watchdog: orion: Use the reference clock on Armada 375 SoC

The 25 MHz reference clock has better stability so its use is prefered over the
core clock. Change the Armada 375 clock initialization to use this reference
clock. To ensure the driver is compatible with an old devicetree, also provide
a fallback path which will silently return to the previous behavior.

While here, add the clock specification to the binding documentation.

Acked-by: Jason Cooper <jason@lakedaemon.net>
Acked-by: Gregory CLEMENT <gregory.clement@free-electrons.com>
Acked-by: Wim Van Sebroeck <wim@iguana.be>
Reviewed-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Tested-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Ezequiel Garcia <ezequiel.garcia@free-electrons.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>

1 files changed, 41 insertions, 1 deletions

diff --git a/drivers/watchdog/orion_wdt.c b/drivers/watchdog/orion_wdt.c
index 00d0741228fc..8cb1ff3bcd90 100644
--- a/drivers/watchdog/orion_wdt.c
+++ b/drivers/watchdog/orion_wdt.c
@@ -114,6 +114,46 @@ static int armada370_wdt_clock_init(struct platform_device *pdev,
         return 0;
 }
 
+static int armada375_wdt_clock_init(struct platform_device *pdev,
+                                    struct orion_watchdog *dev)
+{
+        int ret;
+
+        dev->clk = of_clk_get_by_name(pdev->dev.of_node, "fixed");
+        if (!IS_ERR(dev->clk)) {
+                ret = clk_prepare_enable(dev->clk);
+                if (ret) {
+                        clk_put(dev->clk);
+                        return ret;
+                }
+
+                atomic_io_modify(dev->reg + TIMER_CTRL,
+                                WDT_AXP_FIXED_ENABLE_BIT,
+                                WDT_AXP_FIXED_ENABLE_BIT);
+                dev->clk_rate = clk_get_rate(dev->clk);
+
+                return 0;
+        }
+
+        /* Mandatory fallback for proper devicetree backward compatibility */
+        dev->clk = clk_get(&pdev->dev, NULL);
+        if (IS_ERR(dev->clk))
+                return PTR_ERR(dev->clk);
+
+        ret = clk_prepare_enable(dev->clk);
+        if (ret) {
+                clk_put(dev->clk);
+                return ret;
+        }
+
+        atomic_io_modify(dev->reg + TIMER_CTRL,
+                        WDT_A370_RATIO_MASK(WDT_A370_RATIO_SHIFT),
+                        WDT_A370_RATIO_MASK(WDT_A370_RATIO_SHIFT));
+        dev->clk_rate = clk_get_rate(dev->clk) / WDT_A370_RATIO;
+
+        return 0;
+}
+
 static int armadaxp_wdt_clock_init(struct platform_device *pdev,
                                    struct orion_watchdog *dev)
 {
@@ -394,7 +434,7 @@ static const struct orion_watchdog_data armada375_data = {
         .rstout_mask_bit = BIT(10),
         .wdt_enable_bit = BIT(8),
         .wdt_counter_offset = 0x34,
-        .clock_init = armada370_wdt_clock_init,
+        .clock_init = armada375_wdt_clock_init,
         .enabled = armada375_enabled,
         .start = armada375_start,
         .stop = armada375_stop,