releases/4.6.4/usb-xhci-plat-properly-handle-probe-deferral-for-devm_clk_get.patch

   1 From de95c40d5beaa47f6dc8fe9ac4159b4672b51523 Mon Sep 17 00:00:00 2001
   2 From: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
   3 Date: Wed, 1 Jun 2016 18:09:09 +0300
   4 Subject: usb: xhci-plat: properly handle probe deferral for devm_clk_get()
   5
   6 From: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
   7
   8 commit de95c40d5beaa47f6dc8fe9ac4159b4672b51523 upstream.
   9
  10 On some platforms, the clocks might be registered by a platform
  11 driver. When this is the case, the clock platform driver may very well
  12 be probed after xhci-plat, in which case the first probe() invocation
  13 of xhci-plat will receive -EPROBE_DEFER as the return value of
  14 devm_clk_get().
  15
  16 The current code handles that as a normal error, and simply assumes
  17 that this means that the system doesn't have a clock for the XHCI
  18 controller, and continues probing without calling
  19 clk_prepare_enable(). Unfortunately, this doesn't work on systems
  20 where the XHCI controller does have a clock, but that clock is
  21 provided by another platform driver. In order to fix this situation,
  22 we handle the -EPROBE_DEFER error condition specially, and abort the
  23 XHCI controller probe(). It will be retried later automatically, the
  24 clock will be available, devm_clk_get() will succeed, and the probe()
  25 will continue with the clock prepared and enabled as expected.
  26
  27 In practice, such issue is seen on the ARM64 Marvell 7K/8K platform,
  28 where the clocks are registered by a platform driver.
  29
  30 Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
  31 Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
  32 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  33
  34 ---
  35  drivers/usb/host/xhci-plat.c |    3 +++
  36  1 file changed, 3 insertions(+)
  37
  38 --- a/drivers/usb/host/xhci-plat.c
  39 +++ b/drivers/usb/host/xhci-plat.c
  40 @@ -194,6 +194,9 @@ static int xhci_plat_probe(struct platfo
  41                 ret = clk_prepare_enable(clk);
  42                 if (ret)
  43                         goto put_hcd;
  44 +       } else if (PTR_ERR(clk) == -EPROBE_DEFER) {
  45 +               ret = -EPROBE_DEFER;
  46 +               goto put_hcd;
  47         }
  48
  49         xhci = hcd_to_xhci(hcd);