Right now if you've got earlyprintk enabled on exynos5420-peach-pit
then you'll get a hang on boot. Here's why:
1. The i2c-s3c2410 driver will probe at subsys_initcall. It will
enable its clock and disable it. This is the clock "i2c2".
2. The act of disabling "i2c2" will disable its parents. In this case
the parent is "aclk66_peric". There are no other children of
"aclk66_peric" officially enabled, so "aclk66_peric" will be turned
off (despite being CLK_IGNORE_UNUSED, but that's by design).
3. The next time you try to earlyprintk you'll do so without the UART
clock enabled. That's because the UART clocks are also children of
"aclk66_peric". You'll hang.
There's no good place to put a clock enable for earlyprintk, which is
handled by a bunch of assembly code. The best we can do is to handle
this in the clock driver.
Signed-off-by: Doug Anderson <diand...@chromium.org>
---
drivers/clk/samsung/clk-exynos5420.c | 24 ++++++++++++++++++++++++
1 file changed, 24 insertions(+)
diff --git a/drivers/clk/samsung/clk-exynos5420.c
b/drivers/clk/samsung/clk-exynos5420.c
index 9d7d7ee..1e586be 100644
--- a/drivers/clk/samsung/clk-exynos5420.c
+++ b/drivers/clk/samsung/clk-exynos5420.c
@@ -1172,11 +1172,17 @@ static struct of_device_id ext_clk_match[] __initdata =
{
{ },
};
+/* Keep these clocks on until late_initcall */
+static const char *boot_clocks[] __initconst = {
+ "aclk66_peric",
+};
+
/* register exynos5420 clocks */
static void __init exynos5x_clk_init(struct device_node *np,
enum exynos5x_soc soc)
{
struct samsung_clk_provider *ctx;
+ int i;
if (np) {
reg_base = of_iomap(np, 0);
@@ -1226,6 +1232,12 @@ static void __init exynos5x_clk_init(struct device_node
*np,
}
exynos5420_clk_sleep_init();
+
+ for (i = 0; i < ARRAY_SIZE(boot_clocks); i++) {
+ struct clk *to_enable = __clk_lookup(boot_clocks[i]);
+
+ clk_prepare_enable(to_enable);
+ }
}
static void __init exynos5420_clk_init(struct device_node *np)
@@ -1239,3 +1251,15 @@ static void __init exynos5800_clk_init(struct
device_node *np)
exynos5x_clk_init(np, EXYNOS5800);
}
CLK_OF_DECLARE(exynos5800_clk, "samsung,exynos5800-clock",
exynos5800_clk_init);
+
+static int __init exynos5420_clk_late_init(void)
+{
+ int i;
+
+ for (i = 0; i < ARRAY_SIZE(boot_clocks); i++) {
+ struct clk *to_disable = __clk_lookup(boot_clocks[i]);
+
+ clk_disable_unprepare(to_disable);
+ }
+}
+late_initcall(exynos5420_clk_late_init);
--
1.9.1.423.g4596e3a
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