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Date:   Fri, 11 Sep 2020 11:28:35 -0400
From:   Jim Quinlan <james.quinlan@...adcom.com>
To:     Rob Herring <robh@...nel.org>
Cc:     "open list:PCI NATIVE HOST BRIDGE AND ENDPOINT DRIVERS" 
        <linux-pci@...r.kernel.org>,
        Nicolas Saenz Julienne <nsaenzjulienne@...e.de>,
        Christoph Hellwig <hch@....de>,
        Robin Murphy <robin.murphy@....com>,
        "maintainer:BROADCOM BCM7XXX ARM ARCHITECTURE" 
        <bcm-kernel-feedback-list@...adcom.com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        "moderated list:BROADCOM BCM2711/BCM2835 ARM ARCHITECTURE" 
        <linux-rpi-kernel@...ts.infradead.org>,
        "moderated list:BROADCOM BCM2711/BCM2835 ARM ARCHITECTURE" 
        <linux-arm-kernel@...ts.infradead.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v11 08/11] PCI: brcmstb: Set additional internal memory
 DMA viewport sizes

On Thu, Sep 10, 2020 at 12:17 PM Rob Herring <robh@...nel.org> wrote:
>
> On Mon, Aug 24, 2020 at 03:30:21PM -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@...adcom.com>
> > Acked-by: Florian Fainelli <f.fainelli@...il.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 041b8d109563..7150eaa803c2 100644
> > --- a/drivers/pci/controller/pcie-brcmstb.c
> > +++ b/drivers/pci/controller/pcie-brcmstb.c
> > @@ -57,6 +57,8 @@
> >  #define  PCIE_MISC_MISC_CTRL_MAX_BURST_SIZE_MASK     0x300000
> >  #define  PCIE_MISC_MISC_CTRL_MAX_BURST_SIZE_128              0x0
> >  #define  PCIE_MISC_MISC_CTRL_SCB0_SIZE_MASK          0xf8000000
> > +#define  PCIE_MISC_MISC_CTRL_SCB1_SIZE_MASK          0x07c00000
> > +#define  PCIE_MISC_MISC_CTRL_SCB2_SIZE_MASK          0x0000001f
>
> Perhaps make 0-2 an arg and then you can just do:
>
> u32p_replace_bits(&tmp, scb_size_val, PCIE_MISC_MISC_CTRL_SCB_SIZE_MASK(memc))

I cannot get this to work.  In this case u32p_replace_bits requires
that the mask is a compile-time constant; when "memc" is a variable I
don't see how to do this.
>
> >
> >  #define PCIE_MISC_CPU_2_PCIE_MEM_WIN0_LO             0x400c
> >  #define PCIE_MEM_WIN0_LO(win)        \
> > @@ -154,6 +156,7 @@
> >  #define SSC_STATUS_OFFSET            0x1
> >  #define SSC_STATUS_SSC_MASK          0x400
> >  #define SSC_STATUS_PLL_LOCK_MASK     0x800
> > +#define PCIE_BRCM_MAX_MEMC           3
> >
> >  #define IDX_ADDR(pcie)                       (pcie->reg_offsets[EXT_CFG_INDEX])
> >  #define DATA_ADDR(pcie)                      (pcie->reg_offsets[EXT_CFG_DATA])
> > @@ -259,6 +262,8 @@ struct brcm_pcie {
> >       const int               *reg_field_info;
> >       enum pcie_type          type;
> >       struct reset_control    *rescal;
> > +     int                     num_memc;
> > +     u64                     memc_size[PCIE_BRCM_MAX_MEMC];
> >  };
> >
> >  /*
> > @@ -714,22 +719,44 @@ 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] = 1ULL << fls64(size - 1);
>
> Use roundup_pow_of_two()
The reason I didn't use roundup_pow_of_two() is that it returns a
ulong which on ARM is 32bits and cannot represent  4GB.

>
> > +     } 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);
>
> Use roundup_pow_of_two()
Ditto

Jim Quinlan
Broadcom STB
>
> >
> >       /*
> >        * We validate the inbound memory view even though we should trust
> > @@ -781,12 +808,11 @@ static int brcm_pcie_setup(struct brcm_pcie *pcie)
> >       void __iomem *base = pcie->base;
> >       struct device *dev = pcie->dev;
> >       struct resource_entry *entry;
> > -     unsigned int scb_size_val;
> >       bool ssc_good = false;
> >       struct resource *res;
> >       int num_out_wins = 0;
> >       u16 nlw, cls, lnksta;
> > -     int i, ret;
> > +     int i, ret, memc;
> >       u32 tmp, aspm_support;
> >
> >       /* Reset the bridge */
> > @@ -826,11 +852,17 @@ static int brcm_pcie_setup(struct brcm_pcie *pcie)
> >       writel(upper_32_bits(rc_bar2_offset),
> >              base + PCIE_MISC_RC_BAR2_CONFIG_HI);
> >
> > -     scb_size_val = rc_bar2_size ?
> > -                    ilog2(rc_bar2_size) - 15 : 0xf; /* 0xf is 1GB */
> >       tmp = readl(base + PCIE_MISC_MISC_CTRL);
> > -     u32p_replace_bits(&tmp, scb_size_val,
> > -                       PCIE_MISC_MISC_CTRL_SCB0_SIZE_MASK);
> > +     for (memc = 0; memc < pcie->num_memc; memc++) {
> > +             u32 scb_size_val = ilog2(pcie->memc_size[memc]) - 15;
> > +
> > +             if (memc == 0)
> > +                     u32p_replace_bits(&tmp, scb_size_val, PCIE_MISC_MISC_CTRL_SCB0_SIZE_MASK);
> > +             else if (memc == 1)
> > +                     u32p_replace_bits(&tmp, scb_size_val, PCIE_MISC_MISC_CTRL_SCB1_SIZE_MASK);
> > +             else if (memc == 2)
> > +                     u32p_replace_bits(&tmp, scb_size_val, PCIE_MISC_MISC_CTRL_SCB2_SIZE_MASK);
> > +     }
> >       writel(tmp, base + PCIE_MISC_MISC_CTRL);
> >
> >       /*
> > --
> > 2.17.1
> >

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