[PATCH] ARM: davinci: da8xx: Fix sleeping function called from invalid context

[Sekhar Nori]

On Monday 28 November 2016 09:59 PM, Alexandre Bailon wrote:
> Everytime the usb20 phy is enabled, there is a
> "sleeping function called from invalid context" BUG.

Who calls PHY clk_enable() from non-preemptible context? Can you provide
the call stack?

> usb20_phy_clk_enable(), called with the irq disabled uses
> clk_get() and clk_enable_prepapre() which may sleep.
> Move clk_get() to da8xx_register_usb20_phy_clk() and
> replace clk_prepare_enable() by clk_enable().
> 
> Signed-off-by: Alexandre Bailon <abailon at baylibre.com>
> ---
>  arch/arm/mach-davinci/usb-da8xx.c | 15 +++++++++------
>  1 file changed, 9 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/arm/mach-davinci/usb-da8xx.c b/arch/arm/mach-davinci/usb-da8xx.c
> index b010e5f..c9b5cd4 100644
> --- a/arch/arm/mach-davinci/usb-da8xx.c
> +++ b/arch/arm/mach-davinci/usb-da8xx.c
> @@ -156,23 +156,23 @@ int __init da8xx_register_usb_refclkin(int rate)
>  	return 0;
>  }
>  
> +static struct clk *usb20_clk;
> +
>  static void usb20_phy_clk_enable(struct clk *clk)
>  {
> -	struct clk *usb20_clk;
>  	int err;
>  	u32 val;
>  	u32 timeout = 500000; /* 500 msec */
>  
>  	val = readl(DA8XX_SYSCFG0_VIRT(DA8XX_CFGCHIP2_REG));
>  
> -	usb20_clk = clk_get(&da8xx_usb20_dev.dev, "usb20");
> -	if (IS_ERR(usb20_clk)) {
> +	if (!usb20_clk || IS_ERR(usb20_clk)) {

NULL is a valid clock handle. There is no way clock enable of
usb20_phy_clk can be invoked if its not registered. So, you can assume
that usb20_clk is valid if you get here.

>  		pr_err("could not get usb20 clk: %ld\n", PTR_ERR(usb20_clk));
>  		return;
>  	}
>  
>  	/* The USB 2.O PLL requires that the USB 2.O PSC is enabled as well. */
> -	err = clk_prepare_enable(usb20_clk);
> +	err = clk_enable(usb20_clk);
>  	if (err) {
>  		pr_err("failed to enable usb20 clk: %d\n", err);
>  		clk_put(usb20_clk);
> @@ -197,8 +197,7 @@ static void usb20_phy_clk_enable(struct clk *clk)
>  
>  	pr_err("Timeout waiting for USB 2.0 PHY clock good\n");
>  done:
> -	clk_disable_unprepare(usb20_clk);
> -	clk_put(usb20_clk);
> +	clk_disable(usb20_clk);


I noticed that we are missing clk_disable(usb20_clk) in
usb20_phy_clk_disable(). It will now be easier to do that after this
patch. Can you add that in a separate patch?

>  }
>  
>  static void usb20_phy_clk_disable(struct clk *clk)
> @@ -287,6 +286,10 @@ int __init da8xx_register_usb20_phy_clk(bool use_usb_refclkin)
>  	struct clk *parent;
>  	int ret = 0;
>  
> +	usb20_clk = clk_get(&da8xx_usb20_dev.dev, "usb20");
> +	if (IS_ERR(usb20_clk))
> +		return PTR_ERR(parent);
> +
>  	parent = clk_get(NULL, use_usb_refclkin ? "usb_refclkin" : "pll0_aux");
>  	if (IS_ERR(parent))
>  		return PTR_ERR(parent);

clk_put(usb20_clk) should be called here on failure path.

Thanks,
Sekhar