Re: [PATCH 2/3] clk: samsung: cpu: prepare for adding Exynos5433 CPU clocks

Krzysztof Kozlowski
2016-05-25T08:31:54Z

On 05/24/2016 03:19 PM, Bartlomiej Zolnierkiewicz wrote:
> Exynos5433 uses different register layout for CPU clock registers
> than earlier SoCs so add new code for handling this layout. Also
> add new CLK_CPU_HAS_E5433_REGS_LAYOUT flag to request using it.
>
> There should be no functional change resulting from this patch.
>
> Cc: Kukjin Kim <kgene@kernel.org>
> CC: Krzysztof Kozlowski <k.kozlowski@samsung.com>
> Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
> ---
> drivers/clk/samsung/clk-cpu.c | 131 +++++++++++++++++++++++++++++++++++++++++-
> drivers/clk/samsung/clk-cpu.h | 4 +-
> 2 files changed, 133 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/clk/samsung/clk-cpu.c b/drivers/clk/samsung/clk-cpu.c
> index 813003d..8bf7e80 100644
> --- a/drivers/clk/samsung/clk-cpu.c
> +++ b/drivers/clk/samsung/clk-cpu.c
> @@ -45,6 +45,13 @@
> #define E4210_DIV_STAT_CPU0 0x400
> #define E4210_DIV_STAT_CPU1 0x404
>
> +#define E5433_MUX_SEL2 0x008
> +#define E5433_MUX_STAT2 0x208
> +#define E5433_DIV_CPU0 0x400
> +#define E5433_DIV_CPU1 0x404
> +#define E5433_DIV_STAT_CPU0 0x500
> +#define E5433_DIV_STAT_CPU1 0x504

I got a problem matching it with datasheed. The base is 0x200?

> +
> #define E4210_DIV0_RATIO0_MASK 0x7
> #define E4210_DIV1_HPM_MASK (0x7 << 4)
> #define E4210_DIV1_COPY_MASK (0x7 << 0)
> @@ -253,6 +260,102 @@ static int exynos_cpuclk_post_rate_change(struct clk_notifier_data *ndata,
> }
>
> /*
> + * Helper function to set the 'safe' dividers for the CPU clock. The parameters
> + * div and mask contain the divider value and the register bit mask of the
> + * dividers to be programmed.
> + */
> +static void exynos5433_set_safe_div(void __iomem *base, unsigned long div,
> + unsigned long mask)

Please align the argument.

> +{
> + unsigned long div0;
> +
> + div0 = readl(base + E5433_DIV_CPU0);
> + div0 = (div0 & ~mask) | (div & mask);
> + writel(div0, base + E5433_DIV_CPU0);
> + wait_until_divider_stable(base + E5433_DIV_STAT_CPU0, mask);
> +}
> +
> +/* handler for pre-rate change notification from parent clock */
> +static int exynos5433_cpuclk_pre_rate_change(struct clk_notifier_data *ndata,
> + struct exynos_cpuclk *cpuclk, void __iomem *base)
> +{
> + const struct exynos_cpuclk_cfg_data *cfg_data = cpuclk->cfg;
> + unsigned long alt_prate = clk_get_rate(cpuclk->alt_parent);
> + unsigned long alt_div = 0, alt_div_mask = DIV_MASK;
> + unsigned long div0, div1 = 0, mux_reg;
> + unsigned long flags;
> +
> + /* find out the divider values to use for clock data */
> + while ((cfg_data->prate * 1000) != ndata->new_rate) {
> + if (cfg_data->prate == 0)
> + return -EINVAL;
> + cfg_data++;
> + }
> +
> + spin_lock_irqsave(cpuclk->lock, flags);
> +
> + /*
> + * For the selected PLL clock frequency, get the pre-defined divider
> + * values.
> + */
> + div0 = cfg_data->div0;
> + div1 = cfg_data->div1;
> +
> + /*
> + * If the old parent clock speed is less than the clock speed of
> + * the alternate parent, then it should be ensured that at no point
> + * the armclk speed is more than the old_prate until the dividers are
> + * set. Also workaround the issue of the dividers being set to lower
> + * values before the parent clock speed is set to new lower speed
> + * (this can result in too high speed of armclk output clocks).

In entire sentence: s/speed/rate/

> + */
> + if (alt_prate > ndata->old_rate || ndata->old_rate > ndata->new_rate) {
> + unsigned long tmp_rate = min(ndata->old_rate, ndata->new_rate);
> +
> + alt_div = DIV_ROUND_UP(alt_prate, tmp_rate) - 1;
> + WARN_ON(alt_div >= MAX_DIV);
> +
> + exynos5433_set_safe_div(base, alt_div, alt_div_mask);
> + div0 |= alt_div;
> + }
> +
> + /* select the alternate parent */
> + mux_reg = readl(base + E5433_MUX_SEL2);
> + writel(mux_reg | 1, base + E5433_MUX_SEL2);
> + wait_until_mux_stable(base + E5433_MUX_STAT2, 0, 2);
> +
> + /* alternate parent is active now. set the dividers */
> + writel(div0, base + E5433_DIV_CPU0);
> + wait_until_divider_stable(base + E5433_DIV_STAT_CPU0, DIV_MASK_ALL);
> +
> + writel(div1, base + E5433_DIV_CPU1);
> + wait_until_divider_stable(base + E5433_DIV_STAT_CPU1, DIV_MASK_ALL);
> +
> + spin_unlock_irqrestore(cpuclk->lock, flags);

One blank line please.

> + return 0;
> +}
> +
> +/* handler for post-rate change notification from parent clock */
> +static int exynos5433_cpuclk_post_rate_change(struct clk_notifier_data *ndata,
> + struct exynos_cpuclk *cpuclk, void __iomem *base)
> +{
> + unsigned long div = 0, div_mask = DIV_MASK;
> + unsigned long mux_reg;
> + unsigned long flags;
> +
> + spin_lock_irqsave(cpuclk->lock, flags);
> +
> + /* select apll as the alternate parent */
> + mux_reg = readl(base + E5433_MUX_SEL2);
> + writel(mux_reg & ~1, base + E5433_MUX_SEL2);
> + wait_until_mux_stable(base + E5433_MUX_STAT2, 0, 1);
> +
> + exynos5433_set_safe_div(base, div, div_mask);
> + spin_unlock_irqrestore(cpuclk->lock, flags);

One blank line please.

> + return 0;
> +}
> +
> +/*
> * This notifier function is called for the pre-rate and post-rate change
> * notifications of the parent clock of cpuclk.
> */
> @@ -275,6 +378,29 @@ static int exynos_cpuclk_notifier_cb(struct notifier_block *nb,
> return notifier_from_errno(err);
> }
>
> +/*
> + * This notifier function is called for the pre-rate and post-rate change
> + * notifications of the parent clock of cpuclk.
> + */
> +static int exynos5433_cpuclk_notifier_cb(struct notifier_block *nb,
> + unsigned long event, void *data)
> +{
> + struct clk_notifier_data *ndata = data;
> + struct exynos_cpuclk *cpuclk;
> + void __iomem *base;
> + int err = 0;
> +
> + cpuclk = container_of(nb, struct exynos_cpuclk, clk_nb);
> + base = cpuclk->ctrl_base;
> +
> + if (event == PRE_RATE_CHANGE)
> + err = exynos5433_cpuclk_pre_rate_change(ndata, cpuclk, base);
> + else if (event == POST_RATE_CHANGE)
> + err = exynos5433_cpuclk_post_rate_change(ndata, cpuclk, base);
> +
> + return notifier_from_errno(err);
> +}

Entire function is a duplication of exynos_cpuclk_notifier_cb(), except
the {pre,post}_rate_change. How about checking the flags here and using
only one notifier? Overall the code should be smaller...

Another, more robust solution would be to define new members in:
struct exynos_cpuclk {
int (pre_rate_change) *(....);
int (post_rate_change) *(....);
}
This way the notifier_cb would be exactly the same for all implementations.

Best regards,
Krzysztof

> +
> /* helper function to register a CPU clock */
> int __init exynos_register_cpu_clock(struct samsung_clk_provider *ctx,
> unsigned int lookup_id, const char *name, const char *parent,
> @@ -301,7 +427,10 @@ int __init exynos_register_cpu_clock(struct samsung_clk_provider *ctx,
> cpuclk->ctrl_base = ctx->reg_base + offset;
> cpuclk->lock = &ctx->lock;
> cpuclk->flags = flags;
> - cpuclk->clk_nb.notifier_call = exynos_cpuclk_notifier_cb;
> + if (flags & CLK_CPU_HAS_E5433_REGS_LAYOUT)
> + cpuclk->clk_nb.notifier_call = exynos5433_cpuclk_notifier_cb;
> + else
> + cpuclk->clk_nb.notifier_call = exynos_cpuclk_notifier_cb;
>
> cpuclk->alt_parent = __clk_lookup(alt_parent);
> if (!cpuclk->alt_parent) {
> diff --git a/drivers/clk/samsung/clk-cpu.h b/drivers/clk/samsung/clk-cpu.h
> index 37874d3..d4b6b51 100644
> --- a/drivers/clk/samsung/clk-cpu.h
> +++ b/drivers/clk/samsung/clk-cpu.h
> @@ -57,10 +57,12 @@ struct exynos_cpuclk {
> struct notifier_block clk_nb;
> unsigned long flags;
>
> -/* The CPU clock registers has DIV1 configuration register */
> +/* The CPU clock registers have DIV1 configuration register */
> #define CLK_CPU_HAS_DIV1 (1 << 0)
> /* When ALT parent is active, debug clocks need safe divider values */
> #define CLK_CPU_NEEDS_DEBUG_ALT_DIV (1 << 1)
> +/* The CPU clock registers have Exynos5433-compatible layout */
> +#define CLK_CPU_HAS_E5433_REGS_LAYOUT (1 << 2)
> };
>
> extern int __init exynos_register_cpu_clock(struct samsung_clk_provider *ctx,
>