[U-Boot] [PATCH] Davinci: SPI performance enhancements

[Nick Thompson]

On 21/06/10 15:41, Paulraj, Sandeep wrote:
> 
> 
>>
>> The following restructuring and optimisations increase the SPI
>> read performance from 1.3MiB/s (on da850) to 2.87MiB/s (on da830):
>>
>> Remove continual revaluation of driver state from the core of the
>> copy loop. State can not change during the copy loop, so it is
>> possible to move these evaluations to before the copy loop.
>>
>> Cost is more code space as loop variants are required for each set
>> of possible configurations. The loops are simpler however, so the
>> extra is only 128bytes on da830 with CONFIG_SPI_HALF_DUPLEX
>> defined.
>>
>> Unrolling the first copy loop iteration allows the TX buffer to be
>> pre-loaded reducing SPI clock starvation.
>>
>> Unrolling the last copy loop iteration removes testing for the
>> final loop iteration every time round the loop.
>>
>> Using the RX buffer empty flag as a transfer throttle allows the
>> assumption that it is always safe to write to the TX buffer, so
>> polling of TX buffer full flag can be removed.
>>
>> Signed-off-by: Nick Thompson <nick.thompson at ge.com>
>> ---
>> da850 and da830 are similar devices. The SPI module is common to
>> both, but da850 uses DDR and da830 uses SDRAM. The EVM's might
>> not actually be comparable, but they appear to be at least similar.
>>
>> The speed was tested with a 8MiB transfer from SPI FLASH using:
>>
>> sf read 0xc0008000 0 0x800000
>>
>>  drivers/spi/davinci_spi.c |  195 +++++++++++++++++++++++++++++-----------
> 
> This patch does not apply against Wolfgang's next.
> The patch should be against u-boot/next.

It looks like Delio's patch ended up being pulled into main via Tom's
tree and yours. On u-boot I see 9268236529161312c877e638a14c011fd3c883e1,
but the same commit has id 23911740486c59851df57521c49bfd81ce1865ec on
on u-boot-ti.

I guess this is the source of the confusion? My patch was against
u-boot, not u-boot-ti.

Nick.