| Message ID | 877f3zwwgo.fsf@belgarion.home (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
Dne 8.3.2017 v 17:43 Robert Jarzmik napsal(a): > Petr Cvek <petr.cvek@tul.cz> writes: > > Hi Petr, >> I wasn't able to track the problem to a single patch as the problem occurs at >> random time (from the boot to like a half an hour) and it's maybe dependent on a >> level of a battery charge (maybe because of kernel log writes of charging >> messages). > Mmmh, long reproduction time, that will be bad. Sent log is for a machine which finally died when I tried to start an X server. These debug printks slow it down. >> It seems that most occurrency is during writes on an SD card. Using an SDHC >> card decreases the time to fail. After failure the OS is unavailable (rootfs >> in on the card). > Okay, let me try to make write loop on my SD card to see if I manage to > reproduce this. > I tried to enable and disable soundcard (other part which is using DMA), but it does not have any effect. Concurrent interrupts may have. >> From my poking in the kernel source code it seems there is a probability that pxamci_irq() takes longer to call and its subsequent call pxamci_data_done() isn't fast enough to set [1] >> host->data = NULL; > >> From the DMA side, the DMA done interrupt is generated: >> pxad_chan_handler() -> vchan_cookie_complete() >> ...where a tasklet for vchan_complete() is scheduled > At least that seems to hint the DMA part is sound so for. > The bothering part is the log error "mmc0: DMA error on tx channel". I would > need a bit of guidance here, with the same log with [1] applied. > Probably some cooperation of the DMA engine and the PXA MMC (like that other mail I've sent to you with UDC and g_webcam). I made another version of debug kernel with my own asserts: In pxamci_dma_irq() before dmaengine_tx_status() call I've put: pr_info("!!!cookie=%x complete=%x used=%x\n", host->dma_cookie,chan->completed_cookie,chan->cookie); It gets called only ONCE, just before failure, which values like this: cookie=372 complete=371 used=372 vchan_cyclic_callback() is called only with the soundcard in my machine IMO. I first thought there is regression with vd_completed in pxad_chan_handler() being changed during vchan_cyclic_callback() but it seems not. pxad_tx_status() returns DMA_IN_PROGRESS before the failure. >> , where finally with interrupts enabled (can pxamci_irq() be called here?) the >> callback pxamci_dma_irq() is called. > When DMA completes, there is a tiny window, before pxamci_dma_irq() is called, > when pxamci_irq() can be called, yes. As soon as the spinlock is taken in > pxamci_dma_irq() is taken, no more races. > Does pxamci_dma_irq() depend on pxamci_irq() -> pxamci_data_done() NULLing host->data? >> From my tests it seems at this point [2] the host->data is always NULL and rest >> of the callback is never called. It is called once with a nonempty host->data >> only just before the failure. >> >> During the testing I put udelay(100) at the start of pxamci_dma_irq() and fail >> occurred after like 2 hours (when I for the first time tapped the touchscreen - >> higher CPU usage and interrupts). > Mmm I would need more data here. > > The biggest help I could get would be the pxa dma traces here : > echo -n 'file pxa_dma.c +p' > /sys/kernel/debug/dynamic_debug/control > echo -n 'file virt-dma.c +p' > /sys/kernel/debug/dynamic_debug/control > > And then capture the last traces and send them to me. Last traces before the failure are in the attachment. It was copied (by a continual dmesg dump) from a ssh terminal over infraport (/var/log/messages gets corrupted after MMC DMA error). > > Cheers. >
Petr Cvek <petr.cvek@tul.cz> writes: Ok Petr, I've been trying for days to reproduce without any luck. I had a look at your traces, and I'd like something else when it happens : 1) The patch I provided earlier applied 2) This done (the 'cat' after the bug) : mount -t debugfs none /sys/kernel/debug/ cat /sys/kernel/debug/pxa-dma.0/channels/4/[sd]* Cheers. -- Robert
diff --git a/drivers/mmc/host/pxamci.c b/drivers/mmc/host/pxamci.c index c763b404510f..ed3812b2a34d 100644 --- a/drivers/mmc/host/pxamci.c +++ b/drivers/mmc/host/pxamci.c @@ -571,8 +571,9 @@ static void pxamci_dma_irq(void *param) if (likely(status == DMA_COMPLETE)) { writel(BUF_PART_FULL, host->base + MMC_PRTBUF); } else { - pr_err("%s: DMA error on %s channel\n", mmc_hostname(host->mmc), - host->data->flags & MMC_DATA_READ ? "rx" : "tx"); + pr_err("%s: DMA error on %s channel: %d\n", + mmc_hostname(host->mmc), + host->data->flags & MMC_DATA_READ ? "rx" : "tx", status); host->data->error = -EIO; pxamci_data_done(host, 0); }