linux-kernel - [PATCH v8 3/9] clk: tegra: Ensure that PLLU configuration is applied properly

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Message-Id: <20210516163041.12818-4-digetx@gmail.com>
Date:   Sun, 16 May 2021 19:30:35 +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>,
        Michał Mirosław <mirq-linux@...e.qmqm.pl>
Cc:     Rob Herring <robh+dt@...nel.org>, linux-tegra@...r.kernel.org,
        linux-clk@...r.kernel.org, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org
Subject: [PATCH v8 3/9] clk: tegra: Ensure that PLLU configuration is applied properly

The PLLU (USB) consists of the PLL configuration itself and configuration
of the PLLU outputs. The PLLU programming is inconsistent on T30 vs T114,
where T114 immediately bails out if PLLU is enabled and T30 re-enables
a potentially already enabled PLL (left after bootloader) and then fully
reprograms it, which could be unsafe to do. The correct way should be to
skip enabling of the PLL if it's already enabled and then apply
configuration to the outputs. This patch doesn't fix any known problems,
it's a minor improvement.

Acked-by: Thierry Reding <treding@...dia.com>
Signed-off-by: Dmitry Osipenko <digetx@...il.com>
---
 drivers/clk/tegra/clk-pll.c | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/drivers/clk/tegra/clk-pll.c b/drivers/clk/tegra/clk-pll.c
index 0193cebe8c5a..823a567f2adc 100644
--- a/drivers/clk/tegra/clk-pll.c
+++ b/drivers/clk/tegra/clk-pll.c
@@ -1131,7 +1131,8 @@ static int clk_pllu_enable(struct clk_hw *hw)
 	if (pll->lock)
 		spin_lock_irqsave(pll->lock, flags);
 
-	_clk_pll_enable(hw);
+	if (!clk_pll_is_enabled(hw))
+		_clk_pll_enable(hw);
 
 	ret = clk_pll_wait_for_lock(pll);
 	if (ret < 0)
@@ -1748,15 +1749,13 @@ static int clk_pllu_tegra114_enable(struct clk_hw *hw)
 		return -EINVAL;
 	}
 
-	if (clk_pll_is_enabled(hw))
-		return 0;
-
 	input_rate = clk_hw_get_rate(__clk_get_hw(osc));
 
 	if (pll->lock)
 		spin_lock_irqsave(pll->lock, flags);
 
-	_clk_pll_enable(hw);
+	if (!clk_pll_is_enabled(hw))
+		_clk_pll_enable(hw);
 
 	ret = clk_pll_wait_for_lock(pll);
 	if (ret < 0)
-- 
2.30.2