Re: [RFC 1/5] usb: chipidea: Add support for Tegra20/30/114/124

From: Stephen Warren
Date: Thu May 26 2016 - 17:22:30 EST

On 05/26/2016 03:17 PM, Stephen Warren wrote:
On 05/26/2016 09:40 AM, Thierry Reding wrote:
From: Thierry Reding <treding@xxxxxxxxxx>

All of these Tegra SoC generations have a ChipIdea UDC IP block that can
be used for device mode communication with a host. Implement rudimentary
support that doesn't allow switching between host and device modes.

Are you sure this is correct for Tegra20? I ask because for the /host/
mode driver, there's a "has_hostpc" flag which is set to false for
Tegra20 and true for all other SoCs. In the U-Boot device mode driver
(if not in the kernel driver; I didn't check), there's a concept of "has
hostpc" too. I might expect that flag to be set the same way for both
drivers. That said, I /think/ the host and device HW are unrelated, so
it's possible has_hostpc might be set differently for them.
Unfortunately, we haven't enabled the device mode driver for any Tegra20
system in U-Boot so I can't tell whether we should enable has_hostpc for
Tegra20's device mode driver.

Still, if this code works then I guess it's likely correct...

On the other hand, it looks like the kernel device mode driver might auto-detect this; in core.c:hw_device_init(), I see:

reg = hw_read(ci, CAP_HCCPARAMS, HCCPARAMS_LEN) >>
ci->hw_bank.lpm = reg;

... and in host.c:host_start(), I see:

ehci->has_hostpc = ci->hw_bank.lpm;