Hi Piotr, On Mon, 18 Jun 2018 18:21:22 +0200 Piotr Bugalski <bugalski.piotr@xxxxxxxxx> wrote: > Hello, > > Atmel SAMA5D2 is equipped with two QSPI interfaces. These interfaces can > work as in SPI-compatible mode or use two / four lines to improve > communication speed. At the moment there is QSPI driver strongly tied to > NOR-flash memory and MTD subsystem. > Intention of this change is to provide new driver which will not be tied > to MTD and allows using QSPI with NAND-flash memory or other peripherals > New spi-mem API provides abstraction layer which can disconnect QSPI > from MTD. This driver doesn't support regular SPI interface, it should > be used with spi-mem interface only. Glad to see that people are starting to convert their SPI NOR controller drivers to the SPI mem approach. > Unfortunately SAMA5D2 hardware by default supports only NOR-flash > memory. It allows 24- and 32-bit addressing while NAND-flash requires > 16-bit long. To workaround hardware limitation driver is a bit more > complicated. > > Request to spi-mem contains three fiels: opcode (command), address, > dummy bytes. SAMA5D2 QSPI hardware supports opcode, address, dummy and > option byte where address field can only be 24- or 32- bytes long. > Handling 8-bits long addresses is done using option field. For 16-bits > address behaviour depends of number of requested dummy bits. If there > are 8 or more dummy cycles, address is shifted and sent with first dummy > byte. Otherwise opcode is disabled and first byte of address contains > command opcode (works only if opcode and address use the same buswidth). > The limitation is when 16-bit address is used without enough dummy > cycles and opcode is using different buswidth than address. Other modes > are supported with described workaround. > > It looks like hardware has some limitation in performance. The same issue > exists in current QSPI driver (MTD/nor-flash) and soft-pack (bare-metal > library from Atmel). Without using DMA read speed is much worse than > maximum bandwidth (efficiency 30-40%). Any help with performance > improvement is highly welcome, especially for NAND-flash memories which > offers higher capacity than NOR-flash used with previous driver. > > Best Regards, > Piotr > > Piotr Bugalski (2): > spi: Add QuadSPI driver for Atmel SAMA5D2 > dt-bindings: spi: QuadSPI driver for Atmel SAMA5D2 documentation > > .../devicetree/bindings/spi/spi_atmel-qspi.txt | 41 ++ > drivers/spi/Kconfig | 9 + > drivers/spi/Makefile | 1 + > drivers/spi/spi-atmel-qspi.c | 480 +++++++++++++++++++++ I'd like a solution where we remove the old driver. I definitely don't want to have both in parallel. Did you test the new driver with a SPI NOR to check if it still works correctly? If you did, then I'd suggest that you add a patch updating defconfigs where the SPI_ATMEL_QUADSPI is selected and another patch removing the old driver. > 4 files changed, 531 insertions(+) > create mode 100644 Documentation/devicetree/bindings/spi/spi_atmel-qspi.txt This should be a simple mv from Documentation/devicetree/bindings/mtd/atmel-quadspi.txt to Documentation/devicetree/bindings/spi/spi-atmel-qspi.txt > create mode 100644 drivers/spi/spi-atmel-qspi.c > Thanks, Boris -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
