On Wednesday, July 22, 2015 at 10:38:14 AM, Michal Suchanek wrote: > On 22 July 2015 at 10:24, Marek Vasut <ma...@denx.de> wrote: > > On Wednesday, July 22, 2015 at 10:18:04 AM, Michal Suchanek wrote: > >> On 22 July 2015 at 09:58, Marek Vasut <ma...@denx.de> wrote: > >> > On Wednesday, July 22, 2015 at 09:45:27 AM, Michal Suchanek wrote: > >> >> On 22 July 2015 at 09:33, Marek Vasut <ma...@denx.de> wrote: > >> >> > On Wednesday, July 22, 2015 at 09:30:54 AM, Michal Suchanek wrote: > >> >> >> On 22 July 2015 at 06:49, Vinod Koul <vinod.k...@intel.com> 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. > > It's probably slower to set up DMA for 2-byte commands but it might > work nonetheless.
It is, the overhead will be considerable. It might help the stability though. I'm really looking forward to the results! > I will give it a go. > > >> > 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 ? > > Yes, when the DMA transfer fails the next command fails due to garbage > lying around. However, you can unload the SPI NOR driver, load spidev > driver, and read enough garbage to empty the fifos. Then the flash > identifies as normal again and you can access it. Yikes :( > When the flash is not seated properly and acts autistic you get all > 0xff or all 0 back whatever you send to it, obvously. The > identification by the SPI NOR driver fails then. > > Thanks > > Michal -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
