Re: [PATCH v5] clk: change clk_ops' ->determine_rate() prototype

Stephen Boyd
2015-07-08T00:57:48Z

On 07/07, Boris Brezillon wrote:
> Clock rates are stored in an unsigned long field, but ->determine_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 ->determine_rate() prototype to return 0 or an error code, and pass
> a pointer to a clk_rate_request structure containing the expected target
> rate and the rate constraints imposed by clk users.
>
> The clk_rate_request structure might be extended in the future to contain
> other kind of constraints like the rounding policy, the maximum clock
> inaccuracy or other things that are not yet supported by the CCF
> (power consumption constraints ?).
>
> Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
>
> CC: Jonathan Corbet <corbet@lwn.net>
> CC: Tony Lindgren <tony@atomide.com>
> CC: Ralf Baechle <ralf@linux-mips.org>
> CC: "Emilio López" <emilio@elopez.com.ar>
> CC: Maxime Ripard <maxime.ripard@free-electrons.com>
> CC: Tero Kristo <t-kristo@ti.com>
> CC: Peter De Schrijver <pdeschrijver@nvidia.com>
> CC: Prashant Gaikwad <pgaikwad@nvidia.com>
> CC: Stephen Warren <swarren@wwwdotorg.org>
> CC: Thierry Reding <thierry.reding@gmail.com>
> CC: Alexandre Courbot <gnurou@gmail.com>
> CC: linux-doc@vger.kernel.org
> CC: linux-kernel@vger.kernel.org
> CC: linux-arm-kernel@lists.infradead.org
> CC: linux-omap@vger.kernel.org
> CC: linux-mips@linux-mips.org
> CC: linux-tegra@vger.kernel.org
>
> ---

I'll throw this patch into -next now to see if any other problems
shake out. I'm hoping we get some more acks though, so it'll be
on it's own branch and become immutable in a week or so. One
question below.

> diff --git a/drivers/clk/clk-composite.c b/drivers/clk/clk-composite.c
> index 616f5ae..9e69f34 100644
> --- a/drivers/clk/clk-composite.c
> +++ b/drivers/clk/clk-composite.c
> @@ -99,33 +99,33 @@ static long clk_composite_determine_rate(struct clk_hw *hw, unsigned long rate,
>
> parent_rate = __clk_get_rate(parent);
>
> - tmp_rate = rate_ops->round_rate(rate_hw, rate,
> + tmp_rate = rate_ops->round_rate(rate_hw, req->rate,
> &parent_rate);
> if (tmp_rate < 0)
> continue;
>
> - rate_diff = abs(rate - tmp_rate);
> + rate_diff = abs(req->rate - tmp_rate);
>
> - if (!rate_diff || !*best_parent_p
> + if (!rate_diff || !req->best_parent_hw
> || best_rate_diff > rate_diff) {
> - *best_parent_p = __clk_get_hw(parent);
> - *best_parent_rate = parent_rate;
> + req->best_parent_hw = __clk_get_hw(parent);
> + req->best_parent_rate = parent_rate;
> best_rate_diff = rate_diff;
> best_rate = tmp_rate;
> }
>
> if (!rate_diff)
> - return rate;
> + return 0;
> }
>
> - return best_rate;
> + req->rate = best_rate;
> + return 0;
> } else if (mux_hw && mux_ops && mux_ops->determine_rate) {
> __clk_hw_set_clk(mux_hw, hw);
> - return mux_ops->determine_rate(mux_hw, rate, min_rate,
> - max_rate, best_parent_rate,
> - best_parent_p);
> + return mux_ops->determine_rate(mux_hw, req);
> } else {
> pr_err("clk: clk_composite_determine_rate function called, but no mux or rate callback set!\n");
> + req->rate = 0;
> return 0;

Shouldn't this return an error now? And then assigning req->rate
wouldn't be necessary. Sorry I must have missed this last round.

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