Hi Ulf! My apologies for the delay. On Tue, Mar 02, 2021 at 09:45:02AM +0100, Ulf Hansson wrote: > On Mon, 1 Mar 2021 at 22:59, Marten Lindahl <martenli@xxxxxxxx> wrote: > > > > Hi Ulf! > > > > Thank you for your comments! > > > > On Mon, Mar 01, 2021 at 09:50:56AM +0100, Ulf Hansson wrote: > > > + Adrian > > > > > > On Tue, 16 Feb 2021 at 23:43, Mårten Lindahl <marten.lindahl@xxxxxxxx> wrote: > > > > > > > > Sometimes SD cards that has been run for a long time enters a state > > > > where it cannot by itself be recovered, but needs a power cycle to be > > > > operational again. Card status analysis has indicated that the card can > > > > end up in a state where all external commands are ignored by the card > > > > since it is halted by data timeouts. > > > > > > > > If the card has been heavily used for a long time it can be weared out, > > > > and should typically be replaced. But on some tests, it shows that the > > > > card can still be functional after a power cycle, but as it requires an > > > > operator to do it, the card can remain in a non-operational state for a > > > > long time until the problem has been observed by the operator. > > > > > > > > This patch adds function to power cycle the card in case it does not > > > > respond to a command, and then resend the command if the power cycle > > > > was successful. This procedure will be tested 1 time before giving up, > > > > and resuming host operation as normal. > > > > > > I assume the context above is all about the ioctl interface? > > > > > > > Yes, that's correct. The problem we have seen is triggered by ioctls. > > > > > So, when the card enters this non functional state, have you tried > > > just reading a block through the regular I/O interface. Does it > > > trigger a power cycle of the card - and then makes it functional > > > again? > > > > > > > Yes, we have tried that, and it does trigger a power cycle, making the card > > operational again. But as it requires an operator to trigger it, I thought > > it might be something that could be automated here. At least once. > > Not sure what you mean by operator here? In the end it's a userspace > program running and I assume it can deal with error paths. :-) > > In any case, I understand your point. > Yes, we have a userspace program. So if the userspace program will try to restore the card in a situation such as the one we are trying to solve here, how shall it perform it? Is it expected that a ioctl CMD0 request should be enough, or is there any other support for a userspace program to reset the card? If it falls on a ioctl command to reset the card, how do we handle the case where the ioctl times out anyway? Or is the only way for a userspace program to restore the card, to make a block transfer that fails? Kind regards Mårten > > > > > > > > > > Signed-off-by: Mårten Lindahl <marten.lindahl@xxxxxxxx> > > > > --- > > > > Please note: This might not be the way we want to handle these cases, > > > > but at least it lets us start the discussion. In which cases should the > > > > mmc framework deal with error messages like ETIMEDOUT, and in which > > > > cases should it be handled by userspace? > > > > The mmc framework tries to recover a failed block request > > > > (mmc_blk_mq_rw_recovery) which may end up in a HW reset of the card. > > > > Would it be an idea to act in a similar way when an ioctl times out? > > > > > > Maybe, it's a good idea to allow the similar reset for ioctls as we do > > > for regular I/O requests. My concern with this though, is that we > > > might allow user space to trigger a HW resets a bit too easily - and > > > that could damage the card. > > > > > > Did you consider this? > > > > > > > Yes, that is a valid point, and that is why the power cycle is only tried > > once. But the conditon for this reset is a -ETIMEDOUT, and this is the part of > > this patch where I am myself not sure of if it is enough to check for. Would > > this be an error that you could expect to happen with ioctl requests in other > > situations also, but not necessarily cause by a stalled card? > > Exactly. > > Many different commands can get pushed down to the card through the > mmc ioctl interface. It's difficult to know what error path we should > pick, other than reporting and propagating the error codes. > > [...] > > Kind regards > Uffe
