Re: [PATCH v3 03/13] spi: atmel-quadspi: drop wrappers for iomem accesses

Boris Brezillon
2019-02-02T13:23:59Z

On Sat, 2 Feb 2019 08:44:27 +0000
<Tudor.Ambarus@microchip.com> wrote:

> On 02/02/2019 09:11 AM, Boris Brezillon wrote:
> > On Sat, 2 Feb 2019 04:07:19 +0000
> > <Tudor.Ambarus@microchip.com> wrote:
> >
> >> From: Tudor Ambarus <tudor.ambarus@microchip.com>
> >>
> >> The wrappers hid that the accesses are relaxed. Drop them.
> >>
> >> Suggested-by: Boris Brezillon <bbrezillon@kernel.org>
> >> Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>
> >> ---
> >> v3: no change
> >> v2: new patch
> >>
> >> drivers/spi/atmel-quadspi.c | 47 +++++++++++++++++++--------------------------
> >> 1 file changed, 20 insertions(+), 27 deletions(-)
> >>
> >> diff --git a/drivers/spi/atmel-quadspi.c b/drivers/spi/atmel-quadspi.c
> >> index feeddcb25e1f..131374db0db4 100644
> >> --- a/drivers/spi/atmel-quadspi.c
> >> +++ b/drivers/spi/atmel-quadspi.c
> >> @@ -175,17 +175,6 @@ static const struct qspi_mode sama5d2_qspi_modes[] = {
> >> { 4, 4, 4, QSPI_IFR_WIDTH_QUAD_CMD },
> >> };
> >>
> >> -/* Register access functions */
> >> -static inline u32 qspi_readl(struct atmel_qspi *aq, u32 reg)
> >> -{
> >> - return readl_relaxed(aq->regs + reg);
> >> -}
> >> -
> >> -static inline void qspi_writel(struct atmel_qspi *aq, u32 reg, u32 value)
> >> -{
> >> - writel_relaxed(value, aq->regs + reg);
> >> -}
> >> -
> >> static inline bool is_compatible(const struct spi_mem_op *op,
> >> const struct qspi_mode *mode)
> >> {
> >> @@ -229,6 +218,7 @@ static bool atmel_qspi_supports_op(struct spi_mem *mem,
> >> static int atmel_qspi_exec_op(struct spi_mem *mem, const struct spi_mem_op *op)
> >> {
> >> struct atmel_qspi *aq = spi_controller_get_devdata(mem->spi->master);
> >> + void __iomem *base = aq->regs;
> >
> > Can we name this variable regs instead of base or even get rid of it
> > and dereference aq->regs in the xxx_relaxed() calls (doesn't look like
> > the lines would be over 80 chars even when doing that). With this
> > addressed, you can add:
> >
> > Reviewed-by: Boris Brezillon <bbrezillon@kernel.org>
>
> I chose to introduce the "base" variable when I have at least 2 dereferences in
> a function, as an optimization. In exec_op() for example, there are 6
> dereferences of aq->reqs. Why do you prefer keeping aq->regs?

I tend to not add local variables unless they help improve readability
or optimize things. In this case, I'd expect the compiler to be smart
enough to detect that aq->reqs is used several times and store it in a
register. When it comes to readability, I don't think it improve
things, but that's probably a matter of taste.