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From:   Alexander Dahl <ada@thorsis.com>
To:     linux-arm-kernel@lists.infradead.org
Cc:     Alexandre Belloni <alexandre.belloni@bootlin.com>,
        Boris Brezillon <boris.brezillon@bootlin.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Daniel Lezcano <daniel.lezcano@linaro.org>,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3 0/6] clocksource: rework Atmel TCB timer driver
Date:   Thu, 29 Mar 2018 17:11:08 +0200
Message-ID: <2097113.JiHb7Y1Uf1@ada>
In-Reply-To: <3478710.yJBBt3uoRT@ada>
References: <20180223171558.7037-1-alexandre.belloni@bootlin.com> <20180328155033.GH13942@piout.net> <3478710.yJBBt3uoRT@ada>
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Hei hei,

Am Donnerstag, 29. M=C3=A4rz 2018, 10:01:26 CEST schrieb Alexander Dahl:
> This is the result:
>=20
> INT                NAME          RATE             MAX
>  17 [vel     timer@fffa]  1837 Ints/s     (max:  1912)
>  26 [      vel     eth0]     3 Ints/s     (max:    11)

Above was with v4.16-rc7+, and CONFIG_ATMEL_CLOCKSOURCE_TCB=3Dy,=20
CONFIG_ATMEL_TCLIB=3Dn (as one might see in the name column).

Now, v4.16-rc7+, with CONFIG_ATMEL_CLOCKSOURCE_PIT=3Dy, CONFIG_ATMEL_TCLIB=
=3Dy,=20
CONFIG_ATMEL_TCB_CLKSRC=3Dy (old driver I guess):

INT                NAME          RATE             MAX
 19 [ vel     tc_clkevt]  1898 Ints/s     (max:  1945)
 26 [      vel     eth0]     3 Ints/s     (max:    11)

So the rates here are roughly the same with old and new driver and the same=
=20
kernel source. As Alexandre stated in IRC, the rates should be the same wit=
h=20
old and new driver on the otherwise same kernel source.

I just double checked it, and with the other clocksource on v4.16-rc7+ I ge=
t:

INT                NAME          RATE             MAX
 17 [vel     timer@fffa]  1904 Ints/s     (max:  1922)
 26 [      vel     eth0]     6 Ints/s     (max:     7)

The lower rates I reported yesterday were from older kernels v4.14.29-rt25 =
and=20
v4.15.13, so there might be the question why v4.16-rc7+ has a much higher r=
ate=20
with tc_clkevt? But there's no real difference between tc_clkevt and=20
timer@fffa=E2=80=A6 when both measured with v4.16-rc7+ on this target. I kn=
ow=20
Alexandre has lower rates though, may depend on other parameters.

So for completeness, I just tested the clean v4.16-rc7 without this patch=20
series:=20

INT                NAME          RATE             MAX
 19 [ vel     tc_clkevt]  1903 Ints/s     (max:  1930)
 26 [      vel     eth0]     7 Ints/s     (max:     7)

Basically the same for this one, too.

HTH & Greets
Alex