From: Bryan O'Donoghue <[email protected]>
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 <[email protected]>
Signed-off-by: Alvin (Weike) Chen <[email protected]>
Acked-by: Alan Stern <[email protected]>
Reviewed-by: Jingoo Han <[email protected]>
---
Changlog v5:
* Correct the wrong comment style.
drivers/usb/host/ehci-pci.c | 25 +++++++++++++++++++++++++
1 file changed, 25 insertions(+)
diff --git a/drivers/usb/host/ehci-pci.c b/drivers/usb/host/ehci-pci.c
index 3e86bf4..ca7b964 100644
--- 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_hcd *ehci, struct pci_dev *pdev)
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;
}
--
1.7.9.5
On Wed, Jul 02, 2014 at 01:58:18AM -0700, Chen, Alvin wrote:
> From: Bryan O'Donoghue <[email protected]>
>
> 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 <[email protected]>
> Signed-off-by: Alvin (Weike) Chen <[email protected]>
> Acked-by: Alan Stern <[email protected]>
> Reviewed-by: Jingoo Han <[email protected]>
> ---
> Changlog v5:
> * Correct the wrong comment style.
>
> drivers/usb/host/ehci-pci.c | 25 +++++++++++++++++++++++++
> 1 file changed, 25 insertions(+)
This should go to stable kernel releases as well, right?
thanks,
greg k-h