| From de95c40d5beaa47f6dc8fe9ac4159b4672b51523 Mon Sep 17 00:00:00 2001 |
| From: Thomas Petazzoni <thomas.petazzoni@free-electrons.com> |
| Date: Wed, 1 Jun 2016 18:09:09 +0300 |
| Subject: usb: xhci-plat: properly handle probe deferral for devm_clk_get() |
| |
| 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); |