[AMD Official Use Only - General] Hi, I think there was a fix for this issue applied to the version that was running on 5.15 that didn't seem to make it into the upstream driver. Please see link for reference https://github.com/Xilinx/linux-xlnx/commit/608426961f16ab149b1b699f1c35f7ad244c0720 I think a similar fix to the above patch is may be beneficial? Cheers, Conall. > -----Original Message----- > From: Sean Anderson <sean.anderson@xxxxxxxxx> > Sent: Thursday, March 14, 2024 5:30 PM > To: Jonathan Cameron <jic23@xxxxxxxxxx> > Cc: linux-iio@xxxxxxxxxxxxxxx; O'Griofa, Conall <conall.ogriofa@xxxxxxx>; > linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; Lars-Peter > Clausen <lars@xxxxxxxxxx> > Subject: Re: [PATCH] iio: xilinx-ams: Don't include ams_ctrl_channels in > scan_mask > > Caution: This message originated from an External Source. Use proper caution > when opening attachments, clicking links, or responding. > > > On 3/14/24 11:48, Jonathan Cameron wrote: > > On Mon, 11 Mar 2024 12:28:00 -0400 > > Sean Anderson <sean.anderson@xxxxxxxxx> wrote: > > > >> ams_enable_channel_sequence constructs a "scan_mask" for all the PS > >> and PL channels. This works out fine, since scan_index for these > >> channels is less than 64. However, it also includes the > >> ams_ctrl_channels, where scan_index is greater than 64, triggering > >> undefined behavior. Since we don't need these channels anyway, just > exclude them. > >> > >> Fixes: d5c70627a794 ("iio: adc: Add Xilinx AMS driver") > >> Signed-off-by: Sean Anderson <sean.anderson@xxxxxxxxx> > > > > Hi Sean, > > > > I'd ideally like to understand why we have channels with such large > > scan indexes. Those values should only be used for buffered capture. > > It feels like they are being abused here. Can we set them to -1 > > instead and check based on that? > > For a channel, a scan index of -1 means it can't be captured via the > > buffered interfaces but only accessed via sysfs reads. > > I think that's what we have here? > > From what I can tell, none of the channels support buffered reads. And we can't > naïvely convert the scan_index to -1, since that causes sysfs naming conflicts > (not to mention the compatibility break). > > > > > I just feel like if we leave these as things stand, we will get bitten > > by similar bugs in the future. At least with -1 it should be obvious why! > > There are just as likely to be bugs confusing the PL/PS subdevices... > > FWIW I had no trouble identifying the channels involved with this bug. > > --Sean > > > Jonathan > > > > > >> --- > >> > >> drivers/iio/adc/xilinx-ams.c | 8 ++++++-- > >> 1 file changed, 6 insertions(+), 2 deletions(-) > >> > >> diff --git a/drivers/iio/adc/xilinx-ams.c > >> b/drivers/iio/adc/xilinx-ams.c index a55396c1f8b2..4de7ce598e4d > >> 100644 > >> --- a/drivers/iio/adc/xilinx-ams.c > >> +++ b/drivers/iio/adc/xilinx-ams.c > >> @@ -414,8 +414,12 @@ static void ams_enable_channel_sequence(struct > >> iio_dev *indio_dev) > >> > >> /* Run calibration of PS & PL as part of the sequence */ > >> scan_mask = BIT(0) | BIT(AMS_PS_SEQ_MAX); > >> - for (i = 0; i < indio_dev->num_channels; i++) > >> - scan_mask |= BIT_ULL(indio_dev->channels[i].scan_index); > >> + for (i = 0; i < indio_dev->num_channels; i++) { > >> + const struct iio_chan_spec *chan = > >> + &indio_dev->channels[i]; > >> + > >> + if (chan->scan_index < AMS_CTRL_SEQ_BASE) > >> + scan_mask |= BIT_ULL(chan->scan_index); > >> + } > >> > >> if (ams->ps_base) { > >> /* put sysmon in a soft reset to change the sequence */ > >
