Re: [PATCH] PCI: dwc: designware: don't sleep in atomic context

[Pankaj Dubey]

On 10/12/2017 04:09 PM, David Laight wrote:
> From: Pankaj Dubey
> > Sent: 12 October 2017 08:55
> > In pcie-designware.c many places we are calling "usleep_range" which
> > are in atomic context. This patch fixes these potential BUGs and
> > replaces "usleep_range" with mdelay calls.
> >
> > Signed-off-by: Pankaj Dubey <pankaj.dubey@xxxxxxxxxxx>
> > ---
> >   drivers/pci/dwc/pcie-designware.c | 8 ++++----
> >   drivers/pci/dwc/pcie-designware.h | 3 +--
> >   2 files changed, 5 insertions(+), 6 deletions(-)
> >
> > diff --git a/drivers/pci/dwc/pcie-designware.c b/drivers/pci/dwc/pcie-designware.c
> > index 88abddd..35d19b9 100644
> > --- a/drivers/pci/dwc/pcie-designware.c
> > +++ b/drivers/pci/dwc/pcie-designware.c
> > @@ -138,7 +138,7 @@ static void dw_pcie_prog_outbound_atu_unroll(struct dw_pcie *pci, int index,
> >   		if (val & PCIE_ATU_ENABLE)
> >   			return;
> >
> > -		usleep_range(LINK_WAIT_IATU_MIN, LINK_WAIT_IATU_MAX);
> > +		mdelay(LINK_WAIT_IATU_MIN);
> >   	}
> Spinning for 9ms (possibly 10 times) isn't really a good idea.

Yes. It may not be a good idea, however in our experiment it never hit 
maximum retry count.
I just converted usleep_range to mdelay keeping min time limitation as 
it is, though I
am not sure, how do we arrived on these numbers in original code, may be 
Joao Pinto
from Synopsys have some idea, I will try to do few experiment and try to 
find out what
is sufficient minimum time in our hardware for these mdelay.

Thanks,
Pankaj Dubey
> 	David