Re: linux 4.2-rc1 broken Nokia N900

Michael Welling
2015-07-22T05:13:44Z

On Wed, Jul 22, 2015 at 04:03:07AM +0200, Sebastian Reichel wrote:
> Hi,
>
> On Tue, Jul 21, 2015 at 07:17:41PM -0500, Michael Welling wrote:
> > On Tue, Jul 21, 2015 at 11:34:41AM +0200, Pavel Machek wrote:
> >
> > This code has my head spinning.
> >
> > I found that the errors do not occur when the driver is built into the kernel.
> >
> > I also found that with the patch below the errors go away.
> >
> > Not sure if it is acceptible but see if it fixes things on your side.
> >
> >
> > diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
> > index cf8b91b..3164d13 100644
> > --- a/drivers/spi/spi.c
> > +++ b/drivers/spi/spi.c
> > @@ -1801,11 +1801,11 @@ int spi_setup(struct spi_device *spi)
> > if (!spi->max_speed_hz)
> > spi->max_speed_hz = spi->master->max_speed_hz;
> >
> > - spi_set_cs(spi, false);
> > -
> > if (spi->master->setup)
> > status = spi->master->setup(spi);
> >
> > + spi_set_cs(spi, false);
> > +
> > dev_dbg(&spi->dev, "setup mode %d, %s%s%s%s%u bits/w, %u Hz max --> %d\n",
> > (int) (spi->mode & (SPI_CPOL | SPI_CPHA)),
> > (spi->mode & SPI_CS_HIGH) ? "cs_high, " : "",
>
> mh. maybe a runtime PM issue?

mh?

>
> * external abort on non-linefetch: address cannot be accessed,
> since the module's clocks are disabled
> * built-in works, module not: built-in is probably a little bit
> faster (module must not be loaded from filesystem), so that
> the device has not yet been suspended
> * Before 4.2, omap2_mcspi_set_cs() was called in the setup
> routine, which acquired runtime PM
> * In 4.2, omap2_mcspi_set_cs() seems to be called without a
> prior pm_runtime_get_sync()
> * With your workaround, the device has not yet returned to
> suspend after the runtime PM acquisition in setup()
>
> So I suggest trying the following (compile tested only) patch:
>

It seems you are right.

With this patch the SPI drivers no longer cause data aborts.

I will wait for feedback from Pavel and Pali but it looks like
we have a winner.

> -- Sebastian
>
> diff --git a/drivers/spi/spi-omap2-mcspi.c b/drivers/spi/spi-omap2-mcspi.c
> index 5867384..f7d9ffd 100644
> --- a/drivers/spi/spi-omap2-mcspi.c
> +++ b/drivers/spi/spi-omap2-mcspi.c
> @@ -245,6 +245,7 @@ static void omap2_mcspi_set_enable(const struct spi_device *spi, int enable)
>
> static void omap2_mcspi_set_cs(struct spi_device *spi, bool enable)
> {
> + struct omap2_mcspi *mcspi = spi_master_get_devdata(spi->master);
> u32 l;
>
> /* The controller handles the inverted chip selects
> @@ -255,6 +256,8 @@ static void omap2_mcspi_set_cs(struct spi_device *spi, bool enable)
> enable = !enable;
>
> if (spi->controller_state) {
> + pm_runtime_get_sync(mcspi->dev);
> +

Should the return code should be checked here as with the other
instances of pm_runtime_get_sync?

> l = mcspi_cached_chconf0(spi);
>
> if (enable)
> @@ -263,6 +266,9 @@ static void omap2_mcspi_set_cs(struct spi_device *spi, bool enable)
> l |= OMAP2_MCSPI_CHCONF_FORCE;
>
> mcspi_write_chconf0(spi, l);
> +
> + pm_runtime_mark_last_busy(mcspi->dev);
> + pm_runtime_put_autosuspend(mcspi->dev);
> }
> }
>