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@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@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