Re: [PATCH 4.4 25/31] mmc: dw_mmc: Wait for data transfer after response errors.

[Sasha Levin]

On Thu, Aug 26, 2021 at 08:59:53PM +0900, Nobuhiro Iwamatsu wrote:
> Hi,
>
>
> 2021年8月25日(水) 2:39 Sasha Levin <sashal@xxxxxxxxxx>:
> > From: Doug Anderson <dianders@xxxxxxxxxxxx>
> >
> > [ Upstream commit 46d179525a1f6d16957dcb4624517bc04142b3e7 ]
> >
> > According to the DesignWare state machine description, after we get a
> > "response error" or "response CRC error" we move into data transfer
> > mode. That means that we don't necessarily need to special case
> > trying to deal with the failure right away. We can wait until we are
> > notified that the data transfer is complete (with or without errors)
> > and then we can deal with the failure.
> >
> > It may sound strange to defer dealing with a command that we know will
> > fail anyway, but this appears to fix a bug. During tuning (CMD19) on
> > a specific card on an rk3288-based system, we found that we could get
> > a "response CRC error". Sending the stop command after the "response
> > CRC error" would then throw the system into a confused state causing
> > all future tuning phases to report failure.
> >
> > When in the confused state, the controller would show these (hex codes
> > are interrupt status register):
> >  CMD ERR: 0x00000046 (cmd=19)
> >  CMD ERR: 0x0000004e (cmd=12)
> >  DATA ERR: 0x00000208
> >  DATA ERR: 0x0000020c
> >  CMD ERR: 0x00000104 (cmd=19)
> >  CMD ERR: 0x00000104 (cmd=12)
> >  DATA ERR: 0x00000208
> >  DATA ERR: 0x0000020c
> >  ...
> >  ...
> >
> > It is inherently difficult to deal with the complexity of trying to
> > correctly send a stop command while a data transfer is taking place
> > since you need to deal with different corner cases caused by the fact
> > that the data transfer could complete (with errors or without errors)
> > during various places in sending the stop command (dw_mci_stop_dma,
> > send_stop_abort, etc)
> >
> > Instead of adding a bunch of extra complexity to deal with this, it
> > seems much simpler to just use the more straightforward (and less
> > error-prone) path of letting the data transfer finish. There
> > shouldn't be any huge benefit to sending the stop command slightly
> > earlier, anyway.
> >
> > Signed-off-by: Doug Anderson <dianders@xxxxxxxxxxxx>
> > Signed-off-by: Enric Balletbo i Serra <enric.balletbo@xxxxxxxxxxxxx>
> > Cc: Alim Akhtar <alim.akhtar@xxxxxxxxx>
> > Signed-off-by: Jaehoon Chung <jh80.chung@xxxxxxxxxxx>
> > Signed-off-by: Ulf Hansson <ulf.hansson@xxxxxxxxxx>
> > Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
>
> This commit also requires the following modifications:
>  ba2d139b02ba68: mmc: dw_mmc: Fix occasional hang after tuning on eMMC
>
> Please apply this commit too.

Will do, thanks!

--
Thanks,
Sasha