[RFC v7 03/23] clocksource: em_sti: split clock prepare and enable steps

[Nicolai Stange]

Currently, the em_sti driver prepares and enables the needed clock in
em_sti_enable(), potentially called through its clockevent device's
->set_state_oneshot().

However, the clk_prepare() step may sleep whereas tick_program_event() and
thus, ->set_state_oneshot(), can be called in atomic context.

Split the clk_prepare_enable() in em_sti_enable() into two steps:
- prepare the clock at device probing via clk_prepare()
- and enable it in em_sti_enable() via clk_enable().
Slightly reorder resource initialization in em_sti_probe() in order to
facilitate error handling.

Signed-off-by: Nicolai Stange <nicsta...@gmail.com>
---

Notes:
    Compile-only tested on ARCH=arm.

 drivers/clocksource/em_sti.c | 25 ++++++++++++++++++-------
 1 file changed, 18 insertions(+), 7 deletions(-)

diff --git a/drivers/clocksource/em_sti.c b/drivers/clocksource/em_sti.c
index 19bb179..46750c0 100644
--- a/drivers/clocksource/em_sti.c
+++ b/drivers/clocksource/em_sti.c
@@ -78,7 +78,7 @@ static int em_sti_enable(struct em_sti_priv *p)
        int ret;
 
        /* enable clock */
-       ret = clk_prepare_enable(p->clk);
+       ret = clk_enable(p->clk);
        if (ret) {
                dev_err(&p->pdev->dev, "cannot enable clock\n");
                return ret;
@@ -107,7 +107,7 @@ static void em_sti_disable(struct em_sti_priv *p)
        em_sti_write(p, STI_INTENCLR, 3);
 
        /* stop clock */
-       clk_disable_unprepare(p->clk);
+       clk_disable(p->clk);
 }
 
 static cycle_t em_sti_count(struct em_sti_priv *p)
@@ -303,6 +303,7 @@ static int em_sti_probe(struct platform_device *pdev)
        struct em_sti_priv *p;
        struct resource *res;
        int irq;
+       int ret;
 
        p = devm_kzalloc(&pdev->dev, sizeof(*p), GFP_KERNEL);
        if (p == NULL)
@@ -323,6 +324,13 @@ static int em_sti_probe(struct platform_device *pdev)
        if (IS_ERR(p->base))
                return PTR_ERR(p->base);
 
+       if (devm_request_irq(&pdev->dev, irq, em_sti_interrupt,
+                            IRQF_TIMER | IRQF_IRQPOLL | IRQF_NOBALANCING,
+                            dev_name(&pdev->dev), p)) {
+               dev_err(&pdev->dev, "failed to request low IRQ\n");
+               return -ENOENT;
+       }
+
        /* get hold of clock */
        p->clk = devm_clk_get(&pdev->dev, "sclk");
        if (IS_ERR(p->clk)) {
@@ -330,17 +338,20 @@ static int em_sti_probe(struct platform_device *pdev)
                return PTR_ERR(p->clk);
        }
 
-       if (devm_request_irq(&pdev->dev, irq, em_sti_interrupt,
-                            IRQF_TIMER | IRQF_IRQPOLL | IRQF_NOBALANCING,
-                            dev_name(&pdev->dev), p)) {
-               dev_err(&pdev->dev, "failed to request low IRQ\n");
-               return -ENOENT;
+       ret = clk_prepare(p->clk);
+       if (ret < 0) {
+               dev_err(&pdev->dev, "cannot prepare clock\n");
+               goto err_clk_put;
        }
 
        raw_spin_lock_init(&p->lock);
        em_sti_register_clockevent(p);
        em_sti_register_clocksource(p);
        return 0;
+
+err_clk_put:
+       clk_put(p->clk);
+       return ret;
 }
 
 static int em_sti_remove(struct platform_device *pdev)
-- 
2.10.0