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From:   Christian Eggers <ceggers@arri.de>
To:     Abel Vesa <abel.vesa@nxp.com>
CC:     Michael Turquette <mturquette@baylibre.com>,
        Stephen Boyd <sboyd@kernel.org>,
        Shawn Guo <shawnguo@kernel.org>,
        Sascha Hauer <s.hauer@pengutronix.de>,
        Pengutronix Kernel Team <kernel@pengutronix.de>,
        Fabio Estevam <festevam@gmail.com>,
        NXP Linux Team <linux-imx@nxp.com>,
        <linux-clk@vger.kernel.org>,
        <linux-arm-kernel@lists.infradead.org>,
        <linux-kernel@vger.kernel.org>,
        Stefan Riedmueller <s.riedmueller@phytec.de>,
        Christian Eggers <ceggers@arri.de>
Subject: [PATCH 1/6] clk: imx6ul: disable gpmi_io clock before changing parent clock
Date:   Tue, 25 Jan 2022 09:52:01 +0100
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gpmi_io clock may have been enabled by the boot loader. All children of
enfc_clk_root must be gated in order to prevent glitches during parent
change.

Signed-off-by: Christian Eggers <ceggers@arri.de>
---
 drivers/clk/imx/clk-imx6ul.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/clk/imx/clk-imx6ul.c b/drivers/clk/imx/clk-imx6ul.c
index 520b100bff4b..f599ae50dd9f 100644
--- a/drivers/clk/imx/clk-imx6ul.c
+++ b/drivers/clk/imx/clk-imx6ul.c
@@ -514,6 +514,15 @@ static void __init imx6ul_clocks_init(struct device_node *ccm_node)
 	else if (clk_on_imx6ull())
 		clk_set_parent(hws[IMX6ULL_CLK_EPDC_PRE_SEL]->clk, hws[IMX6UL_CLK_PLL3_PFD2]->clk);
 
+	/*
+	 * gpmi_io clock may have been enabled by the boot loader. All children of
+	 * enfc_clk_root must be gated in order to prevent glitches during parent
+	 * change. The task of re-enabling is left to the gpmi-nand driver.
+	 */
+	if (clk_hw_is_enabled(hws[IMX6UL_CLK_GPMI_IO])) {
+		clk_prepare_enable(hws[IMX6UL_CLK_GPMI_IO]->clk);
+		clk_disable_unprepare(hws[IMX6UL_CLK_GPMI_IO]->clk);
+	}
 	clk_set_parent(hws[IMX6UL_CLK_ENFC_SEL]->clk, hws[IMX6UL_CLK_PLL2_PFD2]->clk);
 }
 
-- 
Christian Eggers
Embedded software developer

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