Re: [PATCH 2/5] pci: endpoint: add support to handle multiple base for mapping outbound memory

Kishon Vijay Abraham I <kishon@xxxxxx> · Thu, 5 Dec 2019 15:52:59 +0530

Hi,

On 28/11/19 2:51 am, Lad, Prabhakar wrote:
Hi Kishon,

Thank you for the review.

On Wed, Nov 27, 2019 at 5:15 AM Kishon Vijay Abraham I <kishon@xxxxxx> wrote:

Hi Prabhakar,

On 07/11/19 1:06 AM, Lad Prabhakar wrote:
From: "Lad, Prabhakar" <prabhakar.mahadev-lad.rj@xxxxxxxxxxxxxx>

rcar pcie controller has support to map multiple memory regions
for mapping the outbound memory in local system, this feature
inspires to add support for handling multiple memory bases in
endpoint framework. In case of multiple memory regions only chunk
or complete region can be mapped and this window needs to be
passed to the controller driver.

Signed-off-by: Lad, Prabhakar <prabhakar.mahadev-lad.rj@xxxxxxxxxxxxxx>
Cc: <linux-rockchip@xxxxxxxxxxxxxxxxxxx>
Cc: Shawn Lin <shawn.lin@xxxxxxxxxxxxxx>
Cc: Heiko Stuebner <heiko@xxxxxxxxx>
Cc: Tom Joseph <tjoseph@xxxxxxxxxxx>
Cc: Jingoo Han <jingoohan1@xxxxxxxxx>
Cc: Gustavo Pimentel <gustavo.pimentel@xxxxxxxxxxxx>
---
  .../pci/controller/dwc/pcie-designware-ep.c   |  30 ++-
  drivers/pci/controller/pcie-cadence-ep.c      |  11 +-
  drivers/pci/controller/pcie-rockchip-ep.c     |  13 +-
  drivers/pci/endpoint/functions/pci-epf-test.c |  29 +--
  drivers/pci/endpoint/pci-epc-core.c           |   7 +-
  drivers/pci/endpoint/pci-epc-mem.c            | 189 ++++++++++++++----
  include/linux/pci-epc.h                       |  43 ++--
  7 files changed, 234 insertions(+), 88 deletions(-)

diff --git a/drivers/pci/controller/dwc/pcie-designware-ep.c b/drivers/pci/controller/dwc/pcie-designware-ep.c
index 3dd2e2697294..8d23c20b9afd 100644
--- a/drivers/pci/controller/dwc/pcie-designware-ep.c
+++ b/drivers/pci/controller/dwc/pcie-designware-ep.c
@@ -195,7 +195,7 @@ static void dw_pcie_ep_unmap_addr(struct pci_epc *epc, u8 func_no,
  }

  static int dw_pcie_ep_map_addr(struct pci_epc *epc, u8 func_no,
-                            phys_addr_t addr,
+                            phys_addr_t addr, int window,
                              u64 pci_addr, size_t size)
  {
       int ret;
@@ -367,6 +367,7 @@ int dw_pcie_ep_raise_msi_irq(struct dw_pcie_ep *ep, u8 func_no,
       unsigned int aligned_offset;
       u16 msg_ctrl, msg_data;
       u32 msg_addr_lower, msg_addr_upper, reg;
+     int window = PCI_EPC_DEFAULT_WINDOW;
       u64 msg_addr;
       bool has_upper;
       int ret;
@@ -390,11 +391,11 @@ int dw_pcie_ep_raise_msi_irq(struct dw_pcie_ep *ep, u8 func_no,
               reg = ep->msi_cap + PCI_MSI_DATA_32;
               msg_data = dw_pcie_readw_dbi(pci, reg);
       }
-     aligned_offset = msg_addr_lower & (epc->mem->page_size - 1);
+     aligned_offset = msg_addr_lower & (epc->mem[window]->page_size - 1);
       msg_addr = ((u64)msg_addr_upper) << 32 |
                       (msg_addr_lower & ~aligned_offset);
-     ret = dw_pcie_ep_map_addr(epc, func_no, ep->msi_mem_phys, msg_addr,
-                               epc->mem->page_size);
+     ret = dw_pcie_ep_map_addr(epc, func_no, ep->msi_mem_phys, window,
+                               msg_addr, epc->mem[window]->page_size);
       if (ret)
               return ret;

@@ -416,6 +417,7 @@ int dw_pcie_ep_raise_msix_irq(struct dw_pcie_ep *ep, u8 func_no,
       u32 reg, msg_data, vec_ctrl;
       u64 tbl_addr, msg_addr, reg_u64;
       void __iomem *msix_tbl;
+     int window = PCI_EPC_DEFAULT_WINDOW;
       int ret;

       reg = ep->msix_cap + PCI_MSIX_TABLE;
@@ -452,8 +454,8 @@ int dw_pcie_ep_raise_msix_irq(struct dw_pcie_ep *ep, u8 func_no,
               return -EPERM;
       }

-     ret = dw_pcie_ep_map_addr(epc, func_no, ep->msi_mem_phys, msg_addr,
-                               epc->mem->page_size);
+     ret = dw_pcie_ep_map_addr(epc, func_no, ep->msi_mem_phys, window,
+                               msg_addr, epc->mem[window]->page_size);
       if (ret)
               return ret;

@@ -466,10 +468,11 @@ int dw_pcie_ep_raise_msix_irq(struct dw_pcie_ep *ep, u8 func_no,

  void dw_pcie_ep_exit(struct dw_pcie_ep *ep)
  {
+     int window = PCI_EPC_DEFAULT_WINDOW;
       struct pci_epc *epc = ep->epc;

       pci_epc_mem_free_addr(epc, ep->msi_mem_phys, ep->msi_mem,
-                           epc->mem->page_size);
+                           epc->mem[window]->page_size);

       pci_epc_mem_exit(epc);
  }
@@ -499,9 +502,12 @@ int dw_pcie_ep_init(struct dw_pcie_ep *ep)
       u32 reg;
       void *addr;
       u8 hdr_type;
+     int window;
       unsigned int nbars;
       unsigned int offset;
       struct pci_epc *epc;
+     size_t msi_page_size;
+     struct pci_epc_mem_window mem_window;
       struct dw_pcie *pci = to_dw_pcie_from_ep(ep);
       struct device *dev = pci->dev;
       struct device_node *np = dev->of_node;
@@ -574,15 +580,17 @@ int dw_pcie_ep_init(struct dw_pcie_ep *ep)
       if (ret < 0)
               epc->max_functions = 1;

-     ret = __pci_epc_mem_init(epc, ep->phys_base, ep->addr_size,
-                              ep->page_size);
+     mem_window.phys_base = ep->phys_base;
+     mem_window.size = ep->addr_size;
+     ret = __pci_epc_mem_init(epc, &mem_window, 1, ep->page_size);
       if (ret < 0) {
               dev_err(dev, "Failed to initialize address space\n");
               return ret;
       }

-     ep->msi_mem = pci_epc_mem_alloc_addr(epc, &ep->msi_mem_phys,
-                                          epc->mem->page_size);
+     msi_page_size = epc->mem[PCI_EPC_DEFAULT_WINDOW]->page_size;
+     ep->msi_mem = pci_epc_mem_alloc_addr(epc, &ep->msi_mem_phys, &window,
+                                          msi_page_size);
       if (!ep->msi_mem) {
               dev_err(dev, "Failed to reserve memory for MSI/MSI-X\n");
               return -ENOMEM;
diff --git a/drivers/pci/controller/pcie-cadence-ep.c b/drivers/pci/controller/pcie-cadence-ep.c
index def7820cb824..7991b38a5350 100644
--- a/drivers/pci/controller/pcie-cadence-ep.c
+++ b/drivers/pci/controller/pcie-cadence-ep.c
@@ -172,7 +172,7 @@ static void cdns_pcie_ep_clear_bar(struct pci_epc *epc, u8 fn,
  }

  static int cdns_pcie_ep_map_addr(struct pci_epc *epc, u8 fn, phys_addr_t addr,
-                              u64 pci_addr, size_t size)
+                              int window, u64 pci_addr, size_t size)
  {
       struct cdns_pcie_ep *ep = epc_get_drvdata(epc);
       struct cdns_pcie *pcie = &ep->pcie;
@@ -434,12 +434,14 @@ static int cdns_pcie_ep_probe(struct platform_device *pdev)
  {
       struct device *dev = &pdev->dev;
       struct device_node *np = dev->of_node;
+     struct pci_epc_mem_window mem_window;
       struct cdns_pcie_ep *ep;
       struct cdns_pcie *pcie;
       struct pci_epc *epc;
       struct resource *res;
       int ret;
       int phy_count;
+     int window;

       ep = devm_kzalloc(dev, sizeof(*ep), GFP_KERNEL);
       if (!ep)
@@ -502,15 +504,16 @@ static int cdns_pcie_ep_probe(struct platform_device *pdev)
       if (of_property_read_u8(np, "max-functions", &epc->max_functions) < 0)
               epc->max_functions = 1;

-     ret = pci_epc_mem_init(epc, pcie->mem_res->start,
-                            resource_size(pcie->mem_res));
+     mem_window.phys_base = pcie->mem_res->start;
+     mem_window.size = resource_size(pcie->mem_res);
+     ret = pci_epc_mem_init(epc, &mem_window, 1);
       if (ret < 0) {
               dev_err(dev, "failed to initialize the memory space\n");
               goto err_init;
       }

       ep->irq_cpu_addr = pci_epc_mem_alloc_addr(epc, &ep->irq_phys_addr,
-                                               SZ_128K);
+                                               &window, SZ_128K);
       if (!ep->irq_cpu_addr) {
               dev_err(dev, "failed to reserve memory space for MSI\n");
               ret = -ENOMEM;
diff --git a/drivers/pci/controller/pcie-rockchip-ep.c b/drivers/pci/controller/pcie-rockchip-ep.c
index d743b0a48988..d59e85c8d319 100644
--- a/drivers/pci/controller/pcie-rockchip-ep.c
+++ b/drivers/pci/controller/pcie-rockchip-ep.c
@@ -256,8 +256,8 @@ static void rockchip_pcie_ep_clear_bar(struct pci_epc *epc, u8 fn,
  }

  static int rockchip_pcie_ep_map_addr(struct pci_epc *epc, u8 fn,
-                                  phys_addr_t addr, u64 pci_addr,
-                                  size_t size)
+                                  phys_addr_t addr, int window,
+                                  u64 pci_addr, size_t size)
  {
       struct rockchip_pcie_ep *ep = epc_get_drvdata(epc);
       struct rockchip_pcie *pcie = &ep->rockchip;
@@ -562,11 +562,13 @@ static const struct of_device_id rockchip_pcie_ep_of_match[] = {

  static int rockchip_pcie_ep_probe(struct platform_device *pdev)
  {
+     struct pci_epc_mem_window mem_window;
       struct device *dev = &pdev->dev;
       struct rockchip_pcie_ep *ep;
       struct rockchip_pcie *rockchip;
       struct pci_epc *epc;
       size_t max_regions;
+     int window;
       int err;

       ep = devm_kzalloc(dev, sizeof(*ep), GFP_KERNEL);
@@ -614,15 +616,16 @@ static int rockchip_pcie_ep_probe(struct platform_device *pdev)
       /* Only enable function 0 by default */
       rockchip_pcie_write(rockchip, BIT(0), PCIE_CORE_PHY_FUNC_CFG);

-     err = pci_epc_mem_init(epc, rockchip->mem_res->start,
-                            resource_size(rockchip->mem_res));
+     mem_window.phys_base = rockchip->mem_res->start;
+     mem_window.size = resource_size(rockchip->mem_res);
+     err = pci_epc_mem_init(epc, &mem_window, 1);
       if (err < 0) {
               dev_err(dev, "failed to initialize the memory space\n");
               goto err_uninit_port;
       }

       ep->irq_cpu_addr = pci_epc_mem_alloc_addr(epc, &ep->irq_phys_addr,
-                                               SZ_128K);
+                                               &window, SZ_128K);
       if (!ep->irq_cpu_addr) {
               dev_err(dev, "failed to reserve memory space for MSI\n");
               err = -ENOMEM;
diff --git a/drivers/pci/endpoint/functions/pci-epf-test.c b/drivers/pci/endpoint/functions/pci-epf-test.c
index 5d74f81ddfe4..475228011703 100644
--- a/drivers/pci/endpoint/functions/pci-epf-test.c
+++ b/drivers/pci/endpoint/functions/pci-epf-test.c
@@ -84,8 +84,10 @@ static int pci_epf_test_copy(struct pci_epf_test *epf_test)
       struct pci_epc *epc = epf->epc;
       enum pci_barno test_reg_bar = epf_test->test_reg_bar;
       struct pci_epf_test_reg *reg = epf_test->reg[test_reg_bar];
+     int window;

-     src_addr = pci_epc_mem_alloc_addr(epc, &src_phys_addr, reg->size);
+     src_addr = pci_epc_mem_alloc_addr(epc, &src_phys_addr,
+                                       &window, reg->size);
       if (!src_addr) {
               dev_err(dev, "Failed to allocate source address\n");
               reg->status = STATUS_SRC_ADDR_INVALID;
@@ -93,15 +95,16 @@ static int pci_epf_test_copy(struct pci_epf_test *epf_test)
               goto err;
       }

-     ret = pci_epc_map_addr(epc, epf->func_no, src_phys_addr, reg->src_addr,
-                            reg->size);
+     ret = pci_epc_map_addr(epc, epf->func_no, src_phys_addr, window,
+                            reg->src_addr, reg->size);
       if (ret) {
               dev_err(dev, "Failed to map source address\n");
               reg->status = STATUS_SRC_ADDR_INVALID;
               goto err_src_addr;
       }

-     dst_addr = pci_epc_mem_alloc_addr(epc, &dst_phys_addr, reg->size);
+     dst_addr = pci_epc_mem_alloc_addr(epc, &dst_phys_addr,
+                                       &window, reg->size);
       if (!dst_addr) {
               dev_err(dev, "Failed to allocate destination address\n");
               reg->status = STATUS_DST_ADDR_INVALID;
@@ -109,8 +112,8 @@ static int pci_epf_test_copy(struct pci_epf_test *epf_test)
               goto err_src_map_addr;
       }

-     ret = pci_epc_map_addr(epc, epf->func_no, dst_phys_addr, reg->dst_addr,
-                            reg->size);
+     ret = pci_epc_map_addr(epc, epf->func_no, dst_phys_addr, window,
+                            reg->dst_addr, reg->size);
       if (ret) {
               dev_err(dev, "Failed to map destination address\n");
               reg->status = STATUS_DST_ADDR_INVALID;
@@ -146,8 +149,9 @@ static int pci_epf_test_read(struct pci_epf_test *epf_test)
       struct pci_epc *epc = epf->epc;
       enum pci_barno test_reg_bar = epf_test->test_reg_bar;
       struct pci_epf_test_reg *reg = epf_test->reg[test_reg_bar];
+     int window;

-     src_addr = pci_epc_mem_alloc_addr(epc, &phys_addr, reg->size);
+     src_addr = pci_epc_mem_alloc_addr(epc, &phys_addr, &window, reg->size);
       if (!src_addr) {
               dev_err(dev, "Failed to allocate address\n");
               reg->status = STATUS_SRC_ADDR_INVALID;
@@ -155,8 +159,8 @@ static int pci_epf_test_read(struct pci_epf_test *epf_test)
               goto err;
       }

-     ret = pci_epc_map_addr(epc, epf->func_no, phys_addr, reg->src_addr,
-                            reg->size);
+     ret = pci_epc_map_addr(epc, epf->func_no, phys_addr, window,
+                            reg->src_addr, reg->size);
       if (ret) {
               dev_err(dev, "Failed to map address\n");
               reg->status = STATUS_SRC_ADDR_INVALID;
@@ -193,13 +197,14 @@ static int pci_epf_test_write(struct pci_epf_test *epf_test)
       void __iomem *dst_addr;
       void *buf;
       phys_addr_t phys_addr;
+     int window;
       struct pci_epf *epf = epf_test->epf;
       struct device *dev = &epf->dev;
       struct pci_epc *epc = epf->epc;
       enum pci_barno test_reg_bar = epf_test->test_reg_bar;
       struct pci_epf_test_reg *reg = epf_test->reg[test_reg_bar];

-     dst_addr = pci_epc_mem_alloc_addr(epc, &phys_addr, reg->size);
+     dst_addr = pci_epc_mem_alloc_addr(epc, &phys_addr, &window, reg->size);
       if (!dst_addr) {
               dev_err(dev, "Failed to allocate address\n");
               reg->status = STATUS_DST_ADDR_INVALID;
@@ -207,8 +212,8 @@ static int pci_epf_test_write(struct pci_epf_test *epf_test)
               goto err;
       }

-     ret = pci_epc_map_addr(epc, epf->func_no, phys_addr, reg->dst_addr,
-                            reg->size);
+     ret = pci_epc_map_addr(epc, epf->func_no, phys_addr, window,
+                            reg->dst_addr, reg->size);
       if (ret) {
               dev_err(dev, "Failed to map address\n");
               reg->status = STATUS_DST_ADDR_INVALID;
diff --git a/drivers/pci/endpoint/pci-epc-core.c b/drivers/pci/endpoint/pci-epc-core.c
index 2091508c1620..289c266c2d90 100644
--- a/drivers/pci/endpoint/pci-epc-core.c
+++ b/drivers/pci/endpoint/pci-epc-core.c
@@ -358,13 +358,15 @@ EXPORT_SYMBOL_GPL(pci_epc_unmap_addr);
   * @epc: the EPC device on which address is allocated
   * @func_no: the endpoint function number in the EPC device
   * @phys_addr: physical address of the local system
+ * @window: index to the window region where PCI address will be mapped
   * @pci_addr: PCI address to which the physical address should be mapped
   * @size: the size of the allocation
   *
   * Invoke to map CPU address with PCI address.
   */
  int pci_epc_map_addr(struct pci_epc *epc, u8 func_no,
-                  phys_addr_t phys_addr, u64 pci_addr, size_t size)
+                  phys_addr_t phys_addr, int window,
+                  u64 pci_addr, size_t size)
  {
       int ret;
       unsigned long flags;
@@ -376,7 +378,8 @@ int pci_epc_map_addr(struct pci_epc *epc, u8 func_no,
               return 0;

       spin_lock_irqsave(&epc->lock, flags);
-     ret = epc->ops->map_addr(epc, func_no, phys_addr, pci_addr, size);
+     ret = epc->ops->map_addr(epc, func_no, phys_addr,
+                              window, pci_addr, size);
       spin_unlock_irqrestore(&epc->lock, flags);

       return ret;
diff --git a/drivers/pci/endpoint/pci-epc-mem.c b/drivers/pci/endpoint/pci-epc-mem.c
index d2b174ce15de..c955f2c97944 100644
--- a/drivers/pci/endpoint/pci-epc-mem.c
+++ b/drivers/pci/endpoint/pci-epc-mem.c
@@ -39,56 +39,77 @@ static int pci_epc_mem_get_order(struct pci_epc_mem *mem, size_t size)
   * __pci_epc_mem_init() - initialize the pci_epc_mem structure
   * @epc: the EPC device that invoked pci_epc_mem_init
   * @phys_base: the physical address of the base
- * @size: the size of the address space
+ * @num_windows: number of windows device supports

struct pci_epc_mem_window is missing here.
oops my bad will fix that.

   * @page_size: size of each page
   *
   * Invoke to initialize the pci_epc_mem structure used by the
   * endpoint functions to allocate mapped PCI address.
   */
-int __pci_epc_mem_init(struct pci_epc *epc, phys_addr_t phys_base, size_t size,
-                    size_t page_size)
+int __pci_epc_mem_init(struct pci_epc *epc, struct pci_epc_mem_window *windows,
+                    int num_windows, size_t page_size)
  {
-     int ret;
-     struct pci_epc_mem *mem;
-     unsigned long *bitmap;
+     struct pci_epc_mem *mem = NULL;
+     unsigned long *bitmap = NULL;
       unsigned int page_shift;
-     int pages;
       int bitmap_size;
+     int pages;
+     int ret;
+     int i;
+
+     epc->mem_windows = 0;
+
+     if (!windows)
+             return -EINVAL;
+
+     if (num_windows <= 0)
+             return -EINVAL;

       if (page_size < PAGE_SIZE)
               page_size = PAGE_SIZE;

       page_shift = ilog2(page_size);
-     pages = size >> page_shift;
-     bitmap_size = BITS_TO_LONGS(pages) * sizeof(long);

-     mem = kzalloc(sizeof(*mem), GFP_KERNEL);
-     if (!mem) {
-             ret = -ENOMEM;
-             goto err;
-     }
+     epc->mem = kcalloc(num_windows, sizeof(*mem), GFP_KERNEL);
+     if (!epc->mem)
+             return -EINVAL;

-     bitmap = kzalloc(bitmap_size, GFP_KERNEL);
-     if (!bitmap) {
-             ret = -ENOMEM;
-             goto err_mem;
-     }
+     for (i = 0; i < num_windows; i++) {
+             pages = windows[i].phys_base >> page_shift;
+             bitmap_size = BITS_TO_LONGS(pages) * sizeof(long);

-     mem->bitmap = bitmap;
-     mem->phys_base = phys_base;
-     mem->page_size = page_size;
-     mem->pages = pages;
-     mem->size = size;
+             mem = kzalloc(sizeof(*mem), GFP_KERNEL);
+             if (!mem) {
+                     ret = -ENOMEM;
+                     goto err_mem;
+             }

-     epc->mem = mem;
+             bitmap = kzalloc(bitmap_size, GFP_KERNEL);
+             if (!bitmap) {
+                     ret = -ENOMEM;
+                     goto err_mem;
+             }
+
+             mem->bitmap = bitmap;
+             mem->window.phys_base = windows[i].phys_base;
+             mem->page_size = page_size;
+             mem->pages = pages;
+             mem->window.size = windows[i].size;
+             mem->window.map_size = 0;
+
+             epc->mem[i] = mem;
+     }
+     epc->mem_windows = num_windows;

       return 0;

  err_mem:
-     kfree(mem);
+     for (; i >= 0; i--) {
+             kfree(mem->bitmap);
+             kfree(epc->mem[i]);
+     }
+     kfree(epc->mem);

-err:
-return ret;
+     return ret;
  }
  EXPORT_SYMBOL_GPL(__pci_epc_mem_init);

@@ -101,48 +122,126 @@ EXPORT_SYMBOL_GPL(__pci_epc_mem_init);
   */
  void pci_epc_mem_exit(struct pci_epc *epc)
  {
-     struct pci_epc_mem *mem = epc->mem;
+     struct pci_epc_mem *mem;
+     int i;
+
+     if (!epc->mem_windows)
+             return;
+
+     for (i = 0; i <= epc->mem_windows; i--) {
+             mem = epc->mem[i];
+             kfree(mem->bitmap);
+             kfree(epc->mem[i]);
+     }
+     kfree(epc->mem);

       epc->mem = NULL;
-     kfree(mem->bitmap);
-     kfree(mem);
+     epc->mem_windows = 0;
  }
  EXPORT_SYMBOL_GPL(pci_epc_mem_exit);

+static int pci_epc_find_best_fit_window(struct pci_epc *epc, size_t size)
+{
+     size_t window_least_size = 0;
+     int best_fit_window = -1;
+     struct pci_epc_mem *mem;
+     size_t actual_size;
+     int i;
+
+     for (i = 0; i < epc->mem_windows; i++) {
+             mem = epc->mem[i];
+
+             /* if chunk from this region is already used skip it */
+             if (mem->window.map_size)
+                     continue;
+
+             actual_size = ALIGN(size, mem->page_size);
+
+             if (best_fit_window == -1) {
+                     best_fit_window = i;
+                     window_least_size = mem->window.size;
+             } else {
+                     if (actual_size <= mem->window.size &&
+                         mem->window.size < window_least_size) {
+                             best_fit_window = i;
+                             window_least_size = mem->window.size;
+                     }
+             }
+     }
+
+     return best_fit_window;
+}
+
  /**
   * pci_epc_mem_alloc_addr() - allocate memory address from EPC addr space
   * @epc: the EPC device on which memory has to be allocated
   * @phys_addr: populate the allocated physical address here
+ * @window: populate the window here which will be used to map PCI address
   * @size: the size of the address space that has to be allocated
   *
   * Invoke to allocate memory address from the EPC address space. This
   * is usually done to map the remote RC address into the local system.
   */
  void __iomem *pci_epc_mem_alloc_addr(struct pci_epc *epc,
-                                  phys_addr_t *phys_addr, size_t size)
+                                  phys_addr_t *phys_addr,
+                                  int *window, size_t size)
  {
+     int best_fit = PCI_EPC_DEFAULT_WINDOW;
+     void __iomem *virt_addr = NULL;
+     struct pci_epc_mem *mem;
+     unsigned int page_shift;
       int pageno;
-     void __iomem *virt_addr;
-     struct pci_epc_mem *mem = epc->mem;
-     unsigned int page_shift = ilog2(mem->page_size);
       int order;

+     if (epc->mem_windows <= 0)
+             return NULL;
+
+     if (epc->mem_windows > 1) {
+             best_fit = pci_epc_find_best_fit_window(epc, size);
+             if (best_fit < 0)
+                     return NULL;
+     }
+
+     mem = epc->mem[best_fit];
       size = ALIGN(size, mem->page_size);
+     if (size > (mem->window.size - mem->window.map_size))
+             return NULL;

Assume I have two mem regions, first region is of size 128MB and the second
region is of size 4GB. If there is a allocation request for 4GB, will the
allocation succeed?

yes it would succeed, the pci_epc_find_best_fit_window() would get the
corresponding window.

Can you step through the algo again? pci_epc_find_best_fit_window() will 
return the first region which is of size 128MB.

Thanks
Kishon






