On Fri, Feb 06, 2015 at 09:13:07AM +0100, Boris Brezillon wrote: > Hi Brian, > > On Thu, 5 Feb 2015 17:08:35 -0800 > Brian Norris <computersforpeace@xxxxxxxxx> wrote: > > On Wed, Feb 04, 2015 at 11:10:28AM +0100, Boris Brezillon wrote: > > > On Mon, 26 Jan 2015 15:56:03 +0100 > > > Maxime Ripard <maxime.ripard@xxxxxxxxxxxxxxxxxx> wrote: > > > > + /* > > > > + * According to the datasheet, when reading > > > > + * from NDDB with BCH enabled, after each 32 > > > > + * bits reads, we have to make sure that the > > > > + * NDSR.RDDREQ bit is set > > > > + */ > > > > > > I know the datasheet says this bit should be checked after each > > > transfer, but I wonder if we shouldn't check it before reading the data. > > > What happens if you drain all the data available in the FIFO ? Is the > > > controller still setting the RDDREQ bit ? > > > > > > Moreover, the datasheet says this RDDREQ bit should be checked after > > > each 32 bytes (not 32 bits) transfer. > > > Testing it after each readl call shouldn't hurt though. > > > > Seems like that could quite possibly kill performance unnecessarily, > > couldn't it? But then, PIO is probably not that fast in the first > > place... > > Absolutety, my point was, it shouldn't hurt from a functional POV, but > yes it will definitely impact performances. OK. > But that's not the first thing I would rework of if you're concerned > about performances: when doing PIO read/write, the page read/write > operations (I mean the part reading the internal fifo) are all done in > interrupt context (called from pxa3xx_nand_irq), and doing this will > prevent any other interrupt from taking place while you are > draining/filling the FIFO :-(. ...which reminds me; the jiffies-based timeout in this patch isn't going to work in interrupt context. So it needs to be replaced either with a tight udelay() loop, or it needs to be moved out of the ISR. > An alternative would be to move this part into the read/write_buf > functions, but that's a lot of work... Yeah, that probably would be preferable, but I suppose it's not urgent either. Brian -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html