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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>,
        Stefan Riedmueller <S.Riedmueller@phytec.de>
Subject: [PATCH 3/6] clk: imx6q: disable gpmi_io and ipt_io clocks before changing parent
Date:   Tue, 25 Jan 2022 09:52:03 +0100
Message-ID: <20220125085206.8508-4-ceggers@arri.de>
In-Reply-To: <20220125085206.8508-1-ceggers@arri.de>
References: <20220125085206.8508-1-ceggers@arri.de>
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gpmi_io and ipt_io clocks 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.

Reparenting of enfc_clk_root may disable pll3_usb_otg. In order to avoid
immediately re-enabling it in imx_register_uart_clocks(), the whole
section has been moved to the bottom of imx6q_clocks_init().

Signed-off-by: Christian Eggers <ceggers@arri.de>
Co-developed-by: Stefan Riedmueller <S.Riedmueller@phytec.de>
Signed-off-by: Stefan Riedmueller <S.Riedmueller@phytec.de>
---
 drivers/clk/imx/clk-imx6q.c | 27 ++++++++++++++++++++-------
 1 file changed, 20 insertions(+), 7 deletions(-)

diff --git a/drivers/clk/imx/clk-imx6q.c b/drivers/clk/imx/clk-imx6q.c
index de36f58d551c..fd5c37095ed0 100644
--- a/drivers/clk/imx/clk-imx6q.c
+++ b/drivers/clk/imx/clk-imx6q.c
@@ -927,13 +927,6 @@ static void __init imx6q_clocks_init(struct device_node *ccm_node)
 	clk_set_parent(hws[IMX6QDL_CLK_IPU2_DI0_SEL]->clk, hws[IMX6QDL_CLK_IPU2_DI0_PRE]->clk);
 	clk_set_parent(hws[IMX6QDL_CLK_IPU2_DI1_SEL]->clk, hws[IMX6QDL_CLK_IPU2_DI1_PRE]->clk);
 
-	/*
-	 * The gpmi needs 100MHz frequency in the EDO/Sync mode,
-	 * We can not get the 100MHz from the pll2_pfd0_352m.
-	 * So choose pll2_pfd2_396m as enfc_sel's parent.
-	 */
-	clk_set_parent(hws[IMX6QDL_CLK_ENFC_SEL]->clk, hws[IMX6QDL_CLK_PLL2_PFD2_396M]->clk);
-
 	if (IS_ENABLED(CONFIG_USB_MXS_PHY)) {
 		clk_prepare_enable(hws[IMX6QDL_CLK_USBPHY1_GATE]->clk);
 		clk_prepare_enable(hws[IMX6QDL_CLK_USBPHY2_GATE]->clk);
@@ -975,5 +968,25 @@ static void __init imx6q_clocks_init(struct device_node *ccm_node)
 	}
 
 	imx_register_uart_clocks(2);
+
+	/*
+	 * The gpmi needs 100MHz frequency in the EDO/Sync mode. We can not get
+	 * the 100MHz from the pll2_pfd0_352m. So choose pll2_pfd2_396m as
+	 * enfc_sel's parent.
+	 *
+	 * gpmi_io and ipt_clk_io clocks 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
+	 * gpio_io is left to the gpmi-nand driver.
+	 */
+	if (clk_hw_is_enabled(hws[IMX6QDL_CLK_GPMI_IO])) {
+		clk_prepare_enable(hws[IMX6QDL_CLK_GPMI_IO]->clk);
+		clk_disable_unprepare(hws[IMX6QDL_CLK_GPMI_IO]->clk);
+	}
+	if (clk_hw_is_enabled(hws[IMX6QDL_CLK_ENFC])) {
+		clk_prepare_enable(hws[IMX6QDL_CLK_ENFC]->clk);
+		clk_disable_unprepare(hws[IMX6QDL_CLK_ENFC]->clk);
+	}
+	clk_set_parent(hws[IMX6QDL_CLK_ENFC_SEL]->clk, hws[IMX6QDL_CLK_PLL2_PFD2_396M]->clk);
 }
 CLK_OF_DECLARE(imx6q, "fsl,imx6q-ccm", imx6q_clocks_init);
-- 
Christian Eggers
Embedded software developer

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