On Tue, Dec 04, 2018 at 10:49:44PM +0300, Sergei Shtylyov wrote:
> Protect the CPG register read-modify-write sequence with a spinlock.
Spinlocks are expensive, I think an explanation of why this is
necessary would be worthwhile.
>
> Signed-off-by: Sergei Shtylyov <sergei.shtylyov@xxxxxxxxxxxxxxxxxx>
>
> ---
> Changes in version 2:
> - new patch.
>
> drivers/clk/renesas/rcar-gen3-cpg.c | 8 ++++++++
> 1 file changed, 8 insertions(+)
>
> Index: renesas-drivers/drivers/clk/renesas/rcar-gen3-cpg.c
> ===================================================================
> --- renesas-drivers.orig/drivers/clk/renesas/rcar-gen3-cpg.c
> +++ renesas-drivers/drivers/clk/renesas/rcar-gen3-cpg.c
> @@ -30,14 +30,19 @@
>
> #define CPG_RCKCR_CKSEL BIT(15) /* RCLK Clock Source Select */
>
> +static spinlock_t cpg_lock;
> +
> static void cpg_reg_modify(void __iomem *reg, u32 clear, u32 set)
> {
> + unsigned long flags;
> u32 val;
>
> + spin_lock_irqsave(&cpg_lock, flags);
> val = readl(reg);
> val &= ~clear;
> val |= set;
> writel(val, reg);
> + spin_unlock_irqrestore(&cpg_lock, flags);
> };
>
> struct cpg_simple_notifier {
> @@ -604,5 +609,8 @@ int __init rcar_gen3_cpg_init(const stru
> if (attr)
> cpg_quirks = (uintptr_t)attr->data;
> pr_debug("%s: mode = 0x%x quirks = 0x%x\n", __func__, mode, cpg_quirks);
> +
> + spin_lock_init(&cpg_lock);
> +
> return 0;
> }
>
