Re: [PATCH] clk: mediatek: Export CPU mux clocks for CPU frequency control

Hi Sascha,

On 4 March 2015 at 19:21, Sascha Hauer s.hauer@pengutronix.de wrote:

On Wed, Mar 04, 2015 at 06:49:11PM +0800, pi-cheng.chen wrote:

...

This patch adds CPU mux clocks which are used by Mediatek cpufreq driver for intermediate clock source switching. This patch is based on Mediatek clock driver patches[1].

[1] http://thread.gmane.org/gmane.linux.kernel/1892436

Signed-off-by: pi-cheng.chen pi-cheng.chen@linaro.org

+static long clk_cpumux_determine_rate(struct clk_hw *hw, unsigned long rate,

•                               unsigned long min_rate,
  

•                               unsigned long max_rate,
  

•                               unsigned long *best_parent_rate,
  

•                               struct clk_hw **best_parent_p)
  

+{

• struct clk *clk = hw->clk, *parent;
  

• unsigned long parent_rate;
  

• int i;
  

• for (i = MAINPLL_INDEX; i >= ARMPLL_INDEX; i--) {
  

•         parent = clk_get_parent_by_index(clk, i);
  

•         if (!parent)
  

•                 return 0;
  

•         if (i == MAINPLL_INDEX) {
  

•                 parent_rate = __clk_get_rate(parent);
  

•                 if (parent_rate == rate)
  

•                         break;
  

•         }
  

•         parent_rate = __clk_round_rate(parent, rate);
  

• }
  

• *best_parent_rate = parent_rate;
  

• *best_parent_p = __clk_get_hw(parent);
  

• return parent_rate;
  

+}

Why this determine_rate hook? If you want to switch the clock to some intermediate parent I would assume you do this explicitly by setting the parent and not implicitly by setting a rate.

I use determine_rate hook here because I am using generic cpufreq-dt driver and I want to make clock switching transparent to cpufreq-dt. I.e. when I am trying to switch the clock from ARMPLL to MAINPLL, I call clk_set_rate() with the rate of MAINPLL, and determine_rate will select MAINPLL as the new parent.

...

+int mtk_clk_register_cpumuxes(struct device_node *node,

•                       struct mtk_composite *clks, int num,
  

•                       struct clk_onecell_data *clk_data)
  

+{

• int i;
  

• struct clk *clk;
  

• struct regmap *regmap;
  

• if (!clk_data)
  

•         return -ENOMEM;
  

• regmap = syscon_node_to_regmap(node);
  

• if (IS_ERR(regmap)) {
  

•         pr_err("Cannot find regmap for %s: %ld\n", node->full_name,
  

•                PTR_ERR(regmap));
  

•         return PTR_ERR(regmap);
  

• }
  

• for (i = 0; i < num; i++) {
  

•         struct mtk_composite *mux = &clks[i];
  

•         clk = mtk_clk_register_cpumux(mux->name, mux->parent_names,
  

•                                       mux->num_parents, regmap,
  

•                                       mux->mux_reg, mux->mux_shift,
  

•                                       mux->mux_width);
  

Pass 'mux' directly instead of dispatching this struct into the individual fields. Also, probably better to move this function to drivers/clk/mediatek/clk-cpumux.c

Will do it. Thanks for reviewing.

Best Regards, Pi-Cheng

Sascha

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