On Fri, Dec 19, 2014 at 10:43:15AM +0800, Jisheng Zhang wrote:
> Dear all,
>
> Is there any issue I need to resolve so that the patch can be merged?
Adding Mika to the loop. He uses the driver a lot (and knows other
people who do)...
> On Wed, 10 Dec 2014 22:26:41 -0800
> Jisheng Zhang <jszhang@xxxxxxxxxxx> wrote:
>
> > readl/writel is too expensive especially on Cortex A9 w/ outer L2 cache.
> > This introduces i2c read/write errors on Marvell BG2/BG2Q SoCs when there
> > are heavy L2 cache maintenance operations at the same time.
> >
> > The driver does not perform DMA, so it's safe to use the relaxed version.
> > From another side, the relaxed io accessor macros are available on all
> > architectures now, so we can use the relaxed versions instead.
> >
> > Signed-off-by: Jisheng Zhang <jszhang@xxxxxxxxxxx>
> > ---
> > drivers/i2c/busses/i2c-designware-core.c | 12 ++++++------
> > 1 file changed, 6 insertions(+), 6 deletions(-)
> >
> > diff --git a/drivers/i2c/busses/i2c-designware-core.c
> > b/drivers/i2c/busses/i2c-designware-core.c index 23628b7..e279948 100644
> > --- a/drivers/i2c/busses/i2c-designware-core.c
> > +++ b/drivers/i2c/busses/i2c-designware-core.c
> > @@ -170,10 +170,10 @@ u32 dw_readl(struct dw_i2c_dev *dev, int offset)
> > u32 value;
> >
> > if (dev->accessor_flags & ACCESS_16BIT)
> > - value = readw(dev->base + offset) |
> > - (readw(dev->base + offset + 2) << 16);
> > + value = readw_relaxed(dev->base + offset) |
> > + (readw_relaxed(dev->base + offset + 2) << 16);
> > else
> > - value = readl(dev->base + offset);
> > + value = readl_relaxed(dev->base + offset);
> >
> > if (dev->accessor_flags & ACCESS_SWAP)
> > return swab32(value);
> > @@ -187,10 +187,10 @@ void dw_writel(struct dw_i2c_dev *dev, u32 b, int
> > offset) b = swab32(b);
> >
> > if (dev->accessor_flags & ACCESS_16BIT) {
> > - writew((u16)b, dev->base + offset);
> > - writew((u16)(b >> 16), dev->base + offset + 2);
> > + writew_relaxed((u16)b, dev->base + offset);
> > + writew_relaxed((u16)(b >> 16), dev->base + offset + 2);
> > } else {
> > - writel(b, dev->base + offset);
> > + writel_relaxed(b, dev->base + offset);
> > }
> > }
> >
>
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