Re: [PATCH v6 4/5] PCI: dwc: ep: Support BAR subrange inbound mapping via Address Match Mode iATU

Niklas Cassel
2026-01-13T10:15:59Z

On Tue, Jan 13, 2026 at 11:37:14AM +0900, Koichiro Den wrote:
> Extend dw_pcie_ep_set_bar() to support inbound mappings for BAR
> subranges using Address Match Mode IB iATU.
>
> Rename the existing BAR-match helper into dw_pcie_ep_ib_atu_bar() and
> introduce dw_pcie_ep_ib_atu_addr() for Address Match Mode. When
> use_submap is set, read the assigned BAR base address and program one
> inbound iATU window per subrange. Validate the submap array before
> programming:
> - each subrange is aligned to pci->region_align
> - subranges cover the whole BAR (no gaps and no overlaps)
> - subranges are sorted in ascending order by offset
>
> Track Address Match Mode mappings and tear them down on clear_bar() and
> on set_bar() error paths to avoid leaving half-programmed state or
> untranslated BAR holes.
>
> Advertise this capability by setting subrange_mapping in the EPC
> features returned from dw_pcie_ep_get_features(). This also sets
> dynamic_inbound_mapping, which is a prerequisite for the subrange
> mapping flow. Note that vNTB already relies on this dynamic inbound
> mapping behavior.
>
> Signed-off-by: Koichiro Den <den@valinux.co.jp>
> ---
> .../pci/controller/dwc/pcie-designware-ep.c | 240 +++++++++++++++++-
> drivers/pci/controller/dwc/pcie-designware.h | 2 +
> 2 files changed, 231 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/pci/controller/dwc/pcie-designware-ep.c b/drivers/pci/controller/dwc/pcie-designware-ep.c
> index 1195d401df19..b2ea2c2c986f 100644
> --- a/drivers/pci/controller/dwc/pcie-designware-ep.c
> +++ b/drivers/pci/controller/dwc/pcie-designware-ep.c
> @@ -139,9 +139,10 @@ static int dw_pcie_ep_write_header(struct pci_epc *epc, u8 func_no, u8 vfunc_no,
> return 0;
> }
>
> -static int dw_pcie_ep_inbound_atu(struct dw_pcie_ep *ep, u8 func_no, int type,
> - dma_addr_t parent_bus_addr, enum pci_barno bar,
> - size_t size)
> +/* BAR Match Mode inbound iATU mapping */
> +static int dw_pcie_ep_ib_atu_bar(struct dw_pcie_ep *ep, u8 func_no, int type,
> + dma_addr_t parent_bus_addr, enum pci_barno bar,
> + size_t size)
> {
> int ret;
> u32 free_win;
> @@ -174,6 +175,208 @@ static int dw_pcie_ep_inbound_atu(struct dw_pcie_ep *ep, u8 func_no, int type,
> return 0;
> }
>
> +/* Inbound mapping bookkeeping for Address Match Mode */
> +struct dw_pcie_ib_map {
> + struct list_head list;
> + enum pci_barno bar;
> + u64 pci_addr;
> + u64 parent_bus_addr;
> + u64 size;
> + u32 index;
> +};
> +
> +static void dw_pcie_ep_clear_ib_maps(struct dw_pcie_ep *ep, enum pci_barno bar)
> +{
> + struct dw_pcie *pci = to_dw_pcie_from_ep(ep);
> + struct dw_pcie_ib_map *m, *tmp;
> + struct device *dev = pci->dev;
> + u32 atu_index;
> +
> + /* Tear down the BAR Match Mode mapping, if any. */
> + if (ep->bar_to_atu[bar]) {
> + atu_index = ep->bar_to_atu[bar] - 1;
> + dw_pcie_disable_atu(pci, PCIE_ATU_REGION_DIR_IB, atu_index);
> + clear_bit(atu_index, ep->ib_window_map);
> + ep->bar_to_atu[bar] = 0;
> + }
> +
> + /* Tear down all Address Match Mode mappings, if any. */
> + guard(spinlock_irqsave)(&ep->ib_map_lock);
> + list_for_each_entry_safe(m, tmp, &ep->ib_map_list, list) {
> + if (m->bar != bar)
> + continue;
> + dw_pcie_disable_atu(pci, PCIE_ATU_REGION_DIR_IB, m->index);
> + clear_bit(m->index, ep->ib_window_map);
> + list_del(&m->list);
> + devm_kfree(dev, m);
> + }
> +}
> +
> +static u64 dw_pcie_ep_read_bar_assigned(struct dw_pcie_ep *ep, u8 func_no,
> + enum pci_barno bar, int flags)
> +{
> + u32 reg = PCI_BASE_ADDRESS_0 + (4 * bar);
> + u32 lo, hi;
> + u64 addr;
> +
> + lo = dw_pcie_ep_readl_dbi(ep, func_no, reg);
> +
> + if (flags & PCI_BASE_ADDRESS_SPACE)
> + return lo & PCI_BASE_ADDRESS_IO_MASK;
> +
> + addr = lo & PCI_BASE_ADDRESS_MEM_MASK;
> + if (!(flags & PCI_BASE_ADDRESS_MEM_TYPE_64))
> + return addr;
> +
> + hi = dw_pcie_ep_readl_dbi(ep, func_no, reg + 4);
> + return addr | ((u64)hi << 32);
> +}
> +
> +static int dw_pcie_ep_validate_submap(struct dw_pcie_ep *ep,
> + const struct pci_epf_bar_submap *submap,
> + unsigned int num_submap, size_t bar_size)
> +{
> + struct dw_pcie *pci = to_dw_pcie_from_ep(ep);
> + u32 align = pci->region_align;
> + size_t expected = 0;
> + size_t size, off;
> + unsigned int i;
> +
> + if (!align || !IS_ALIGNED(bar_size, align))
> + return -EINVAL;
> +
> + /*
> + * The array is expected to be sorted by offset before calling this
> + * helper. With sorted entries, we can enforce a strict, gapless
> + * decomposition of the BAR:
> + * - each entry has a non-zero size
> + * - offset/size/phys_addr are aligned to pci->region_align
> + * - each entry lies within the BAR range
> + * - entries are contiguous (no overlaps, no holes)
> + * - the entries exactly cover the whole BAR
> + *
> + * Note: dw_pcie_prog_inbound_atu() also checks alignment for
> + * offset/phys_addr, but validating up-front avoids partially
> + * programming iATU windows in vain.
> + */
> + for (i = 0; i < num_submap; i++) {
> + off = submap[i].offset;
> + size = submap[i].size;
> +
> + if (!size)
> + return -EINVAL;
> +
> + if (!IS_ALIGNED(size, align) || !IS_ALIGNED(off, align))
> + return -EINVAL;
> +
> + if (!IS_ALIGNED(submap[i].phys_addr, align))
> + return -EINVAL;
> +
> + if (off > bar_size || size > bar_size - off)
> + return -EINVAL;
> +
> + /* Enforce contiguity (no overlaps, no holes). */
> + if (off != expected)
> + return -EINVAL;
> +
> + expected += size;
> + }
> + if (expected != bar_size)
> + return -EINVAL;
> +
> + return 0;
> +}
> +
> +/* Address Match Mode inbound iATU mapping */
> +static int dw_pcie_ep_ib_atu_addr(struct dw_pcie_ep *ep, u8 func_no, int type,
> + const struct pci_epf_bar *epf_bar)
> +{
> + const struct pci_epf_bar_submap *submap = epf_bar->submap;
> + struct dw_pcie *pci = to_dw_pcie_from_ep(ep);
> + enum pci_barno bar = epf_bar->barno;
> + struct device *dev = pci->dev;
> + u64 pci_addr, parent_bus_addr;
> + struct dw_pcie_ib_map *new;
> + u64 size, off, base;
> + unsigned long flags;
> + int free_win, ret;
> + unsigned int i;
> +
> + if (!epf_bar->num_submap || !submap || !epf_bar->size)
> + return -EINVAL;
> +
> + ret = dw_pcie_ep_validate_submap(ep, submap, epf_bar->num_submap,
> + epf_bar->size);
> + if (ret)
> + return ret;
> +
> + base = dw_pcie_ep_read_bar_assigned(ep, func_no, bar, epf_bar->flags);
> + if (!base) {
> + dev_err(dev,
> + "BAR%u not assigned, cannot set up sub-range mappings\n",
> + bar);
> + return -EINVAL;
> + }
> +
> + /* Tear down any existing mappings before (re)programming. */
> + dw_pcie_ep_clear_ib_maps(ep, bar);
> +
> + for (i = 0; i < epf_bar->num_submap; i++) {
> + off = submap[i].offset;
> + size = submap[i].size;
> + parent_bus_addr = submap[i].phys_addr;
> +
> + if (off > (~0ULL) - base) {
> + ret = -EINVAL;
> + goto err;
> + }
> +
> + pci_addr = base + off;
> +
> + new = devm_kzalloc(dev, sizeof(*new), GFP_KERNEL);
> + if (!new) {
> + ret = -ENOMEM;
> + goto err;
> + }
> +
> + spin_lock_irqsave(&ep->ib_map_lock, flags);
> +
> + free_win = find_first_zero_bit(ep->ib_window_map,
> + pci->num_ib_windows);
> + if (free_win >= pci->num_ib_windows) {
> + spin_unlock_irqrestore(&ep->ib_map_lock, flags);
> + devm_kfree(dev, new);
> + ret = -ENOSPC;
> + goto err;
> + }
> + set_bit(free_win, ep->ib_window_map);
> +
> + new->bar = bar;
> + new->index = free_win;
> + new->pci_addr = pci_addr;
> + new->parent_bus_addr = parent_bus_addr;
> + new->size = size;
> + list_add_tail(&new->list, &ep->ib_map_list);
> +
> + spin_unlock_irqrestore(&ep->ib_map_lock, flags);
> +
> + ret = dw_pcie_prog_inbound_atu(pci, free_win, type,
> + parent_bus_addr, pci_addr, size);
> + if (ret) {
> + spin_lock_irqsave(&ep->ib_map_lock, flags);
> + list_del(&new->list);
> + clear_bit(free_win, ep->ib_window_map);
> + spin_unlock_irqrestore(&ep->ib_map_lock, flags);
> + devm_kfree(dev, new);
> + goto err;
> + }
> + }
> + return 0;
> +err:
> + dw_pcie_ep_clear_ib_maps(ep, bar);
> + return ret;
> +}
> +
> static int dw_pcie_ep_outbound_atu(struct dw_pcie_ep *ep,
> struct dw_pcie_ob_atu_cfg *atu)
> {
> @@ -204,17 +407,15 @@ static void dw_pcie_ep_clear_bar(struct pci_epc *epc, u8 func_no, u8 vfunc_no,
> struct dw_pcie_ep *ep = epc_get_drvdata(epc);
> struct dw_pcie *pci = to_dw_pcie_from_ep(ep);
> enum pci_barno bar = epf_bar->barno;
> - u32 atu_index = ep->bar_to_atu[bar] - 1;
>
> - if (!ep->bar_to_atu[bar])
> + if (!ep->epf_bar[bar])
> return;
>
> __dw_pcie_ep_reset_bar(pci, func_no, bar, epf_bar->flags);
>
> - dw_pcie_disable_atu(pci, PCIE_ATU_REGION_DIR_IB, atu_index);
> - clear_bit(atu_index, ep->ib_window_map);
> + dw_pcie_ep_clear_ib_maps(ep, bar);
> +
> ep->epf_bar[bar] = NULL;
> - ep->bar_to_atu[bar] = 0;
> }
>
> static unsigned int dw_pcie_ep_get_rebar_offset(struct dw_pcie *pci,
> @@ -408,8 +609,12 @@ static int dw_pcie_ep_set_bar(struct pci_epc *epc, u8 func_no, u8 vfunc_no,
> else
> type = PCIE_ATU_TYPE_IO;
>
> - ret = dw_pcie_ep_inbound_atu(ep, func_no, type, epf_bar->phys_addr, bar,
> - size);
> + if (epf_bar->use_submap)
> + ret = dw_pcie_ep_ib_atu_addr(ep, func_no, type, epf_bar);
> + else
> + ret = dw_pcie_ep_ib_atu_bar(ep, func_no, type,
> + epf_bar->phys_addr, bar, size);
> +
> if (ret)
> return ret;
>
> @@ -626,11 +831,22 @@ static const struct pci_epc_features*
> dw_pcie_ep_get_features(struct pci_epc *epc, u8 func_no, u8 vfunc_no)
> {
> struct dw_pcie_ep *ep = epc_get_drvdata(epc);
> + struct pci_epc_features *features;
>
> if (!ep->ops->get_features)
> return NULL;
>
> - return ep->ops->get_features(ep);
> + features = ep->ops->get_features(ep);
> + if (!features)
> + return NULL;
> +
> + /* All DWC-based glue drivers support dynamic inbound mapping */
> + features->dynamic_inbound_mapping = true;

I think you should create a separate patch, before this patch, that simply
sets:
features->dynamic_inbound_mapping = true;

Since that is technically a different feature, independent of this
feature, so it deserves its own patch.

With that fixed, this patch looks good to me:
Reviewed-by: Niklas Cassel <cassel@kernel.org>

> +
> + /* All DWC-based glue drivers support inbound subrange mapping */
> + features->subrange_mapping = true;
> +
> + return features;
> }
>
> static const struct pci_epc_ops epc_ops = {
> @@ -1120,6 +1336,8 @@ int dw_pcie_ep_init(struct dw_pcie_ep *ep)
> struct device *dev = pci->dev;
>
> INIT_LIST_HEAD(&ep->func_list);
> + INIT_LIST_HEAD(&ep->ib_map_list);
> + spin_lock_init(&ep->ib_map_lock);
> ep->msi_iatu_mapped = false;
> ep->msi_msg_addr = 0;
> ep->msi_map_size = 0;
> diff --git a/drivers/pci/controller/dwc/pcie-designware.h b/drivers/pci/controller/dwc/pcie-designware.h
> index 4dda9a38d46b..969b1f32dddf 100644
> --- a/drivers/pci/controller/dwc/pcie-designware.h
> +++ b/drivers/pci/controller/dwc/pcie-designware.h
> @@ -479,6 +479,8 @@ struct dw_pcie_ep {
> phys_addr_t *outbound_addr;
> unsigned long *ib_window_map;
> unsigned long *ob_window_map;
> + struct list_head ib_map_list;
> + spinlock_t ib_map_lock;
> void __iomem *msi_mem;
> phys_addr_t msi_mem_phys;
> struct pci_epf_bar *epf_bar[PCI_STD_NUM_BARS];
> --
> 2.51.0
>