From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wr0-f194.google.com ([209.85.128.194]:41667 "EHLO mail-wr0-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934938AbeBMMOS (ORCPT ); Tue, 13 Feb 2018 07:14:18 -0500 From: Philipp Rossak To: wens@csie.org, a.zummo@towertech.it, alexandre.belloni@free-electrons.com Cc: linux-kernel@vger.kernel.org, linux-sunxi@googlegroups.com, linux-rtc@vger.kernel.org Subject: [PATCH v2] rtc: ac100: Fix ac100 determine rate bug Date: Tue, 13 Feb 2018 13:14:14 +0100 Message-Id: <20180213121414.7000-1-embed3d@gmail.com> Sender: linux-rtc-owner@vger.kernel.org List-ID: This patch fixes a bug, that prevents the Allwinner A83T and the A80 from a successful boot. You can find the shortend trace below: Unable to handle kernel NULL pointer dereference at virtual address 00000000 pgd = (ptrval) [00000000] *pgd=00000000 Internal error: Oops: 5 [#1] SMP ARM Modules linked in: CPU: 0 PID: 49 Comm: kworker/0:1 Not tainted 4.15.0-10190-gb89e32ccd1be #2 Hardware name: Allwinner sun8i Family Workqueue: events deferred_probe_work_func PC is at clk_hw_get_rate+0x0/0x34 LR is at ac100_clkout_determine_rate+0x48/0x19c [ ... ] (clk_hw_get_rate) from (ac100_clkout_determine_rate+0x48/0x19c) (ac100_clkout_determine_rate) from (clk_core_set_rate_nolock+0x3c/0x1a0) (clk_core_set_rate_nolock) from (clk_set_rate+0x30/0x88) (clk_set_rate) from (of_clk_set_defaults+0x200/0x364) (of_clk_set_defaults) from (platform_drv_probe+0x18/0xb0) To fix that bug, we first check if the return of the clk_hw_get_parent_by_index is non zero. If it is zero we skip that clock parent. The BUG report could be found here: https://lkml.org/lkml/2018/2/10/198 Fixes: 04940631b8d2 ("rtc: ac100: Add clk output support") Signed-off-by: Philipp Rossak --- Changes in v2: * add tag Fixes: ... to commit message * add comment to if statement why we are doing this check drivers/rtc/rtc-ac100.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) diff --git a/drivers/rtc/rtc-ac100.c b/drivers/rtc/rtc-ac100.c index 8ff9dc3fe5bf..ba73201d8cc1 100644 --- a/drivers/rtc/rtc-ac100.c +++ b/drivers/rtc/rtc-ac100.c @@ -183,7 +183,17 @@ static int ac100_clkout_determine_rate(struct clk_hw *hw, for (i = 0; i < num_parents; i++) { struct clk_hw *parent = clk_hw_get_parent_by_index(hw, i); - unsigned long tmp, prate = clk_hw_get_rate(parent); + unsigned long tmp, prate; + + /* + * We purposefully left open the possibility to use the clock + * from the codec side but it is not implemented right now. + * Thus we need to check if the parent exists. + */ + if (!parent) + continue; + + prate = clk_hw_get_rate(parent); tmp = ac100_clkout_round_rate(hw, req->rate, prate); -- 2.11.0