linux-kernel - [PATCH 1/6] clk: imx6ul: disable gpmi_io clock before changing parent clock

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Message-ID: <20220125085206.8508-2-ceggers@arri.de>
Date:   Tue, 25 Jan 2022 09:52:01 +0100
From:   Christian Eggers <ceggers@...i.de>
To:     Abel Vesa <abel.vesa@....com>
CC:     Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        Shawn Guo <shawnguo@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        Fabio Estevam <festevam@...il.com>,
        NXP Linux Team <linux-imx@....com>,
        <linux-clk@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>,
        Stefan Riedmueller <s.riedmueller@...tec.de>,
        Christian Eggers <ceggers@...i.de>
Subject: [PATCH 1/6] clk: imx6ul: disable gpmi_io clock before changing parent clock

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@...i.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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