Re: linux 4.2-rc1 broken Nokia N900

Pali Rohár
2015-07-28T08:39:39Z

On Saturday 25 July 2015 10:55:50 Pali Rohár wrote:
> On Wednesday 22 July 2015 04:03:07 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?
> >
> > * 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:
> >
> > -- 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);
> > +
> > 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);
> > }
> > }
>
> This patch fix spi bus for me.
>
> Tested-by: Pali Rohár <pali.rohar@gmail.com>
>

Sebastian or Michael: Can you add check for pm_runtime_get_sync()
function and send patch for including in mainline kernel?

--
Pali Rohár
pali.rohar@gmail.com