misc: atmel_tclib: get and use slow clock

Commit dca1a4b5ff6e ("clk: at91: keep slow clk enabled to prevent system
hang") added a workaround for the slow clock as it is not properly handled
by its users.

Get and use the slow clock as it is necessary for the timer counters.

Signed-off-by: Boris Brezillon <[e-mail]>
Signed-off-by: Alexandre Belloni <[e-mail]>
Acked-by: Greg Kroah-Hartman <[e-mail]>
Acked-by: Daniel Lezcano <[e-mail]>
Acked-by: Thierry Reding <[e-mail]>

drivers/clocksource/tcb_clksrc.c

···
 	struct clk *t2_clk = tc->clk[2];
 	int irq = tc->irq[2];
 
-	/* try to enable t2 clk to avoid future errors in mode change */
-	ret = clk_prepare_enable(t2_clk);
+	ret = clk_prepare_enable(tc->slow_clk);
 	if (ret)
 		return ret;
+
+	/* try to enable t2 clk to avoid future errors in mode change */
+	ret = clk_prepare_enable(t2_clk);
+	if (ret) {
+		clk_disable_unprepare(tc->slow_clk);
+		return ret;
+	}
+
 	clk_disable(t2_clk);
 
 	clkevt.regs = tc->regs;
···
 	ret = request_irq(irq, ch2_irq, IRQF_TIMER, "tc_clkevt", &clkevt);
 	if (ret) {
 		clk_unprepare(t2_clk);
+		clk_disable_unprepare(tc->slow_clk);
 		return ret;
 	}
 

drivers/misc/atmel_tclib.c

···
 	if (IS_ERR(clk))
 		return PTR_ERR(clk);
 
+	tc->slow_clk = devm_clk_get(&pdev->dev, "slow_clk");
+	if (IS_ERR(tc->slow_clk))
+		return PTR_ERR(tc->slow_clk);
+
 	r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 	tc->regs = devm_ioremap_resource(&pdev->dev, r);
 	if (IS_ERR(tc->regs))

drivers/pwm/pwm-atmel-tcb.c

···
 	 */
 	if (i == 5) {
 		i = slowclk;
-		rate = 32768;
+		rate = clk_get_rate(tc->slow_clk);
 		min = div_u64(NSEC_PER_SEC, rate);
 		max = min << tc->tcb_config->counter_width;
 
···
 
 	tcbpwm = devm_kzalloc(&pdev->dev, sizeof(*tcbpwm), GFP_KERNEL);
 	if (tcbpwm == NULL) {
-		atmel_tc_free(tc);
+		err = -ENOMEM;
 		dev_err(&pdev->dev, "failed to allocate memory\n");
-		return -ENOMEM;
+		goto err_free_tc;
 	}
 
 	tcbpwm->chip.dev = &pdev->dev;
···
 	tcbpwm->chip.npwm = NPWM;
 	tcbpwm->tc = tc;
 
+	err = clk_prepare_enable(tc->slow_clk);
+	if (err)
+		goto err_free_tc;
+
 	spin_lock_init(&tcbpwm->lock);
 
 	err = pwmchip_add(&tcbpwm->chip);
-	if (err < 0) {
-		atmel_tc_free(tc);
-		return err;
-	}
+	if (err < 0)
+		goto err_disable_clk;
 
 	platform_set_drvdata(pdev, tcbpwm);
 
 	return 0;
+
+err_disable_clk:
+	clk_disable_unprepare(tcbpwm->tc->slow_clk);
+
+err_free_tc:
+	atmel_tc_free(tc);
+
+	return err;
 }
 
 static int atmel_tcb_pwm_remove(struct platform_device *pdev)
 {
 	struct atmel_tcb_pwm_chip *tcbpwm = platform_get_drvdata(pdev);
 	int err;
+
+	clk_disable_unprepare(tcbpwm->tc->slow_clk);
 
 	err = pwmchip_remove(&tcbpwm->chip);
 	if (err < 0)

include/linux/atmel_tc.h

···
 	const struct atmel_tcb_config *tcb_config;
 	int			irq[3];
 	struct clk		*clk[3];
+	struct clk		*slow_clk;
 	struct list_head	node;
 	bool			allocated;
 };