On Fri, Dec 18, 2015 at 09:41:47PM +0100, Marc Kleine-Budde wrote:
> On 12/18/2015 09:17 PM, Damien Riegel wrote:
> > Technologic Systems provides an IP compatible with the SJA1000,
> > instantiated in an FPGA. Because of some bus widths issue, access to
> > registers is made through a "window" that works like this:
> >
> > base + 0x0: address to read/write
> > base + 0x2: 8-bit register value
> >
> > This commit adds a new compatible device, "technologic,sja1000", with
> > read and write functions using the window mechanism.
> >
> > Signed-off-by: Damien Riegel <damien.rie...@savoirfairelinux.com>
> > ---
> > drivers/net/can/sja1000/sja1000_platform.c | 30
> > ++++++++++++++++++++++++++++--
> > 1 file changed, 28 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/net/can/sja1000/sja1000_platform.c
> > b/drivers/net/can/sja1000/sja1000_platform.c
> > index 0552ed4..6cbf251 100644
> > --- a/drivers/net/can/sja1000/sja1000_platform.c
> > +++ b/drivers/net/can/sja1000/sja1000_platform.c
> > @@ -70,6 +70,18 @@ static void sp_write_reg32(const struct sja1000_priv
> > *priv, int reg, u8 val)
> > iowrite8(val, priv->reg_base + reg * 4);
> > }
> >
> > +static u8 ts4800_read_reg16(const struct sja1000_priv *priv, int reg)
> > +{
> > + sp_write_reg16(priv, 0, reg);
> > + return sp_read_reg16(priv, 2);
>
> This is racy, please add a spinlock.
>
> > +}
> > +
> > +static void ts4800_write_reg16(const struct sja1000_priv *priv, int reg,
> > u8 val)
> > +{
> > + sp_write_reg16(priv, 0, reg);
> > + sp_write_reg16(priv, 2, val);
>
> This is racy, too.
>
> Have a look at https://marc.info/?l=linux-can&m=137149497403825&w=2
Thank you for the link. In my situation, I don't think there is a race
issue at the bus level, so a per-device spinlock should be enough. Would
that be an acceptable patch? It would look a lot like the patch you
suggested in the thread you linked, just rebased on current version.
Thanks,
Damien
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