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[PATCH 4.6 25/31] usb: xhci-plat: properly handle probe deferral for devm_clk_get()

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4.6-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

commit de95c40d5beaa47f6dc8fe9ac4159b4672b51523 upstream.

On some platforms, the clocks might be registered by a platform
driver. When this is the case, the clock platform driver may very well
be probed after xhci-plat, in which case the first probe() invocation
of xhci-plat will receive -EPROBE_DEFER as the return value of
devm_clk_get().

The current code handles that as a normal error, and simply assumes
that this means that the system doesn't have a clock for the XHCI
controller, and continues probing without calling
clk_prepare_enable(). Unfortunately, this doesn't work on systems
where the XHCI controller does have a clock, but that clock is
provided by another platform driver. In order to fix this situation,
we handle the -EPROBE_DEFER error condition specially, and abort the
XHCI controller probe(). It will be retried later automatically, the
clock will be available, devm_clk_get() will succeed, and the probe()
will continue with the clock prepared and enabled as expected.

In practice, such issue is seen on the ARM64 Marvell 7K/8K platform,
where the clocks are registered by a platform driver.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/usb/host/xhci-plat.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/drivers/usb/host/xhci-plat.c
+++ b/drivers/usb/host/xhci-plat.c
@@ -194,6 +194,9 @@ static int xhci_plat_probe(struct platfo
 		ret = clk_prepare_enable(clk);
 		if (ret)
 			goto put_hcd;
+	} else if (PTR_ERR(clk) == -EPROBE_DEFER) {
+		ret = -EPROBE_DEFER;
+		goto put_hcd;
 	}
 
 	xhci = hcd_to_xhci(hcd);

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[PATCH 4.6 00/31] 4.6.4-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-07-07 03:20 +0200
  [PATCH 4.6 11/31] bpf, perf: delay release of BPF prog after grace period Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-07-07 03:20 +0200
  [PATCH 4.6 20/31] usb: musb: only restore devctl when session was set in backup Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-07-07 03:20 +0200
  [PATCH 4.6 03/31] net: Dont forget pr_fmt on net_dbg_ratelimited for CONFIG_DYNAMIC_DEBUG Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-07-07 03:20 +0200
  [PATCH 4.6 05/31] kcm: fix /proc memory leak Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-07-07 03:30 +0200
  [PATCH 4.6 07/31] netem: fix a use after free Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-07-07 03:30 +0200
  [PATCH 4.6 08/31] ipmr/ip6mr: Initialize the last assert time of mfc entries. Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-07-07 03:30 +0200
  [PATCH 4.6 04/31] sit: correct IP protocol used in ipip6_err Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-07-07 03:30 +0200
  [PATCH 4.6 25/31] usb: xhci-plat: properly handle probe deferral for devm_clk_get() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-07-07 03:40 +0200
  [PATCH 4.6 01/31] net_sched: fix pfifo_head_drop behavior vs backlog Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-07-07 03:40 +0200
  [PATCH 4.6 23/31] usb: musb: host: correct cppi dma channel for isoch transfer Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-07-07 03:40 +0200
  [PATCH 4.6 10/31] sock_diag: do not broadcast raw socket destruction Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-07-07 03:40 +0200
  [PATCH 4.6 18/31] usb: quirks: Fix sorting Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-07-07 03:40 +0200
  [PATCH 4.6 27/31] xhci: Fix handling timeouted commands on hosts in weird states. Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-07-07 03:40 +0200
  [PATCH 4.6 16/31] crypto: user - re-add size check for CRYPTO_MSG_GETALG Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-07-07 03:40 +0200
  [PATCH 4.6 30/31] usb: host: ehci-tegra: Grab the correct UTMI pads reset Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-07-07 03:40 +0200
  [PATCH 4.6 19/31] usb: quirks: Add no-lpm quirk for Acer C120 LED Projector Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-07-07 03:40 +0200
  [PATCH 4.6 21/31] usb: musb: Stop bulk endpoint while queue is rotated Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-07-07 03:40 +0200
  [PATCH 4.6 14/31] crypto: vmx - Increase priority of aes-cbc cipher Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-07-07 03:40 +0200
  [PATCH 4.6 26/31] USB: xhci: Add broken streams quirk for Frescologic device id 1009 Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-07-07 03:40 +0200
  [PATCH 4.6 02/31] act_ipt: fix a bind refcnt leak Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-07-07 03:40 +0200
  [PATCH 4.6 31/31] usb: dwc3: exynos: Fix deferred probing storm. Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-07-07 03:40 +0200
  [PATCH 4.6 17/31] USB: uas: Fix slave queue_depth not being set Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-07-07 03:40 +0200
  [PATCH 4.6 13/31] AX.25: Close socket connection on session completion Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-07-07 03:40 +0200
  [PATCH 4.6 12/31] neigh: Explicitly declare RCU-bh read side critical section in neigh_xmit() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-07-07 03:40 +0200
  [PATCH 4.6 28/31] USB: mos7720: delete parport Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-07-07 03:40 +0200
  [PATCH 4.6 15/31] crypto: ux500 - memmove the right size Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-07-07 03:40 +0200
  [PATCH 4.6 22/31] usb: musb: Ensure rx reinit occurs for shared_fifo endpoints Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-07-07 03:40 +0200
  Re: [PATCH 4.6 00/31] 4.6.4-stable review Heinz Diehl <htd+ml@fritha.org> - 2016-07-07 14:50 +0200
    Re: [PATCH 4.6 00/31] 4.6.4-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-07-07 21:20 +0200
  Re: [PATCH 4.6 00/31] 4.6.4-stable review Guenter Roeck <linux@roeck-us.net> - 2016-07-07 15:40 +0200
  Re: [PATCH 4.6 00/31] 4.6.4-stable review Shuah Khan <shuahkh@osg.samsung.com> - 2016-07-08 05:50 +0200
    Re: [PATCH 4.6 00/31] 4.6.4-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-07-09 07:20 +0200

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