[PATCH v2 2/5] spi: spi-ti-qspi: add mmap mode read support
vigneshr at ti.com
Wed Nov 4 22:16:09 PST 2015
On 11/04/2015 08:11 PM, Mark Brown wrote:
> On Tue, Nov 03, 2015 at 03:36:11PM +0530, Vignesh R wrote:
>> + ti_qspi_enable_memory_map(spi);
>> + ti_qspi_setup_mmap_read(spi, read_opcode, addr_width,
>> + dummy_bytes);
>> + memcpy_fromio(buf, qspi->mmap_base + from, len);
>> + *retlen = len;
>> + ti_qspi_disable_memory_map(spi);
> We'll be constantly enabling and disabling memory mapping with this.
> I'm not sure that's a meaningful cost given that it doesn't actually
> remap anything but rather just switches hardware modes, we can always
> optimise it later if it is.
Hmm, I will move the ti_qspi_disable_memory_map() call to
ti_qspi_start_transfer_one(), so that mmap mode is disabled only when
normal SPI bus transfer is requested. Further, "mmap_enabled" status
flag can be used to determine whether mode switch is required or not.
This should help to overcome enabling and disabling memory mapping
between successive mmap read requests.
More information about the linux-arm-kernel