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Subject[PATCH] USB: host: ehci: allow tine of highspeed nak-count
Date
From: Ben Dooks <ben.dooks@codethink.co.uk>

At least some systems benefit with less scheduling if the NAK count
value is set higher than the default 4. For instance a Tegra3 with
an SMSC9512 showed less interrupt load when this was changed to 14.

To allow the changing of this value, add a sysfs node to each of
the controllers to allow run-time changing.

Signed-off-by: Ben Dooks <ben.dooks@codethink.co.uk>
---
drivers/usb/host/ehci-hcd.c | 1 +
drivers/usb/host/ehci-q.c | 4 +--
drivers/usb/host/ehci-sysfs.c | 52 +++++++++++++++++++++++++++++++++--
drivers/usb/host/ehci.h | 1 +
4 files changed, 54 insertions(+), 4 deletions(-)

diff --git a/drivers/usb/host/ehci-hcd.c b/drivers/usb/host/ehci-hcd.c
index 8608ac513fb7..799262951f41 100644
--- a/drivers/usb/host/ehci-hcd.c
+++ b/drivers/usb/host/ehci-hcd.c
@@ -526,6 +526,7 @@ static int ehci_init(struct usb_hcd *hcd)
hw->hw_qtd_next = EHCI_LIST_END(ehci);
ehci->async->qh_state = QH_STATE_LINKED;
hw->hw_alt_next = QTD_NEXT(ehci, ehci->async->dummy->qtd_dma);
+ ehci->nak_tune_hs = EHCI_TUNE_RL_HS;

/* clear interrupt enables, set irq latency */
if (log2_irq_thresh < 0 || log2_irq_thresh > 6)
diff --git a/drivers/usb/host/ehci-q.c b/drivers/usb/host/ehci-q.c
index 327630405695..ccb754893b5a 100644
--- a/drivers/usb/host/ehci-q.c
+++ b/drivers/usb/host/ehci-q.c
@@ -898,12 +898,12 @@ qh_make (
case USB_SPEED_HIGH: /* no TT involved */
info1 |= QH_HIGH_SPEED;
if (type == PIPE_CONTROL) {
- info1 |= (EHCI_TUNE_RL_HS << 28);
+ info1 |= ehci->nak_tune_hs << 28;
info1 |= 64 << 16; /* usb2 fixed maxpacket */
info1 |= QH_TOGGLE_CTL; /* toggle from qtd */
info2 |= (EHCI_TUNE_MULT_HS << 30);
} else if (type == PIPE_BULK) {
- info1 |= (EHCI_TUNE_RL_HS << 28);
+ info1 |= ehci->nak_tune_hs << 28;
/* The USB spec says that high speed bulk endpoints
* always use 512 byte maxpacket. But some device
* vendors decided to ignore that, and MSFT is happy
diff --git a/drivers/usb/host/ehci-sysfs.c b/drivers/usb/host/ehci-sysfs.c
index 8f75cb7b197c..d710d35282a6 100644
--- a/drivers/usb/host/ehci-sysfs.c
+++ b/drivers/usb/host/ehci-sysfs.c
@@ -145,19 +145,66 @@ static ssize_t uframe_periodic_max_store(struct device *dev,
}
static DEVICE_ATTR_RW(uframe_periodic_max);

+static ssize_t nak_tune_hs_show(struct device *dev,
+ struct device_attribute *attr,
+ char *buf)
+{
+ struct ehci_hcd *ehci;
+
+ ehci = hcd_to_ehci(dev_get_drvdata(dev));
+ return scnprintf(buf, PAGE_SIZE, "%d\n", ehci->nak_tune_hs);
+}
+
+static ssize_t nak_tune_hs_store(struct device *dev,
+ struct device_attribute *attr,
+ const char *buf, size_t count)
+{
+ struct ehci_hcd *ehci;
+ unsigned val;
+ unsigned long flags;
+
+ ehci = hcd_to_ehci(dev_get_drvdata(dev));
+
+ if (kstrtouint(buf, 0, &val) < 0)
+ return -EINVAL;
+
+ if (val >= 15) {
+ ehci_info(ehci, "invalid value for nak_tune_hs (%d)\n", val);
+ return -EINVAL;
+ }
+
+ spin_lock_irqsave (&ehci->lock, flags);
+ ehci->nak_tune_hs = val;
+ spin_unlock_irqrestore (&ehci->lock, flags);
+ return count;
+}
+
+static DEVICE_ATTR_RW(nak_tune_hs);

static inline int create_sysfs_files(struct ehci_hcd *ehci)
{
struct device *controller = ehci_to_hcd(ehci)->self.controller;
int i = 0;

+ i = device_create_file(controller, &dev_attr_nak_tune_hs);
+ if (i)
+ goto out;
+
+ i = device_create_file(controller, &dev_attr_uframe_periodic_max);
+ if (i)
+ goto out_nak;
+
/* with integrated TT there is no companion! */
if (!ehci_is_TDI(ehci))
i = device_create_file(controller, &dev_attr_companion);
if (i)
- goto out;
+ goto out_all;

- i = device_create_file(controller, &dev_attr_uframe_periodic_max);
+ return 0;
+out_all:
+ device_remove_file(controller, &dev_attr_uframe_periodic_max);
+out_nak:
+ device_remove_file(controller, &dev_attr_nak_tune_hs);
out:
return i;
}
@@ -170,5 +217,6 @@ static inline void remove_sysfs_files(struct ehci_hcd *ehci)
if (!ehci_is_TDI(ehci))
device_remove_file(controller, &dev_attr_companion);

+ device_remove_file(controller, &dev_attr_nak_tune_hs);
device_remove_file(controller, &dev_attr_uframe_periodic_max);
}
diff --git a/drivers/usb/host/ehci.h b/drivers/usb/host/ehci.h
index c8e9a48e1d51..1fb6f1ad8128 100644
--- a/drivers/usb/host/ehci.h
+++ b/drivers/usb/host/ehci.h
@@ -154,6 +154,7 @@ struct ehci_hcd { /* one per controller */
dma_addr_t periodic_dma;
struct list_head intr_qh_list;
unsigned i_thresh; /* uframes HC might cache */
+ u32 nak_tune_hs;

union ehci_shadow *pshadow; /* mirror hw periodic table */
struct list_head intr_unlink_wait;
--
2.19.1
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