xhci: Convert xhci_handshake() to use readl_poll_timeout_atomic() [Linux 5.2]

xhci: Convert xhci_handshake() to use readl_poll_timeout_atomic() [Linux 5.2]

This Linux kernel change "xhci: Convert xhci_handshake() to use readl_poll_timeout_atomic()" is included in the Linux 5.2 release. This change is authored by Andrey Smirnov <andrew.smirnov [at] gmail.com> on Wed May 22 14:34:01 2019 +0300. The commit for this change in Linux stable tree is f7fac17 (patch).

xhci: Convert xhci_handshake() to use readl_poll_timeout_atomic()

Xhci_handshake() implements the algorithm already captured by
readl_poll_timeout_atomic(). Convert the former to use the latter to
avoid repetition.

Turned out this patch also fixes a bug on the AMD Stoneyridge platform
where usleep(1) sometimes takes over 10ms.
This means a 5 second timeout can easily take over 15 seconds which will
trigger the watchdog and reboot the system.

[Add info about patch fixing a bug to commit message -Mathias]
Signed-off-by: Andrey Smirnov <[email protected]>
Tested-by: Raul E Rangel <[email protected]>
Reviewed-by: Raul E Rangel <[email protected]>
Cc: <[email protected]>
Signed-off-by: Mathias Nyman <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>

There are 22 lines of Linux source code added/deleted in this change. Code changes to Linux kernel are as follows.

 drivers/usb/host/xhci.c | 22 ++++++++++------------
 1 file changed, 10 insertions(+), 12 deletions(-)

diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
index 048a675..20db378 100644
--- a/drivers/usb/host/xhci.c
+++ b/drivers/usb/host/xhci.c
@@ -9,6 +9,7 @@
  */

 #include <linux/pci.h>
+#include <linux/iopoll.h>
 #include <linux/irq.h>
 #include <linux/log2.h>
 #include <linux/module.h>
@@ -52,7 +53,6 @@ static bool td_on_ring(struct xhci_td *td, struct xhci_ring *ring)
    return false;
 }

-/* TODO: copied from ehci-hcd.c - can this be refactored? */
 /*
  * xhci_handshake - spin reading hc until handshake completes or fails
  * @ptr: address of hc register to be read
@@ -69,18 +69,16 @@ static bool td_on_ring(struct xhci_td *td, struct xhci_ring *ring)
 int xhci_handshake(void __iomem *ptr, u32 mask, u32 done, int usec)
 {
    u32 result;
+   int ret;

-   do {
-       result = readl(ptr);
-       if (result == ~(u32)0)      /* card removed */
-           return -ENODEV;
-       result &= mask;
-       if (result == done)
-           return 0;
-       udelay(1);
-       usec--;
-   } while (usec > 0);
-   return -ETIMEDOUT;
+   ret = readl_poll_timeout_atomic(ptr, result,
+                   (result & mask) == done ||
+                   result == U32_MAX,
+                   1, usec);
+   if (result == U32_MAX)      /* card removed */
+       return -ENODEV;
+
+   return ret;
 }

 /*

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