[v2] clk: tegra: pll: Improve PLLM enable-state detection

Commit Message

Dmitry Osipenko July 8, 2020, 7:46 a.m. UTC

Power Management Controller (PMC) can override the PLLM clock settings,
including the enable-state. Although PMC could only act as a second level
gate, meaning that PLLM needs to be enabled by the Clock and Reset
Controller (CaR) anyways if we want it to be enabled. Hence, when PLLM is
overridden by PMC, it needs to be enabled by CaR and ungated by PMC in
order to be functional. Please note that this patch doesn't fix any known
problem, and thus, it's merely a minor improvement.

Link: https://lore.kernel.org/linux-arm-kernel/20191210120909.GA2703785@ulmo/T/
Signed-off-by: Dmitry Osipenko <[e-mail]>
---

Changelog:

v2: - Added clarifying comment to the code.

    - Prettified the code.

 drivers/clk/tegra/clk-pll.c | 22 ++++++++++++++++------
 1 file changed, 16 insertions(+), 6 deletions(-)

Comments

Dmitry Osipenko July 8, 2020, 7:49 a.m. UTC | #1

08.07.2020 10:46, Dmitry Osipenko пишет:
> -	return val & PLL_BASE_ENABLE ? 1 : 0;
> +	return val & PLL_BASE_ENABLE;

This was unintended change that caught my eve only after sending out the
email, woops :) Please let me make a v3 shortly.

Patch

diff --git a/drivers/clk/tegra/clk-pll.c b/drivers/clk/tegra/clk-pll.c
index b2d39a66f0fa..f700356efe3e 100644
--- a/drivers/clk/tegra/clk-pll.c
+++ b/drivers/clk/tegra/clk-pll.c
@@ -327,20 +327,30 @@  int tegra_pll_wait_for_lock(struct tegra_clk_pll *pll)
 	return clk_pll_wait_for_lock(pll);
 }
 
+static bool pllm_pmc_clk_enabled(struct tegra_clk_pll *pll)
+{
+	u32 val = readl_relaxed(pll->pmc + PMC_PLLP_WB0_OVERRIDE);
+
+	return !(val & PMC_PLLP_WB0_OVERRIDE_PLLM_OVERRIDE) ||
+		(val & PMC_PLLP_WB0_OVERRIDE_PLLM_ENABLE);
+}
+
 static int clk_pll_is_enabled(struct clk_hw *hw)
 {
 	struct tegra_clk_pll *pll = to_clk_pll(hw);
 	u32 val;
 
-	if (pll->params->flags & TEGRA_PLLM) {
-		val = readl_relaxed(pll->pmc + PMC_PLLP_WB0_OVERRIDE);
-		if (val & PMC_PLLP_WB0_OVERRIDE_PLLM_OVERRIDE)
-			return val & PMC_PLLP_WB0_OVERRIDE_PLLM_ENABLE ? 1 : 0;
-	}
+	/*
+	 * Power Management Controller (PMC) can override the PLLM clock
+	 * settings, including the enable-state. The PLLM is enabled when
+	 * PLLM's CaR state is ON and when PLLM isn't disabled by PMC.
+	 */
+	if ((pll->params->flags & TEGRA_PLLM) && !pllm_pmc_clk_enabled(pll))
+		return 0;
 
 	val = pll_readl_base(pll);
 
-	return val & PLL_BASE_ENABLE ? 1 : 0;
+	return val & PLL_BASE_ENABLE;
 }
 
 static void _clk_pll_enable(struct clk_hw *hw)