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

[Hans de Goede]

Hi,

On 16-02-18 14:47, Andy Shevchenko wrote:
> On Fri, Feb 16, 2018 at 12:47 PM, Hans de Goede <hdegoede@xxxxxxxxxx> 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