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

Tero Kristo
2015-07-13T09:01:05Z

On 07/08/2015 03:57 AM, Stephen Boyd wrote:
> 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.

Gave this patch a quick test on the boards I have access to, and didn't
notice any obvious problems.

So, for the TI parts:

Acked-by: Tero Kristo <t-kristo@ti.com>

>
>> 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.
>