Date: Fri, 23 Jan 2009 11:30:53 +0100 From: Bernd Walter <ticso@cicely7.cicely.de> To: Alexander Motin <mav@FreeBSD.org> Cc: freebsd-arm@FreeBSD.org, ticso@cicely7.cicely.de, ticso@cicely.de Subject: Re: Mount root from SD card? Message-ID: <20090123103053.GR50103@cicely7.cicely.de> In-Reply-To: <200901231117070000@1426712698> References: <200901231117070000@1426712698>
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On Fri, Jan 23, 2009 at 11:17:06AM +0200, Alexander Motin wrote: > > Right now I'm only getting ~900kB/s (890-919) and we can do much > > better, no? > > I have started from alike values with sdmmc driver, but with multiblock transfers and 4 bits bus I have reached top possible for my controller 15Mbytes/s. Multiblock transfers are very important to reduce number of interrupts. Not only that - they are important for card internal optimization. Especially with writing a transfer can issue read-modify-write cycles on the large cell blocks and writing a 16k FS block in 32 card transactions is not very perfect. Especially many MLC cards have a large write transaction overhead. With reading it just means opening the cells for reading, but some card designs are slow with this as well. -- B.Walter <bernd@bwct.de> http://www.bwct.de Modbus/TCP Ethernet I/O Baugruppen, ARM basierte FreeBSD Rechner uvm.
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