This is a note to let you know that I've just added the patch titled
usb: dwc3: ulpi: Replace CPU-based busyloop with Protocol-based one
to my usb git tree which can be found at git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git in the usb-linus branch.
The patch will show up in the next release of the linux-next tree (usually sometime within the next 24 hours during the week.)
The patch will hopefully also be merged in Linus's tree for the next -rc kernel release.
If you have any questions about this process, please let me know.
From fca3f138105727c3a22edda32d02f91ce1bf11c9 Mon Sep 17 00:00:00 2001
From: Serge Semin Sergey.Semin@baikalelectronics.ru Date: Thu, 10 Dec 2020 11:50:07 +0300 Subject: usb: dwc3: ulpi: Replace CPU-based busyloop with Protocol-based one
Originally the procedure of the ULPI transaction finish detection has been developed as a simple busy-loop with just decrementing counter and no delays. It's wrong since on different systems the loop will take a different time to complete. So if the system bus and CPU are fast enough to overtake the ULPI bus and the companion PHY reaction, then we'll get to take a false timeout error. Fix this by converting the busy-loop procedure to take the standard bus speed, address value and the registers access mode into account for the busy-loop delay calculation.
Here is the way the fix works. It's known that the ULPI bus is clocked with 60MHz signal. In accordance with [1] the ULPI bus protocol is created so to spend 5 and 6 clock periods for immediate register write and read operations respectively, and 6 and 7 clock periods - for the extended register writes and reads. Based on that we can easily pre-calculate the time which will be needed for the controller to perform a requested IO operation. Note we'll still preserve the attempts counter in case if the DWC USB3 controller has got some internals delays.
[1] UTMI+ Low Pin Interface (ULPI) Specification, Revision 1.1, October 20, 2004, pp. 30 - 36.
Fixes: 88bc9d194ff6 ("usb: dwc3: add ULPI interface support") Acked-by: Heikki Krogerus heikki.krogerus@linux.intel.com Signed-off-by: Serge Semin Sergey.Semin@baikalelectronics.ru Link: https://lore.kernel.org/r/20201210085008.13264-3-Sergey.Semin@baikalelectron... Cc: stable stable@vger.kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/usb/dwc3/ulpi.c | 18 +++++++++++++++--- 1 file changed, 15 insertions(+), 3 deletions(-)
diff --git a/drivers/usb/dwc3/ulpi.c b/drivers/usb/dwc3/ulpi.c index 3cc4f4970c05..54c877f7b51d 100644 --- a/drivers/usb/dwc3/ulpi.c +++ b/drivers/usb/dwc3/ulpi.c @@ -7,6 +7,8 @@ * Author: Heikki Krogerus heikki.krogerus@linux.intel.com */
+#include <linux/delay.h> +#include <linux/time64.h> #include <linux/ulpi/regs.h>
#include "core.h" @@ -17,12 +19,22 @@ DWC3_GUSB2PHYACC_ADDR(ULPI_ACCESS_EXTENDED) | \ DWC3_GUSB2PHYACC_EXTEND_ADDR(a) : DWC3_GUSB2PHYACC_ADDR(a))
-static int dwc3_ulpi_busyloop(struct dwc3 *dwc) +#define DWC3_ULPI_BASE_DELAY DIV_ROUND_UP(NSEC_PER_SEC, 60000000L) + +static int dwc3_ulpi_busyloop(struct dwc3 *dwc, u8 addr, bool read) { + unsigned long ns = 5L * DWC3_ULPI_BASE_DELAY; unsigned int count = 1000; u32 reg;
+ if (addr >= ULPI_EXT_VENDOR_SPECIFIC) + ns += DWC3_ULPI_BASE_DELAY; + + if (read) + ns += DWC3_ULPI_BASE_DELAY; + while (count--) { + ndelay(ns); reg = dwc3_readl(dwc->regs, DWC3_GUSB2PHYACC(0)); if (reg & DWC3_GUSB2PHYACC_DONE) return 0; @@ -47,7 +59,7 @@ static int dwc3_ulpi_read(struct device *dev, u8 addr) reg = DWC3_GUSB2PHYACC_NEWREGREQ | DWC3_ULPI_ADDR(addr); dwc3_writel(dwc->regs, DWC3_GUSB2PHYACC(0), reg);
- ret = dwc3_ulpi_busyloop(dwc); + ret = dwc3_ulpi_busyloop(dwc, addr, true); if (ret) return ret;
@@ -71,7 +83,7 @@ static int dwc3_ulpi_write(struct device *dev, u8 addr, u8 val) reg |= DWC3_GUSB2PHYACC_WRITE | val; dwc3_writel(dwc->regs, DWC3_GUSB2PHYACC(0), reg);
- return dwc3_ulpi_busyloop(dwc); + return dwc3_ulpi_busyloop(dwc, addr, false); }
static const struct ulpi_ops dwc3_ulpi_ops = {