xhci: Some Evaluate Context commands must succeed.

The upcoming USB 3.0 Link PM patches will introduce new API to enable
and disable low-power link states.  We must be able to disable LPM in
order to reset a device, or place the device into U3 (device suspend).
Therefore, we need to make sure the Evaluate Context command to disable
the LPM timeouts can't fail due to there being no room on the command
ring.

Introduce a new flag to the function that queues the Evaluate Context
command, command_must_succeed.  This tells the ring handler that a TRB
has already been reserved for the command (by incrementing
xhci->cmd_ring_reserved_trbs), and basically ensures that prepare_ring()
won't fail.  A similar flag was already implemented for the Configure
Endpoint command queuing function.

All functions that currently call xhci_configure_endpoint() to issue an
Evaluate Context command pass "false" for the "must_succeed" parameter,
so this patch should have no effect on current xHCI driver behavior.

Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>

drivers/usb/host/xhci-ring.c

@@ -3609,12 +3609,12 @@ int xhci_queue_configure_endpoint(struct xhci_hcd *xhci, dma_addr_t in_ctx_ptr,
 
 /* Queue an evaluate context command TRB */
 int xhci_queue_evaluate_context(struct xhci_hcd *xhci, dma_addr_t in_ctx_ptr,
-		u32 slot_id)
+		u32 slot_id, bool command_must_succeed)
 {
 	return queue_command(xhci, lower_32_bits(in_ctx_ptr),
 			upper_32_bits(in_ctx_ptr), 0,
 			TRB_TYPE(TRB_EVAL_CONTEXT) | SLOT_ID_FOR_TRB(slot_id),
-			false);
+			command_must_succeed);
 }
 
 /*

drivers/usb/host/xhci.c

@@ -2446,7 +2446,7 @@ static int xhci_configure_endpoint(struct xhci_hcd *xhci,
 				udev->slot_id, must_succeed);
 	else
 		ret = xhci_queue_evaluate_context(xhci, in_ctx->dma,
-				udev->slot_id);
+				udev->slot_id, must_succeed);
 	if (ret < 0) {
 		if (command)
 			list_del(&command->cmd_list);

drivers/usb/host/xhci.h

@@ -1757,7 +1757,7 @@ int xhci_queue_isoc_tx_prepare(struct xhci_hcd *xhci, gfp_t mem_flags,
 int xhci_queue_configure_endpoint(struct xhci_hcd *xhci, dma_addr_t in_ctx_ptr,
 		u32 slot_id, bool command_must_succeed);
 int xhci_queue_evaluate_context(struct xhci_hcd *xhci, dma_addr_t in_ctx_ptr,
-		u32 slot_id);
+		u32 slot_id, bool command_must_succeed);
 int xhci_queue_reset_ep(struct xhci_hcd *xhci, int slot_id,
 		unsigned int ep_index);
 int xhci_queue_reset_device(struct xhci_hcd *xhci, u32 slot_id);