From: Alexandre Belloni <alexandre.belloni@bootlin.com>
To: Philipp Rossak <embed3d@gmail.com>
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
Date: Thu, 1 Mar 2018 10:59:44 +0100 [thread overview]
Message-ID: <20180301095944.GT1479@piout.net> (raw)
In-Reply-To: <20180226211901.9805-1-embed3d@gmail.com>
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 <embed3d@gmail.com>
> ---
>
> 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
prev parent reply other threads:[~2018-03-01 9:59 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-02-26 21:19 [PATCH v4] rtc: ac100: Fix ac100 determine rate bug Philipp Rossak
2018-02-27 9:09 ` Maxime Ripard
2018-03-01 9:59 ` Alexandre Belloni [this message]
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