From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933402AbcGGBb6 (ORCPT ); Wed, 6 Jul 2016 21:31:58 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:50069 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933078AbcGGBTe (ORCPT ); Wed, 6 Jul 2016 21:19:34 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Thomas Petazzoni , Mathias Nyman Subject: [PATCH 4.6 25/31] usb: xhci-plat: properly handle probe deferral for devm_clk_get() Date: Wed, 6 Jul 2016 18:19:15 -0700 Message-Id: <20160707011558.528685856@linuxfoundation.org> X-Mailer: git-send-email 2.9.0 In-Reply-To: <20160707011557.518104444@linuxfoundation.org> References: <20160707011557.518104444@linuxfoundation.org> User-Agent: quilt/0.64 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 4.6-stable review patch. If anyone has any objections, please let me know. ------------------ From: Thomas Petazzoni 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 Signed-off-by: Mathias Nyman Signed-off-by: Greg Kroah-Hartman --- 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);