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Date: Sat, 13 Aug 2016 18:42:51 +0100 From: Ben Hutchings <ben@...adent.org.uk> To: linux-kernel@...r.kernel.org, stable@...r.kernel.org CC: akpm@...ux-foundation.org, "Thomas Petazzoni" <thomas.petazzoni@...e-electrons.com>, "Mathias Nyman" <mathias.nyman@...ux.intel.com>, "Greg Kroah-Hartman" <gregkh@...uxfoundation.org> Subject: [PATCH 3.16 172/305] usb: xhci-plat: properly handle probe deferral for devm_clk_get() 3.16.37-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Thomas Petazzoni <thomas.petazzoni@...e-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@...e-electrons.com> Signed-off-by: Mathias Nyman <mathias.nyman@...ux.intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org> [bwh: Backported to 3.16: correct error label here is unmap_registers] Signed-off-by: Ben Hutchings <ben@...adent.org.uk> --- 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 @@ -154,6 +154,9 @@ static int xhci_plat_probe(struct platfo ret = clk_prepare_enable(clk); if (ret) goto unmap_registers; + } else if (PTR_ERR(clk) == -EPROBE_DEFER) { + ret = -EPROBE_DEFER; + goto unmap_registers; } if (of_device_is_compatible(pdev->dev.of_node,
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