Messages in this thread | | | Subject | Re: [PATCH] PCI: dwc: Warn only for non-prefetchable memory resource size >4GB | From | Vidya Sagar <> | Date | Tue, 19 May 2020 22:38:39 +0530 |
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On 19-May-20 8:28 PM, Lorenzo Pieralisi wrote: > External email: Use caution opening links or attachments > > > On Tue, May 19, 2020 at 07:25:02PM +0530, Vidya Sagar wrote: >> >> >> On 18-May-20 9:24 PM, Lorenzo Pieralisi wrote: >>> External email: Use caution opening links or attachments >>> >>> >>> On Wed, May 13, 2020 at 05:35:08PM -0500, Bjorn Helgaas wrote: >>>> [+cc Alan; please cc authors of relevant commits, >>>> updated Andrew's email address] >>>> >>>> On Thu, May 14, 2020 at 12:38:55AM +0530, Vidya Sagar wrote: >>>>> commit 9e73fa02aa009 ("PCI: dwc: Warn if MEM resource size exceeds max for >>>>> 32-bits") enables warning for MEM resources of size >4GB but prefetchable >>>>> memory resources also come under this category where sizes can go beyond >>>>> 4GB. Avoid logging a warning for prefetchable memory resources. >>>>> >>>>> Signed-off-by: Vidya Sagar <vidyas@nvidia.com> >>>>> --- >>>>> drivers/pci/controller/dwc/pcie-designware-host.c | 3 ++- >>>>> 1 file changed, 2 insertions(+), 1 deletion(-) >>>>> >>>>> diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c b/drivers/pci/controller/dwc/pcie-designware-host.c >>>>> index 42fbfe2a1b8f..a29396529ea4 100644 >>>>> --- a/drivers/pci/controller/dwc/pcie-designware-host.c >>>>> +++ b/drivers/pci/controller/dwc/pcie-designware-host.c >>>>> @@ -366,7 +366,8 @@ int dw_pcie_host_init(struct pcie_port *pp) >>>>> pp->mem = win->res; >>>>> pp->mem->name = "MEM"; >>>>> mem_size = resource_size(pp->mem); >>>>> - if (upper_32_bits(mem_size)) >>>>> + if (upper_32_bits(mem_size) && >>>>> + !(win->res->flags & IORESOURCE_PREFETCH)) >>>>> dev_warn(dev, "MEM resource size exceeds max for 32 bits\n"); >>>>> pp->mem_size = mem_size; >>>>> pp->mem_bus_addr = pp->mem->start - win->offset; >>> >>> That warning was added for a reason - why should not we log legitimate >>> warnings ? AFAIU having resources larger than 4GB can lead to undefined >>> behaviour given the current ATU programming API. >> Yeah. I'm all for a warning if the size is larger than 4GB in case of >> non-prefetchable window as one of the ATU outbound translation >> channels is being used, > > Is it true for all DWC host controllers ? Or there may be another > exception whereby we would be forced to disable this warning altogether > ?I think so. As I see from the code, ATU's Region-0 is used for config space translation Region-1 is used for non-prefetchable memory translation Region-2 is used for I/O translation So, there is no region reserved for translating prefetchable memory regions.
> >> but, we are not employing any ATU outbound translation channel for > > What does this mean ? "we are not employing any ATU outbound...", is > this the tegra driver ? And what guarantees that this warning is not > legitimate on DWC host controllers that do use the ATU outbound > translation for prefetchable windows ? Not Tegra driver but Tegra HW. Tegra HW doesn't need any ATU outbound translation for prefetchable (for that matter any 1-to-1 mapping to generate memory transactions on the PCIe bus). The Warning is still valid for both Tegra and other DWC based controllers for non-prefetchable memory translation.
> > Can DWC maintainers chime in and clarify please ? > >> prefetchable window and they can be greater than 4GB in size for all >> right reasons. So, logging a warning for prefetchable region doesn't >> seem correct to me. Please let me know if my understanding is wrong. > > I think your patch is wrong and it is applied on top of a patch that > is wrong too, so I won't apply yours and it is likely I will revert > Alan's because it seems to solve nothing (and warn spuriously). > > It is time for people who maintain DWC please to speak up because I > don't have the HW details required to make a judgment. > > Lorenzo > >> - Vidya Sagar >>> >>> Alan ? I want to understand what's the best course of action before >>> merging these patches. >>> >>> Lorenzo >>>
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