linux-kernel - Re: [PATCH v2 0/2] clocksource/meson6

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Message-ID: <a83b92fb-5950-01b8-521d-7b05939dce3a@linaro.org>
Date:   Fri, 23 Nov 2018 07:15:19 +0100
From:   Daniel Lezcano <daniel.lezcano@...aro.org>
To:     Martin Blumenstingl <martin.blumenstingl@...glemail.com>
Cc:     linux-amlogic@...ts.infradead.org, linux-kernel@...r.kernel.org,
        tglx@...utronix.de, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v2 0/2] clocksource/meson6_timer: implement ARM delay
 timer

On 22/11/2018 23:12, Martin Blumenstingl wrote:
> Hi Daniel,
> 
> On Sun, Nov 18, 2018 at 2:27 AM Daniel Lezcano
> <daniel.lezcano@...aro.org> wrote:
>>
>> On 15/11/2018 23:46, Martin Blumenstingl wrote:
>>> While trying to add support for the ARM TWD Timer and the ARM Global
>>> Timer on Meson8, Meson8b and Meson8m2 (ARM Cortex-A5 and Cortex-A9 SoCs)
>>> I did a review of the existing driver.
>>> Unfortunately I found it hard to review because the pre-processor
>>> #defines did not match the names from the public S805 datasheet. Thus
>>> patch #1 adjusts these. No functional changes here, this is just
>>> preparation work for patch #2.
>>>
>>> Using the ARM Global Timer (drivers/clocksource/arm_global_timer.c)
>>> would have given us a timer-based delay implementation (so udelay() and
>>> friends would use the timer instead of using a loop-based delay
>>> implementation). Unfortunately we can't use the ARM Global Timer yet
>>> because it's input clock is derived from the CPU clock (which can change
>>> once we enable CPU frequency scaling on these SoCs, for which I will be
>>> sending patches in the near future).
>>> Amlogic's 3.10 kernel uses Timer E as delay timer which (with the
>>> current configuration) has a resolution of 1us. So patch #2 uses
>>> register_current_timer_delay() to register Timer E as ARM delay timer
>>> (which will be especially useful as we have to use udelay() when
>>> changing the CPU clocks during DVFS).
>>>
>>>
>>> Changes since v1 at [0]:
>>> - convert the enums for the input clock (meson6_timera_input_clock and
>>>   meson6_timere_input_clock) to simple #defines as these are register
>>>   values and not something driver-internal. All other register values
>>>   are #defines so it makes sense that these are #defines as well.
>>>
>>>
>>> [0] https://patchwork.kernel.org/cover/10658591/
>>>
>>>
>>> Martin Blumenstingl (2):
>>>   clocksource: meson6_timer: use register names from the datasheet
>>>   clocksource: meson6_timer: implement ARM delay timer
>>>
>>>  drivers/clocksource/meson6_timer.c | 128 +++++++++++++++++++----------
>>>  1 file changed, 85 insertions(+), 43 deletions(-)
>>
>> Both applied, thanks!
> thank you for taking my patches
> 
> I have one question more: can you please push these patches to a
> repository/branch which is included in -next?
> I'm asking because I'd like to send patches that enable CPU frequency
> scaling on Meson8, Meson8b and Meson8m2. The code to change the CPU
> clock calls udelay(), which (in this special case) needs a delay timer
> to work properly (we can't use jiffies as we're using udelay() *while*
> changing the CPU clock).

branch pushed [1], should appear in linux-next very soon.

  -- Daniel

[1]
https://git.linaro.org/people/daniel.lezcano/linux.git/log/?h=clockevents/next


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