[U-Boot] net: cpsw: am335x: Drop constant link checking from rx/tx path's

[Tom Rini <trini@ti.com>]

On Mon, Aug 25, 2014 at 11:26:19AM +0200, Stefan Roese wrote:

> We noticed on the DXR2 platform (AM335x with a SMSC LAN9303 switch connected
> to the CPSW MAC) that the network performance in U-Boot is quite poor. Only
> when the transfer is started without a cable connected, and the cable is
> plugged after the first timeout "T" occured, an increased in performance
> can be seen. Debugging has revealed, that the cpsw driver has constant
> link checking builtin into the rx and tx functions. This results in the
> bad performance and seems to be unnecessary. The link has already been
> checked in the init function, before the transfer is started. This usually
> is sufficient.
> 
> BTW: I have seen no other network driver in U-Boot so far, that constantly
> checks for link in the rx / tx functions.
> 
> The performance numbers on the DXR2 board are:
> 
> 0.56 MiB/s	cpsw_check_link() in rx and tx path
> 0.87 MiB/s	cpsw_check_link() only in tx path
> 1.0  MiB/s	cpsw_check_link() only in rx path
> 2.7  MiB/s	no cpsw_check_link() in rx and tx path
> 
> So with this patch the network performance on DXR2 increases from 0.56
> to 2.7 MiB/s (nearly 5 times as fast).
> 
> Signed-off-by: Stefan Roese <sr@denx.de>
> Tested-by: Samuel Egli <samuel.egli@siemens.com>
> Tested-by: Heiko Schocher <hs@denx.de>
> Cc: Vladimir Koutny <vladimir.koutny@streamunlimited.com>
> Cc: Mugunthan V N <mugunthanvnm@ti.com>
> Cc: Joe Hershberger <joe.hershberger@gmail.com>
> Cc: Tom Rini <trini@ti.com>

Applied to u-boot/master, thanks!

-- 
Tom
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