[PATCH 29/37] PCI: dwc: dra7xx: Workaround for errata id i870

[Kishon Vijay Abraham I]

According to errata i870, access to the PCIe slave port
that are not 32-bit aligned will result in incorrect mapping
to TLP Address and Byte enable fields.

Accessing non 32-bit aligned data causes incorrect data in the target
buffer if memcpy is used. Implement the workaround for this
errata here.

Signed-off-by: Kishon Vijay Abraham I <kis...@ti.com>
---
 drivers/pci/dwc/pci-dra7xx.c |   50 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 50 insertions(+)

diff --git a/drivers/pci/dwc/pci-dra7xx.c b/drivers/pci/dwc/pci-dra7xx.c
index 333aa56..7666e3e 100644
--- a/drivers/pci/dwc/pci-dra7xx.c
+++ b/drivers/pci/dwc/pci-dra7xx.c
@@ -26,6 +26,8 @@
 #include <linux/pm_runtime.h>
 #include <linux/resource.h>
 #include <linux/types.h>
+#include <linux/mfd/syscon.h>
+#include <linux/regmap.h>
 
 #include "pcie-designware.h"
 
@@ -531,6 +533,48 @@ static int dra7xx_pcie_enable_phy(struct dra7xx_pcie 
*dra7xx)
        {},
 };
 
+/*
+ * dra7xx_pcie_ep_legacy_mode: workaround for AM572x/AM571x Errata i870
+ * @dra7xx: the dra7xx device where the workaround should be applied
+ *
+ * Access to the PCIe slave port that are not 32-bit aligned will result
+ * in incorrect mapping to TLP Address and Byte enable fields. Therefore,
+ * byte and half-word accesses are not possible to byte offset 0x1, 0x2, or
+ * 0x3.
+ *
+ * To avoid this issue set PCIE_SS1_AXI2OCP_LEGACY_MODE_ENABLE to 1.
+ */
+static int dra7xx_pcie_ep_legacy_mode(struct device *dev)
+{
+       int ret;
+       struct device_node *np = dev->of_node;
+       struct regmap *regmap;
+       unsigned int reg;
+       unsigned int field;
+
+       regmap = syscon_regmap_lookup_by_phandle(np, "syscon-legacy-mode");
+       if (IS_ERR(regmap)) {
+               dev_dbg(dev, "can't get syscon-legacy-mode\n");
+               return -EINVAL;
+       }
+
+       if (of_property_read_u32_index(np, "syscon-legacy-mode", 1, &reg)) {
+               dev_err(dev, "couldn't get legacy mode register offset\n");
+               return -EINVAL;
+       }
+
+       if (of_property_read_u32_index(np, "syscon-legacy-mode", 2, &field)) {
+               dev_err(dev, "can't get bit field for setting legacy mode\n");
+               return -EINVAL;
+       }
+
+       ret = regmap_update_bits(regmap, reg, field, field);
+       if (ret)
+               dev_err(dev, "failed to set legacy mode\n");
+
+       return ret;
+}
+
 static int __init dra7xx_pcie_probe(struct platform_device *pdev)
 {
        u32 reg;
@@ -643,6 +687,7 @@ static int __init dra7xx_pcie_probe(struct platform_device 
*pdev)
        case DW_PCIE_RC_TYPE:
                dra7xx_pcie_writel(dra7xx, PCIECTRL_TI_CONF_DEVICE_TYPE,
                                   DEVICE_TYPE_RC);
+
                ret = dra7xx_add_pcie_port(dra7xx, pdev);
                if (ret < 0)
                        goto err_gpio;
@@ -650,6 +695,11 @@ static int __init dra7xx_pcie_probe(struct platform_device 
*pdev)
        case DW_PCIE_EP_TYPE:
                dra7xx_pcie_writel(dra7xx, PCIECTRL_TI_CONF_DEVICE_TYPE,
                                   DEVICE_TYPE_EP);
+
+               ret = dra7xx_pcie_ep_legacy_mode(dev);
+               if (ret)
+                       goto err_gpio;
+
                ret = dra7xx_add_pcie_ep(dra7xx, pdev);
                if (ret < 0)
                        goto err_gpio;
-- 
1.7.9.5

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