On Wed, Apr 01, 2015 at 04:21:50PM +0100, Andy Pont wrote:
> Hi David,
>
> <snipped for brevity>
>
> > for (i = 0; i < len; i++) {
> > /* wait till TX register is empty (TXS == 1) */
> > + start = get_timer(0);
> > while (!(readl(&ds->regs->channel[ds->slave.cs].chstat) &
> > OMAP3_MCSPI_CHSTAT_TXS)) {
> > - if (--timeout <= 0) {
> > + if (get_timer(start) > SPI_WAIT_TIMEOUT) {
> > printf("SPI TXS timed out, status=0x%08x\n",
> > readl(&ds->regs->channel[ds-
> > >slave.cs].chstat));
> > return -1;
>
> I have a couple of questions...
>
> Firstly, when in SPL is there access to the get_timer() function?We call timer_init() from board_init_r() in SPL, prior to diving down into loading (or checking for Falcon vs Regular) so this is safe. > Secondly, when using Falcon mode to load Linux directly from SPI (Falcon > mode) then we want to maximise the throughput and save every CPU cycle we > possibly can. Adding yet another function call into the for loop and hence > calling it a couple of million times seems, on the face of it, like it is > going to slow things down. I'd like to see measurements to prove me wrong but this both seems like a bad idea (optimizing by being incorrect, this gives us a correct timeout check like other drivers do) and really unlikely I would think to be noticable. Since we'll be doing the same code-paths in both regular and SPL, trying to time things (by loading a big file) would be easy enough I think. Thanks! -- Tom
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