On Thu, Nov 01, 2012 at 03:28:17PM +0100, Marek Vasut wrote: > Dear Wolfram Sang, > > > This I2C master can do DMA and PIOQUEUE (PIO with FIFO). Originally, > > only PIOQEUE > > PIOQUEUE ;-) Yup, right! > > > was supported, then DMA support was added. The original > > intention was to keep PIOQUEUE since it has less overhead what is nice > > for small transfers. However, runtime switching between PIOQEUE and DMA > > depending on the transfer size never worked despite a lot of trying. > > Since PIOQUEUE mode itself was flaky (polling at places where interrupts > > failed to work) and the implementation also imposed a size limit for > > transfers, it is best to remove the support altogether which makes the > > driver a lot cleaner and more robust. If somebody really wants less > > overhead, plain PIO mode could still be implemented with the addidtional > > advantage that this mode is also available on MX23, too. > > Yes, looks to be the way to go. > > Reviewed-by: Marek Vasut <marex@xxxxxxx> Thanks. BTW have you tried combining all i2c-messages (msgs[]) of the transfer into one DMA chain? That would reduce overhead, too, no? Regards, Wolfram -- Pengutronix e.K. | Wolfram Sang | Industrial Linux Solutions | http://www.pengutronix.de/ |
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