From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.bootlin.com ([62.4.15.54]:36489 "EHLO mail.bootlin.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S967231AbeCAJ74 (ORCPT ); Thu, 1 Mar 2018 04:59:56 -0500 Date: Thu, 1 Mar 2018 10:59:44 +0100 From: Alexandre Belloni To: Philipp Rossak Cc: wens@csie.org, a.zummo@towertech.it, maxime.ripard@bootlin.com, mturquette@baylibre.com, sboyd@codeaurora.org, linux-kernel@vger.kernel.org, linux-sunxi@googlegroups.com, linux-rtc@vger.kernel.org, linux-clk@vger.kernel.org, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH v4] rtc: ac100: Fix ac100 determine rate bug Message-ID: <20180301095944.GT1479@piout.net> References: <20180226211901.9805-1-embed3d@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <20180226211901.9805-1-embed3d@gmail.com> Sender: linux-rtc-owner@vger.kernel.org List-ID: On 26/02/2018 at 22:19:01 +0100, Philipp Rossak wrote: > This patch fixes a bug, that prevents the Allwinner A83T and the A80 > from a successful boot. > > The bug is there since v4.16-rc1 and appeared after the clk branch was > merged. > > 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 v4: > * add more information to the comment > Changes in v3: > * add information when the bug appeared > * make the comment more clear > 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 | 24 +++++++++++++++++++++++- > 1 file changed, 23 insertions(+), 1 deletion(-) > Applied, thanks. -- Alexandre Belloni, Bootlin (formerly Free Electrons) Embedded Linux and Kernel engineering https://bootlin.com