From: Evan Green <evgreen@chromium.org>
To: Bjorn Andersson <bjorn.andersson@linaro.org>
Cc: Stephen Boyd <swboyd@chromium.org>,
Andy Gross <agross@kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
linux-arm-msm <linux-arm-msm@vger.kernel.org>,
Venkata Narendra Kumar Gutta <vnkgutta@codeaurora.org>
Subject: Re: [PATCH v2 0/2] Avoid regmap debugfs collisions in qcom llcc driver
Date: Wed, 9 Oct 2019 10:59:30 -0700 [thread overview]
Message-ID: <CAE=gft53-N+kWZKQO6YRAT0NBX_zrGYkqTUWOGrK2mT5Krf+3w@mail.gmail.com> (raw)
In-Reply-To: <20191009174622.GN6390@tuxbook-pro>
On Wed, Oct 9, 2019 at 10:46 AM Bjorn Andersson
<bjorn.andersson@linaro.org> wrote:
>
> On Wed 09 Oct 09:01 PDT 2019, Evan Green wrote:
>
> > On Tue, Oct 8, 2019 at 6:58 PM Stephen Boyd <swboyd@chromium.org> wrote:
> > >
> > > Quoting Bjorn Andersson (2019-10-08 16:55:04)
> > > > On Tue 08 Oct 16:45 PDT 2019, Stephen Boyd wrote:
> > > > > @@ drivers/soc/qcom/llcc-slice.c
> > > > >
> > > > > static struct llcc_drv_data *drv_data = (void *) -EPROBE_DEFER;
> > > > >
> > > > > --static const struct regmap_config llcc_regmap_config = {
> > > > > +-static struct regmap_config llcc_regmap_config = {
> > > > > - .reg_bits = 32,
> > > > > - .reg_stride = 4,
> > > > > - .val_bits = 32,
> > > > > @@ drivers/soc/qcom/llcc-slice.c: static struct regmap *qcom_llcc_init_mmio(struct
> > > > > {
> > > > > struct resource *res;
> > > > > void __iomem *base;
> > > > > -+ static struct regmap_config llcc_regmap_config = {
> > > > > ++ struct regmap_config llcc_regmap_config = {
> > > >
> > > > Now that this isn't static I like the end result better. Not sure about
> > > > the need for splitting it in two patches, but if Evan is happy I'll take
> > > > it.
> > > >
> > >
> > > Well I split it into bug fix and micro-optimization so backport choices
> > > can be made. But yeah, I hope Evan is happy enough to provide a
> > > reviewed-by tag!
> >
> > It's definitely better without the static local since it no longer has
> > the cognitive trap, but I still don't really get why we're messing
> > with the global v. local aspect of it. We're now inconsistent with
> > every other caller of this function, and for what exactly? We've
> > traded some data space for a call to memset() and some instructions. I
> > would have thought anecdotally that memory was the cheaper thing (ie
> > cpu speeds stopped increasing awhile ago, but memory is still getting
> > cheaper).
> >
>
> The reason for making the structure local is because it's being modified
> per instance, meaning it would still work as long as
> qcom_llcc_init_mmio() is never called concurrently for two llcc
> instances. But the correctness outweighs the performance degradation of
> setting it up on the stack in my view.
>
I hadn't considered the concurrency aspect of the change, since I had
anchored myself on the static local. I'm convinced. Might be worth
mentioning that in the commit message.
For the series:
Reviewed-by: Evan Green <evgreen@chromium.org>
next prev parent reply other threads:[~2019-10-09 18:00 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-08 23:45 [PATCH v2 0/2] Avoid regmap debugfs collisions in qcom llcc driver Stephen Boyd
2019-10-08 23:45 ` [PATCH v2 1/2] soc: qcom: llcc: Name regmaps to avoid collisions Stephen Boyd
2019-10-09 15:25 ` Evan Green
2019-10-08 23:45 ` [PATCH v2 2/2] soc: qcom: llcc: Move regmap config to local variable Stephen Boyd
2019-10-08 23:55 ` [PATCH v2 0/2] Avoid regmap debugfs collisions in qcom llcc driver Bjorn Andersson
2019-10-09 1:58 ` Stephen Boyd
2019-10-09 16:01 ` Evan Green
2019-10-09 17:46 ` Bjorn Andersson
2019-10-09 17:59 ` Evan Green [this message]
2019-10-10 3:57 ` Bjorn Andersson
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='CAE=gft53-N+kWZKQO6YRAT0NBX_zrGYkqTUWOGrK2mT5Krf+3w@mail.gmail.com' \
--to=evgreen@chromium.org \
--cc=agross@kernel.org \
--cc=bjorn.andersson@linaro.org \
--cc=linux-arm-msm@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=swboyd@chromium.org \
--cc=vnkgutta@codeaurora.org \
/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).