On Thu, Apr 01, 2010 at 01:15:20AM +0100, Martin Guy wrote: > On 3/25/10, Mika Westerberg <mika.westerb...@iki.fi> wrote: > > > > This patch adds an SPI master driver for the Cirrus EP93xx SPI > > controller found > > > > in EP93xx chips (EP9301, EP9302, EP9307, EP9312 and EP9315). > > > > > > > > Driver currently supports only interrupt driven mode but in future we > > may add > > > > polling mode support as well. > > I've been staring more at this again and it looks (2 clock > strangenesses and extensive control reg setting apart) like good code. > I have another question: like the Cirrus driver, this takes 100% CPU > doing busy wait for the current transfer to complete.
Hi, I tried to find out whether the driver did something wrong to get into busylooping but couldn't find anything. In case of MMC/SD cards, through mmc_spi, transfer sizes are >= 512 bytes at a time and FIFO size is only 8 bytes (or words) so the CPU is expected to be pretty busy serving interrupts from the SSP. I'm about to post updated series with your comments addressed. I also added support for polling transfers. > Given that this driver is interrupt-based, is there any reason why it > can't do something else in the meanwhile? > Not that that's a reason not to include it in 2.6.35 - it works well > and we can think whether to make it more efficient in N+1... >From the User's guide, it seems that the controller is able to support DMA as well (via two M2M channels). Maybe we can add support for that in subsequent versions? Thanks, MW ------------------------------------------------------------------------------ Download Intel® Parallel Studio Eval Try the new software tools for yourself. Speed compiling, find bugs proactively, and fine-tune applications for parallel performance. See why Intel Parallel Studio got high marks during beta. http://p.sf.net/sfu/intel-sw-dev _______________________________________________ spi-devel-general mailing list spi-devel-general@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/spi-devel-general
