usb: dwc3: ulpi: Replace CPU-based busyloop with Protocol-based one

commit fca3f138105727c3a22edda32d02f91ce1bf11c9 upstream

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@baikalelectronics.ru
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[sudip: adjust context]
Signed-off-by: Sudip Mukherjee <sudipm.mukherjee@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/usb/dwc3/ulpi.c b/drivers/usb/dwc3/ulpi.c
index 231f7cf5c7b281929c96ad4cba46d34bc0cb7d4c..bc2dd9499ea034bab0a7076c2fc294161acd1943 100644 (file)
--- a/drivers/usb/dwc3/ulpi.c
+++ b/drivers/usb/dwc3/ulpi.c
@@ -10,6 +10,8 @@
  * published by the Free Software Foundation.
  */
 
+#include <linux/delay.h>
+#include <linux/time64.h>
 #include <linux/ulpi/regs.h>
 
 #include "core.h"
@@ -20,12 +22,22 @@
                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;
@@ -50,7 +62,7 @@ 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;
 
@@ -74,7 +86,7 @@ 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 = {