2011-07-08 16:28:50 SPI nvRAM with linux kernel
Timothy Stotts (UNITED STATES)
Message: 102263
I am looking for a recommendation for an SPI nvRAM that has a driver available for the stable uClinux kernel. Desired capacity is 32 kilobyte or larger.
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2011-07-08 16:51:16 Re: SPI nvRAM with linux kernel
Mike Frysinger (UNITED STATES)
Message: 102265
so you want a SPI flash. we dont maintain a list of devices between releases, but you can look it up easily.
in u-boot, look at drivers/mtd/spi/*.c
in linux, look at drivers/mtd/devices/m25p80.c
if you're going to boot off it, avoid non-power-of-two flashes from atmel as the on-chip bootrom cannot support it
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2011-07-08 17:13:31 Re: SPI nvRAM with linux kernel
Timothy Stotts (UNITED STATES)
Message: 102268
Thanks Mike. I am actually referring to Non-Volatile SRAM, not flash, with infinite read/write cycles and millions of possible RECALL/STORE operations on power down. Hence the small storage capacity of kilobytes instead of megabytes.
For example:
www.cypress.com/?mpn=CY14B101P-SFXI
I am certain that the mainline kernel has drivers for this kind of device as the PPC and SPARC desktops use devices like these for the settings of their BIOS equivalent; but I do not know if it supports out-of-the-box a device of this kind over SPI.
So far I have looked under SPI and RTC (many chips includes RTCs), but have not found a good match for my requirements. I am not familiar where a driver for this type of device would reside within the kernel source.
Thanks.
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2011-07-08 17:33:40 Re: SPI nvRAM with linux kernel
Mike Frysinger (UNITED STATES)
Message: 102269
when it's part of the bios, often times there are dedicated rom funcs to assist in accessing things, so the fact that it's a device on a spi bus is hidden
we've never used devices like this before on Blackfin systems. since it's a cypress part, perhaps ask cypress about linux support ?
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2011-07-14 15:21:22 Re: SPI nvRAM with linux kernel
Peter Gombos (HUNGARY)
Message: 102411
Hi,
We used to use Ramtron FRAM SPI chips. It is a really good circuit. I modified an spi mtd driver to emulate flash chip and mounted as yaffs2 device.