linux-kernel - [PATCH 3.18 42/52] clk: imx6q: reset exclusive gates on init

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Message-Id: <20190124190149.632897993@linuxfoundation.org>
Date:   Thu, 24 Jan 2019 20:20:06 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Lucas Stach <l.stach@...gutronix.de>,
        Dong Aisheng <Aisheng.dong@....com>,
        Stephen Boyd <sboyd@...nel.org>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 3.18 42/52] clk: imx6q: reset exclusive gates on init

3.18-stable review patch.  If anyone has any objections, please let me know.

------------------

[ Upstream commit f7542d817733f461258fd3a47d77da35b2d9fc81 ]

The exclusive gates may be set up in the wrong way by software running
before the clock driver comes up. In that case the exclusive setup is
locked in its initial state, as the complementary function can't be
activated without disabling the initial setup first.

To avoid this lock situation, reset the exclusive gates to the off
state and allow the kernel to provide the proper setup.

Signed-off-by: Lucas Stach <l.stach@...gutronix.de>
Reviewed-by: Dong Aisheng <Aisheng.dong@....com>
Signed-off-by: Stephen Boyd <sboyd@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 arch/arm/mach-imx/clk-imx6q.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/arch/arm/mach-imx/clk-imx6q.c b/arch/arm/mach-imx/clk-imx6q.c
index 5474a76803f0..936ed9bae595 100644
--- a/arch/arm/mach-imx/clk-imx6q.c
+++ b/arch/arm/mach-imx/clk-imx6q.c
@@ -222,8 +222,12 @@ static void __init imx6q_clocks_init(struct device_node *ccm_node)
 	 * lvds1_gate and lvds2_gate are pseudo-gates.  Both can be
 	 * independently configured as clock inputs or outputs.  We treat
 	 * the "output_enable" bit as a gate, even though it's really just
-	 * enabling clock output.
+	 * enabling clock output. Initially the gate bits are cleared, as
+	 * otherwise the exclusive configuration gets locked in the setup done
+	 * by software running before the clock driver, with no way to change
+	 * it.
 	 */
+	writel(readl(base + 0x160) & ~0x3c00, base + 0x160);
 	clk[IMX6QDL_CLK_LVDS1_GATE] = imx_clk_gate_exclusive("lvds1_gate", "lvds1_sel", base + 0x160, 10, BIT(12));
 	clk[IMX6QDL_CLK_LVDS2_GATE] = imx_clk_gate_exclusive("lvds2_gate", "lvds2_sel", base + 0x160, 11, BIT(13));
 
-- 
2.19.1