Subject: Re: [PATCH v3 4/4] PCI: cadence: Use "dma-ranges" instead of "cdns,no-bar-match-nbits" property

From: Kishon Vijay Abraham I <[email-masked]>
Date: Thu, 21 May 2020 17:43:02 +0530

Rob,

On 5/21/2020 9:00 AM, Kishon Vijay Abraham I wrote:
> Hi Rob,
> 
> On 5/19/2020 10:41 PM, Rob Herring wrote:
>> On Fri, May 8, 2020 at 7:07 AM Kishon Vijay Abraham I <[email-masked]> wrote:
>>>
>>> Cadence PCIe core driver (host mode) uses "cdns,no-bar-match-nbits"
>>> property to configure the number of bits passed through from PCIe
>>> address to internal address in Inbound Address Translation register.
>>> This only used the NO MATCH BAR.
>>>
>>> However standard PCI dt-binding already defines "dma-ranges" to
>>> describe the address ranges accessible by PCIe controller. Add support
>>> in Cadence PCIe host driver to parse dma-ranges and configure the
>>> inbound regions for BAR0, BAR1 and NO MATCH BAR. Cadence IP specifies
>>> maximum size for BAR0 as 256GB, maximum size for BAR1 as 2 GB, so if
>>> the dma-ranges specifies a size larger than the maximum allowed, the
>>> driver will split and configure the BARs.
>>
>> Would be useful to know what your dma-ranges contains now.
>>
>>
>>> Legacy device tree binding compatibility is maintained by retaining
>>> support for "cdns,no-bar-match-nbits".
>>>
>>> Signed-off-by: Kishon Vijay Abraham I <[email-masked]>
>>> ---
>>>  .../controller/cadence/pcie-cadence-host.c    | 141 ++++++++++++++++--
>>>  drivers/pci/controller/cadence/pcie-cadence.h |  17 ++-
>>>  2 files changed, 141 insertions(+), 17 deletions(-)
>>>
>>> diff --git a/drivers/pci/controller/cadence/pcie-cadence-host.c b/drivers/pci/controller/cadence/pcie-cadence-host.c
>>> index 6ecebb79057a..2485ecd8434d 100644
>>> --- a/drivers/pci/controller/cadence/pcie-cadence-host.c
>>> +++ b/drivers/pci/controller/cadence/pcie-cadence-host.c
>>> @@ -11,6 +11,12 @@
>>>
>>>  #include "pcie-cadence.h"
>>>
>>> +static u64 cdns_rp_bar_max_size[] = {
>>> +       [RP_BAR0] = _ULL(128 * SZ_2G),
>>> +       [RP_BAR1] = SZ_2G,
>>> +       [RP_NO_BAR] = SZ_64T,
>>> +};
>>> +
>>>  void __iomem *cdns_pci_map_bus(struct pci_bus *bus, unsigned int devfn,
>>>                                int where)
>>>  {
>>> @@ -106,6 +112,117 @@ static int cdns_pcie_host_init_root_port(struct cdns_pcie_rc *rc)
>>>         return 0;
>>>  }
>>>
>>> +static void cdns_pcie_host_bar_ib_config(struct cdns_pcie_rc *rc,
>>> +                                        enum cdns_pcie_rp_bar bar,
>>> +                                        u64 cpu_addr, u32 aperture)
>>> +{
>>> +       struct cdns_pcie *pcie = &rc->pcie;
>>> +       u32 addr0, addr1;
>>> +
>>> +       addr0 = CDNS_PCIE_AT_IB_RP_BAR_ADDR0_NBITS(aperture) |
>>> +               (lower_32_bits(cpu_addr) & GENMASK(31, 8));
>>> +       addr1 = upper_32_bits(cpu_addr);
>>> +       cdns_pcie_writel(pcie, CDNS_PCIE_AT_IB_RP_BAR_ADDR0(bar), addr0);
>>> +       cdns_pcie_writel(pcie, CDNS_PCIE_AT_IB_RP_BAR_ADDR1(bar), addr1);
>>> +}
>>> +
>>> +static int cdns_pcie_host_bar_config(struct cdns_pcie_rc *rc,
>>> +                                    struct resource_entry *entry,
>>> +                                    enum cdns_pcie_rp_bar *index)
>>> +{
>>> +       u64 cpu_addr, pci_addr, size, winsize;
>>> +       struct cdns_pcie *pcie = &rc->pcie;
>>> +       struct device *dev = pcie->dev;
>>> +       enum cdns_pcie_rp_bar bar;
>>> +       unsigned long flags;
>>> +       u32 aperture;
>>> +       u32 value;
>>> +
>>> +       cpu_addr = entry->res->start;
>>> +       flags = entry->res->flags;
>>> +       pci_addr = entry->res->start - entry->offset;
>>> +       size = resource_size(entry->res);
>>> +       bar = *index;
>>> +
>>> +       if (entry->offset) {
>>> +               dev_err(dev, "Cannot map PCI addr: %llx to CPU addr: %llx\n",
>>> +                       pci_addr, cpu_addr);
>>
>> Would be a bit more clear to say PCI addr must equal CPU addr.
>>
>>> +               return -EINVAL;
>>> +       }
>>> +
>>> +       value = cdns_pcie_readl(pcie, CDNS_PCIE_LM_RC_BAR_CFG);
>>> +       while (size > 0) {
>>> +               if (bar > RP_NO_BAR) {
>>> +                       dev_err(dev, "Failed to map inbound regions!\n");
>>> +                       return -EINVAL;
>>> +               }
>>> +
>>> +               winsize = size;
>>> +               if (size > cdns_rp_bar_max_size[bar])
>>> +                       winsize = cdns_rp_bar_max_size[bar];
>>> +
>>> +               aperture = ilog2(winsize);
>>> +
>>> +               cdns_pcie_host_bar_ib_config(rc, bar, cpu_addr, aperture);
>>> +
>>> +               if (bar == RP_NO_BAR)
>>> +                       break;
>>> +
>>> +               if (winsize + cpu_addr >= SZ_4G) {
>>> +                       if (!(flags & IORESOURCE_PREFETCH))
>>> +                               value |= LM_RC_BAR_CFG_CTRL_MEM_64BITS(bar);
>>> +                       value |= LM_RC_BAR_CFG_CTRL_PREF_MEM_64BITS(bar);
>>> +               } else {
>>> +                       if (!(flags & IORESOURCE_PREFETCH))
>>> +                               value |= LM_RC_BAR_CFG_CTRL_MEM_32BITS(bar);
>>> +                       value |= LM_RC_BAR_CFG_CTRL_PREF_MEM_32BITS(bar);
>>> +               }
>>> +
>>> +               value |= LM_RC_BAR_CFG_APERTURE(bar, aperture);
>>> +
>>> +               size -= winsize;
>>> +               cpu_addr += winsize;
>>> +               bar++;
>>> +       }
>>> +       cdns_pcie_writel(pcie, CDNS_PCIE_LM_RC_BAR_CFG, value);
>>> +       *index = bar;
>>> +
>>> +       return 0;
>>> +}
>>> +
>>> +static int cdns_pcie_host_map_dma_ranges(struct cdns_pcie_rc *rc)
>>> +{
>>> +       enum cdns_pcie_rp_bar bar = RP_BAR0;
>>> +       struct cdns_pcie *pcie = &rc->pcie;
>>> +       struct device *dev = pcie->dev;
>>> +       struct device_node *np = dev->of_node;
>>> +       struct pci_host_bridge *bridge;
>>> +       struct resource_entry *entry;
>>> +       u32 no_bar_nbits = 32;
>>> +       int err;
>>> +
>>> +       bridge = pci_host_bridge_from_priv(rc);
>>> +       if (!bridge)
>>> +               return -ENOMEM;
>>> +
>>> +       if (list_empty(&bridge->dma_ranges)) {
>>> +               of_property_read_u32(np, "cdns,no-bar-match-nbits",
>>> +                                    &no_bar_nbits);
>>> +               cdns_pcie_host_bar_ib_config(rc, RP_NO_BAR, 0x0, no_bar_nbits);
>>> +               return 0;
>>> +       }
>>> +
>>> +       resource_list_for_each_entry(entry, &bridge->dma_ranges) {
>>> +               err = cdns_pcie_host_bar_config(rc, entry, &bar);
>>
>> Seems like this should have some better logic to pick which BAR to
>> use. Something like find the biggest region and then find the smallest
>> BAR that it fits in. Then get the next biggest...
> 
> Okay, I'll change this something like for each region, find the smallest BAR
> that it fits in and if there is no BAR big enough to hold the region, split the
> region to see if can be fitted using multiple BARs. I don't see the purpose of
> finding the biggest region first since at all times we'll only use the smallest
> BAR to fit.

Nevermind, I realized finding the biggest region is useful. I have sent a patch
adding support for that.

Thanks
Kishon

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