pl35x-nand-controller: Enable dynamically setting clk rate in NAND.

arch/arm/boot/dts/xilinx/ni-zynq.dtsi

@@ -140,6 +140,16 @@
 
 &smcc {
 	status = "okay";
+	/*
+	 * NI Zynq based devices require different memclk frequency
+	 * for different timing modes
+	 */
+	memclk-timing-frequency = <0 83333333>,
+				<1 166666666>,
+				<2 166666666>,
+				<3 166666666>,
+				<4 166666666>,
+				<5 166666666>;
 };
 
 &nfc0 {

drivers/mtd/nand/raw/pl35x-nand-controller.c

@@ -795,6 +795,28 @@ static int pl35x_nfc_exec_op(struct nand_chip *chip,
 				      op, check_only);
 }
 
+static unsigned long of_get_memclk_freq(const struct device_node *np, const int timing_mode)
+{
+	int memclk_frequency, i, total_elements;
+	u32 memclk_mode;
+
+	total_elements = of_property_count_u32_elems(np, "memclk-timing-frequency");
+	if (total_elements <= 0)
+		return 0;
+
+	for (i = 0; i < total_elements; i = i+2) {
+		of_property_read_u32_index(np, "memclk-timing-frequency", i, &memclk_mode);
+		if (memclk_mode == timing_mode) {
+			of_property_read_u32_index(np, "memclk-timing-frequency",
+				i+1, &memclk_frequency);
+			return memclk_frequency;
+		}
+	}
+
+	pr_err("Failed to find matching memclk timing mode %d\n", timing_mode);
+	return 0;
+}
+
 static int pl35x_nfc_setup_interface(struct nand_chip *chip, int cs,
 				     const struct nand_interface_config *conf)
 {
@@ -804,6 +826,8 @@ static int pl35x_nfc_setup_interface(struct nand_chip *chip, int cs,
 	const struct nand_sdr_timings *sdr;
 	unsigned int period_ns, val;
 	struct clk *mclk;
+	unsigned long memclk_of_timing_freq;
+	int ret = 0;
 
 	sdr = nand_get_sdr_timings(conf);
 	if (IS_ERR(sdr))
@@ -815,6 +839,23 @@ static int pl35x_nfc_setup_interface(struct nand_chip *chip, int cs,
 		return PTR_ERR(mclk);
 	}
 
+	/*
+	 * NI Zynq based devices require different rates for different timing modes
+	 * so we need to set the rate according to the timing modes
+	 */
+	memclk_of_timing_freq = of_get_memclk_freq(
+		nfc->dev->parent->of_node,
+		conf->timings.mode);
+
+	if (memclk_of_timing_freq) {
+		ret = clk_set_rate(mclk, memclk_of_timing_freq);
+		if (ret) {
+			pr_err("Failed to set memclk timing frequency to %lu\n",
+				memclk_of_timing_freq);
+			return ret;
+		}
+	}
+
 	/*
 	 * SDR timings are given in pico-seconds while NFC timings must be
 	 * expressed in NAND controller clock cycles. We use the TO_CYCLE()