Hello Doug,
On 05/29/2014 11:21 PM, Doug Anderson wrote:
> 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 <dianders@xxxxxxxxxxxx>
> ---
> drivers/clk/samsung/clk-exynos5420.c | 24 ++++++++++++++++++++++++
> 1 file changed, 24 insertions(+)
>
I tested your patch and it solves the issue for me, so feel free to add
Tested-by: Javier Martinez Canillas <javier.martinez@xxxxxxxxxxxxxxx>
Just one trivial comment below:
> 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);
>
You should return 0 here.
Best regards,
Javier
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