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 <[e-mail]>
Reviewed-by: Peng Fan <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Abel Vesa <[e-mail]>

drivers/clk/imx/clk-composite-7ulp.c

···
 
 #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>
···
 	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
···
 	writel(val, gate->reg);
 
 	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;
 }