Re: [PATCH 09/12] usb: roles: Add Intel XHCI USB role switch driver

Hans de Goede
2018-02-25T13:29:25Z

Hi,

On 16-02-18 14:47, Andy Shevchenko wrote:
> On Fri, Feb 16, 2018 at 12:47 PM, Hans de Goede <hdegoede@redhat.com> wrote:
>> Various Intel SoCs (Cherry Trail, Broxton and others) have an internal USB
>> role switch for swiching the OTG USB data lines between the xHCI host
>> controller and the dwc3 gadget controller.
>>
>> Note on some Cherry Trail systems there is ACPI/AML code listening to
>> edge interrupts on the id-pin (through an _AIE ACPI method) and switching
>> the role between ROLE_HOST and ROLE_NONE based on the id-pin. Note it does
>> not set the role to ROLE_DEVICE, because device-mode is usually not used
>> under Windows.
>>
>> The presence of AML code which modifies the cfg0 reg (on some systems)
>> means that we our read/write/modify of cfg0 may race with the AML code
>> doing the same to avoid this we take the global ACPI lock while doing
>> the read/write/modify.
>
>> +/* register definition */
>> +#define DUAL_ROLE_CFG0 0x68
>> +#define SW_VBUS_VALID (1 << 24)
>> +#define SW_IDPIN_EN (1 << 21)
>> +#define SW_IDPIN (1 << 20)
>> +
>> +#define DUAL_ROLE_CFG1 0x6c
>> +#define HOST_MODE (1 << 29)
>
> Does it make sense to use BIT() macro above?

Yes, fixed for v2.

>
>
>> +struct intel_xhci_acpi_match {
>> + const char *hid;
>> + int hrv;
>> +};
>
> Consider to unify with struct acpi_ac_bl.

That is not a bad idea, but probably best done as a follow-up commit,
since this patch-set already touches enough subsystems as is.

I just added this to my TODO:
-Add acpi_find_dev_present() helprt which takes an array of and returns a
pointer to (or NULL):
struct acpi_dev_present_match {
const char *hid;
const char *uid;
int hrv;
};
And use this in drivers/acpi/ac.c drivers/acpi/battery.c,
drivers/usb/roles/intel-xhci-usb-role-switch.c, ...

>> +static const struct intel_xhci_acpi_match allow_userspace_ctrl_ids[] = {
>> + { "INT33F4", 3 }, /* X-Powers AXP288 PMIC */
>> +};
>> +
>> +static int intel_xhci_usb_set_role(struct device *dev, enum usb_role role)
>> +{
>> + struct intel_xhci_usb_data *data = dev_get_drvdata(dev);
>> + unsigned long timeout;
>> + acpi_status status;
>
>> + u32 glk = -1U;
>
> I prefer to see consistency and moreover less confusing set, like
>
> ~0U

Looks like a chose a bad example as user of the
acpi_acquire_global_lock() function, others don't init this at all
because it is not necessary.

>
>> + u32 val;
>> +
>> + /*
>> + * On many CHT devices ACPI event (_AEI) handlers read / modify /
>> + * write the cfg0 register, just like we do. Take the ACPI lock
>> + * to avoid us racing with the AML code.
>> + */
>> + status = acpi_acquire_global_lock(ACPI_WAIT_FOREVER, &glk);
>
> FOREVER?!
> Wouldn't be slightly long under certain circumstances?

The mode-switch itself may take up-to 600ms, so I don't think any
delays caused by this will be a problem. This is just some weird
ACPI-subsys-ism where instead of just having a mutex and using
mutex_trylock() where necessary, the ACPICA code has its own
private timeout handling. I'm sure if I were to just do a mutex_lock()
here nobody would fall over that. The FOREVER just makes this look
scarier then it really is, in theory any mutex_lock() call can wait
forever.

>> + if (ACPI_FAILURE(status) && status != AE_NOT_CONFIGURED) {
>> + dev_err(dev, "Error could not acquire lock\n");
>> + return -EIO;
>> + }
>
>> + acpi_release_global_lock(glk);
>
>> + /* Polling on CFG1 register to confirm mode switch.*/
>> + do {
>> + val = readl(data->base + DUAL_ROLE_CFG1);
>
>> + if (!!(val & HOST_MODE) == (role == USB_ROLE_HOST))
>
> I would prefer ^ instead of first ==, but it's up to you.
>
>> + return 0;
>> +
>> + /* Interval for polling is set to about 5 - 10 ms */
>> + usleep_range(5000, 10000);
>> + } while (time_before(jiffies, timeout));
>> +
>> + dev_warn(dev, "Timeout waiting for role-switch\n");
>> + return -ETIMEDOUT;
>> +}
>
>> +static int intel_xhci_usb_probe(struct platform_device *pdev)
>> +{
>> + struct device *dev = &pdev->dev;
>> + struct intel_xhci_usb_data *data;
>> + struct resource *res;
>> + resource_size_t size;
>> + int i, ret;
>> +
>> + res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
>
>> + size = (res->end + 1) - res->start;
>
> resource_size()

Fixed for v2.

>> + data->base = devm_ioremap_nocache(dev, res->start, size);
>
> So, what's wrong with devm_ioremap_resource() ?
> ...which also prints an error message.

Nothing, I inherited this from the Android X86 patches this is
based on, fixed for v2.

>
>> + if (IS_ERR(data->base)) {
>> + ret = PTR_ERR(data->base);
>
>> + dev_err(dev, "Error iomaping registers: %d\n", ret);
>
> At least printing return code is useless. Driver core does this.
>
>> + return ret;
>> + }
>> +
>
>> + data->role_sw = usb_role_switch_register(dev, &sw_desc);
>> + if (IS_ERR(data->role_sw)) {
>> + ret = PTR_ERR(data->role_sw);
>
>> + dev_err(dev, "Error registering role-switch: %d\n", ret);
>
> Ditto.

Ok, both dropped.

>
>> + return ret;
>> + }
>> +
>> + return 0;
>> +}
>
>> +static const struct platform_device_id intel_xhci_usb_table[] = {
>> + { .name = DRV_NAME },
>
>> + {},
>
> No comma, please.

Fixed for v2.

Regards,

Hans