From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S935301AbeBMNcO (ORCPT ); Tue, 13 Feb 2018 08:32:14 -0500 Received: from mail.free-electrons.com ([62.4.15.54]:53793 "EHLO mail.free-electrons.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S935222AbeBMNcN (ORCPT ); Tue, 13 Feb 2018 08:32:13 -0500 Date: Tue, 13 Feb 2018 14:32:01 +0100 From: Maxime Ripard To: Philipp Rossak Cc: wens@csie.org, a.zummo@towertech.it, alexandre.belloni@free-electrons.com, linux-kernel@vger.kernel.org, linux-sunxi@googlegroups.com, linux-rtc@vger.kernel.org Subject: Re: [linux-sunxi] [PATCH v2] rtc: ac100: Fix ac100 determine rate bug Message-ID: <20180213133201.kwq4aatpts7nerc2@flea.lan> References: <20180213121414.7000-1-embed3d@gmail.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="2wq7o7ftvpg2t3d5" Content-Disposition: inline In-Reply-To: <20180213121414.7000-1-embed3d@gmail.com> User-Agent: NeoMutt/20171215 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --2wq7o7ftvpg2t3d5 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Tue, Feb 13, 2018 at 01:14:14PM +0100, Philipp Rossak wrote: > This patch fixes a bug, that prevents the Allwinner A83T and the A80 > from a successful boot. You can find the shortend trace below: Since when is it there? > Unable to handle kernel NULL pointer dereference at virtual address > 00000000 > pgd =3D (ptrval) > [00000000] *pgd=3D00000000 > 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 >=20 > [ ... ] >=20 > (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) >=20 > 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. >=20 > The BUG report could be found here: https://lkml.org/lkml/2018/2/10/198 >=20 > Fixes: 04940631b8d2 ("rtc: ac100: Add clk output support") Should it be sent to stable? > Signed-off-by: Philipp Rossak > --- >=20 > Changes in v2: > * add tag Fixes: ... to commit message > * add comment to if statement why we are doing this check >=20 > drivers/rtc/rtc-ac100.c | 12 +++++++++++- > 1 file changed, 11 insertions(+), 1 deletion(-) >=20 > 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, > =20 > for (i =3D 0; i < num_parents; i++) { > struct clk_hw *parent =3D clk_hw_get_parent_by_index(hw, i); > - unsigned long tmp, prate =3D 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 =3D clk_hw_get_rate(parent); clk_hw_get_num_parents should return the exact number of parents, which is going to be 1 if you only have one parent, like all DTS seems to have. If not, then it should be explained in the comment and / or fixed properly. Maxime --=20 Maxime Ripard, Bootlin (formerly Free Electrons) Embedded Linux and Kernel engineering http://bootlin.com --2wq7o7ftvpg2t3d5 Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAABCAAdFiEE0VqZU19dR2zEVaqr0rTAlCFNr3QFAlqC6NAACgkQ0rTAlCFN r3RoSBAAk4nxd4PISUCAekki9exnTstZGIPl4RX3Jf5v/01wUTtXhzzABiXQcu8d im3SJUjnWDAy7DsEHso/jJAjSOsdylc3ZGvj8NfN9QUogC0aZ/PjrZg3xz5hEfnM 8sbklyElVvRR6iDHU+C8LQGpTDHviDPHaHkzHHOKQFUCXYucjYxyhaEL50Ih1XmQ /0BiAmo6cIvIB9oZg7LXNp9aYUlIqMzIE7YELiBCYqwVU6tXe4CKkzjMTTmhoPyf r/jMocvzAmtBIH1gKjrD88iCFxDK8bU9qyP/tUXCuEMOWC5pMUlNkU4E47cRYOgh UHPLJUyc3VGwr59HHE3sK1e3UIyokA60hvgZtT06o3+50pRUgAukf86vw9KCKSjU FXGL3VWGgAeN+rJmahu1dRlEKYjyO48Ppqtl3/sCuZa3uG3Cun4myhVtYF3f9lD9 7IjDV7zglXPRy4V0WxSkqtFAa6jh7GVs8e6Dns3C4zFQI2x/JR9bmM5X9OYgsEcl HbxoFyaqABYdb3p9vS5uOJKTSH4KjhbGiCmvmFuppkMqosF9O0JGEozUXKMZwIEP uK8XVAteNWF4lq5HkKR62Kelx0cSinV65WYPvMFii0Rk5RXMiLtZ46KAk3n9zUS2 jWGNt7vw2MZLlni+lpv6uJFlPb2qfCC6KqXVcSD0gTyAHmvWcVY= =rPDX -----END PGP SIGNATURE----- --2wq7o7ftvpg2t3d5--