i2c: amd-asf: Add routine to handle the ASF slave process

Add support for handling ASF slave process events as described in the AMD
ASF databook. This involves implementing the correct programming sequence
to manage each ASF packet appropriately.

Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Co-developed-by: Sanket Goswami <Sanket.Goswami@amd.com>
Signed-off-by: Sanket Goswami <Sanket.Goswami@amd.com>
Signed-off-by: Shyam Sundar S K <Shyam-sundar.S-k@amd.com>
Signed-off-by: Andi Shyti <andi.shyti@kernel.org>

Author: Shyam Sundar S K

drivers/i2c/busses/i2c-amd-asf-plat.c

@@ -11,6 +11,7 @@
 
 #include <linux/bitops.h>
 #include <linux/device.h>
+#include <linux/devm-helpers.h>
 #include <linux/errno.h>
 #include <linux/gfp_types.h>
 #include <linux/i2c.h>
@@ -33,21 +34,90 @@
 #define ASF_CLK_EN	17
 
 /* ASF address offsets */
+#define ASFINDEX	(0x07 + piix4_smba)
 #define ASFLISADDR	(0x09 + piix4_smba)
 #define ASFSTA		(0x0A + piix4_smba)
 #define ASFSLVSTA	(0x0D + piix4_smba)
+#define ASFDATARWPTR	(0x11 + piix4_smba)
+#define ASFSETDATARDPTR	(0x12 + piix4_smba)
 #define ASFDATABNKSEL	(0x13 + piix4_smba)
 #define ASFSLVEN	(0x15 + piix4_smba)
 
 #define ASF_BLOCK_MAX_BYTES	72
+#define ASF_ERROR_STATUS	GENMASK(3, 1)
 
 struct amd_asf_dev {
 	struct i2c_adapter adap;
 	struct i2c_client *target;
+	struct delayed_work work_buf;
 	struct sb800_mmio_cfg mmio_cfg;
 	struct resource *port_addr;
 };
 
+static void amd_asf_process_target(struct work_struct *work)
+{
+	struct amd_asf_dev *dev = container_of(work, struct amd_asf_dev, work_buf.work);
+	unsigned short piix4_smba = dev->port_addr->start;
+	u8 data[ASF_BLOCK_MAX_BYTES];
+	u8 bank, reg, cmd;
+	u8 len, idx, val;
+
+	/* Read target status register */
+	reg = inb_p(ASFSLVSTA);
+
+	/* Check if no error bits are set in target status register */
+	if (reg & ASF_ERROR_STATUS) {
+		/* Set bank as full */
+		cmd = 0;
+		reg |= GENMASK(3, 2);
+		outb_p(reg, ASFDATABNKSEL);
+	} else {
+		/* Read data bank */
+		reg = inb_p(ASFDATABNKSEL);
+		bank = (reg & BIT(3)) ? 1 : 0;
+
+		/* Set read data bank */
+		if (bank) {
+			reg |= BIT(4);
+			reg &= ~BIT(3);
+		} else {
+			reg &= ~BIT(4);
+			reg &= ~BIT(2);
+		}
+
+		/* Read command register */
+		outb_p(reg, ASFDATABNKSEL);
+		cmd = inb_p(ASFINDEX);
+		len = inb_p(ASFDATARWPTR);
+		for (idx = 0; idx < len; idx++)
+			data[idx] = inb_p(ASFINDEX);
+
+		/* Clear data bank status */
+		if (bank) {
+			reg |= BIT(3);
+			outb_p(reg, ASFDATABNKSEL);
+		} else {
+			reg |= BIT(2);
+			outb_p(reg, ASFDATABNKSEL);
+		}
+	}
+
+	outb_p(0, ASFSETDATARDPTR);
+	if (cmd & BIT(0))
+		return;
+
+	/*
+	 * Although i2c_slave_event() returns an appropriate error code, we
+	 * don't check it here because we're operating in the workqueue context.
+	 */
+	i2c_slave_event(dev->target, I2C_SLAVE_WRITE_REQUESTED, &val);
+	for (idx = 0; idx < len; idx++) {
+		val = data[idx];
+		i2c_slave_event(dev->target, I2C_SLAVE_WRITE_RECEIVED, &val);
+	}
+	i2c_slave_event(dev->target, I2C_SLAVE_STOP, &val);
+}
+
 static void amd_asf_update_ioport_target(unsigned short piix4_smba, u8 bit,
 					 unsigned long offset, bool set)
 {
@@ -207,10 +277,29 @@ static const struct i2c_algorithm amd_asf_smbus_algorithm = {
 	.functionality = amd_asf_func,
 };
 
+static irqreturn_t amd_asf_irq_handler(int irq, void *ptr)
+{
+	struct amd_asf_dev *dev = ptr;
+	unsigned short piix4_smba = dev->port_addr->start;
+	u8 target_int = inb_p(ASFSTA);
+
+	if (target_int & BIT(6)) {
+		/* Target Interrupt */
+		outb_p(target_int | BIT(6), ASFSTA);
+		schedule_delayed_work(&dev->work_buf, HZ);
+	} else {
+		/* Controller Interrupt */
+		amd_asf_update_ioport_target(piix4_smba, ASF_SLV_INTR, SMBHSTSTS, true);
+	}
+
+	return IRQ_HANDLED;
+}
+
 static int amd_asf_probe(struct platform_device *pdev)
 {
 	struct device *dev = &pdev->dev;
 	struct amd_asf_dev *asf_dev;
+	int ret, irq;
 
 	asf_dev = devm_kzalloc(dev, sizeof(*asf_dev), GFP_KERNEL);
 	if (!asf_dev)
@@ -221,6 +310,18 @@ static int amd_asf_probe(struct platform_device *pdev)
 	if (!asf_dev->port_addr)
 		return dev_err_probe(dev, -EINVAL, "missing IO resources\n");
 
+	ret = devm_delayed_work_autocancel(dev, &asf_dev->work_buf, amd_asf_process_target);
+	if (ret)
+		return dev_err_probe(dev, ret, "failed to create work queue\n");
+
+	irq = platform_get_irq(pdev, 0);
+	if (irq < 0)
+		return dev_err_probe(dev, irq, "missing IRQ resources\n");
+
+	ret = devm_request_irq(dev, irq, amd_asf_irq_handler, IRQF_SHARED, "amd_asf", asf_dev);
+	if (ret)
+		return dev_err_probe(dev, ret, "Unable to request irq: %d for use\n", irq);
+
 	asf_dev->adap.owner = THIS_MODULE;
 	asf_dev->adap.algo = &amd_asf_smbus_algorithm;
 	asf_dev->adap.dev.parent = dev;