linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
To: linux-amlogic@lists.infradead.org, linux-clk@vger.kernel.org,
	jbrunet@baylibre.com, narmstrong@baylibre.com
Cc: linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org, mturquette@baylibre.com,
	sboyd@kernel.org,
	Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Subject: [RFC v1 0/7] Meson8b: make the CPU clock mutable
Date: Wed, 14 Nov 2018 23:57:18 +0100	[thread overview]
Message-ID: <20181114225725.2821-1-martin.blumenstingl@googlemail.com> (raw)

This allows changing the CPU clock on the 32-bit Amlogic Meson SoCs
(Meson8, Meson8b and Meson8m2).
CPU frequency scaling will be enabled with a separate series by adding
the CPU clock and the OPP tables to meson8.dtsi and meson8b.dtsi.

While changing the CPU frequency (sys_pll or any of it's post-dividers)
we need to run the CPU clock off the XTAL clock. Otherwise the system
will lock up because we need to disable the sys_pll to change it's
rate.

This also makes the clk-pll's .enable hook a no-op if the clock is
already enabled. Otherwise we're getting lockups when calling the
first clk_{prepare_}enable on the sys_pll or any of it's children (as
the CCF propagates the enable event up to the sys_pll). This is because
the .enable hook unconditionally disables and enables the clock.
However, we can't disable that clock (not even temporarily) if the CPU
is running off sys_pll.

Additionally this adds support for more M/N combinations in sys_pll to
achieve all of the OPPs on Meson8b and all OPPs <= 1608 MHz on Meson8
and Meson8m2.

Compared to Amlogic's 3.10 kernel there's one notable difference: we
are actually allowing changes to the sys_pll. Amlogic's kernel sets
sys_pll to a fixed rate during boot and then uses a timer generate a
"virtual clock rate" by toggling between various dividers (for example:
sys_pll is set to 1536MHz. to achieve 1008MHz they are toggling every
2500us between 1536MHZ and 768MHz so the average over <period, for
example one second> is 1008MHz).
I could reproduce any situation where changing sys_pll failed (for
example due to high temperature). To prove that I ran "stress --cpu 4"
for multiple hours and then cycled through all available CPU
frequencies (while keeping "stress" running in the background). This
worked fine on my Meson8b Odroid-C1 and EC-100 boards as well as my
Meson8m2 board.


Martin Blumenstingl (7):
  clk: meson: meson8b: run from the XTAL when changing the CPU frequency
  clk: meson: meson8b: do not use cpu_div3 for cpu_scale_out_sel
  clk: meson: clk-pll: check if the clock is already enabled
  clk: meson: clk-pll: add the is_enabled function in the clk_ops
  clk: meson: meson8b: mark the CPU clock as CLK_IS_CRITICAL
  clk: meson: meson8b: add support for more M/N values in sys_pll
  clk: meson: meson8b: allow changing the CPU clock tree

 drivers/clk/meson/clk-pll.c | 23 +++++++++
 drivers/clk/meson/meson8b.c | 94 +++++++++++++++++++++++++++++++++----
 2 files changed, 108 insertions(+), 9 deletions(-)

-- 
2.19.1


             reply	other threads:[~2018-11-14 22:57 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-11-14 22:57 Martin Blumenstingl [this message]
2018-11-14 22:57 ` [RFC v1 1/7] clk: meson: meson8b: run from the XTAL when changing the CPU frequency Martin Blumenstingl
2018-11-15  9:53   ` Jerome Brunet
2018-11-14 22:57 ` [RFC v1 2/7] clk: meson: meson8b: do not use cpu_div3 for cpu_scale_out_sel Martin Blumenstingl
2018-11-15  9:42   ` Jerome Brunet
2018-11-14 22:57 ` [RFC v1 3/7] clk: meson: clk-pll: check if the clock is already enabled Martin Blumenstingl
2018-11-15  9:14   ` Jerome Brunet
2018-11-14 22:57 ` [RFC v1 4/7] clk: meson: clk-pll: add the is_enabled function in the clk_ops Martin Blumenstingl
2018-11-15  9:16   ` Jerome Brunet
2018-11-14 22:57 ` [RFC v1 5/7] clk: meson: meson8b: mark the CPU clock as CLK_IS_CRITICAL Martin Blumenstingl
2018-11-15  9:46   ` Jerome Brunet
2018-11-14 22:57 ` [RFC v1 6/7] clk: meson: meson8b: add support for more M/N values in sys_pll Martin Blumenstingl
2018-11-15  9:41   ` Jerome Brunet
2018-11-14 22:57 ` [RFC v1 7/7] clk: meson: meson8b: allow changing the CPU clock tree Martin Blumenstingl
2018-11-15  9:46   ` Jerome Brunet
2018-11-15 10:08 ` [RFC v1 0/7] Meson8b: make the CPU clock mutable Neil Armstrong

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=20181114225725.2821-1-martin.blumenstingl@googlemail.com \
    --to=martin.blumenstingl@googlemail.com \
    --cc=jbrunet@baylibre.com \
    --cc=linux-amlogic@lists.infradead.org \
    --cc=linux-arm-kernel@lists.infradead.org \
    --cc=linux-clk@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=mturquette@baylibre.com \
    --cc=narmstrong@baylibre.com \
    --cc=sboyd@kernel.org \
    --subject='Re: [RFC v1 0/7] Meson8b: make the CPU clock mutable' \
    /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).