mtd: nand: atmel_nand: retrieve NFC clock

Retrieve the NFC clock to make sure it is enabled. Make that optional to ensure
compatibility with previous device trees but document it as mandatory so newer
device trees will include it.
Signed-off-by: Boris BREZILLON <boris.brezillon@free-electrons.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Acked-by: Josh Wu <josh.wu@atmel.com>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>

Documentation/devicetree/bindings/mtd/atmel-nand.txt

@@ -36,6 +36,7 @@ Optional properties:
     - reg : should specify the address and size used for NFC command registers,
             NFC registers and NFC Sram. NFC Sram address and size can be absent
             if don't want to use it.
+    - clocks: phandle to the peripheral clock
   - Optional properties:
     - atmel,write-by-sram: boolean to enable NFC write by sram.
 
@@ -98,6 +99,7 @@ nand0: nand@40000000 {
 		compatible = "atmel,sama5d3-nfc";
 		#address-cells = <1>;
 		#size-cells = <1>;
+		clocks = <&hsmc_clk>
 		reg = <
 			0x70000000 0x10000000	/* NFC Command Registers */
 			0xffffc000 0x00000070	/* NFC HSMC regs */

drivers/mtd/nand/atmel_nand.c

@@ -27,6 +27,7 @@
  *
  */
 
+#include <linux/clk.h>
 #include <linux/dma-mapping.h>
 #include <linux/slab.h>
 #include <linux/module.h>
@@ -96,6 +97,8 @@ struct atmel_nfc {
 	bool			use_nfc_sram;
 	bool			write_by_sram;
 
+	struct clk		*clk;
+
 	bool			is_initialized;
 	struct completion	comp_ready;
 	struct completion	comp_cmd_done;
@@ -2248,6 +2251,7 @@ static int atmel_nand_nfc_probe(struct platform_device *pdev)
 {
 	struct atmel_nfc *nfc = &nand_nfc;
 	struct resource *nfc_cmd_regs, *nfc_hsmc_regs, *nfc_sram;
+	int ret;
 
 	nfc_cmd_regs = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 	nfc->base_cmd_regs = devm_ioremap_resource(&pdev->dev, nfc_cmd_regs);
@@ -2279,8 +2283,28 @@ static int atmel_nand_nfc_probe(struct platform_device *pdev)
 	nfc_writel(nfc->hsmc_regs, IDR, 0xffffffff);
 	nfc_readl(nfc->hsmc_regs, SR);	/* clear the NFC_SR */
 
+	nfc->clk = devm_clk_get(&pdev->dev, NULL);
+	if (!IS_ERR(nfc->clk)) {
+		ret = clk_prepare_enable(nfc->clk);
+		if (ret)
+			return ret;
+	} else {
+		dev_warn(&pdev->dev, "NFC clock missing, update your Device Tree");
+	}
+
 	nfc->is_initialized = true;
 	dev_info(&pdev->dev, "NFC is probed.\n");
+
+	return 0;
+}
+
+static int atmel_nand_nfc_remove(struct platform_device *pdev)
+{
+	struct atmel_nfc *nfc = &nand_nfc;
+
+	if (!IS_ERR(nfc->clk))
+		clk_disable_unprepare(nfc->clk);
+
 	return 0;
 }
 
@@ -2297,6 +2321,7 @@ static struct platform_driver atmel_nand_nfc_driver = {
 		.of_match_table = of_match_ptr(atmel_nand_nfc_match),
 	},
 	.probe = atmel_nand_nfc_probe,
+	.remove = atmel_nand_nfc_remove,
 };
 
 static struct platform_driver atmel_nand_driver = {