Re: [PATCH v9 09/12] PCI: brcmstb: Set additional internal memory DMA viewport sizes

[Jim Quinlan <james.quinlan@broadcom.com>]

fls64
On Sat, Aug 1, 2020 at 1:39 PM Nicolas Saenz Julienne
<nsaenzjulienne@suse.de> wrote:
>
> Hi Jim,
>
> On Fri, 2020-07-24 at 16:33 -0400, Jim Quinlan wrote:
> > The Raspberry Pi (RPI) is currently the only chip using this driver
> > (pcie-brcmstb.c).  There, only one memory controller is used, without an
> > extension region, and the SCB0 viewport size is set to the size of the
> > first and only dma-range region.  Other BrcmSTB SOCs have more complicated
> > memory configurations that require setting additional viewport sizes.
> >
> > BrcmSTB PCIe controllers are intimately connected to the memory
> > controller(s) on the SOC.  The SOC may have one to three memory
> > controllers; they are indicated by the term SCBi.  Each controller has a
> > base region and an optional extension region.  In physical memory, the base
> > and extension regions of a controller are not adjacent, but in PCIe-space
> > they are.
> >
> > There is a "viewport" for each memory controller that allows DMA from
> > endpoint devices.  Each viewport's size must be set to a power of two, and
> > that size must be equal to or larger than the amount of memory each
> > controller supports which is the sum of base region and its optional
> > extension.  Further, the 1-3 viewports are also adjacent in PCIe-space.
> >
> > Unfortunately the viewport sizes cannot be ascertained from the
> > "dma-ranges" property so they have their own property, "brcm,scb-sizes".
> > This is because dma-range information does not indicate what memory
> > controller it is associated.  For example, consider the following case
> > where the size of one dma-range is 2GB and the second dma-range is 1GB:
> >
> >     /* Case 1: SCB0 size set to 4GB */
> >     dma-range0: 2GB (from memc0-base)
> >     dma-range1: 1GB (from memc0-extension)
> >
> >     /* Case 2: SCB0 size set to 2GB, SCB1 size set to 1GB */
> >     dma-range0: 2GB (from memc0-base)
> >     dma-range1: 1GB (from memc0-extension)
> >
> > By just looking at the dma-ranges information, one cannot tell which
> > situation applies. That is why an additional property is needed.  Its
> > length indicates the number of memory controllers being used and each value
> > indicates the viewport size.
> >
> > Note that the RPI DT does not have a "brcm,scb-sizes" property value,
> > as it is assumed that it only requires one memory controller and no
> > extension.  So the optional use of "brcm,scb-sizes" will be backwards
> > compatible.
> >
> > One last layer of complexity exists: all of the viewports sizes must be
> > added and rounded up to a power of two to determine what the "BAR" size is.
> > Further, an offset must be given that indicates the base PCIe address of
> > this "BAR".  The use of the term BAR is typically associated with endpoint
> > devices, and the term is used here because the PCIe HW may be used as an RC
> > or an EP.  In the former case, all of the system memory appears in a single
> > "BAR" region in PCIe memory.  As it turns out, BrcmSTB PCIe HW is rarely
> > used in the EP role and its system of mapping memory is an artifact that
> > requires multiple dma-ranges regions.
> >
> > Signed-off-by: Jim Quinlan <james.quinlan@broadcom.com>
> > Acked-by: Florian Fainelli <f.fainelli@gmail.com>
> > ---
> >  drivers/pci/controller/pcie-brcmstb.c | 68 ++++++++++++++++++++-------
> >  1 file changed, 50 insertions(+), 18 deletions(-)
> >
> > diff --git a/drivers/pci/controller/pcie-brcmstb.c b/drivers/pci/controller/pcie-brcmstb.c
> > index 8dacb9d3b7b6..3ef2d37cc43b 100644
> > --- a/drivers/pci/controller/pcie-brcmstb.c
> > +++ b/drivers/pci/controller/pcie-brcmstb.c
> > @@ -715,22 +720,44 @@ static inline int brcm_pcie_get_rc_bar2_size_and_offset(struct brcm_pcie *pcie,
> >                                                       u64 *rc_bar2_offset)
> >  {
> >       struct pci_host_bridge *bridge = pci_host_bridge_from_priv(pcie);
> > -     struct device *dev = pcie->dev;
> >       struct resource_entry *entry;
> > +     struct device *dev = pcie->dev;
> > +     u64 lowest_pcie_addr = ~(u64)0;
> > +     int ret, i = 0;
> > +     u64 size = 0;
> >
> > -     entry = resource_list_first_type(&bridge->dma_ranges, IORESOURCE_MEM);
> > -     if (!entry)
> > -             return -ENODEV;
> > +     resource_list_for_each_entry(entry, &bridge->dma_ranges) {
> > +             u64 pcie_beg = entry->res->start - entry->offset;
> >
> > +             size += entry->res->end - entry->res->start + 1;
> > +             if (pcie_beg < lowest_pcie_addr)
> > +                     lowest_pcie_addr = pcie_beg;
> > +     }
> >
> > -     /*
> > -      * The controller expects the inbound window offset to be calculated as
> > -      * the difference between PCIe's address space and CPU's. The offset
> > -      * provided by the firmware is calculated the opposite way, so we
> > -      * negate it.
> > -      */
> > -     *rc_bar2_offset = -entry->offset;
> > -     *rc_bar2_size = 1ULL << fls64(entry->res->end - entry->res->start);
> > +     if (lowest_pcie_addr == ~(u64)0) {
> > +             dev_err(dev, "DT node has no dma-ranges\n");
> > +             return -EINVAL;
> > +     }
> > +
> > +     ret = of_property_read_variable_u64_array(pcie->np, "brcm,scb-sizes", pcie->memc_size, 1,
> > +                                               PCIE_BRCM_MAX_MEMC);
> > +
> > +     if (ret <= 0) {
> > +             /* Make an educated guess */
> > +             pcie->num_memc = 1;
> > +             pcie->memc_size[0] = 1 << fls64(size - 1);
>
> You need to 1ULL here.
Got it.
Thanks,
Jim
>
> Regards,
> Nicolas
>
> > +     } else {
> > +             pcie->num_memc = ret;
> > +     }
> > +
> > +     /* Each memc is viewed through a "port" that is a power of 2 */
> > +     for (i = 0, size = 0; i < pcie->num_memc; i++)
> > +             size += pcie->memc_size[i];
> > +
> > +     /* System memory starts at this address in PCIe-space */
> > +     *rc_bar2_offset = lowest_pcie_addr;
> > +     /* The sum of all memc views must also be a power of 2 */
> > +     *rc_bar2_size = 1ULL << fls64(size - 1);
> >
> >       /*
> >        * We validate the inbound memory view even though we should trust
>