On Fri, Jul 13, 2012 at 07:18:35PM +0530, Shubhrajyoti Datta wrote:
> Hello,
>
> On Fri, Jul 13, 2012 at 7:14 PM, Jayachandran C
> <jayachandranc@xxxxxxxxxxxxxxxxx> wrote:
> > From: Ganesan Ramalingam <ganesanr@xxxxxxxxxxxx>
> >
> > Some architectures supports only 16-bit or 32-bit read/write access to
> > their IO space. Add a 'reg-io-width' platform and OF parameter which
> > specifies the IO width to support these platforms.
> >
> > reg-io-width can be specified as 1, 2 or 4, and has a default value
> > of 1 if it is unspecified.
> >
> > Signed-off-by: Ganesan Ramalingam <ganesanr@xxxxxxxxxxxx>
> > Signed-off-by: Jayachandran C <jayachandranc@xxxxxxxxxxxxxxxxx>
> > ---
> > .../devicetree/bindings/i2c/i2c-ocores.txt | 2 ++
> > drivers/i2c/busses/i2c-ocores.c | 21 ++++++++++++++++++--
> > include/linux/i2c-ocores.h | 1 +
> > 3 files changed, 22 insertions(+), 2 deletions(-)
> >
> > diff --git a/Documentation/devicetree/bindings/i2c/i2c-ocores.txt b/Documentation/devicetree/bindings/i2c/i2c-ocores.txt
> > index 1c9334b..c15781f 100644
> > --- a/Documentation/devicetree/bindings/i2c/i2c-ocores.txt
> > +++ b/Documentation/devicetree/bindings/i2c/i2c-ocores.txt
> > @@ -10,6 +10,7 @@ Required properties:
> >
> > Optional properties:
> > - reg-shift : device register offsets are shifted by this value
> > +- reg-io-width : io register width in bytes (1, 2 or 4)
> > - regstep : deprecated, use reg-shift above
> >
> > Example:
> > @@ -23,6 +24,7 @@ Example:
> > clock-frequency = <20000000>;
> >
> > reg-shift = <0>; /* 8 bit registers */
> > + reg-io-width = <1>; /* 8 bit read/write */
> >
> > dummy@60 {
> > compatible = "dummy";
> > diff --git a/drivers/i2c/busses/i2c-ocores.c b/drivers/i2c/busses/i2c-ocores.c
> > index 721ead9..de3b119 100644
> > --- a/drivers/i2c/busses/i2c-ocores.c
> > +++ b/drivers/i2c/busses/i2c-ocores.c
> > @@ -30,6 +30,7 @@
> > struct ocores_i2c {
> > void __iomem *base;
> > u32 reg_shift;
> > + u32 reg_io_width;
> > wait_queue_head_t wait;
> > struct i2c_adapter adap;
> > struct i2c_msg *msg;
> > @@ -72,12 +73,22 @@ struct ocores_i2c {
> >
> > static inline void oc_setreg(struct ocores_i2c *i2c, int reg, u8 value)
> > {
> > - iowrite8(value, i2c->base + (reg << i2c->reg_shift));
> > + if (i2c->reg_io_width == 4)
> > + iowrite32(value, i2c->base + (reg << i2c->reg_shift));
> > + else if (i2c->reg_io_width == 2)
> > + iowrite16(value, i2c->base + (reg << i2c->reg_shift));
> > + else
> > + iowrite8(value, i2c->base + (reg << i2c->reg_shift));
> > }
> >
> > static inline u8 oc_getreg(struct ocores_i2c *i2c, int reg)
>
> Should the return type be changed.
> Now that it is returning more that than 8 bits.
>
> Did I miss something?
Only 8 bits of the register is significant, so even if we read 16 or 32
bits only the lowest 8 bits are returned.
JC.
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