netdev - Re: [PATCH 2/5] netdev: bfin_mac: fix malformed UDP packet transmission when polling with KGDB

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Date:	Fri, 29 May 2009 06:46:46 -0400
From:	Mike Frysinger <vapier.adi@...il.com>
To:	David Miller <davem@...emloft.net>
Cc:	netdev@...r.kernel.org, uclinux-dist-devel@...ckfin.uclinux.org,
	sonic.zhang@...log.com, cooloney@...nel.org
Subject: Re: [PATCH 2/5] netdev: bfin_mac: fix malformed UDP packet 
	transmission when polling with KGDB

On Fri, May 29, 2009 at 05:04, David Miller wrote:
> From: Mike Frysinger <vapier@...too.org>
>> From: Sonic Zhang <sonic.zhang@...log.com>
>>
>> Make sure data is really written into the registers before enabling DMA.
>> Otherwise, the EMAC DMA controller may transfer out a malformed packet.
>> This patch may also fix netperf bugs or scp bugs.
>>
>> Signed-off-by: Sonic Zhang <sonic.zhang@...log.com>
>> Signed-off-by: Mike Frysinger <vapier.adi@...il.com>
>> Signed-off-by: Bryan Wu <cooloney@...nel.org>
>
> Instead of using this incredibly non-portable blackfin specific SSYNC
> thing

that doesnt make sense -- this is a completely non-portable Blackfin
specific driver.  everything in it uses Blackfin macros to access
Blackfin MMRs because this is a device that only exists on Blackfin
chips.

> why not read back a register from the device to ensure the
> register writes hit the chip just like other drivers do?

because that isnt how the Blackfin hardware works in general, and
certainly not how the DMA hardware works.

> If that doesn't work, enhance your commit message to describe (in
> detail) why SSYNC is the only way to make this work properly.

this is how it always is for all Blackfin on-chip registers, and the
hardware manual specifically dictates using SSYNC.
-mike
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