clk: imx: Add common API for masking MMDC handshake

All i.MX6 SoCs need to mask unused MMDC channel's handshake
for low power modes, this patch provides common API for masking
the MMDC channel passed from caller.
Signed-off-by: Anson Huang <Anson.Huang@nxp.com>
Reviewed-by: Dong Aisheng <aisheng.dong@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

drivers/clk/imx/clk.c

 // SPDX-License-Identifier: GPL-2.0
 #include <linux/clk.h>
 #include <linux/err.h>
+#include <linux/io.h>
 #include <linux/of.h>
 #include <linux/slab.h>
 #include <linux/spinlock.h>
 #include "clk.h"
 
+#define CCM_CCDR			0x4
+#define CCDR_MMDC_CH0_MASK		BIT(17)
+#define CCDR_MMDC_CH1_MASK		BIT(16)
+
 DEFINE_SPINLOCK(imx_ccm_lock);
 
+void __init imx_mmdc_mask_handshake(void __iomem *ccm_base,
+				    unsigned int chn)
+{
+	unsigned int reg;
+
+	reg = readl_relaxed(ccm_base + CCM_CCDR);
+	reg |= chn == 0 ? CCDR_MMDC_CH0_MASK : CCDR_MMDC_CH1_MASK;
+	writel_relaxed(reg, ccm_base + CCM_CCDR);
+}
+
 void __init imx_check_clocks(struct clk *clks[], unsigned int count)
 {
 	unsigned i;

drivers/clk/imx/clk.h

@@ -10,6 +10,7 @@ extern spinlock_t imx_ccm_lock;
 void imx_check_clocks(struct clk *clks[], unsigned int count);
 void imx_check_clk_hws(struct clk_hw *clks[], unsigned int count);
 void imx_register_uart_clocks(struct clk ** const clks[]);
+void imx_mmdc_mask_handshake(void __iomem *ccm_base, unsigned int chn);
 
 extern void imx_cscmr1_fixup(u32 *val);