Hello Nick,
On 17/06/2010, at 17:02, Nick Thompson wrote:
On 01/06/10 12:36, Delio Brignoli wrote:
I have updated this patch based on the comments [1] by Wolfgang Denk and removed unused variables. [1][http://lists.denx.de/pipermail/u-boot/2010-May/071728.html]
[...]
I have an alternative patch that tries to be even quicker, but I don't have the same platform as Delio, so can't compare like with like.
I will test your patch on my L138 and let you know.
In essence, it splits up read and write operations to avoid testing pointers in every loop iteration. It also unrolls the last iteration so that it doesn't have to test for loop ending twice each time round. Finally it avoids bit setting/clearing on each iteration when the results would only turn out to be the same anyway.
I am wondering if it is OK to split reading and writing: when I wrote the patch I assumed that spi_xfer() was supposed to be able to read and write to two distinct buffers at the same time. As I understand it, your patch allows spi_xfer() to be either a read or a write operation but not both and I do not know if this semantic change is acceptable. Maybe Sekhar or Sandeep can clarify this.
Thanks -- Delio