Re: [PATCH 1/2] clk: change clk_ops' ->round_rate() prototype

Heiko Stübner
2015-04-19T12:13:04Z

Hi Boris,

Am Freitag, 17. April 2015, 09:29:28 schrieb Boris Brezillon:
> Clock rates are stored in an unsigned long field, but ->round_rate()
> (which returns a rounded rate from a requested one) returns a long
> value (errors are reported using negative error codes), which can lead
> to long overflow if the clock rate exceed 2Ghz.
>
> Change ->round_rate() prototype to return 0 or an error code, and pass the
> requested rate as a pointer so that it can be adjusted depending on
> hardware capabilities.
>
> Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
> ---

On a rk3288-veyron-pinky with the fix described below:
Tested-by: Heiko Stuebner <heiko@sntech.de>

> diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
> index fa5a00e..1462ddc 100644
> --- a/drivers/clk/clk.c
> +++ b/drivers/clk/clk.c
> @@ -1640,8 +1643,10 @@ static struct clk_core *clk_calc_new_rates(struct
> clk_core *clk, &parent_hw);
> parent = parent_hw ? parent_hw->core : NULL;
> } else if (clk->ops->round_rate) {
> - new_rate = clk->ops->round_rate(clk->hw, rate,
> - &best_parent_rate);
> + if (clk->ops->round_rate(clk->hw, &new_rate,
> + &best_parent_rate))
> + return NULL;
> +
> if (new_rate < min_rate || new_rate > max_rate)
> return NULL;
> } else if (!parent || !(clk->flags & CLK_SET_RATE_PARENT)) {

This is using new_rate uninitialized when calling into the round_rate
callback. Which in turn pushed my PLLs up to 2.2GHz :-)

I guess you'll need something like the following:

diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index db4e4b2..afc7733 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -1605,6 +1605,7 @@ static struct clk_core *clk_calc_new_rates(struct clk_core *clk,
&parent_hw);
parent = parent_hw ? parent_hw->core : NULL;
} else if (clk->ops->round_rate) {
+ new_rate = rate;
if (clk->ops->round_rate(clk->hw, &new_rate,
&best_parent_rate))
return NULL;

> diff --git a/drivers/clk/rockchip/clk-pll.c b/drivers/clk/rockchip/clk-pll.c
> index f8d3baf..bd408ef 100644
> --- a/drivers/clk/rockchip/clk-pll.c
> +++ b/drivers/clk/rockchip/clk-pll.c
> @@ -63,8 +63,8 @@ static const struct rockchip_pll_rate_table
> *rockchip_get_pll_settings( return NULL;
> }
>
> -static long rockchip_pll_round_rate(struct clk_hw *hw,
> - unsigned long drate, unsigned long *prate)
> +static int rockchip_pll_round_rate(struct clk_hw *hw,
> + unsigned long *drate, unsigned long *prate)
> {
> struct rockchip_clk_pll *pll = to_rockchip_clk_pll(hw);
> const struct rockchip_pll_rate_table *rate_table = pll->rate_table;
> @@ -72,12 +72,15 @@ static long rockchip_pll_round_rate(struct clk_hw *hw,
>
> /* Assumming rate_table is in descending order */
> for (i = 0; i < pll->rate_count; i++) {
> - if (drate >= rate_table[i].rate)
> - return rate_table[i].rate;
> + if (*drate >= rate_table[i].rate) {
> + *drate = rate_table[i].rate;
> + return 0;
> + }
> }
>
> /* return minimum supported value */
> - return rate_table[i - 1].rate;
> + *drate = rate_table[i - 1].rate;
> + return 0;
> }
>
> /*

The rockchip-part:
Reviewed-by: Heiko Stuebner <heiko@sntech.de>

And as I've stumbled onto this recently too, the clock-maintainership has
expanded to Stephen Boyd and linux-clk@vger.kernel.org .

Heiko