From: Andrew Lunn <andrew@lunn.ch>
To: Chris Healy <cphealy@gmail.com>
Cc: Andy Duan <fugang.duan@nxp.com>,
David Miller <davem@davemloft.net>,
netdev <netdev@vger.kernel.org>,
Florian Fainelli <f.fainelli@gmail.com>,
Heiner Kallweit <hkallweit1@gmail.com>
Subject: Re: [EXT] [PATCH net-next v2 1/3] net: ethernet: fec: Replace interrupt driven MDIO with polled IO
Date: Sun, 19 Apr 2020 02:35:01 +0200 [thread overview]
Message-ID: <20200419003501.GE836632@lunn.ch> (raw)
In-Reply-To: <CAFXsbZpVSiMYpUaOR=+UEGBgx5kSTzGcftbPe=PPkj_xWhy=bA@mail.gmail.com>
On Sat, Apr 18, 2020 at 03:39:17PM -0700, Chris Healy wrote:
> I did some profiling using an oscilloscope with my NXP Vybrid based
> platform to see what different "sleep_us" values resulted in for start
> of MDIO to start of MDIO transaction times. Here's what I found:
>
> 0 - ~38us to ~40us
> 1 - ~48us to ~64us
> 2 - ~48us to ~64us
> 3 - ~48us to ~64us
> 4 - ~48us to ~64us
> 4 - ~48us to ~64us
> 5 - ~48us to ~64us
> 6 - ~48us to ~64us
> 7 - ~48us to ~64us
> 8 - ~48us to ~64us
> 9 - ~56us to ~88us
> 10 - ~56us to ~112us
>
> Basically, with the "sleep_us" value set to 0, I would get the
> shortest inter transaction times with a very low variance. Once I
> went to a non-zero value, the inter transaction time went up, as well
> as the variance, which I suppose makes sense....
Thanks for these numbers. They are suggesting that udelay() is quite
expensive, and is probably taking longer than we expect. I might
instrument the function to see what is happening.
Andrew
next prev parent reply other threads:[~2020-04-19 0:35 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-18 0:03 [PATCH net-next v2 0/3] FEC MDIO speedups Andrew Lunn
2020-04-18 0:03 ` [PATCH net-next v2 1/3] net: ethernet: fec: Replace interrupt driven MDIO with polled IO Andrew Lunn
2020-04-18 13:55 ` [EXT] " Andy Duan
2020-04-18 22:39 ` Chris Healy
2020-04-19 0:35 ` Andrew Lunn [this message]
2020-04-19 6:22 ` Andy Duan
2020-04-19 20:47 ` Andrew Lunn
2020-04-18 16:21 ` Fabio Estevam
2020-04-18 21:06 ` Florian Fainelli
2020-04-18 0:03 ` [PATCH net-next v2 2/3] net: ethernet: fec: Allow configuration of MDIO bus speed Andrew Lunn
2020-04-18 0:34 ` Florian Fainelli
2020-04-18 14:23 ` Andrew Lunn
2020-04-18 16:01 ` Florian Fainelli
2020-04-18 16:49 ` Andrew Lunn
2020-04-18 21:07 ` Florian Fainelli
2020-04-18 21:08 ` Florian Fainelli
2020-04-18 0:03 ` [PATCH net-next v2 3/3] net: ethernet: fec: Allow the MDIO preamble to be disabled Andrew Lunn
2020-04-18 0:39 ` Florian Fainelli
2020-04-18 14:27 ` Andrew Lunn
2020-04-18 16:02 ` Florian Fainelli
2020-04-18 21:09 ` Florian Fainelli
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