bus: imx-weim: guard against timing configuration conflicts

When specifying weim child devices, there is a risk that more than
one timing setting is specified for the same chip select.

The driver cannot support such a configuration.

In case of conflict, this patch will print a warning to the log,
and will ignore the child node in question.

In this example, node acme@1 will be ignored, as it tries to modify
timing settings for CS0:

&weim {
	acme@0 {
		compatible = "acme,whatever";
		reg = <0 0 0x100>;
		fsl,weim-cs-timing = <something>;
	};
	acme@1 {
		compatible = "acme,whatnot";
		reg = <0 0x500 0x100>;
		fsl,weim-cs-timing = <something else>;
	};
};

However in this example, the driver will be happy:

&weim {
        acme@0 {
                compatible = "acme,whatever";
                reg = <0 0 0x100>;
                fsl,weim-cs-timing = <something>;
        };
        acme@1 {
                compatible = "acme,whatnot";
                reg = <0 0x500 0x100>;
                fsl,weim-cs-timing = <something>;
        };
};

Signed-off-by: Sven Van Asbroeck <TheSven73@googlemail.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

1 files changed, 32 insertions, 3 deletions

diff --git a/drivers/bus/imx-weim.c b/drivers/bus/imx-weim.c
index 1a0e0277a404..db74334ca5ef 100644
--- a/drivers/bus/imx-weim.c
+++ b/drivers/bus/imx-weim.c
@@ -46,8 +46,18 @@ static const struct imx_weim_devtype imx51_weim_devtype = {
 };
 
 #define MAX_CS_REGS_COUNT       6
+#define MAX_CS_COUNT            6
 #define OF_REG_SIZE             3
 
+struct cs_timing {
+        bool is_applied;
+        u32 regs[MAX_CS_REGS_COUNT];
+};
+
+struct cs_timing_state {
+        struct cs_timing cs[MAX_CS_COUNT];
+};
+
 static const struct of_device_id weim_id_table[] = {
         /* i.MX1/21 */
         { .compatible = "fsl,imx1-weim", .data = &imx1_weim_devtype, },
@@ -112,15 +122,20 @@ err:
 }
 
 /* Parse and set the timing for this device. */
-static int __init weim_timing_setup(struct device_node *np, void __iomem *base,
-                                    const struct imx_weim_devtype *devtype)
+static int __init weim_timing_setup(struct device *dev,
+                                    struct device_node *np, void __iomem *base,
+                                    const struct imx_weim_devtype *devtype,
+                                    struct cs_timing_state *ts)
 {
         u32 cs_idx, value[MAX_CS_REGS_COUNT];
         int i, ret;
         int reg_idx, num_regs;
+        struct cs_timing *cst;
 
         if (WARN_ON(devtype->cs_regs_count > MAX_CS_REGS_COUNT))
                 return -EINVAL;
+        if (WARN_ON(devtype->cs_count > MAX_CS_COUNT))
+                return -EINVAL;
 
         ret = of_property_read_u32_array(np, "fsl,weim-cs-timing",
                                          value, devtype->cs_regs_count);
@@ -146,10 +161,23 @@ static int __init weim_timing_setup(struct device_node *np, void __iomem *base,
                 if (cs_idx >= devtype->cs_count)
                         return -EINVAL;
 
+                /* prevent re-configuring a CS that's already been configured */
+                cst = &ts->cs[cs_idx];
+                if (cst->is_applied && memcmp(value, cst->regs,
+                                        devtype->cs_regs_count * sizeof(u32))) {
+                        dev_err(dev, "fsl,weim-cs-timing conflict on %pOF", np);
+                        return -EINVAL;
+                }
+
                 /* set the timing for WEIM */
                 for (i = 0; i < devtype->cs_regs_count; i++)
                         writel(value[i],
                                 base + cs_idx * devtype->cs_stride + i * 4);
+                if (!cst->is_applied) {
+                        cst->is_applied = true;
+                        memcpy(cst->regs, value,
+                                devtype->cs_regs_count * sizeof(u32));
+                }
         }
 
         return 0;
@@ -163,6 +191,7 @@ static int __init weim_parse_dt(struct platform_device *pdev,
         const struct imx_weim_devtype *devtype = of_id->data;
         struct device_node *child;
         int ret, have_child = 0;
+        struct cs_timing_state ts = {};
 
         if (devtype == &imx50_weim_devtype) {
                 ret = imx_weim_gpr_setup(pdev);
@@ -171,7 +200,7 @@ static int __init weim_parse_dt(struct platform_device *pdev,
         }
 
         for_each_available_child_of_node(pdev->dev.of_node, child) {
-                ret = weim_timing_setup(child, base, devtype);
+                ret = weim_timing_setup(&pdev->dev, child, base, devtype, &ts);
                 if (ret)
                         dev_warn(&pdev->dev, "%pOF set timing failed.\n",
                                 child);