From: Stephen Boyd <sboyd@kernel.org>
To: Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
Marek Vasut <marek.vasut@gmail.com>
Cc: linux-clk@vger.kernel.org, linux-renesas-soc@vger.kernel.org,
Marek Vasut <marek.vasut+renesas@gmail.com>,
Alexey Firago <alexey_firago@mentor.com>
Subject: Re: [PATCH] clk: vc5: Abort clock configuration without upstream clock
Date: Fri, 28 Dec 2018 14:30:16 -0800 [thread overview]
Message-ID: <154603621662.179992.6055107804025821286@swboyd.mtv.corp.google.com> (raw)
In-Reply-To: <3220bca0-486d-08a8-7575-34c961ed1261@gmail.com>
Quoting Marek Vasut (2018-12-16 09:14:29)
> On 12/16/2018 08:19 AM, Laurent Pinchart wrote:
> > Hi Marek,
> >
> > Thank you for the patch.
> >
> > On Saturday, 15 December 2018 02:55:19 EET Marek Vasut wrote:
> >> In case the upstream clock are not set, which can happen in case the
> >> VC5 has no valid upstream clock, the $src variable is used uninited
> >> by regmap_update_bits(). Check for this condition and return -EINVAL
> >> in such case.
> >
> > Note that the probe() function will fail in this case, so vc5_mux_set_parent()
> > won't be reached.
> >
> >> Note that in case the VC5 has no valid upstream clock, the VC5 can
> >> not operate correctly. That is a hardware property of the VC5. The
> >> internal oscilator present in some VC5 models is also considered
> >> upstream clock.
> >>
> >> Signed-off-by: Marek Vasut <marek.vasut+renesas@gmail.com>
> >> Cc: Alexey Firago <alexey_firago@mentor.com>
> >> Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> >> Cc: Stephen Boyd <sboyd@kernel.org>
> >> Cc: linux-renesas-soc@vger.kernel.org
> >> ---
> >> NOTE: This is an updated version of:
> >> https://patchwork.kernel.org/patch/10731699/
> >> ---
> >> drivers/clk/clk-versaclock5.c | 4 +++-
> >> 1 file changed, 3 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/drivers/clk/clk-versaclock5.c b/drivers/clk/clk-versaclock5.c
> >> index 5b393e711e94..b10801506518 100644
> >> --- a/drivers/clk/clk-versaclock5.c
> >> +++ b/drivers/clk/clk-versaclock5.c
> >> @@ -262,8 +262,10 @@ static int vc5_mux_set_parent(struct clk_hw *hw, u8
> >> index)
> >>
> >> if (vc5->clk_mux_ins == VC5_MUX_IN_XIN)
> >> src = VC5_PRIM_SRC_SHDN_EN_XTAL;
> >> - if (vc5->clk_mux_ins == VC5_MUX_IN_CLKIN)
> >> + else if (vc5->clk_mux_ins == VC5_MUX_IN_CLKIN)
> >> src = VC5_PRIM_SRC_SHDN_EN_CLKIN;
> >> + else
> >> + return -EINVAL;
> >> }
> >
> > I'd rather go for Stephen's approach if the goal is just to silence a warning
> > for a condition that can't happen in practice.
>
> Sure, probe will fail, but it's safer to handle the possibility that
> probe() is broken and this code is reached by properly handling the
> failure instead of doing something obviously wrong (like configuring the
> hardware with value 0).
I'm fine with this approach. Laurent?
next prev parent reply other threads:[~2018-12-28 22:30 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-12-15 0:55 [PATCH] clk: vc5: Abort clock configuration without upstream clock Marek Vasut
2018-12-16 7:19 ` Laurent Pinchart
2018-12-16 17:14 ` Marek Vasut
2018-12-28 22:30 ` Stephen Boyd [this message]
2018-12-29 16:34 ` Laurent Pinchart
2019-01-09 18:49 ` Stephen Boyd
2019-01-09 18:54 ` Stephen Boyd
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