pl35x-nand-controller: Enable dynamic clk rate setting

Bluefin devices require different clk frequencies to be set at
different timing modes. Enable the memclk rate to be set according
to the specifications in the device tree. If the device tree does
not have this memclk-timing-frequency property specified, the driver
proceeds as usual.

Signed-off-by: deooi <deborah.ooi@ni.com>

Author: deooi

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

@@ -140,6 +140,16 @@
 
 &smcc {
 	status = "okay";
+	/*
+	 * Bluefin 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 +795,25 @@ 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)
+{
+	struct property	*prop;
+	const __be32 *cur;
+	int memclk_frequency = 0;
+	u32 memclk_mode;
+
+	of_property_for_each_u32(np, "memclk-timing-frequency", prop, cur, memclk_mode) {
+		if (timing_mode != memclk_mode)
+			continue;
+	
+		of_property_read_u32_index(np, "memclk-timing-frequency",
+						(cur - (__be32 *)prop->value) / sizeof(u32) + 1, 
+						&memclk_frequency);
+		return memclk_frequency;
+	}
+	return 0;
+}
+
 static int pl35x_nfc_setup_interface(struct nand_chip *chip, int cs,
 				     const struct nand_interface_config *conf)
 {
@@ -804,6 +823,8 @@ 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 +836,23 @@ static int pl35x_nfc_setup_interface(struct nand_chip *chip, int cs,
 		return PTR_ERR(mclk);
 	}
 
+	/*
+	 * Bluefin 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()