On Wednesday, July 22, 2015 at 10:18:04 AM, Michal Suchanek wrote: > On 22 July 2015 at 09:58, Marek Vasut <marex@xxxxxxx> wrote: > > 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 ? > > The SPI driver uses PIO for short transfers and DMA for transfers > longer than the controller FIFO. This seems to be the standard way to > do things.It works flawlessly so long as submitting overly long DMA > programs is avoided. Can you try doing JUST DMA, no PIO ? I remember seeing some bus synchronisation issues when I did mixed PIO/DMA on the MXS and it was nasty to track down. Just give pure DMA a go to see if the thing stabilizes somehow. > > Do you have the option to connect a bus analyzer? > > I can probably offer you some tools, I'm in Prague ... > > The flash chip is accessible when removing the bottom cover. It is > VSOP8 package slightly lower than SOP8 so attaching clips to it might > be a bit problematic. That's the only accessible part. Everything > other than SPI is inside the SoC. That might be doable, though you might want to try the above thing first. > Since SPI has no verification whatsoever the chip might be completely > dead and you can still read fine all zeroes or all ones when > attempting a read from it. I observed this behaviour when I used a > flash chip in a socket and it was not firmly seated. It was with a > different SPI controller, though. You should run into issues as soon as the SPI NOR framework tries to read status register, no ? -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
