xhci: tegra: Delay for disabling LFPS detector

BugLink: https://bugs.launchpad.net/bugs/1915195
commit da7e0c3c2909a3d9bf8acfe1db3cb213bd7febfb upstream.

Occasionally, we are seeing some SuperSpeed devices resumes right after
being directed to U3. This commits add 500us delay to ensure LFPS
detector is disabled before sending ACK to firmware.

[   16.099363] tegra-xusb 70090000.usb: entering ELPG
[   16.104343] tegra-xusb 70090000.usb: 2-1 isn't suspended: 0x0c001203
[   16.114576] tegra-xusb 70090000.usb: not all ports suspended: -16
[   16.120789] tegra-xusb 70090000.usb: entering ELPG failed

The register write passes through a few flop stages of 32KHz clock domain.
NVIDIA ASIC designer reviewed RTL and suggests 500us delay.

Cc: stable@vger.kernel.org
Signed-off-by: JC Kuo <jckuo@nvidia.com>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Link: https://lore.kernel.org/r/20210115161907.2875631-3-mathias.nyman@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: William Breathitt Gray <william.gray@canonical.com>

diff --git a/drivers/usb/host/xhci-tegra.c b/drivers/usb/host/xhci-tegra.c
index b8e24ccba9f3ec636f0a5eaccc21d0bad8e8e0be..6087b1fa530f8bca8dbd29f0cc36f8b0f7b40277 100644 (file)
--- a/drivers/usb/host/xhci-tegra.c
+++ b/drivers/usb/host/xhci-tegra.c
@@ -562,6 +562,13 @@ static void tegra_xusb_mbox_handle(struct tegra_xusb *tegra,
                                                                     enable);
                        if (err < 0)
                                break;
+
+                       /*
+                        * wait 500us for LFPS detector to be disabled before
+                        * sending ACK
+                        */
+                       if (!enable)
+                               usleep_range(500, 1000);
                }
 
                if (err < 0) {