extcon-max3355.txt
@@ -0,0 +1,21 @@
+MAX3355 USB OTG chip

Need manufactor information as following :
-> Maxim MAX3355

Would be Maxim enough? Or perhaps I should use Maxim Integrated [Products]?

You haven't replied to my questions.

+--------------------
+
+MAX3355 integrates a charge pump and comparators to enable a system with an
+integrated USB OTG dual-role transceiver to function as a USB OTG dual-role
+device.
+
+Required properties:
+- compatible: should be "maxim,max3355";
+- maxim,shdn-gpio: should contain a phandle and GPIO specifier for the
GPIO pin
+ connected to the MAX3355's SHDN# pin;
+- maxim,id-gpio: should contain a phandle and GPIO specifier for the GPIO pin
+ connected to the MAX3355's ID_OUT pin.
+
+Example (Koelsch board):
+
+ usb-otg {
+ compatible = "maxim,max3355";
+ maxim,shdn-gpio = <&gpio2 4 GPIO_ACTIVE_LOW>;
+ maxim,id-gpio = <&gpio5 31 GPIO_ACTIVE_HIGH>;

Kernel already supported the gpio helper function to get gpio from devicetree.
I prefer use follwoing style by using of_get_gpio()/of_get_gpio_flags() in
include/linux/of_gpio.h.

gpios = <&gpio2 4 GPIO_ACTIVE_LOW>, <&gpio5 31 GPIO_ACTIVE_HIGH>;

OK, though Documentation/devicetree/bindings/gpio/gpio.txt does not seem
to insist on using this one...

Moreover, it now says "gpios" isn't allowed for the new bindings. So I have to strongly disagree here...

[...]

+static irqreturn_t max3355_id_irq(int irq, void *dev_id)
+{
+ struct max3355_data *data = dev_id;
+ int id = gpio_get_value(data->id_gpio);
+
+ extcon_set_cable_state(data->edev, "USB-HOST", !id);

You have to get the gpio flag in the devicetree by using of_get_gpio_flags()
function
and then you would set the cable state according to gpio state and flag.

I'm sorry but I just don't see why I have to do it. This is not a generic
GPIO driver, and the polarities of the GPIOs are determined solely by the
MAX3355 specs.

Again, got not reply...

[...]
+static int max3355_probe(struct platform_device *pdev)
+{
+ struct device_node *np = pdev->dev.of_node;
+ struct max3355_data *data;
+ int gpio, irq, ret;
+
+ data = devm_kzalloc(&pdev->dev, sizeof(struct max3355_data),
+ GFP_KERNEL);
+ if (!data)
+ return -ENOMEM;
+
+ data->edev = devm_extcon_dev_allocate(&pdev->dev, max3355_cable);
+ if (IS_ERR(data->edev)) {
+ dev_err(&pdev->dev, "failed to allocate extcon device\n");
+ return PTR_ERR(data->edev);
+ }
+ data->edev->name = kstrdup(np->name, GFP_KERNEL);
+
+ gpio = of_get_named_gpio(np, "maxim,id-gpio", 0);

Use of_get_gpio() or of_get_gpio_flags().

OK, I'll use the first one.

No, I won't due to not being able to use "gpios" anymore.

[...]

+
+ ret = devm_request_threaded_irq(&pdev->dev, irq, NULL, max3355_id_irq,
+ IRQF_TRIGGER_RISING |
+ IRQF_TRIGGER_FALLING | IRQF_ONESHOT,

Is it right to add both RISING and FALLING trigger?

How else I'm supposed to know when the OTG ID signal goes low and high?

and need to add IRQF_NO_SUSPEND to wakeup from suspend state when interrupt
happen.

Hm, are you sure we want to wake up on plugging another kind of USB cable?

No reply to that as well...

[...]
+static struct platform_driver max3355_driver = {
+ .probe = max3355_probe,
+ .driver = {
+ .name = "extcon-max3355",
+ .of_match_table = max3355_match_table,
+ .owner = THIS_MODULE,
+ },
+};
+
+module_platform_driver(max3355_driver);
+

Don't need un-used blank line.

I don't understand. There's empty line in such case in extcon-gpio.c...

No reply...

[...]

Thanks,
Chanwoo Choi

MBR, Sergei

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