Re: [PATCH v5 09/12] PCI: brcmstb: Set internal memory viewport sizes

From: Bjorn Helgaas
Date: Wed Jun 17 2020 - 23:01:45 EST

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On Wed, Jun 17, 2020 at 01:28:12PM -0400, Jim Quinlan wrote:
> Hello Bjorn,
>
> On Tue, Jun 16, 2020 at 6:05 PM Bjorn Helgaas <helgaas@xxxxxxxxxx> wrote:
> >
> > On Tue, Jun 16, 2020 at 04:55:16PM -0400, Jim Quinlan wrote:
> > > BrcmSTB PCIe controllers are intimately connected to the memory
> > > controller(s) on the SOC. There is a "viewport" for each memory controller
> > > that allows inbound accesses to CPU memory. 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.
> >
> > This describes some requirements, but doesn't actually say what this
> > patch *does*.
> >
> > I *think* it reads the viewport sizes from the "brcm,scb-sizes" DT
> > property instead of computing something from "dma-ranges". Looks like
> > it also adds support for SCB1 and SCB2.
> >
> > Those seem interesting, but don't really come through in the subject
> > or even the commit log.
> >
> > If I understand correctly, this is all for DMA ("inbound accesses to
> > CPU memory"). I think it would be worth mentioning "DMA", since
> > that's the common term for this.
>
>
> I have changed the commit message to the text below. Please let me
> know if it requires more work
> Thanks, Jim
>
> PCI: brcmstb: Set internal memory DMA viewport sizes

Did you not set the viewport sizes before?

> BrcmSTB PCIe controllers are intimately connected to the memory
> controller(s) on the SOC. There is a "viewport" for each memory controller
> that allows inbound DMA acceses to CPU memory. 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. Unfortunately the viewport
> sizes cannot be ascertained from the "dma-ranges" property so they have
> their own property, "brcm,scb-sizes".

s/inbound DMA acceses to CPU memory/DMA/

"Accesses" is redundant since the "A" in "DMA" stands for "access".
I'm not sure "inbound" adds anything and might confuse since DMA may
be either a read or write of CPU memory.

I assume *all* drivers need to know the address and size of regions in
"dma-ranges". Is there something special about this device that means
it needs something different?

I guess it's the base/extension split? That couldn't be described as
two separate DMA ranges?

Could/should the new property have a name somehow related to
"dma-ranges"?

Should "dma-ranges" be documented in
Documentation/devicetree/bindings/pci/pci.txt instead of the
individual device bindings?

> There may be 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 are not
> adjacent, but in PCIe-space they are. Further, the 1-3 viewports are also
> adjacent in PCIe-space.
>
> The SCB settings work in conjunction with the "dma-ranges' offsets to
> enable non-identity mappings between system memory and PCIe space.

s/ranges'/ranges"/ (mismatched quotes)

This describes the hardware, but still doesn't actually say what this
patch *does*.

If I'm a user, why do I want this patch? Does it fix something that
didn't work before? Does it increase the amount of DMA-able memory?

What does this mean in terms of backwards compatibility with old DTs?
Does this work with old DTs that don't have "brcm,scb-sizes"? Maybe
this is all related to specific devices that weren't supported before,
so there *are* no old DTs for them? I can't tell from the binding
update or the patch that this is related to specific devices.

> > > Signed-off-by: Jim Quinlan <james.quinlan@xxxxxxxxxxxx>
> > > Acked-by: Florian Fainelli <f.fainelli@xxxxxxxxx>
> > > ---
> > > 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 9189406fd35c..39f77709c6a2 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
> > >
> > > #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])
> > > @@ -260,6 +263,8 @@ 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];
> > > };
> > >
> > > /*
> > > @@ -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);
> > > + } 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
> > > @@ -782,12 +809,11 @@ 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 */
> > > @@ -824,11 +850,17 @@ 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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Previous message: Hyeonki Hong: "[PATCH] [v2] pinctrl: meson: fix drive strength register and bit calculation"
In reply to: Jim Quinlan: "Re: [PATCH v5 09/12] PCI: brcmstb: Set internal memory viewport sizes"
Next in thread: Jim Quinlan: "Re: [PATCH v5 09/12] PCI: brcmstb: Set internal memory viewport sizes"
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