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 <[email protected]> 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). Thanks, NeilBrown
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