From: Bjorn Helgaas > Sent: 20 October 2017 19:19 > On Fri, Oct 13, 2017 at 09:10:38AM +0530, Pankaj Dubey wrote: > > > > > > 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. > > Just based on the preceding comment, it looks like the wait is > essential because subsequent config and I/O accesses won't work > correctly until the ATU enable takes effect. > > If we timeout here, I suspect it's because something is seriously > wrong in the hardware, so I doubt there's any point in trying to > minimize the timeout period. If something is that broken, it doesn't > matter whether we wait 9ms or 900ms. Even one 9ms wait is extreme. How long does this usually take? ... David
