linux-kernel - [PATCH v2 1/2] clk: tegra: divider: Add missing check for enable-bit on rate's recalculation

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Date:   Tue, 23 Jul 2019 05:52:44 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Michael Turquette <mturquette@...libre.com>,
        Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Peter De Schrijver <pdeschrijver@...dia.com>,
        Prashant Gaikwad <pgaikwad@...dia.com>,
        Stephen Boyd <sboyd@...nel.org>
Cc:     linux-clk@...r.kernel.org, linux-tegra@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH v2 1/2] clk: tegra: divider: Add missing check for enable-bit on rate's recalculation

Unset "enable" bit means that divider is in bypass mode, hence it doesn't
have any effect in that case. Please note that there are no known bugs
caused by the missing check.

Signed-off-by: Dmitry Osipenko <digetx@...il.com>
---

Changelog:

v2: Changed the commit's description from 'Fix' to 'Add' in response to the
    Stephen's Boyd question about the need to backport the patch into stable
    kernels. The backporting is not really needed.

 drivers/clk/tegra/clk-divider.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/clk/tegra/clk-divider.c b/drivers/clk/tegra/clk-divider.c
index e76731fb7d69..f33c19045386 100644
--- a/drivers/clk/tegra/clk-divider.c
+++ b/drivers/clk/tegra/clk-divider.c
@@ -40,8 +40,13 @@ static unsigned long clk_frac_div_recalc_rate(struct clk_hw *hw,
 	int div, mul;
 	u64 rate = parent_rate;
 
-	reg = readl_relaxed(divider->reg) >> divider->shift;
-	div = reg & div_mask(divider);
+	reg = readl_relaxed(divider->reg);
+
+	if ((divider->flags & TEGRA_DIVIDER_UART) &&
+	    !(reg & PERIPH_CLK_UART_DIV_ENB))
+		return rate;
+
+	div = (reg >> divider->shift) & div_mask(divider);
 
 	mul = get_mul(divider);
 	div += mul;
-- 
2.22.0