USB: EHCI: AMD periodic frame list table quirk

On AMD SB700/SB800/Hudson-2/3 platforms, USB EHCI controller may read/write
to memory space not allocated to USB controller if there is longer than
normal latency on DMA read encountered. In this condition the exposure will
be encountered only if the driver has following format of Periodic Frame
List link pointer structure:

For any idle periodic schedule, the Frame List link pointers that have the
T-bit set to 1 intending to terminate the use of frame list link pointer
as a physical memory pointer.

Idle periodic schedule Frame List Link pointer shoule be in the following
format to avoid the issue:

Frame list link pointer should be always contains a valid pointer to a
inactive QHead with T-bit set to 0.

Signed-off-by: Andiry Xu <andiry.xu@amd.com>
Acked-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 24 insertions, 2 deletions

diff --git a/drivers/usb/host/ehci-mem.c b/drivers/usb/host/ehci-mem.c
index d36e4e75e08..12f70c302b0 100644
--- a/drivers/usb/host/ehci-mem.c
+++ b/drivers/usb/host/ehci-mem.c
@@ -141,6 +141,10 @@ static void ehci_mem_cleanup (struct ehci_hcd *ehci)
 		qh_put (ehci->async);
 	ehci->async = NULL;
 
+	if (ehci->dummy)
+		qh_put(ehci->dummy);
+	ehci->dummy = NULL;
+
 	/* DMA consistent memory and pools */
 	if (ehci->qtd_pool)
 		dma_pool_destroy (ehci->qtd_pool);
@@ -227,8 +231,26 @@ static int ehci_mem_init (struct ehci_hcd *ehci, gfp_t flags)
 	if (ehci->periodic == NULL) {
 		goto fail;
 	}
-	for (i = 0; i < ehci->periodic_size; i++)
-		ehci->periodic [i] = EHCI_LIST_END(ehci);
+
+	if (ehci->use_dummy_qh) {
+		struct ehci_qh_hw	*hw;
+		ehci->dummy = ehci_qh_alloc(ehci, flags);
+		if (!ehci->dummy)
+			goto fail;
+
+		hw = ehci->dummy->hw;
+		hw->hw_next = EHCI_LIST_END(ehci);
+		hw->hw_qtd_next = EHCI_LIST_END(ehci);
+		hw->hw_alt_next = EHCI_LIST_END(ehci);
+		hw->hw_token &= ~QTD_STS_ACTIVE;
+		ehci->dummy->hw = hw;
+
+		for (i = 0; i < ehci->periodic_size; i++)
+			ehci->periodic[i] = ehci->dummy->qh_dma;
+	} else {
+		for (i = 0; i < ehci->periodic_size; i++)
+			ehci->periodic[i] = EHCI_LIST_END(ehci);
+	}
 
 	/* software shadow of hardware table */
 	ehci->pshadow = kcalloc(ehci->periodic_size, sizeof(void *), flags);