Certain Altera FPGAs have an ARM-based Hard Processor System (HPS) that
includes two DesignWare Watchdog Timer peripherals. Problems occur if
both are enabled in the device tree as the "dw_wdt" driver only supports
a single device, using a static variable (`dw_wdt`) to hold its state.
Typically, the timer queue gets corrupted, leading to a kernel Oops.
Use bit 1 of `dw_wdt.state` to indicate that a device has already been
probed, and reject attempts to probe extra devices.
Signed-off-by: Ian Abbott <abbotti@xxxxxxxxx>
---
drivers/watchdog/dw_wdt.c | 25 ++++++++++++++++++++-----
1 file changed, 20 insertions(+), 5 deletions(-)
diff --git a/drivers/watchdog/dw_wdt.c b/drivers/watchdog/dw_wdt.c
index 249ef09..cece633 100644
--- a/drivers/watchdog/dw_wdt.c
+++ b/drivers/watchdog/dw_wdt.c
@@ -61,6 +61,7 @@ MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started "
/* dw_wdt.state bit numbers */
#define DW_WDT_IN_USE 0
+#define DW_WDT_PROBED 1
static struct {
void __iomem *regs;
@@ -335,17 +336,26 @@ static int dw_wdt_drv_probe(struct platform_device *pdev)
int ret;
struct resource *mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+ if (test_and_set_bit(DW_WDT_PROBED, &dw_wdt.state)) {
+ pr_err("This driver only supports one device\n");
+ return -ENODEV;
+ }
+
dw_wdt.regs = devm_ioremap_resource(&pdev->dev, mem);
- if (IS_ERR(dw_wdt.regs))
- return PTR_ERR(dw_wdt.regs);
+ if (IS_ERR(dw_wdt.regs)) {
+ ret = PTR_ERR(dw_wdt.regs);
+ goto out_unmark_probed;
+ }
dw_wdt.clk = devm_clk_get(&pdev->dev, NULL);
- if (IS_ERR(dw_wdt.clk))
- return PTR_ERR(dw_wdt.clk);
+ if (IS_ERR(dw_wdt.clk)) {
+ ret = PTR_ERR(dw_wdt.clk);
+ goto out_unmark_probed;
+ }
ret = clk_prepare_enable(dw_wdt.clk);
if (ret)
- return ret;
+ goto out_unmark_probed;
ret = misc_register(&dw_wdt_miscdev);
if (ret)
@@ -366,6 +376,9 @@ static int dw_wdt_drv_probe(struct platform_device *pdev)
out_disable_clk:
clk_disable_unprepare(dw_wdt.clk);
+out_unmark_probed:
+ clear_bit(DW_WDT_PROBED, &dw_wdt.state);
+
return ret;
}
@@ -377,6 +390,8 @@ static int dw_wdt_drv_remove(struct platform_device *pdev)
clk_disable_unprepare(dw_wdt.clk);
+ clear_bit(DW_WDT_PROBED, &dw_wdt.state);
+
return 0;
}
--
2.1.4
--
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