From: Paul Burton <paulburton@kernel.org>
To: Paul Cercueil <paul@crapouillou.net>, Zhou Yanjie <zhouyanjie@zoho.com>
Cc: linux-mips@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-clk@vger.kernel.org, devicetree@vger.kernel.org,
robh+dt@kernel.org, paul.burton@mips.com,
mturquette@baylibre.com, sboyd@kernel.org, mark.rutland@arm.com,
syq@debian.org, sernia.zhou@foxmail.com, zhenwenjin@gmail.com
Subject: Re: [PATCH 1/5] clk: Ingenic: Adjust code to make it compatible with X1830.
Date: Tue, 10 Dec 2019 14:55:03 -0800 [thread overview]
Message-ID: <20191210225503.nf77ksu2sznngbp2@lantea.localdomain> (raw)
In-Reply-To: <1575026622.3.2@crapouillou.net>
Hi Paul, Zhou,
On Fri, Nov 29, 2019 at 12:23:42PM +0100, Paul Cercueil wrote:
> > > > @@ -93,8 +93,17 @@ ingenic_pll_recalc_rate(struct clk_hw *hw,
> > > > \x7f\x7funsigned long parent_rate)
> > > > n += pll_info->n_offset;
> > > > od_enc = ctl >> pll_info->od_shift;
> > > > od_enc &= GENMASK(pll_info->od_bits - 1, 0);
> > > > - bypass = !pll_info->no_bypass_bit &&
> > > > - !!(ctl & BIT(pll_info->bypass_bit));
> > > > +
> > > > + if (pll_info->version >= CGU_X1830) {
> > > > + spin_lock_irqsave(&cgu->lock, flags);
> > > > + ctl = readl(cgu->base + pll_info->reg[0]);
> > > > + spin_unlock_irqrestore(&cgu->lock, flags);
> > >
> > > Why the spinlock?
> > >
> >
> > The original code used spinlock when reading the control register,
> > so when reading this new control register, I think it should also
> > be added with spinlock.
>
> Well, the original code looks wrong to me. There's nothing to protect here.
>
> Maybe @Paul Burton can shed some light?
I wish I could remember, but I agree it seems pointless here. The only
way I can think it could be of any use is if writes to the CGU register
we're accessing aren't atomic (ie. if we could observe a partially
completed write), but I don't believe that's the case.
So Zhou, if you want to drop the spinlock here from your X1830 path &
ideally also add a patch to remove it in the non-X1830 path that would
be great.
Thanks,
Paul
next prev parent reply other threads:[~2019-12-10 22:54 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-27 3:32 clk: Ingenic: Add support for the X1830 and add USB clk for X1000 Zhou Yanjie
2019-11-27 3:32 ` [PATCH 1/5] clk: Ingenic: Adjust code to make it compatible with X1830 Zhou Yanjie
2019-11-27 17:37 ` Paul Cercueil
2019-11-28 6:29 ` Zhou Yanjie
2019-11-29 11:23 ` Paul Cercueil
2019-12-10 22:55 ` Paul Burton [this message]
2019-11-27 3:32 ` [PATCH 2/5] dt-bindings: clock: Add X1830 bindings Zhou Yanjie
2019-12-05 20:38 ` Rob Herring
2019-11-27 3:32 ` [PATCH 3/5] clk: Ingenic: Add CGU driver for X1830 Zhou Yanjie
2019-11-27 3:32 ` [PATCH 4/5] dt-bindings: clock: Add USB OTG clock for X1000 Zhou Yanjie
2019-11-27 17:19 ` Paul Cercueil
2019-11-28 5:44 ` Zhou Yanjie
2019-11-27 3:32 ` [PATCH 5/5] clk: Ingenic: " Zhou Yanjie
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20191210225503.nf77ksu2sznngbp2@lantea.localdomain \
--to=paulburton@kernel.org \
--cc=devicetree@vger.kernel.org \
--cc=linux-clk@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mips@vger.kernel.org \
--cc=mark.rutland@arm.com \
--cc=mturquette@baylibre.com \
--cc=paul.burton@mips.com \
--cc=paul@crapouillou.net \
--cc=robh+dt@kernel.org \
--cc=sboyd@kernel.org \
--cc=sernia.zhou@foxmail.com \
--cc=syq@debian.org \
--cc=zhenwenjin@gmail.com \
--cc=zhouyanjie@zoho.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).