Hi Liam,
On Mon, Aug 17, 2020 at 7:38 PM Liam Beguin <[email protected]> wrote: > From: Liam Beguin <[email protected]> > > Start by reading the content of the VENDOR_SPECIFIC2 register and update > each bit field based on device properties when defined. > > The use of bit masks prevents fields from overriding each other and > enables users to clear bits which are set by default, like datapolarity > in this instance. > > Signed-off-by: Liam Beguin <[email protected]> > --- > Changes since v1: > - use set_mask_bits > > Changes since v2: > - fix missing bit shift dropped in v2 > - rebase on 5.9-rc1 > > drivers/phy/ti/phy-tusb1210.c | 27 +++++++++++++++++---------- > 1 file changed, 17 insertions(+), 10 deletions(-) > > diff --git a/drivers/phy/ti/phy-tusb1210.c b/drivers/phy/ti/phy-tusb1210.c > index d8d0cc11d187..358842b5790f 100644 > --- a/drivers/phy/ti/phy-tusb1210.c > +++ b/drivers/phy/ti/phy-tusb1210.c > @@ -14,8 +14,11 @@ > > #define TUSB1210_VENDOR_SPECIFIC2 0x80 > #define TUSB1210_VENDOR_SPECIFIC2_IHSTX_SHIFT 0 > +#define TUSB1210_VENDOR_SPECIFIC2_IHSTX_MASK GENMASK(3, 0) > #define TUSB1210_VENDOR_SPECIFIC2_ZHSDRV_SHIFT 4 > +#define TUSB1210_VENDOR_SPECIFIC2_ZHSDRV_MASK GENMASK(5, 4) > #define TUSB1210_VENDOR_SPECIFIC2_DP_SHIFT 6 > +#define TUSB1210_VENDOR_SPECIFIC2_DP_MASK BIT(6) > > struct tusb1210 { > struct ulpi *ulpi; > @@ -118,23 +121,27 @@ static int tusb1210_probe(struct ulpi *ulpi) > * diagram optimization and DP/DM swap. > */ > > + reg = ulpi_read(ulpi, TUSB1210_VENDOR_SPECIFIC2); > + > /* High speed output drive strength configuration */ > - device_property_read_u8(&ulpi->dev, "ihstx", &val); > - reg = val << TUSB1210_VENDOR_SPECIFIC2_IHSTX_SHIFT; > + if (!device_property_read_u8(&ulpi->dev, "ihstx", &val)) > + reg = set_mask_bits(®, > TUSB1210_VENDOR_SPECIFIC2_IHSTX_MASK, > + val << > TUSB1210_VENDOR_SPECIFIC2_IHSTX_SHIFT); Triggered by your patches to add support for cmpxchg on u8 pointers to various architectures (which is a valuable goal in itself ;-), I decided to have a look at the underlying problem you were facing. IMHO, using set_mask_bits() is overkill here. That helper is meant to update individual bits in a variable that may be accessed concurrently, hence its use of cmpxchg(). In this driver, you just want to modify a local variable, by clearing a field, and setting some bits. No concurrency is involved. Perhaps using FIELD_PREP() from include/linux/bitfield.h is more appropriate? Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- [email protected] In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds
