From: Jacky Bai <ping.bai@nxp.com>
Date: Fri, 1 Aug 2025 07:21:53 +0000 (+0800)
Subject: clk: imx: Add some delay before deassert the reset
X-Git-Tag: v6.19-rc1~58^2^3^2~3
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=25b47635f8729e9536d2652774bd509532eaa522;p=thirdparty%2Fkernel%2Flinux.git

clk: imx: Add some delay before deassert the reset

Some of the PCCs on i.MX8ULP have a sw_rst bit to control the peripheral
reset through SW method. For peripherals like GPU that need sync reset,
some delay is necessary befere & after release the reset to make sure the
HW is reset into a known status. So add some delay before & after release
reset.

Signed-off-by: Jacky Bai <ping.bai@nxp.com>
Reviewed-by: Peng Fan <peng.fan@nxp.com>
Link: https://lore.kernel.org/r/20250801072153.1974428-1-ping.bai@nxp.com
Signed-off-by: Abel Vesa <abel.vesa@linaro.org>
---

diff --git a/drivers/clk/imx/clk-composite-7ulp.c b/drivers/clk/imx/clk-composite-7ulp.c
index 8ed2e0ad2769c..37d2fc197be67 100644
--- a/drivers/clk/imx/clk-composite-7ulp.c
+++ b/drivers/clk/imx/clk-composite-7ulp.c
@@ -7,6 +7,7 @@
 
 #include <linux/bits.h>
 #include <linux/clk-provider.h>
+#include <linux/delay.h>
 #include <linux/err.h>
 #include <linux/io.h>
 #include <linux/slab.h>
@@ -36,6 +37,9 @@ static int pcc_gate_enable(struct clk_hw *hw)
 	if (ret)
 		return ret;
 
+	/* Make sure the IP's clock is ready before release reset */
+	udelay(1);
+
 	spin_lock_irqsave(gate->lock, flags);
 	/*
 	 * release the sw reset for peripherals associated with
@@ -47,6 +51,15 @@ static int pcc_gate_enable(struct clk_hw *hw)
 
 	spin_unlock_irqrestore(gate->lock, flags);
 
+	/*
+	 * Read back the register to make sure the previous write has been
+	 * done in the target HW register. For IP like GPU, after deassert
+	 * the reset, need to wait for a while to make sure the sync reset
+	 * is done
+	 */
+	readl(gate->reg);
+	udelay(1);
+
 	return 0;
 }