LKML Archive on lore.kernel.org
help / color / mirror / Atom feed
From: Jerome Brunet <jbrunet@baylibre.com>
To: Stephen Boyd <sboyd@codeaurora.org>
Cc: Michael Turquette <mturquette@baylibre.com>,
	linux-clk@vger.kernel.org, linux-kernel@vger.kernel.org,
	Russell King <linux@armlinux.org.uk>,
	Linus Walleij <linus.walleij@linaro.org>,
	Quentin Schulz <quentin.schulz@free-electrons.com>,
	Kevin Hilman <khilman@baylibre.com>,
	Maxime Ripard <maxime.ripard@free-electrons.com>
Subject: Re: [PATCH v5 00/10] clk: implement clock rate protection mechanism
Date: Fri, 02 Feb 2018 13:50:28 +0100	[thread overview]
Message-ID: <1517575828.3153.23.camel@baylibre.com> (raw)
In-Reply-To: <20180201174307.GC23162@codeaurora.org>

On Thu, 2018-02-01 at 09:43 -0800, Stephen Boyd wrote:
> > > > Applied to clk-protect-rate, with the exception that I did not apply
> > > > "clk: fix CLK_SET_RATE_GATE with clock rate protection" as it breaks
> > > > qcom clk code.
> > > > 
> > > > Stephen, do you plan to fix up the qcom clock code so that the
> > > > SET_RATE_GATE improvement can go in?
> > > > 
> > > 
> > > I started working on it a while back. Let's see if I can finish
> > > it off this weekend.
> > > 
> > 
> > Hi Stephen,
> > 
> > Have you been able find something to fix the qcom code regarding this issue ?
> > 
> 
> This is what I have. I'm unhappy with a few things. First, I made
> a spinlock for each clk, which is overkill. Most likely, just a
> single spinlock is needed per clk-controller device. Second, I
> haven't finished off the branch/gate part, so gating/ungating of
> branches needs to be locked as well to prevent branches from
> turning on while rates change. And finally, the 'branches' list is
> duplicating a bunch of information about the child clks of an
> RCG, so it feels like we need a core framework API to enable and
> disable clks forcibly while remembering what is enabled/disabled
> or at least to walk the clk tree and call some function.

Looks similar to Mike's CCR idea ;)

> 
> The spinlock per clk-controller is duplicating the regmap lock we
> already have, so we may want a regmap API to grab the lock, and
> then another regmap API to do reads/writes without grabbing the
> lock, and then finally release the lock with a regmap unlock API.

There is 'regsequence' for multiple write in a burst, but that's only if you do
write only ... I suppose you are more in read/update/writeback mode, so it
probably does not help much.

Maybe we could extend regmap's regsequence, to do a sequence of
regmap_update_bits() ?

Another possibility could be to provide your own lock/unlock ops when
registering the regmap. With this, you might be able to supply your own spinlock
to regmap. This is already supported by regmap, would it help ?

> This part is mostly an optimization, but it would be nice to have
> so that multiple writes could be done in sequence. This way, the
> RCG code could do the special locking sequence and the branch
> code could do the fire and forget single bit update.

  reply	other threads:[~2018-02-02 12:51 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-12-01 21:51 Jerome Brunet
2017-12-01 21:51 ` [PATCH v5 01/10] clk: fix incorrect usage of ENOSYS Jerome Brunet
2017-12-01 21:51 ` [PATCH v5 02/10] clk: take the prepare lock out of clk_core_set_parent Jerome Brunet
2017-12-01 21:51 ` [PATCH v5 03/10] clk: add clk_core_set_phase_nolock function Jerome Brunet
2017-12-01 21:51 ` [PATCH v5 04/10] clk: rework calls to round and determine rate callbacks Jerome Brunet
2017-12-01 21:51 ` [PATCH v5 05/10] clk: use round rate to bail out early in set_rate Jerome Brunet
2017-12-01 21:51 ` [PATCH v5 06/10] clk: add clock protection mechanism to clk core Jerome Brunet
2017-12-01 21:51 ` [PATCH v5 07/10] clk: cosmetic changes to clk_summary debugfs entry Jerome Brunet
2017-12-01 21:51 ` [PATCH v5 08/10] clk: fix CLK_SET_RATE_GATE with clock rate protection Jerome Brunet
2018-03-30  8:20   ` Jerome Brunet
2017-12-01 21:51 ` [PATCH v5 09/10] clk: add clk_rate_exclusive api Jerome Brunet
2017-12-01 21:52 ` [PATCH v5 10/10] clk: fix set_rate_range when current rate is out of range Jerome Brunet
2017-12-20  0:38 ` [PATCH v5 00/10] clk: implement clock rate protection mechanism Michael Turquette
2017-12-20 17:45   ` Jerome Brunet
2017-12-22  2:15   ` Stephen Boyd
2018-01-29  9:22     ` Jerome Brunet
2018-02-01 17:43       ` Stephen Boyd
2018-02-02 12:50         ` Jerome Brunet [this message]
2018-04-23 18:21           ` Michael Turquette
2018-05-24 14:53             ` Jerome Brunet

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=1517575828.3153.23.camel@baylibre.com \
    --to=jbrunet@baylibre.com \
    --cc=khilman@baylibre.com \
    --cc=linus.walleij@linaro.org \
    --cc=linux-clk@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux@armlinux.org.uk \
    --cc=maxime.ripard@free-electrons.com \
    --cc=mturquette@baylibre.com \
    --cc=quentin.schulz@free-electrons.com \
    --cc=sboyd@codeaurora.org \
    --subject='Re: [PATCH v5 00/10] clk: implement clock rate protection mechanism' \
    /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

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).