[U-Boot] [PATCH v2 80/80] dm: usb: Add a README for driver model

[Jim Lin]

There are some typos. Please correct them, thanks.

On 03/26/2015 02:23 AM, Simon Glass wrote:
> Add some documentation describing how USB is implemented with USB. This
> might make things easier for people to understand.
>
> Signed-off-by: Simon Glass <sjg at chromium.org>
> ---
>
> Changes in v2:
> - Rewrite and expand series to support driver model fully
>
>   doc/driver-model/usb-info.txt | 415 ++++++++++++++++++++++++++++++++++++++++++
>   1 file changed, 415 insertions(+)
>   create mode 100644 doc/driver-model/usb-info.txt
>
> diff --git a/doc/driver-model/usb-info.txt b/doc/driver-model/usb-info.txt
> new file mode 100644
> index 0000000..3762b6c
> --- /dev/null
> +++ b/doc/driver-model/usb-info.txt
> @@ -0,0 +1,415 @@
> +How USB works with driver model
> +===============================
> +
> +Introduction
> +------------
> +
> +Driver model USB support makes use of existing features but changes how
> +drivers are found. This document provides some information intended to help
> +understand how things work with USB in U-Boot when driver model is enabled.
> +
> +
> +Enabling driver model for USB
> +-----------------------------
> +
> +A new CONFIG_DM_USB option is provided to enable driver model for USB. This
> +causes the USB uclass to be included, and drops the equivalent code in
> +usb.c. In particular the usb_init() function is then implemented by the
> +uclass.
> +
> +
> +Support for ECHI and XCHI
EHCI
XHCI

> +-------------------------
> +
> +So far OHCI is not supported. Both EHCI and XHCI drivers should be declared
> +as drivers in the USB uclass. For example:
> +
> +static const struct udevice_id ehci_usb_ids[] = {
> +	{ .compatible = "nvidia,tegra20-ehci", .data = USB_CTLR_T20 },
> +	{ .compatible = "nvidia,tegra30-ehci", .data = USB_CTLR_T30 },
> +	{ .compatible = "nvidia,tegra114-ehci", .data = USB_CTLR_T114 },
> +	{ }
> +};
> +
> +U_BOOT_DRIVER(usb_ehci) = {
> +	.name	= "ehci_tegra",
> +	.id	= UCLASS_USB,
> +	.of_match = ehci_usb_ids,
> +	.ofdata_to_platdata = ehci_usb_ofdata_to_platdata,
> +	.probe = tegra_ehci_usb_probe,
> +	.remove = tegra_ehci_usb_remove,
> +	.ops	= &ehci_usb_ops,
> +	.platdata_auto_alloc_size = sizeof(struct usb_platdata),
> +	.priv_auto_alloc_size = sizeof(struct fdt_usb),
> +	.flags	= DM_FLAG_ALLOC_PRIV_DMA,
> +};
> +
> +Here ehci_usb_ids is used to list the controllers that the driver supports.
> +Each has its own data value. Controllers must be in the UCLASS_USB uclass.
> +
> +The ofdata_to_platdata() method allows the controller driver to grab any
> +necessary settings from the device tree.
> +
> +The ops here are ehci_usb_ops. All EHCI drivers will use these same ops in
> +most cases, since they are all ECHI-compatible. For ECHI there are also some
EHCI-compatible
For EHCI
> +special operations that can be overriden when calling ehci_register().
overridden

> +This defines a single controller, containing a root hub (which is required).
> +The hub is emulated by a hub emulator, and the emulated hub has a single
> +flash stick to emulate on one of its ports.
> +
> +When 'usb start' is used, the following 'dm tree' output will be available:
> +
> + usb         [ + ]    `-- usb at 1
> + usb_hub     [ + ]        `-- hub
> + usb_emul    [ + ]            |-- hub-emul
> + usb_emul    [ + ]            |   `-- flash-stick
> + usb_mass_st [ + ]            `-- usb_mass_storage
> +
> +
> +This may look a confusing. Most of it mirrors the device tree, but the
may look confusing
--nvpublic