In addition to my other comments: On Tue, Nov 10, 2015 at 10:59:55AM +0530, Vignesh R wrote: > In addition to providing direct access to SPI bus, some spi controller > hardwares (like ti-qspi) provide special memory mapped port > to accesses SPI flash devices in order to increase read performance. > This means the controller can automatically send the SPI signals > required to read data from the SPI flash device. > For this, spi controller needs to know flash specific information 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(SoC specific) 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/DMA. > > Introduce spi_mtd_mmap_read() interface to support memory mapped read > over SPI flash devices. SPI master drivers can implement this callback to > support memory mapped read interfaces. m25p80 flash driver and other > flash drivers can call this to request memory mapped read. The interface > should only be used MTD flashes and cannot be used with other SPI devices. > > Signed-off-by: Vignesh R <vigneshr@xxxxxx> > --- ... > diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h > index cce80e6dc7d1..2f2c431b8917 100644 > --- a/include/linux/spi/spi.h > +++ b/include/linux/spi/spi.h > @@ -361,6 +361,11 @@ static inline void spi_unregister_driver(struct spi_driver *sdrv) > * @handle_err: the subsystem calls the driver to handle an error that occurs > * in the generic implementation of transfer_one_message(). > * @unprepare_message: undo any work done by prepare_message(). > + * @spi_mtd_mmap_read: some spi-controller hardwares provide memory. > + * Flash drivers (like m25p80) can request memory > + * mapped read via this method. This interface > + * should only be used by mtd flashes and cannot be > + * used by other spi devices. > * @cs_gpios: Array of GPIOs to use as chip select lines; one per CS > * number. Any individual value may be -ENOENT for CS lines that > * are not GPIOs (driven by the SPI controller itself). > @@ -507,6 +512,11 @@ struct spi_master { > struct spi_message *message); > int (*unprepare_message)(struct spi_master *master, > struct spi_message *message); > + 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 is seeming to be a longer and longer list of arguments. I know MTD has a bad habit of long argument lists (which then cause a ton of unnecessary churn when things need changed in the API), but perhaps we can limit the damage to the SPI layer. Perhaps this deserves a struct to encapsulate all the flash read arguments? Like: struct spi_flash_read_message { loff_t from; size_t len; size_t *retlen; void *buf; u8 read_opcode; u8 addr_width; u8 dummy_bits; // additional fields to describe rx_nbits for opcode/addr/data }; struct spi_master { ... int (*spi_flash_read)(struct spi_device *spi, struct spi_flash_message *msg); }; > > /* > * These hooks are for drivers that use a generic implementation ... Brian -- 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