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From:   Paul Cercueil <paul@crapouillou.net>
To:     Thomas Gleixner <tglx@linutronix.de>,
        Daniel Lezcano <daniel.lezcano@linaro.org>,
        Rob Herring <robh+dt@kernel.org>,
        Thierry Reding <thierry.reding@gmail.com>,
        Mark Rutland <mark.rutland@arm.com>,
        Ralf Baechle <ralf@linux-mips.org>,
        Paul Burton <paul.burton@mips.com>,
        Jonathan Corbet <corbet@lwn.net>
Cc:     od@zcrc.me, Mathieu Malaterre <malat@debian.org>,
        linux-pwm@vger.kernel.org, devicetree@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-watchdog@vger.kernel.org,
        linux-mips@linux-mips.org, linux-doc@vger.kernel.org,
        linux-clk@vger.kernel.org, Paul Cercueil <paul@crapouillou.net>
Subject: [PATCH v7 08/24] watchdog: jz4740: Use WDT clock provided by TCU driver
Date:   Tue, 21 Aug 2018 19:16:19 +0200
Message-Id: <20180821171635.22740-9-paul@crapouillou.net>
In-Reply-To: <20180821171635.22740-1-paul@crapouillou.net>
References: <20180821171635.22740-1-paul@crapouillou.net>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Instead of requesting the "ext" clock and handling the watchdog clock
divider and gating in the watchdog driver, we now request and use the
"wdt" clock that is supplied by the ingenic-timer "TCU" driver.

The major benefit is that the watchdog's clock rate and parent can now
be specified from within devicetree, instead of hardcoded in the driver.

Also, this driver won't poke anymore into the TCU registers to
enable/disable the clock, as this is now handled by the TCU driver.

On the bad side, we break the ABI with devicetree - as we now request a
different clock. In this very specific case it is still okay, as every
Ingenic JZ47xx-based board out there compile the devicetree within the
kernel; so it's still time to push breaking changes, in order to get a
clean devicetree that won't break once it musn't.

Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
---

Notes:
     v5: New patch
    
     v6: - Split regmap change to new patch 09/24
         - The code now sets the WDT clock to the smallest rate possible and
           calculates the maximum timeout from that
    
     v7: No change

 drivers/watchdog/Kconfig      |  2 +
 drivers/watchdog/jz4740_wdt.c | 86 +++++++++++++++++--------------------------
 2 files changed, 36 insertions(+), 52 deletions(-)

diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
index 9af07fd92763..834222abbbdb 100644
--- a/drivers/watchdog/Kconfig
+++ b/drivers/watchdog/Kconfig
@@ -1476,7 +1476,9 @@ config INDYDOG
 config JZ4740_WDT
 	tristate "Ingenic jz4740 SoC hardware watchdog"
 	depends on MACH_JZ4740 || MACH_JZ4780
+	depends on COMMON_CLK
 	select WATCHDOG_CORE
+	select INGENIC_TIMER
 	help
 	  Hardware driver for the built-in watchdog timer on Ingenic jz4740 SoCs.
 
diff --git a/drivers/watchdog/jz4740_wdt.c b/drivers/watchdog/jz4740_wdt.c
index ec4d99a830ba..1d504ecf45e1 100644
--- a/drivers/watchdog/jz4740_wdt.c
+++ b/drivers/watchdog/jz4740_wdt.c
@@ -26,25 +26,9 @@
 #include <linux/err.h>
 #include <linux/of.h>
 
-#include <asm/mach-jz4740/timer.h>
-
 #define JZ_REG_WDT_TIMER_DATA     0x0
 #define JZ_REG_WDT_COUNTER_ENABLE 0x4
 #define JZ_REG_WDT_TIMER_COUNTER  0x8
-#define JZ_REG_WDT_TIMER_CONTROL  0xC
-
-#define JZ_WDT_CLOCK_PCLK 0x1
-#define JZ_WDT_CLOCK_RTC  0x2
-#define JZ_WDT_CLOCK_EXT  0x4
-
-#define JZ_WDT_CLOCK_DIV_SHIFT   3
-
-#define JZ_WDT_CLOCK_DIV_1    (0 << JZ_WDT_CLOCK_DIV_SHIFT)
-#define JZ_WDT_CLOCK_DIV_4    (1 << JZ_WDT_CLOCK_DIV_SHIFT)
-#define JZ_WDT_CLOCK_DIV_16   (2 << JZ_WDT_CLOCK_DIV_SHIFT)
-#define JZ_WDT_CLOCK_DIV_64   (3 << JZ_WDT_CLOCK_DIV_SHIFT)
-#define JZ_WDT_CLOCK_DIV_256  (4 << JZ_WDT_CLOCK_DIV_SHIFT)
-#define JZ_WDT_CLOCK_DIV_1024 (5 << JZ_WDT_CLOCK_DIV_SHIFT)
 
 #define DEFAULT_HEARTBEAT 5
 #define MAX_HEARTBEAT     2048
@@ -65,7 +49,8 @@ MODULE_PARM_DESC(heartbeat,
 struct jz4740_wdt_drvdata {
 	struct watchdog_device wdt;
 	void __iomem *base;
-	struct clk *rtc_clk;
+	struct clk *clk;
+	unsigned long clk_rate;
 };
 
 static int jz4740_wdt_ping(struct watchdog_device *wdt_dev)
@@ -80,31 +65,12 @@ static int jz4740_wdt_set_timeout(struct watchdog_device *wdt_dev,
 				    unsigned int new_timeout)
 {
 	struct jz4740_wdt_drvdata *drvdata = watchdog_get_drvdata(wdt_dev);
-	unsigned int rtc_clk_rate;
-	unsigned int timeout_value;
-	unsigned short clock_div = JZ_WDT_CLOCK_DIV_1;
-
-	rtc_clk_rate = clk_get_rate(drvdata->rtc_clk);
-
-	timeout_value = rtc_clk_rate * new_timeout;
-	while (timeout_value > 0xffff) {
-		if (clock_div == JZ_WDT_CLOCK_DIV_1024) {
-			/* Requested timeout too high;
-			* use highest possible value. */
-			timeout_value = 0xffff;
-			break;
-		}
-		timeout_value >>= 2;
-		clock_div += (1 << JZ_WDT_CLOCK_DIV_SHIFT);
-	}
+	u16 timeout_value = (u16)(drvdata->clk_rate * new_timeout);
 
 	writeb(0x0, drvdata->base + JZ_REG_WDT_COUNTER_ENABLE);
-	writew(clock_div, drvdata->base + JZ_REG_WDT_TIMER_CONTROL);
 
 	writew((u16)timeout_value, drvdata->base + JZ_REG_WDT_TIMER_DATA);
 	writew(0x0, drvdata->base + JZ_REG_WDT_TIMER_COUNTER);
-	writew(clock_div | JZ_WDT_CLOCK_RTC,
-		drvdata->base + JZ_REG_WDT_TIMER_CONTROL);
 
 	writeb(0x1, drvdata->base + JZ_REG_WDT_COUNTER_ENABLE);
 
@@ -114,7 +80,13 @@ static int jz4740_wdt_set_timeout(struct watchdog_device *wdt_dev,
 
 static int jz4740_wdt_start(struct watchdog_device *wdt_dev)
 {
-	jz4740_timer_enable_watchdog();
+	struct jz4740_wdt_drvdata *drvdata = watchdog_get_drvdata(wdt_dev);
+	int ret;
+
+	ret = clk_prepare_enable(drvdata->clk);
+	if (ret)
+		return ret;
+
 	jz4740_wdt_set_timeout(wdt_dev, wdt_dev->timeout);
 
 	return 0;
@@ -125,7 +97,7 @@ static int jz4740_wdt_stop(struct watchdog_device *wdt_dev)
 	struct jz4740_wdt_drvdata *drvdata = watchdog_get_drvdata(wdt_dev);
 
 	writeb(0x0, drvdata->base + JZ_REG_WDT_COUNTER_ENABLE);
-	jz4740_timer_disable_watchdog();
+	clk_disable_unprepare(drvdata->clk);
 
 	return 0;
 }
@@ -163,26 +135,42 @@ MODULE_DEVICE_TABLE(of, jz4740_wdt_of_matches);
 
 static int jz4740_wdt_probe(struct platform_device *pdev)
 {
+	struct device *dev = &pdev->dev;
 	struct jz4740_wdt_drvdata *drvdata;
 	struct watchdog_device *jz4740_wdt;
 	struct resource	*res;
+	long rate;
 	int ret;
 
-	drvdata = devm_kzalloc(&pdev->dev, sizeof(struct jz4740_wdt_drvdata),
-			       GFP_KERNEL);
+	drvdata = devm_kzalloc(dev, sizeof(*drvdata), GFP_KERNEL);
 	if (!drvdata)
 		return -ENOMEM;
 
-	if (heartbeat < 1 || heartbeat > MAX_HEARTBEAT)
-		heartbeat = DEFAULT_HEARTBEAT;
+	drvdata->clk = devm_clk_get(&pdev->dev, "wdt");
+	if (IS_ERR(drvdata->clk)) {
+		dev_err(&pdev->dev, "cannot find WDT clock\n");
+		return PTR_ERR(drvdata->clk);
+	}
+
+	/* Set smallest clock possible */
+	rate = clk_round_rate(drvdata->clk, 1);
+	if (rate < 0)
+		return rate;
 
+	ret = clk_set_rate(drvdata->clk, rate);
+	if (ret)
+		return ret;
+
+	drvdata->clk_rate = rate;
 	jz4740_wdt = &drvdata->wdt;
 	jz4740_wdt->info = &jz4740_wdt_info;
 	jz4740_wdt->ops = &jz4740_wdt_ops;
-	jz4740_wdt->timeout = heartbeat;
 	jz4740_wdt->min_timeout = 1;
-	jz4740_wdt->max_timeout = MAX_HEARTBEAT;
-	jz4740_wdt->parent = &pdev->dev;
+	jz4740_wdt->max_timeout = 0xffff / rate;
+	jz4740_wdt->timeout = clamp(heartbeat,
+				    jz4740_wdt->min_timeout,
+				    jz4740_wdt->max_timeout);
+	jz4740_wdt->parent = dev;
 	watchdog_set_nowayout(jz4740_wdt, nowayout);
 	watchdog_set_drvdata(jz4740_wdt, drvdata);
 
@@ -191,12 +179,6 @@ static int jz4740_wdt_probe(struct platform_device *pdev)
 	if (IS_ERR(drvdata->base))
 		return PTR_ERR(drvdata->base);
 
-	drvdata->rtc_clk = devm_clk_get(&pdev->dev, "rtc");
-	if (IS_ERR(drvdata->rtc_clk)) {
-		dev_err(&pdev->dev, "cannot find RTC clock\n");
-		return PTR_ERR(drvdata->rtc_clk);
-	}
-
 	ret = devm_watchdog_register_device(&pdev->dev, &drvdata->wdt);
 	if (ret < 0)
 		return ret;
-- 
2.11.0