From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-wr0-x233.google.com ([2a00:1450:400c:c0c::233]) by bombadil.infradead.org with esmtps (Exim 4.90_1 #2 (Red Hat Linux)) id 1fGkg0-0002UW-7j for linux-mtd@lists.infradead.org; Thu, 10 May 2018 12:28:06 +0000 Received: by mail-wr0-x233.google.com with SMTP id h5-v6so1841696wrm.4 for ; Thu, 10 May 2018 05:27:53 -0700 (PDT) Subject: Re: [PATCH/RFC] mtd: spi-nor: honour max_message_size for spi-nor writes. To: NeilBrown , Boris Brezillon Cc: David Woodhouse , Brian Norris , Richard Weinberger , linux-mtd@lists.infradead.org, linux-kernel@vger.kernel.org References: <87efj1kw9u.fsf@notabene.neil.brown.name> <20180509160240.23ef11f2@bbrezillon> <87vabwa2gm.fsf@notabene.neil.brown.name> <87mux7afkv.fsf@notabene.neil.brown.name> From: Marek Vasut Message-ID: <1bb32a4e-55cf-f5f2-60f5-2213f31d54ac@gmail.com> Date: Thu, 10 May 2018 14:27:51 +0200 MIME-Version: 1.0 In-Reply-To: <87mux7afkv.fsf@notabene.neil.brown.name> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On 05/10/2018 01:57 PM, NeilBrown wrote: > On Thu, May 10 2018, Marek Vasut wrote: > >> On 05/10/2018 12:28 AM, NeilBrown wrote: >>> On Wed, May 09 2018, Boris Brezillon wrote: >>> >>>> On Fri, 27 Apr 2018 16:18:05 +1000 >>>> NeilBrown wrote: >>>> >>>>> Hi, >>>>> I've labeled this an RFC because I'm really not sure about removing the >>>>> error path from spi_nor_write() -- maybe that really matters. But on >>>>> my hardware, performing multiple small spi writes to the flash seems >>>>> to work. >>>>> >>>>> The spi driver is drivers/staging/mt7621-spi. Possibly this needs to >>>>> use DMA instead of a FIFO (assuming the hardware can) - or maybe >>>>> drivers/spi/spi-mt65xx.c can be made to work on this hardware, though >>>>> that is for an ARM SOC and mt7621 is a MIPS SOC. >>>>> >>>>> I note that openwrt has similar patches: >>>>> target/linux/generic/pending-4.14/450-mtd-spi-nor-allow-NOR-driver-to-write-fewer-bytes-th.patch >>>>> >>>>> They also change the spi driver to do a short write, rather >>>>> than change m25p80 to request a short write. >>>>> >>>>> Is there something horribly wrong with this? >>>> >>>> Marek, any opinion on this patch? >>>> >>> >>> Hi, >>> thanks for following up. >>> I have since found that I don't need this patch, though maybe others >>> still do(??). >>> My hardware can only send 36 bytes and receive 32 in a single >>> transaction. However I can run a sequence of transactions >>> to process a whole message no matter how large that message is. As >>> long as I keep chip-select asserted, all the slave device sees is that >>> the clock period isn't quite constant, and the slave shouldn't care >>> much about that. >>> When reading from flash, I found that handling large messages with >>> multiple hardware transactions was 50% faster than breaking the >>> read down into lots of 32 byte messages. >>> >>> So, I won't object if this patch is forgotten. Thanks for >>> your time anyway. >> >> Nice, which hardware is that ? > > Mediatek MT7621 SOC (particularly in the gnubee.org NAS platform). On nice, a mips, good to see someone still cares about mips :) -- Best regards, Marek Vasut