clk: at91: avoid sleeping early

It is not allowed to sleep to early in the boot process and this may lead
to kernel issues if the bootloader didn't prepare the slow clock and main
clock.

This results in the following error and dump stack on the AriettaG25:
   bad: scheduling from the idle thread!

Ensure it is possible to sleep, else simply have a delay.

Reported-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lkml.kernel.org/r/20190920153906.20887-1-alexandre.belloni@bootlin.com
Fixes: 80eded6ce8bb ("clk: at91: add slow clks driver")
Tested-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>

2 files changed, 20 insertions, 5 deletions

diff --git a/drivers/clk/at91/clk-main.c b/drivers/clk/at91/clk-main.c
index 87083b3a2769..37c22667e831 100644
--- a/drivers/clk/at91/clk-main.c
+++ b/drivers/clk/at91/clk-main.c
@@ -297,7 +297,10 @@ static int clk_main_probe_frequency(struct regmap *regmap)
                 regmap_read(regmap, AT91_CKGR_MCFR, &mcfr);
                 if (mcfr & AT91_PMC_MAINRDY)
                         return 0;
-                usleep_range(MAINF_LOOP_MIN_WAIT, MAINF_LOOP_MAX_WAIT);
+                if (system_state < SYSTEM_RUNNING)
+                        udelay(MAINF_LOOP_MIN_WAIT);
+                else
+                        usleep_range(MAINF_LOOP_MIN_WAIT, MAINF_LOOP_MAX_WAIT);
         } while (time_before(prep_time, timeout));
 
         return -ETIMEDOUT;
diff --git a/drivers/clk/at91/sckc.c b/drivers/clk/at91/sckc.c
index 9bfe9a28294a..fac0ca56d42d 100644
--- a/drivers/clk/at91/sckc.c
+++ b/drivers/clk/at91/sckc.c
@@ -76,7 +76,10 @@ static int clk_slow_osc_prepare(struct clk_hw *hw)
 
         writel(tmp | osc->bits->cr_osc32en, sckcr);
 
-        usleep_range(osc->startup_usec, osc->startup_usec + 1);
+        if (system_state < SYSTEM_RUNNING)
+                udelay(osc->startup_usec);
+        else
+                usleep_range(osc->startup_usec, osc->startup_usec + 1);
 
         return 0;
 }
@@ -187,7 +190,10 @@ static int clk_slow_rc_osc_prepare(struct clk_hw *hw)
 
         writel(readl(sckcr) | osc->bits->cr_rcen, sckcr);
 
-        usleep_range(osc->startup_usec, osc->startup_usec + 1);
+        if (system_state < SYSTEM_RUNNING)
+                udelay(osc->startup_usec);
+        else
+                usleep_range(osc->startup_usec, osc->startup_usec + 1);
 
         return 0;
 }
@@ -288,7 +294,10 @@ static int clk_sam9x5_slow_set_parent(struct clk_hw *hw, u8 index)
 
         writel(tmp, sckcr);
 
-        usleep_range(SLOWCK_SW_TIME_USEC, SLOWCK_SW_TIME_USEC + 1);
+        if (system_state < SYSTEM_RUNNING)
+                udelay(SLOWCK_SW_TIME_USEC);
+        else
+                usleep_range(SLOWCK_SW_TIME_USEC, SLOWCK_SW_TIME_USEC + 1);
 
         return 0;
 }
@@ -533,7 +542,10 @@ static int clk_sama5d4_slow_osc_prepare(struct clk_hw *hw)
                 return 0;
         }
 
-        usleep_range(osc->startup_usec, osc->startup_usec + 1);
+        if (system_state < SYSTEM_RUNNING)
+                udelay(osc->startup_usec);
+        else
+                usleep_range(osc->startup_usec, osc->startup_usec + 1);
         osc->prepared = true;
 
         return 0;