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Date: Mon, 13 Feb 2017 07:39:21 +0000 From: Nicholas Mc Guire <der.herr@...r.at> To: Boris Brezillon <boris.brezillon@...e-electrons.com> Cc: Mika Westerberg <mika.westerberg@...ux.intel.com>, Cyrille Pitchen <cyrille.pitchen@...el.com>, Marek Vasut <marek.vasut@...il.com>, David Woodhouse <dwmw2@...radead.org>, Brian Norris <computersforpeace@...il.com>, Richard Weinberger <richard@....at>, linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH RFC] spi-nor: provide a range for poll_timout On Sun, Feb 12, 2017 at 10:59:23PM +0100, Boris Brezillon wrote: > +Mika > > On Sun, 12 Feb 2017 17:42:57 +0100 > Nicholas Mc Guire <der.herr@...r.at> wrote: > > > The overall poll time here is INTEL_SPI_TIMEOUT * 1000 which is > > 5000 * 1000 - so 5seconds and it is coded as a tight loop here delay_us > > to readl_poll_timeout() is set to 0. As this is never called in an atomic > > context sleeping should be no issue and there is no reasons for the > > tight-loop here. > > Hm, let's wait for Mika's feedback on this one. BTW, can you please Cc > him on you other spi-nor/intel patches and prefix your patches with the > driver name ('mtd: spi-nor: intel: ') so that we know where the changes > are made (without this prefix it looks like you're touching core files)? > will do - just saw that his email shows up in git plame which I normally also include along with what scripts/get_maintainer.pl -f shows - sorry for the ommision. thx! hofrat > > > > > Signed-off-by: Nicholas Mc Guire <der.herr@...r.at> > > --- > > > > Problem located by experimental coccinelle script: > > ./drivers/mtd/spi-nor/intel-spi.c:265:8-26: WARNING: usleep_range min=0 for delay INTEL_SPI_TIMEOUT * 1000 > > ./drivers/mtd/spi-nor/intel-spi.c:274:8-26: WARNING: usleep_range min=0 for delay INTEL_SPI_TIMEOUT * 1000 > > > > The rational for setting the delay_us here to 40 is that readx_poll_timeout() > > will take delay_us >> 2 + 1 as min value and that should be at least 10us (see > > Documentation/timers/timers-howto.txt). Ideally the delay would be made > > even larger to keep the load on the hrtimer subsystem low as these delays > > here do not seem to be critical. Someone that knows the details of this device > > would need to check if a larger delay would be ok here. > > > > Patch was compile tested with: multi_v7_defconfig (implies CONFIG_MTD_SPI_NOR=y) > > one coccicheck finding reported and one spars finding (in separate patches) > > > > Patch is against 4.10-rc6 (localversion-next is next-20170210) > > > > drivers/mtd/spi-nor/intel-spi.c | 4 ++-- > > 1 file changed, 2 insertions(+), 2 deletions(-) > > > > diff --git a/drivers/mtd/spi-nor/intel-spi.c b/drivers/mtd/spi-nor/intel-spi.c > > index a10f602..371bcf9 100644 > > --- a/drivers/mtd/spi-nor/intel-spi.c > > +++ b/drivers/mtd/spi-nor/intel-spi.c > > @@ -263,7 +263,7 @@ static int intel_spi_wait_hw_busy(struct intel_spi *ispi) > > u32 val; > > > > return readl_poll_timeout(ispi->base + HSFSTS_CTL, val, > > - !(val & HSFSTS_CTL_SCIP), 0, > > + !(val & HSFSTS_CTL_SCIP), 40, > > INTEL_SPI_TIMEOUT * 1000); > > } > > > > @@ -272,7 +272,7 @@ static int intel_spi_wait_sw_busy(struct intel_spi *ispi) > > u32 val; > > > > return readl_poll_timeout(ispi->sregs + SSFSTS_CTL, val, > > - !(val & SSFSTS_CTL_SCIP), 0, > > + !(val & SSFSTS_CTL_SCIP), 40, > > INTEL_SPI_TIMEOUT * 1000); > > } > > >
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