clk: tegra: pll: Add pre/post rate-change hooks

There is a need to temporarily re-parent CCLK away from PLLX if PLLX's
rate is about to change. The newly introduced PLL pre/post rate-change
hooks allow to handle such case.
Acked-by: Peter De Schrijver <pdeschrijver@nvidia.com>
Tested-by: Peter Geis <pgwipeout@gmail.com>
Tested-by: Marcel Ziswiler <marcel@ziswiler.com>
Tested-by: Jasper Korten <jja2000@gmail.com>
Tested-by: David Heidelberg <david@ixit.cz>
Tested-by: Nicolas Chauvet <kwizart@gmail.com>
Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>

drivers/clk/tegra/clk-pll.c

@@ -744,13 +744,19 @@ static int _program_pll(struct clk_hw *hw, struct tegra_clk_pll_freq_table *cfg,
 
 	state = clk_pll_is_enabled(hw);
 
+	if (state && pll->params->pre_rate_change) {
+		ret = pll->params->pre_rate_change();
+		if (WARN_ON(ret))
+			return ret;
+	}
+
 	_get_pll_mnp(pll, &old_cfg);
 
 	if (state && pll->params->defaults_set && pll->params->dyn_ramp &&
 			(cfg->m == old_cfg.m) && (cfg->p == old_cfg.p)) {
 		ret = pll->params->dyn_ramp(pll, cfg);
 		if (!ret)
-			return 0;
+			goto done;
 	}
 
 	if (state) {
@@ -772,6 +778,10 @@ static int _program_pll(struct clk_hw *hw, struct tegra_clk_pll_freq_table *cfg,
 		pll_clk_start_ss(pll);
 	}
 
+done:
+	if (state && pll->params->post_rate_change)
+		pll->params->post_rate_change();
+
 	return ret;
 }
 

drivers/clk/tegra/clk.h

@@ -266,6 +266,10 @@ struct tegra_clk_pll;
  *				disabled.
  * @dyn_ramp:			Callback which can be used to define a custom
  *				dynamic ramp function for a given PLL.
+ * @pre_rate_change:		Callback which is invoked just before changing
+ *				PLL's rate.
+ * @post_rate_change:		Callback which is invoked right after changing
+ *				PLL's rate.
  *
  * Flags:
  * TEGRA_PLL_USE_LOCK - This flag indicated to use lock bits for
@@ -342,6 +346,8 @@ struct tegra_clk_pll_params {
 	void	(*set_defaults)(struct tegra_clk_pll *pll);
 	int	(*dyn_ramp)(struct tegra_clk_pll *pll,
 			struct tegra_clk_pll_freq_table *cfg);
+	int	(*pre_rate_change)(void);
+	void	(*post_rate_change)(void);
 };
 
 #define TEGRA_PLL_USE_LOCK BIT(0)