diff options
| author | Zixun LI <admin@hifiphile.com> | 2025-06-02 17:45:08 +0200 |
|---|---|---|
| committer | Mattijs Korpershoek <mkorpershoek@kernel.org> | 2025-06-16 11:56:19 +0200 |
| commit | ca036308a513759e3e4cbe9f8191861c3232c611 (patch) | |
| tree | 37f9aef04a97543fb32cb70211aa12146d6673b6 | |
| parent | 9de873b4c3098c0662d4adaeb1cc31be4e6d2688 (diff) | |
usb: gadget: atmel: reliably generate disconnect by disabling controller
Contrary to the datasheet, setting both DETACH and PULLD_DIS bits to 1
does not always drive the DP and DM lines to high-impedance. This
prevents the host from reliably detecting a USB disconnect and subsequent
reconnect.
The symptom is that the first gadget command (e.g., dhcp) succeeds, while
subsequent commands (e.g., nfs) fail.
Disabling and re-enabling the controller entirely, instead of toggling the
PULLD_DIS bit, reliably generates a disconnect event.
The Linux driver works correctly because gadget_disconnect/gadget_connect
are always followed by gadget_udc_start/gadget_udc_stop. In U-Boot
pullup() is used solely.
This behavior has been observed on the SAM9X60-Curiosity and
AT91SAM9G25-EK boards and has been reported to Microchip.
Signed-off-by: Zixun LI <admin@hifiphile.com>
Link: https://lore.kernel.org/r/20250602-pullup-v1-1-edcde5a050dd@hifiphile.com
[mkorpershoek: reworded commit title + comment to usba_udc_pullup()]
Signed-off-by: Mattijs Korpershoek <mkorpershoek@kernel.org>
| -rw-r--r-- | drivers/usb/gadget/atmel_usba_udc.c | 14 |
1 files changed, 7 insertions, 7 deletions
diff --git a/drivers/usb/gadget/atmel_usba_udc.c b/drivers/usb/gadget/atmel_usba_udc.c index f9326f0a7e7..72f68dba3a7 100644 --- a/drivers/usb/gadget/atmel_usba_udc.c +++ b/drivers/usb/gadget/atmel_usba_udc.c @@ -521,16 +521,16 @@ usba_udc_set_selfpowered(struct usb_gadget *gadget, int is_selfpowered) static int usba_udc_pullup(struct usb_gadget *gadget, int is_on) { struct usba_udc *udc = to_usba_udc(gadget); - u32 ctrl; - - ctrl = usba_readl(udc, CTRL); + /* + * Some chips don't reliably drive DP/DM lines to high impedance when + * using the DETACH/PULLD_DIS bits. + * To ensure a reliable disconnect, power cycle the controller instead + */ if (is_on) - ctrl &= ~USBA_DETACH; + usba_writel(udc, CTRL, USBA_ENABLE_MASK); else - ctrl |= USBA_DETACH; - - usba_writel(udc, CTRL, ctrl); + usba_writel(udc, CTRL, USBA_DISABLE_MASK); return 0; } |