ehci: hsic: Add device tree entry for ITC
ITC (interrupt threshold control) is the maximum rate at which
usb controller generates interrupts. ITC interval is measured
in micro frames (which is 125us). Device tree entry will help
configure ITC per controller and per platform.
Change-Id: Ibdb8f806c8334042025cad33744160594cfcca80
Signed-off-by: Vamsi Krishna <vskrishn@codeaurora.org>
diff --git a/Documentation/devicetree/bindings/usb/msm-ehci-hsic.txt b/Documentation/devicetree/bindings/usb/msm-ehci-hsic.txt
index a3a9935..70bf993 100644
--- a/Documentation/devicetree/bindings/usb/msm-ehci-hsic.txt
+++ b/Documentation/devicetree/bindings/usb/msm-ehci-hsic.txt
@@ -49,6 +49,21 @@
depend on suitable handshake with the IPA peer.
- qcom,ahb-async-bridge-bypass: if present AHB ASYNC bridge will be bypassed such that
the bridge on the slave AHB is always used.
+- hsic,log2-itc: itc (interrupt threshold control) defines rate at which usb
+ controller will issue interrupts. It represents max interrupt interval
+ measured in micro frames. In high speed USB, each micro frame is 125us.
+ Valid values are from zero to six. Zero is default. Higher ITC value will
+ result in higher interrupt latency and can impact overall data latency.
+
+ log2-itc - Max interrupt threshold
+ -------- -----------------------
+ 0 (2^0 = 1) 1 micro frame interrupt threshold aka 125us interrupt threshold
+ 1 (2^1 = 2) 2 micro frame interrupt threshold aka 250us interrupt threshold
+ 2 (2^2 = 4) 4 micro frame interrupt threshold aka 500us interrupt threshold
+ 3 (2^3 = 8) 8 micro frame interrupt threshold aka 1ms interrupt threshold
+ 4 (2^4 = 16) 16 micro frame interrupt threshold aka 2ms interrupt threshold
+ 5 (2^5 = 32) 32 micro frame interrupt threshold aka 4ms interrupt threshold
+ 6 (2^6 = 64) 64 micro frame interrupt threshold aka 8ms interrupt threshold
- Refer to "Documentation/devicetree/bindings/arm/msm/msm_bus.txt" for
below optional properties:
diff --git a/drivers/usb/host/ehci-msm-hsic.c b/drivers/usb/host/ehci-msm-hsic.c
index f16a0b6..14c3323 100644
--- a/drivers/usb/host/ehci-msm-hsic.c
+++ b/drivers/usb/host/ehci-msm-hsic.c
@@ -1878,6 +1878,10 @@
&pdata->strobe_pad_offset);
of_property_read_u32(node, "hsic,data-pad-offset",
&pdata->data_pad_offset);
+ of_property_read_u32(node, "hsic,log2-itc",
+ &pdata->log2_irq_thresh);
+ if (pdata->log2_irq_thresh > 6)
+ pdata->log2_irq_thresh = 0;
pdata->bus_scale_table = msm_bus_cl_get_pdata(pdev);