linux-kernel - [PATCH 2/2] clk: rockchip: limit clock rate in the rockchip_fractional

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Message-Id: <1513872282-5370-3-git-send-email-al.kochet@gmail.com>
Date:   Thu, 21 Dec 2017 19:04:42 +0300
From:   Alexander Kochetkov <al.kochet@...il.com>
To:     linux-clk@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-rockchip@...ts.infradead.org
Cc:     Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...eaurora.org>,
        Heiko Stuebner <heiko@...ech.de>,
        Elaine Zhang <zhangqing@...k-chips.com>,
        Alexander Kochetkov <al.kochet@...il.com>
Subject: [PATCH 2/2] clk: rockchip: limit clock rate in the rockchip_fractional_approximation()

rockchip_fractional_approximation() can choose clock rate that can
be larger than one configured using clk_set_max_rate(). Request
to setup correct clock rate whose parent rate will be adjusted
to out of range value will fail with -EINVAL.

Fixes: commit 5d890c2df900 ("clk: rockchip: add special approximation
to fix up fractional clk's jitter").

Signed-off-by: Alexander Kochetkov <al.kochet@...il.com>
---
 drivers/clk/rockchip/clk.c |    7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/clk/rockchip/clk.c b/drivers/clk/rockchip/clk.c
index 35dbd63..3c1fb0d 100644
--- a/drivers/clk/rockchip/clk.c
+++ b/drivers/clk/rockchip/clk.c
@@ -175,6 +175,7 @@ static void rockchip_fractional_approximation(struct clk_hw *hw,
 {
 	struct clk_fractional_divider *fd = to_clk_fd(hw);
 	unsigned long p_rate, p_parent_rate;
+	unsigned long min_rate = 0, max_rate = 0;
 	struct clk_hw *p_parent;
 	unsigned long scale;
 
@@ -182,6 +183,12 @@ static void rockchip_fractional_approximation(struct clk_hw *hw,
 	if ((rate * 20 > p_rate) && (p_rate % rate != 0)) {
 		p_parent = clk_hw_get_parent(clk_hw_get_parent(hw));
 		p_parent_rate = clk_hw_get_rate(p_parent);
+		clk_hw_get_boundaries(clk_hw_get_parent(hw),
+			&min_rate, &max_rate);
+		if (p_parent_rate < min_rate)
+			p_parent_rate = min_rate;
+		if (p_parent_rate > max_rate)
+			p_parent_rate = max_rate;
 		*parent_rate = p_parent_rate;
 	}
 
-- 
1.7.9.5