Driver for the Atmel on-chip SSC on AT32AP and AT91

The Synchronous Serial Controller (SSC) on Atmel microprocessors are
capable of tranceiving many frame based protocols, like I2S.  Tested on the
AT32AP7000/ATSTK1000.

This driver is used in the ALSA sound driver for the AT73C213 external DAC
on the ATSTK1000 development board for AVR32.  This sound driver will be
submitted soon.

Hardware documentation can be found in the AT32AP7000 data sheet, which can
be downloaded from
http://www.atmel.com/dyn/products/datasheets.asp?family_id=682

[akpm@linux-foundation.org: init spinlock at compile time]
Signed-off-by: Hans-Christian Egtvedt <hcegtvedt@atmel.com>
Acked-by: Haavard Skinnemoen <hskinnemoen@atmel.com>
Cc: David Brownell <david-b@pacbell.net>
Cc: Andrew Victor <andrew@sanpeople.com>
Cc: Patrice Vilchez <patrice.vilchez@rfo.atmel.com>
Cc: Nicolas Ferre <nicolas.ferre@rfo.atmel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

3 files changed, 187 insertions, 0 deletions

diff --git a/drivers/misc/Kconfig b/drivers/misc/Kconfig
index 73e248f..346c44e 100644
--- a/drivers/misc/Kconfig
+++ b/drivers/misc/Kconfig
@@ -203,4 +203,16 @@ config THINKPAD_ACPI_BAY
 	  If you are not sure, say Y here.
 
 
+config ATMEL_SSC
+	tristate "Device driver for Atmel SSC peripheral"
+	depends on AVR32 || ARCH_AT91
+	---help---
+	  This option enables device driver support for Atmel Syncronized
+	  Serial Communication peripheral (SSC).
+
+	  The SSC peripheral supports a wide variety of serial frame based
+	  communications, i.e. I2S, SPI, etc.
+
+	  If unsure, say N.
+
 endif # MISC_DEVICES
diff --git a/drivers/misc/Makefile b/drivers/misc/Makefile
index b5ce0e3..a24c614 100644
--- a/drivers/misc/Makefile
+++ b/drivers/misc/Makefile
@@ -7,6 +7,7 @@ obj-$(CONFIG_IBM_ASM)		+= ibmasm/
 obj-$(CONFIG_HDPU_FEATURES)	+= hdpuftrs/
 obj-$(CONFIG_MSI_LAPTOP)     += msi-laptop.o
 obj-$(CONFIG_ASUS_LAPTOP)     += asus-laptop.o
+obj-$(CONFIG_ATMEL_SSC)		+= atmel-ssc.o
 obj-$(CONFIG_LKDTM)		+= lkdtm.o
 obj-$(CONFIG_TIFM_CORE)       	+= tifm_core.o
 obj-$(CONFIG_TIFM_7XX1)       	+= tifm_7xx1.o
diff --git a/drivers/misc/atmel-ssc.c b/drivers/misc/atmel-ssc.c
new file mode 100644
index 0000000..058ccac
--- /dev/null
+++ b/drivers/misc/atmel-ssc.c
@@ -0,0 +1,174 @@
+/*
+ * Atmel SSC driver
+ *
+ * Copyright (C) 2007 Atmel Corporation
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/platform_device.h>
+#include <linux/list.h>
+#include <linux/clk.h>
+#include <linux/err.h>
+#include <linux/io.h>
+#include <linux/list.h>
+#include <linux/spinlock.h>
+#include <linux/atmel-ssc.h>
+
+/* Serialize access to ssc_list and user count */
+static DEFINE_SPINLOCK(user_lock);
+static LIST_HEAD(ssc_list);
+
+struct ssc_device *ssc_request(unsigned int ssc_num)
+{
+	int ssc_valid = 0;
+	struct ssc_device *ssc;
+
+	spin_lock(&user_lock);
+	list_for_each_entry(ssc, &ssc_list, list) {
+		if (ssc->pdev->id == ssc_num) {
+			ssc_valid = 1;
+			break;
+		}
+	}
+
+	if (!ssc_valid) {
+		spin_unlock(&user_lock);
+		dev_dbg(&ssc->pdev->dev, "could not find requested device\n");
+		return ERR_PTR(-ENODEV);
+	}
+
+	if (ssc->user) {
+		spin_unlock(&user_lock);
+		dev_dbg(&ssc->pdev->dev, "module busy\n");
+		return ERR_PTR(-EBUSY);
+	}
+	ssc->user++;
+	spin_unlock(&user_lock);
+
+	clk_enable(ssc->clk);
+
+	return ssc;
+}
+EXPORT_SYMBOL(ssc_request);
+
+void ssc_free(struct ssc_device *ssc)
+{
+	spin_lock(&user_lock);
+	if (ssc->user) {
+		ssc->user--;
+		clk_disable(ssc->clk);
+	} else {
+		dev_dbg(&ssc->pdev->dev, "device already free\n");
+	}
+	spin_unlock(&user_lock);
+}
+EXPORT_SYMBOL(ssc_free);
+
+static int __init ssc_probe(struct platform_device *pdev)
+{
+	int retval = 0;
+	struct resource *regs;
+	struct ssc_device *ssc;
+
+	ssc = kzalloc(sizeof(struct ssc_device), GFP_KERNEL);
+	if (!ssc) {
+		dev_dbg(&pdev->dev, "out of memory\n");
+		retval = -ENOMEM;
+		goto out;
+	}
+
+	regs = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	if (!regs) {
+		dev_dbg(&pdev->dev, "no mmio resource defined\n");
+		retval = -ENXIO;
+		goto out_free;
+	}
+
+	ssc->clk = clk_get(&pdev->dev, "pclk");
+	if (IS_ERR(ssc->clk)) {
+		dev_dbg(&pdev->dev, "no pclk clock defined\n");
+		retval = -ENXIO;
+		goto out_free;
+	}
+
+	ssc->pdev = pdev;
+	ssc->regs = ioremap(regs->start, regs->end - regs->start + 1);
+	if (!ssc->regs) {
+		dev_dbg(&pdev->dev, "ioremap failed\n");
+		retval = -EINVAL;
+		goto out_clk;
+	}
+
+	/* disable all interrupts */
+	clk_enable(ssc->clk);
+	ssc_writel(ssc->regs, IDR, ~0UL);
+	ssc_readl(ssc->regs, SR);
+	clk_disable(ssc->clk);
+
+	ssc->irq = platform_get_irq(pdev, 0);
+	if (!ssc->irq) {
+		dev_dbg(&pdev->dev, "could not get irq\n");
+		retval = -ENXIO;
+		goto out_unmap;
+	}
+
+	spin_lock(&user_lock);
+	list_add_tail(&ssc->list, &ssc_list);
+	spin_unlock(&user_lock);
+
+	platform_set_drvdata(pdev, ssc);
+
+	dev_info(&pdev->dev, "Atmel SSC device at 0x%p (irq %d)\n",
+			ssc->regs, ssc->irq);
+
+	goto out;
+
+out_unmap:
+	iounmap(ssc->regs);
+out_clk:
+	clk_put(ssc->clk);
+out_free:
+	kfree(ssc);
+out:
+	return retval;
+}
+
+static int __devexit ssc_remove(struct platform_device *pdev)
+{
+	struct ssc_device *ssc = platform_get_drvdata(pdev);
+
+	spin_lock(&user_lock);
+	iounmap(ssc->regs);
+	clk_put(ssc->clk);
+	list_del(&ssc->list);
+	kfree(ssc);
+	spin_unlock(&user_lock);
+
+	return 0;
+}
+
+static struct platform_driver ssc_driver = {
+	.remove		= __devexit_p(ssc_remove),
+	.driver		= {
+		.name		= "ssc",
+	},
+};
+
+static int __init ssc_init(void)
+{
+	return platform_driver_probe(&ssc_driver, ssc_probe);
+}
+module_init(ssc_init);
+
+static void __exit ssc_exit(void)
+{
+	platform_driver_unregister(&ssc_driver);
+}
+module_exit(ssc_exit);
+
+MODULE_AUTHOR("Hans-Christian Egtvedt <hcegtvedt@atmel.com>");
+MODULE_DESCRIPTION("SSC driver for Atmel AVR32 and AT91");
+MODULE_LICENSE("GPL");