[PATCH v3] usb: dwc3: add disable u2mac linestate check quirk

[Rob Herring]

On Wed, Apr 19, 2017 at 08:11:38PM +0800, William Wu wrote:
> This patch adds a quirk to disable USB 2.0 MAC linestate check
> during HS transmit. Refer the dwc3 databook, we can use it for
> some special platforms if the linestate not reflect the expected
> line state(J) during transmission.
> 
> When use this quirk, the controller implements a fixed 40-bit
> TxEndDelay after the packet is given on UTMI and ignores the
> linestate during the transmit of a token (during token-to-token
> and token-to-data IPGAP).
> 
> On some rockchip platforms (e.g. rk3399), it requires to disable
> the u2mac linestate check to decrease the SSPLIT token to SETUP
> token inter-packet delay from 566ns to 466ns, and fix the issue
> that FS/LS devices not recognized if inserted through USB 3.0 HUB.
> 
> Signed-off-by: William Wu <william.wu at rock-chips.com>
> ---
> Changes in v3:
> - change quirk name
> - only read and write GUCTL1 if dwc3 version >= 2.50a
> 
> Changes in v2:
> - fix coding style
> 
>  Documentation/devicetree/bindings/usb/dwc3.txt |  2 ++

Acked-by: Rob Herring <robh at kernel.org> 

>  drivers/usb/dwc3/core.c                        | 20 ++++++++++++++------
>  drivers/usb/dwc3/core.h                        |  4 ++++
>  3 files changed, 20 insertions(+), 6 deletions(-)