Message-Id: <20210702225145.2643303-1-martin.blumenstingl@googlemail.com>
Date:   Sat,  3 Jul 2021 00:51:39 +0200
From:   Martin Blumenstingl <martin.blumenstingl@...glemail.com>
To:     linux-clk@...r.kernel.org, sboyd@...nel.org
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Martin Blumenstingl <martin.blumenstingl@...glemail.com>
Subject: [PATCH v1 0/6] clk: switch dividers to .determine_rate

This is a continuation of patch #2 ("clk: divider: Switch from
.round_rate to .determine_rate by default", [0]) from my other series:
"clk: meson: rounding for fast clocks on 32-bit SoCs" [1]

That patch caused NULL dereferences in various drivers which are still
accessing clk_divider_ops.round_rate directly (which got removed in the
mentioned patch).

Guenter Roeck found this issue first on Freescale i.MX6 Ultralite and
reported it here: [2]
Later on Marek Szyprowski reported that BCM2835 is also affected: [3]

With this improved version of the patch I am taking a more definsive
approach as suggested by Stephen Boyd. Instead of dropping
clk_divider_ops.round_rate we're now keeping it and adding
clk_divider_ops.determine_rate. CCF core already prefers
.determine_rate over .round_rate so the new implementation is used by
default.

To simplify the transition to .determine_rate in the future this
updated series now has five extra patches to port over the drivers
which used clk_divider_ops.round_rate over to
clk_divider_ops.determine_rate.

I have compile-tested all patches. Additionally the imx patch is
runtime-tested using Guenter Roeck's suggestion (thanks!):
$ qemu-system-arm -M mcimx6ul-evk -m 512M -kernel arch/arm/boot/zImage -dtb arch/arm/boot/dts/imx6ul-14x14-evk.dtb -append "console=ttymxc0 loglevel=8 earlycon earlyprintk" -monitor stdio

This series is based on clk-next commit 783d08bd02f5d3 ("Revert "clk:
divider: Switch from .round_rate to .determine_rate by default"clk-next").
My suggestion is to let all patches go through clk-next (instead of
individual driver trees) as the first patch in this series is a pre-
condition for the other ones.


[0] https://patchwork.kernel.org/project/linux-clk/patch/20210627223959.188139-3-martin.blumenstingl@googlemail.com/
[1] https://patchwork.kernel.org/project/linux-clk/cover/20210627223959.188139-1-martin.blumenstingl@googlemail.com/
[2] https://lore.kernel.org/linux-clk/20210701202540.GA1085600@roeck-us.net/
[3] https://lore.kernel.org/linux-clk/e21c34a3-2586-057d-013b-6c8ec094d1a8@samsung.com/


Martin Blumenstingl (6):
  clk: divider: Implement and wire up .determine_rate by default
  clk: imx: clk-divider-gate: Switch to clk_divider.determine_rate
  clk: bcm2835: Switch to clk_divider.determine_rate
  clk: stm32f4: Switch to clk_divider.determine_rate
  clk: stm32h7: Switch to clk_divider.determine_rate
  clk: stm32mp1: Switch to clk_divider.determine_rate

 drivers/clk/bcm/clk-bcm2835.c      |  9 ++++-----
 drivers/clk/clk-divider.c          | 23 +++++++++++++++++++++++
 drivers/clk/clk-stm32f4.c          |  8 ++++----
 drivers/clk/clk-stm32h7.c          |  8 ++++----
 drivers/clk/clk-stm32mp1.c         | 10 +++-------
 drivers/clk/imx/clk-divider-gate.c | 10 +++++-----
 6 files changed, 43 insertions(+), 25 deletions(-)

-- 
2.32.0

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