[U-Boot] [PATCH 1/3] spi: Add zynq qspi controller driver

[thomas.langer at lantiq.com]

Hi Jagan,

> +
> +/* Definitions of the flash commands - Flash insts in ascending order */
> +#define ZYNQ_QSPI_FLASH_INST_WRSR	0x01	/* Write status register */
> +#define ZYNQ_QSPI_FLASH_INST_PP		0x02	/* Page program */
> +#define ZYNQ_QSPI_FLASH_INST_WRDS	0x04	/* Write disable */
> +#define ZYNQ_QSPI_FLASH_INST_RDSR1	0x05	/* Read status register 1 */
> +#define ZYNQ_QSPI_FLASH_INST_WREN	0x06	/* Write enable */
> +#define ZYNQ_QSPI_FLASH_INST_AFR	0x0B	/* Fast read data bytes */
> +#define ZYNQ_QSPI_FLASH_INST_BE_4K	0x20	/* Erase 4KiB block */
> +#define ZYNQ_QSPI_FLASH_INST_RDSR2	0x35	/* Read status register 2 */
> +#define ZYNQ_QSPI_FLASH_INST_BE_32K	0x52	/* Erase 32KiB block */
> +#define ZYNQ_QSPI_FLASH_INST_RDID	0x9F	/* Read JEDEC ID */
> +#define ZYNQ_QSPI_FLASH_INST_SE		0xD8	/* Sector erase (usually 64KB)*/

As I have written some time ago, I think it is a bad idea to parse the
flash commands in the spi driver!
The flash driver, who wants to write these commands and should know the details,
which parts of the message needs to be send as dual/quad transfer, should 
provide this information to the spi driver (probably as flags for spi_xfer())

A first idea for the flags:
- the X refers to different numbers, as required by the flash (depending on the
addressing mode (3/4 byte) or if the address is already sent as DUAL/QUAD)
SPI_XFER_X_DUAL
SPI_XFER_X_QUAD

So having 0-5 for X should be enough to support all flashes
-> 0 if the command is already in DUAL/QUAD mode
-> 5 for command + 4byte address
(I am not sure about dummy bytes on read)

So for example: 
switch to dual transfer after first byte: SPI_XFER_1_DUAL
switch to QUAD transfer after 4 bytes (e.g. 3byte address): SPI_XFER_4_QUAD

Then only the flash driver needs to know these requirements, depending on 
manufacturer and chip type, and the spi driver just "reacts" on the flags.
Otherwise this driver has to be extended each time a new command is added to 
the flash driver (as you did in some later patches!)

Best regards,
Thomas