linux-kernel - [PATCH v3] clk: tegra: pll: Improve PLLM enable-state detection

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-Id: <20200708075418.25295-1-digetx@gmail.com>
Date:   Wed,  8 Jul 2020 10:54:18 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Peter De Schrijver <pdeschrijver@...dia.com>,
        Prashant Gaikwad <pgaikwad@...dia.com>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>
Cc:     linux-tegra@...r.kernel.org, linux-clk@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH v3] clk: tegra: pll: Improve PLLM enable-state detection

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 <digetx@...il.com>
---

Changelog:

v3: - Dropped unintended code change that was accidentally added to v2.

v2: - Added clarifying comment to the code.

    - Prettified the code.

 drivers/clk/tegra/clk-pll.c | 20 +++++++++++++++-----
 1 file changed, 15 insertions(+), 5 deletions(-)

diff --git a/drivers/clk/tegra/clk-pll.c b/drivers/clk/tegra/clk-pll.c
index b2d39a66f0fa..37cfcd6836c9 100644
--- a/drivers/clk/tegra/clk-pll.c
+++ b/drivers/clk/tegra/clk-pll.c
@@ -327,16 +327,26 @@ 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);
 
-- 
2.26.0