xhci: Reserve one command for USB3 LPM disable.

We want to do everything we can to ensure that USB 3.0 Link Power
Management (LPM) can be disabled when it is enabled.  If LPM can't be
disabled, we can't suspend USB 3.0 devices, or reset them.  To make sure
we can submit the command to disable LPM, allocate a command in the
xhci_hcd structure, and reserve one TRB on the command ring.

We only need one command per xHCI driver instance, because LPM is only
disabled or enabled while the USB core is holding the bandwidth_mutex
that is shared between the xHCI USB 2.0 and USB 3.0 roothubs.  The
bandwidth_mutex will be held until the command completes, or times out.

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

diff --git a/drivers/usb/host/xhci-mem.c b/drivers/usb/host/xhci-mem.c
index 497ed7723e4453142a22427cd0e201fa802739be..ec4338eec8262c520d785e53e32f269b02dfabd8 100644 (file)
--- a/drivers/usb/host/xhci-mem.c
+++ b/drivers/usb/host/xhci-mem.c
@@ -1815,6 +1815,8 @@ void xhci_mem_cleanup(struct xhci_hcd *xhci)
        xhci->event_ring = NULL;
        xhci_dbg(xhci, "Freed event ring\n");
 
+       if (xhci->lpm_command)
+               xhci_free_command(xhci, xhci->lpm_command);
        xhci->cmd_ring_reserved_trbs = 0;
        if (xhci->cmd_ring)
                xhci_ring_free(xhci, xhci->cmd_ring);
@@ -2377,6 +2379,16 @@ int xhci_mem_init(struct xhci_hcd *xhci, gfp_t flags)
        xhci_write_64(xhci, val_64, &xhci->op_regs->cmd_ring);
        xhci_dbg_cmd_ptrs(xhci);
 
+       xhci->lpm_command = xhci_alloc_command(xhci, true, true, flags);
+       if (!xhci->lpm_command)
+               goto fail;
+
+       /* Reserve one command ring TRB for disabling LPM.
+        * Since the USB core grabs the shared usb_bus bandwidth mutex before
+        * disabling LPM, we only need to reserve one TRB for all devices.
+        */
+       xhci->cmd_ring_reserved_trbs++;
+
        val = xhci_readl(xhci, &xhci->cap_regs->db_off);
        val &= DBOFF_MASK;
        xhci_dbg(xhci, "// Doorbell array is located at offset 0x%x"

diff --git a/drivers/usb/host/xhci.h b/drivers/usb/host/xhci.h
index 59248449b254ac01818306cfc14a413d8bff33d5..f5cb7417f231a45bbeec14da3ed84a1dd278336f 100644 (file)
--- a/drivers/usb/host/xhci.h
+++ b/drivers/usb/host/xhci.h
@@ -1426,6 +1426,8 @@ struct xhci_hcd {
        /* slot enabling and address device helpers */
        struct completion       addr_dev;
        int slot_id;
+       /* For USB 3.0 LPM enable/disable. */
+       struct xhci_command             *lpm_command;
        /* Internal mirror of the HW's dcbaa */
        struct xhci_virt_device *devs[MAX_HC_SLOTS];
        /* For keeping track of bandwidth domains per roothub. */