[U-Boot] [PATCH v2 1/2] spi: ti_qspi: use 128 bit transfer mode when writing to flash

[Jagan Teki]

On Wed, Sep 7, 2016 at 3:18 PM, Vignesh R <vigneshr at ti.com> wrote:
> TI QSPI has four 32 bit data registers which can be used to transfer 16
> bytes of data at once. The register group QSPI_SPI_DATA_REG_3,
> QSPI_SPI_DATA_REG_2, QSPI_SPI_DATA_REG_1 and QSPI_SPI_DATA_REG is
> treated as a single 128-bit word for shifting data in and out. The bit
> at QSPI_SPI_DATA_REG_3[31] position is the first bit to be shifted out
> in case of 128 bit transfer mode. Therefore the first byte to be written
> to flash should be at QSPI_SPI_DATA_REG_3[31-25] position.
> Instead of writing 1 byte at a time when interacting with SPI NOR flash,
> make use of all the four registers so that 16 bytes can be transferred
> in one go.
>
> With this patch, the flash write speed increases from ~250KBs/ to
> ~650KB/s on DRA74 EVM.
>
> Signed-off-by: Vignesh R <vigneshr at ti.com>
> Reviewed-by: Tom Rini <trini at konsulko.com>

Reviewed-by: Jagan Teki <jteki at openedev.com>

thanks!
-- 
Jagan Teki
Free Software Engineer | www.openedev.com
U-Boot, Linux | Upstream Maintainer
Hyderabad, India.