From: Dmitry Osipenko <digetx@gmail.com>
Date: Wed, 18 Dec 2019 21:44:05 +0300
Subject: clk: tegra: divider: Check UART's divider enable-bit state on rate's
 recalculation

Git-commit: cf83a28f281fb3cce090e1b99d31b26baef9c13b
Patch-mainline: v5.6-rc1
References: jsc#SLE-15847

UART clock is divided using divisor values from DLM/DLL registers when
enable-bit is unset in clk register and clk's divider configuration isn't
taken onto account in this case. This doesn't cause any problems, but
let's add a check for the divider's enable-bit state, for consistency.

Acked-by: Peter De Schrijver <pdeschrijver@nvidia.com>
Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Mian Yousaf Kaukab <yousaf.kaukab@suse.com>
---
 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 ca0de5f11f84..38daf483ddf1 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;
-- 
2.26.2