[PATCH v6 72/87] usb: dwc3: ep0: flush and invalidate cache around ep0 transfers

[Anders Roxell <anders.roxell@linaro.org>]

The dwc3 driver was synced from Linux v6.16. In Linux the DMA api keeps
the trb and the buffers in sync with the controller. In u-boot the ep0
trb and buffers come from dma_alloc_coherent, which is just cached
memory, not coherent. Nothing syncs them around the controller dma, so
we must flush and invalidate by hand.

U-boot did this before, the resync dropped it. Without cache maintenance
the controller reads a stale trb and a stale buffer, and reads back stale
status. The device answers GET_DESCRIPTOR with garbage, so the host fails
to enumerate with -71 (EPROTO).

Flush the trb and the buffer before the controller reads them. Invalidate
the setup packet, the status write back and the OUT data buffer after the
controller writes them.

Reported-by: Anshul Dalal <anshuld@ti.com>
Signed-off-by: Anders Roxell <anders.roxell@linaro.org>
---
 drivers/usb/dwc3/ep0.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/usb/dwc3/ep0.c b/drivers/usb/dwc3/ep0.c
index e81404e11405..f82c0f7e6dec 100644
--- a/drivers/usb/dwc3/ep0.c
+++ b/drivers/usb/dwc3/ep0.c
@@ -55,6 +55,9 @@ static void dwc3_ep0_prepare_one_trb(struct dwc3_ep *dep,
 	else
 		trb->ctrl |= (DWC3_TRB_CTRL_IOC
 				| DWC3_TRB_CTRL_LST);
+
+	dwc3_flush_cache((uintptr_t)buf_dma, len);
+	dwc3_flush_cache((uintptr_t)trb, sizeof(*trb));
 }
 
 static int dwc3_ep0_start_trans(struct dwc3_ep *dep)
@@ -812,6 +815,8 @@ static void dwc3_ep0_inspect_setup(struct dwc3 *dwc,
 	int ret = -EINVAL;
 	u32 len;
 
+	dwc3_invalidate_cache((uintptr_t)ctrl, sizeof(*ctrl));
+
 	if (!dwc->gadget_driver || !dwc->softconnect || !dwc->connected)
 		goto out;
 
@@ -857,6 +862,8 @@ static void dwc3_ep0_complete_data(struct dwc3 *dwc,
 	dwc->ep0_next_event = DWC3_EP0_NRDY_STATUS;
 	trb = dwc->ep0_trb;
 
+	dwc3_invalidate_cache((uintptr_t)trb, sizeof(*trb) * 2);
+
 	r = next_request(&ep0->pending_list);
 	if (!r)
 		return;
@@ -874,6 +881,9 @@ static void dwc3_ep0_complete_data(struct dwc3 *dwc,
 
 	length = trb->size & DWC3_TRB_SIZE_MASK;
 	transferred = ur->length - length;
+
+	if (ur->buf && !r->direction)
+		dwc3_invalidate_cache((uintptr_t)ur->dma, ur->length);
 	ur->actual += transferred;
 
 	if ((IS_ALIGNED(ur->length, ep0->endpoint.maxpacket) &&
-- 
2.53.0