[PATCH 3.10 08/55] USB: ehci-pci: USB host controller support for Intel Quark X1000

From: Greg Kroah-Hartman
Date: Wed Sep 03 2014 - 19:53:18 EST

3.10-stable review patch. If anyone has any objections, please let me know.


From: Bryan O'Donoghue <bryan.odonoghue@xxxxxxxxx>

commit 6e693739e9b603b3ca9ce0d4f4178f0633458465 upstream.

The EHCI packet buffer in/out threshold is programmable for Intel Quark X1000
USB host controller, and the default value is 0x20 dwords. The in/out threshold
can be programmed to 0x80 dwords (512 Bytes) to maximize the perfomrance,
but only when isochronous/interrupt transactions are not initiated by the USB
host controller. This patch is to reconfigure the packet buffer in/out
threshold as maximal as possible to maximize the performance, and 0x7F dwords
(508 Bytes) should be used because the USB host controller initiates
isochronous/interrupt transactions.

Signed-off-by: Bryan O'Donoghue <bryan.odonoghue@xxxxxxxxx>
Signed-off-by: Alvin (Weike) Chen <alvin.chen@xxxxxxxxx>
Acked-by: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
Reviewed-by: Jingoo Han <jg1.han@xxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

drivers/usb/host/ehci-pci.c | 25 +++++++++++++++++++++++++
1 file changed, 25 insertions(+)

--- a/drivers/usb/host/ehci-pci.c
+++ b/drivers/usb/host/ehci-pci.c
@@ -35,6 +35,21 @@ static const char hcd_name[] = "ehci-pci
#define PCI_DEVICE_ID_INTEL_CE4100_USB 0x2e70

+#define PCI_DEVICE_ID_INTEL_QUARK_X1000_SOC 0x0939
+static inline bool is_intel_quark_x1000(struct pci_dev *pdev)
+ return pdev->vendor == PCI_VENDOR_ID_INTEL &&
+ pdev->device == PCI_DEVICE_ID_INTEL_QUARK_X1000_SOC;
+ * 0x84 is the offset of in/out threshold register,
+ * and it is the same offset as the register of 'hostpc'.
+ */
+#define intel_quark_x1000_insnreg01 hostpc
+/* Maximum usable threshold value is 0x7f dwords for both IN and OUT */
+#define INTEL_QUARK_X1000_EHCI_MAX_THRESHOLD 0x007f007f

/* called after powerup, by probe or system-pm "wakeup" */
static int ehci_pci_reinit(struct ehci_hcd *ehci, struct pci_dev *pdev)
@@ -50,6 +65,16 @@ static int ehci_pci_reinit(struct ehci_h
if (!retval)
ehci_dbg(ehci, "MWI active\n");

+ /* Reset the threshold limit */
+ if (is_intel_quark_x1000(pdev)) {
+ /*
+ * For the Intel QUARK X1000, raise the I/O threshold to the
+ * maximum usable value in order to improve performance.
+ */
+ ehci_writel(ehci, INTEL_QUARK_X1000_EHCI_MAX_THRESHOLD,
+ ehci->regs->intel_quark_x1000_insnreg01);
+ }
return 0;

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/