[PATCH v5 04/12] PCI: brcmstb: add dma-range mapping for inbound traffic

[Jim Quinlan]

The Broadcom STB PCIe host controller is intimately related to the
memory subsystem.  This close relationship adds complexity to how cpu
system memory is mapped to PCIe memory.  Ideally, this mapping is an
identity mapping, or an identity mapping off by a constant.  Not so in
this case.

Consider the Broadcom reference board BCM97445LCC_4X8 which has 6 GB
of system memory.  Here is how the PCIe controller maps the
system memory to PCIe memory:

  memc0-a@[        0....3fffffff] <=> pci@[        0....3fffffff]
  memc0-b@[100000000...13fffffff] <=> pci@[ 40000000....7fffffff]
  memc1-a@[ 40000000....7fffffff] <=> pci@[ 80000000....bfffffff]
  memc1-b@[300000000...33fffffff] <=> pci@[ c0000000....ffffffff]
  memc2-a@[ 80000000....bfffffff] <=> pci@[100000000...13fffffff]
  memc2-b@[c00000000...c3fffffff] <=> pci@[140000000...17fffffff]

Although there are some "gaps" that can be added between the
individual mappings by software, the permutation of memory regions for
the most part is fixed by HW.  The solution of having something close
to an identity mapping is not possible.

The idea behind this HW design is that the same PCIe module can
act as an RC or EP, and if it acts as an EP it concatenates all
of system memory into a BAR so anything can be accessed.  Unfortunately,
when the PCIe block is in the role of an RC it also presents this
"BAR" to downstream PCIe devices, rather than offering an identity map
between its system memory and PCIe space.

Suppose that an endpoint driver allocs some DMA memory.  Suppose this
memory is located at 0x6000_0000, which is in the middle of memc1-a.
The driver wants a dma_addr_t value that it can pass on to the EP to
use.  Without doing any custom mapping, the EP will use this value for
DMA: the driver will get a dma_addr_t equal to 0x6000_0000.  But this
won't work; the device needs a dma_addr_t that reflects the PCIe space
address, namely 0xa000_0000.

So, essentially the solution to this problem must modify the
dma_addr_t returned by the DMA routines routines.  The method to do
this is to redefine the __dma_to_phys() and __phys_to_dma() functions
of the ARM, ARM64, and MIPS architectures.  This commit sets up the
infrastructure in the Brcm PCIe controller to prepare for this, while
there is three other subsequent commits to implement/redefine these
two functions for the three target architectures.

Signed-off-by: Jim Quinlan <jim2101024@xxxxxxxxx>
---
 drivers/pci/controller/pcie-brcmstb.c | 130 ++++++++++++++++++++++++++++++----
 include/soc/brcmstb/common.h          |  16 +++++
 2 files changed, 133 insertions(+), 13 deletions(-)

diff --git a/drivers/pci/controller/pcie-brcmstb.c b/drivers/pci/controller/pcie-brcmstb.c
index 9c87d10..abfa429 100644
--- a/drivers/pci/controller/pcie-brcmstb.c
+++ b/drivers/pci/controller/pcie-brcmstb.c
@@ -21,6 +21,7 @@
 #include <linux/printk.h>
 #include <linux/sizes.h>
 #include <linux/slab.h>
+#include <soc/brcmstb/common.h>
 #include <soc/brcmstb/memory_api.h>
 #include <linux/string.h>
 #include <linux/types.h>
@@ -321,6 +322,7 @@ static void __iomem *brcm_pcie_map_conf(struct pci_bus *bus, unsigned int devfn,
 	(((val) & ~reg##_##field##_MASK) | \
 	 (reg##_##field##_MASK & (field_val << reg##_##field##_SHIFT)))
 
+static struct of_pci_range *brcm_dma_ranges;
 static phys_addr_t scb_size[BRCM_MAX_SCB];
 static int num_memc;
 static int num_pcie;
@@ -599,6 +601,79 @@ static inline void brcm_pcie_perst_set(struct brcm_pcie *pcie,
 		WR_FLD_RB(pcie->base, PCIE_MISC_PCIE_CTRL, PCIE_PERSTB, !val);
 }
 
+static int brcm_pcie_parse_map_dma_ranges(struct brcm_pcie *pcie)
+{
+	int i;
+	struct of_pci_range_parser parser;
+	struct device_node *dn = pcie->dn;
+
+	/*
+	 * Parse dma-ranges property if present.  If there are multiple
+	 * PCIe controllers, we only have to parse from one of them since
+	 * the others will have an identical mapping.
+	 */
+	if (!of_pci_dma_range_parser_init(&parser, dn)) {
+		struct of_pci_range *p;
+		unsigned int max_ranges = (parser.end - parser.range)
+			/ parser.np;
+
+		/* Add a null entry to indicate the end of the array */
+		brcm_dma_ranges = kcalloc(max_ranges + 1,
+					  sizeof(struct of_pci_range),
+					  GFP_KERNEL);
+		if (!brcm_dma_ranges)
+			return -ENOMEM;
+
+		p = brcm_dma_ranges;
+		while (of_pci_range_parser_one(&parser, p))
+			p++;
+	}
+
+	for (i = 0, num_memc = 0; i < BRCM_MAX_SCB; i++) {
+		u64 size = brcmstb_memory_memc_size(i);
+
+		if (size == (u64)-1) {
+			dev_err(pcie->dev, "cannot get memc%d size", i);
+			return -EINVAL;
+		} else if (size) {
+			scb_size[i] = roundup_pow_of_two_64(size);
+			num_memc++;
+		} else {
+			break;
+		}
+	}
+
+	return 0;
+}
+
+dma_addr_t brcm_phys_to_dma(struct device *dev, phys_addr_t paddr)
+{
+	struct of_pci_range *p;
+
+	if (!dev || !dev_is_pci(dev))
+		return (dma_addr_t)paddr;
+	for (p = brcm_dma_ranges; p && p->size; p++)
+		if (paddr >= p->cpu_addr && paddr < (p->cpu_addr + p->size))
+			return (dma_addr_t)(paddr - p->cpu_addr + p->pci_addr);
+
+	return (dma_addr_t)paddr;
+}
+
+phys_addr_t brcm_dma_to_phys(struct device *dev, dma_addr_t dev_addr)
+{
+	struct of_pci_range *p;
+
+	if (!dev || !dev_is_pci(dev))
+		return (phys_addr_t)dev_addr;
+	for (p = brcm_dma_ranges; p && p->size; p++)
+		if (dev_addr >= p->pci_addr
+		    && dev_addr < (p->pci_addr + p->size))
+			return (phys_addr_t)
+				(dev_addr - p->pci_addr + p->cpu_addr);
+
+	return (phys_addr_t)dev_addr;
+}
+
 static int brcm_pcie_add_controller(struct brcm_pcie *pcie)
 {
 	int i, ret = 0;
@@ -610,6 +685,10 @@ static int brcm_pcie_add_controller(struct brcm_pcie *pcie)
 		goto done;
 	}
 
+	ret = brcm_pcie_parse_map_dma_ranges(pcie);
+	if (ret)
+		goto done;
+
 	/* Determine num_memc and their sizes */
 	for (i = 0, num_memc = 0; i < BRCM_MAX_SCB; i++) {
 		u64 size = brcmstb_memory_memc_size(i);
@@ -639,8 +718,13 @@ static int brcm_pcie_add_controller(struct brcm_pcie *pcie)
 static void brcm_pcie_remove_controller(struct brcm_pcie *pcie)
 {
 	mutex_lock(&brcm_pcie_lock);
-	if (--num_pcie == 0)
-		num_memc = 0;
+	if (--num_pcie > 0)
+		goto out;
+
+	kfree(brcm_dma_ranges);
+	brcm_dma_ranges = NULL;
+	num_memc = 0;
+out:
 	mutex_unlock(&brcm_pcie_lock);
 }
 
@@ -747,11 +831,37 @@ static int brcm_pcie_setup(struct brcm_pcie *pcie)
 	 */
 	rc_bar2_size = roundup_pow_of_two_64(total_mem_size);
 
-	/*
-	 * Set simple configuration based on memory sizes
-	 * only.  We always start the viewport at address 0.
-	 */
-	rc_bar2_offset = 0;
+	if (brcm_dma_ranges) {
+		/*
+		 * The best-case scenario is to place the inbound
+		 * region in the first 4GB of pcie-space, as some
+		 * legacy devices can only address 32bits.
+		 * We would also like to put the MSI under 4GB
+		 * as well, since some devices require a 32bit
+		 * MSI target address.
+		 */
+		if (total_mem_size <= 0xc0000000ULL &&
+		    rc_bar2_size <= 0x100000000ULL) {
+			rc_bar2_offset = 0;
+		} else {
+			/*
+			 * The system memory is 4GB or larger so we
+			 * cannot start the inbound region at location
+			 * 0 (since we have to allow some space for
+			 * outbound memory @ 3GB).  So instead we
+			 * start it at the 1x multiple of its size
+			 */
+			rc_bar2_offset = rc_bar2_size;
+		}
+
+	} else {
+		/*
+		 * Set simple configuration based on memory sizes
+		 * only.  We always start the viewport at address 0,
+		 * and set the MSI target address accordingly.
+		 */
+		rc_bar2_offset = 0;
+	}
 
 	tmp = lower_32_bits(rc_bar2_offset);
 	tmp = INSERT_FIELD(tmp, PCIE_MISC_RC_BAR2_CONFIG_LO, SIZE,
@@ -969,7 +1079,6 @@ static int brcm_pcie_probe(struct platform_device *pdev)
 	struct brcm_pcie *pcie;
 	struct resource *res;
 	void __iomem *base;
-	u32 tmp;
 	struct pci_host_bridge *bridge;
 	struct pci_bus *child;
 
@@ -986,11 +1095,6 @@ static int brcm_pcie_probe(struct platform_device *pdev)
 		return -EINVAL;
 	}
 
-	if (of_property_read_u32(dn, "dma-ranges", &tmp) == 0) {
-		dev_err(&pdev->dev, "cannot yet handle dma-ranges\n");
-		return -EINVAL;
-	}
-
 	data = of_id->data;
 	pcie->reg_offsets = data->offsets;
 	pcie->reg_field_info = data->reg_field_info;
diff --git a/include/soc/brcmstb/common.h b/include/soc/brcmstb/common.h
index cfb5335..a7f19e0 100644
--- a/include/soc/brcmstb/common.h
+++ b/include/soc/brcmstb/common.h
@@ -12,4 +12,20 @@
 
 bool soc_is_brcmstb(void);
 
+#if defined(CONFIG_PCIE_BRCMSTB)
+dma_addr_t brcm_phys_to_dma(struct device *dev, phys_addr_t paddr);
+phys_addr_t brcm_dma_to_phys(struct device *dev, dma_addr_t dev_addr);
+#else
+static inline dma_addr_t brcm_phys_to_dma(struct device *dev, phys_addr_t paddr)
+{
+	return (dma_addr_t)paddr;
+}
+
+static inline phys_addr_t brcm_dma_to_phys(struct device *dev,
+					   dma_addr_t dev_addr)
+{
+	return (phys_addr_t)dev_addr;
+}
+#endif
+
 #endif /* __SOC_BRCMSTB_COMMON_H__ */
-- 
1.9.0.138.g2de3478