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Subject[PATCH v3 3/3] bus: imx-weim: guard against timing configuration conflicts
Date
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>
---
drivers/bus/imx-weim.c | 33 ++++++++++++++++++++++++++++++---
1 file changed, 30 insertions(+), 3 deletions(-)

diff --git a/drivers/bus/imx-weim.c b/drivers/bus/imx-weim.c
index 5452d22d1bd8..dfe74b8c512a 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_REGS 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_REGS];
+};
+
static const struct of_device_id weim_id_table[] = {
/* i.MX1/21 */
{ .compatible = "fsl,imx1-weim", .data = &imx1_weim_devtype, },
@@ -112,11 +122,14 @@ static int __init imx_weim_gpr_setup(struct platform_device *pdev)
}

/* 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, reg_idx, num_regs;
+ struct cs_timing *cst;

if (WARN_ON(devtype->cs_regs_count > MAX_CS_REGS_COUNT))
return -EINVAL;
@@ -145,10 +158,23 @@ 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;
@@ -162,6 +188,7 @@ 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);
@@ -170,7 +197,7 @@ 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);
--
2.17.1
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