On Wednesday, July 22, 2015 at 09:45:27 AM, Michal Suchanek wrote: > On 22 July 2015 at 09:33, Marek Vasut <marex@xxxxxxx> wrote: > > On Wednesday, July 22, 2015 at 09:30:54 AM, Michal Suchanek wrote: > >> On 22 July 2015 at 06:49, Vinod Koul <vinod.koul@xxxxxxxxx> wrote: > >> > On Tue, Jul 21, 2015 at 10:14:11AM +0200, Michal Suchanek wrote: > >> >> > Or alternatively we could publish the limitations of the channel > >> >> > using capabilities so SPI knows I have a dmaengine channel and it > >> >> > can transfer max N length transfers so would be able to break > >> >> > rather than guessing it or coding in DT. Yes it may come from DT > >> >> > but that should be dmaengine driver rather than client driver :) > >> >> > > >> >> > This can be done by dma_get_slave_caps(chan, &caps) > >> >> > > >> >> > And we add max_length as one more parameter to existing set > >> >> > > >> >> > Also all this could be handled in generic SPI-dmaengine layer so > >> >> > that individual drivers don't have to code it in > >> >> > > >> >> > Let me know if this idea is okay, I can push the dmaengine bits... > >> >> > >> >> It would be ok if there was a fixed limit. However, the limit depends > >> >> on SPI slave settings. Presumably for other buses using the dmaengine > >> >> the limit would depend on the bus or slave settings as well. I do not > >> >> see a sane way of passing this all the way to the dmaengine driver. > >> > > >> > I don't see why this should be client (SPI) dependent. The max length > >> > supported is a dmaengine constraint, typically flowing from max > >> > blocks/length it can transfer. Know this limit can allow clients to > >> > split transfers. > >> > >> In practice on the board I have the maximum transfer length before it > >> fails depends on SPI bus speed which is set up per slave. I did not > >> try searching the space of possible settings thorougly and settled for > >> a setting that gives reasonable speed and transfer length. > > > > This looks more like a signal integrity issue though. > > It certainly does on the surface. However, when wrong data is > delivered over the SPI bus (such as when I use wrong phase setting) > the SPI controller happily delivers wrong data over PIO. > > The failure I am seeing is that the pl330 DMA program which repeatedly > waits for data from the SPI controller never finishes the read loop > and does not signal the interrupt. It seems it also leaves some data > in a FIFO somewhere so next command on the flash returns garbage and > fails. I observed something similar on MXS (mx28) SPI block. Do you use mixed PIO/DMA mode perhaps ? Do you have the option to connect a bus analyzer? I can probably offer you some tools, I'm in Prague ... Best regards, Marek Vasut -- To unsubscribe from this list: send the line "unsubscribe dmaengine" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
