On 15 September 2015 at 00:05, Mark Brown <broonie@xxxxxxxxxx> wrote: > On Fri, Sep 04, 2015 at 04:55:33PM +0530, Jagan Teki wrote: >> On 4 September 2015 at 13:59, Vignesh R <vigneshr@xxxxxx> wrote: > >> > + * @spi_mtd_mmap_read: some spi-controller hardwares provide memory >> > + * mapped interface to communicate with mtd flashes. >> > + * For this, spi controller needs to know flash >> > + * memory settings like read command to use, dummy >> > + * bytes and address width. Once these settings are >> > + * populated in hardware registers, any read >> > + * accesses to flash's memory map region(as defined >> > + * by SoC) through memcpy or mem-to-mem DMA copy >> > + * will be handled by controller hardware. The >> > + * hardware will automatically generate spi signals >> > + * required to read data from flash and present it >> > + * to CPU or DMA. SPI master drivers can use this >> > + * callback to implement memory mapped read >> > + * interface. Flash driver (like m25p80) requests >> > + * memory mapped read via this method. The interface >> > + * should only be used mtd flashes and cannot be >> > + * used with other spi devices. > > This comment is *way* too verbose - probably you just need up to the > "Once" here. > >> > + int (*spi_mtd_mmap_read)(struct spi_device *spi, >> > + loff_t from, size_t len, size_t *retlen, >> > + u_char *buf, u8 read_opcode, >> > + u8 addr_width, u8 dummy_bytes); > >> This looks un-manageable to know spi core or master knows what are the >> command or opcode used by spi-nor flash and also I think mmap support >> seems to be flash related or any justification this is spi bus >> master/controller feature? > > There seem to be a reasonable number of SPI controllers out there which > have as an extension the ability to do memory mapped reads but are > otherwise perfectly normal SPI controllers and which rely on that for > everything except reads. This is true, but exposing direct spi-nor arguments or features like read_opcode, addr_width or dummy_byte to spi layer isn't fine? because for spi layer there is a spi to flash transition mtd m25p80.c is there to handle is it? thanks! -- Jagan | openedev. -- 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
