[PATCH v3 2/7] mmc: atmel-mci: prepare clk before calling enable

[Thomas Petazzoni]

Dear Boris BREZILLON,

On Tue, 16 Jul 2013 17:06:48 +0200, Boris BREZILLON wrote:

>  	buf = kmalloc(ATMCI_REGS_SIZE, GFP_KERNEL);
>  	if (!buf)
> @@ -389,9 +391,13 @@ static int atmci_regs_show(struct seq_file *s, void *v)
>  	 * consistent.
>  	 */
>  	spin_lock_bh(&host->lock);
> -	clk_enable(host->mck);
> +	ret = clk_prepare_enable(host->mck);

I am not very familiar with the spin_lock_bh() variant, but are you
sure we are allowed to sleep within a spin_lock_bh()-protected critical
section?

Remember that clk_prepare_enable() calls both ->prepare() and
->enable() for the clock, and ->prepare() is allowed to sleep, while
->enable() is guaranteed not to sleep.

Therefore, clk_prepare() is usually called at probe time, while
clk_enable() is called whenever enabling/disabling the clock is really
needed. So not all clk_enable() can transparently be converted into a
clk_prepare_enable().

Best regards,

Thomas
-- 
Thomas Petazzoni, Free Electrons
Kernel, drivers, real-time and embedded Linux
development, consulting, training and support.
http://free-electrons.com