linux-kernel - [PATCH 3/4] mfd: tqmx86: add detection for MachXO2 I2C controller

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Message-ID: <932c7e543ced2fa8969453ba9685445d7ef0c9ad.1760525985.git.matthias.schiffer@ew.tq-group.com>
Date: Wed, 15 Oct 2025 13:03:08 +0200
From: Matthias Schiffer <matthias.schiffer@...tq-group.com>
To: Andi Shyti <andi.shyti@...nel.org>
Cc: linux-i2c@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux@...tq-group.com,
	Matthias Schiffer <matthias.schiffer@...tq-group.com>
Subject: [PATCH 3/4] mfd: tqmx86: add detection for MachXO2 I2C controller

The TQMx86 PLD may contain two kinds of I2C controllers: the previously
supported OpenCores I2C, or the MachXO2 I2C. Add support for the latter.

Signed-off-by: Matthias Schiffer <matthias.schiffer@...tq-group.com>
---
 drivers/mfd/tqmx86.c | 39 ++++++++++++++++++++++++++++++++++-----
 1 file changed, 34 insertions(+), 5 deletions(-)

diff --git a/drivers/mfd/tqmx86.c b/drivers/mfd/tqmx86.c
index 3c6f158bf1a45..6447406f5026f 100644
--- a/drivers/mfd/tqmx86.c
+++ b/drivers/mfd/tqmx86.c
@@ -13,6 +13,7 @@
 #include <linux/io.h>
 #include <linux/mfd/core.h>
 #include <linux/module.h>
+#include <linux/platform_data/i2c-machxo2.h>
 #include <linux/platform_data/i2c-ocores.h>
 #include <linux/platform_device.h>
 
@@ -57,6 +58,8 @@
 #define TQMX86_REG_I2C_DETECT	0x7
 #define TQMX86_REG_I2C_DETECT_OCORES	0xa5
 
+#define TQMX86_REG_I2C_IEN	0x9
+
 static uint gpio_irq;
 module_param(gpio_irq, uint, 0);
 MODULE_PARM_DESC(gpio_irq, "GPIO IRQ number (valid parameters: 7, 9, 12)");
@@ -248,27 +251,53 @@ static int tqmx86_setup_i2c_ocores(struct device *dev, const char *label,
 				sizeof(platform_data), irq);
 }
 
+static int tqmx86_setup_i2c_machxo2(struct device *dev, const char *label,
+				    unsigned long i2c_base, int clock_khz, u8 irq)
+{
+	const struct machxo2_i2c_platform_data platform_data = {
+		.clock_khz = clock_khz,
+		.bus_khz = 100,
+	};
+
+	return tqmx86_setup_i2c(dev, "i2c-machxo2", i2c_base, &platform_data,
+				sizeof(platform_data), irq);
+}
+
 static int tqmx86_detect_i2c(struct device *dev, const char *label,
 			     unsigned long i2c_base, int clock_khz, u8 irq,
 			     const struct i2c_board_info *devices,
 			     size_t num_devices, void __iomem *io_base,
 			     u8 irq_reg_shift)
 {
-	u8 i2c_det;
+	u8 i2c_det, i2c_ien;
 
 	if (tqmx86_setup_irq(dev, label, irq, io_base, irq_reg_shift))
 		irq = 0;
 
 	/*
-	 * The I2C_DETECT register is in the range assigned to the I2C driver
-	 * later, so we don't extend TQMX86_IOSIZE. Use inb() for this one-off
-	 * access instead of ioport_map + unmap.
+	 * These registers are in the range assigned to the I2C driver
+	 * later, so we don't extend TQMX86_IOSIZE. Use inb() for these one-off
+	 * accesses instead of ioport_map + unmap.
+	 *
+	 * There are 3 cases to distinguish:
+	 *
+	 * - ocores: i2c_det is a TQMx86-specific register that always contains
+	 *   the value 0xa5. i2c_ien is unused and reads as 0xff.
+	 * - machxo2: i2c_det is the data register can read as any value.
+	 *   i2c_ien is the interrupt enable register; the upper nibble is
+	 *   reserved and always reads as 0.
+	 * - none: both i2c_det and i2c_ien read as 0xff if no I2C controller
+	 *   exists at a given base address.
 	 */
 	i2c_det = inb(i2c_base + TQMX86_REG_I2C_DETECT);
+	i2c_ien = inb(i2c_base + TQMX86_REG_I2C_IEN);
 
-	if (i2c_det == TQMX86_REG_I2C_DETECT_OCORES)
+	if (i2c_det == TQMX86_REG_I2C_DETECT_OCORES && i2c_ien == 0xff)
 		return tqmx86_setup_i2c_ocores(dev, label, i2c_base, clock_khz,
 					       irq, devices, num_devices);
+	else if ((i2c_ien & 0xf0) == 0x00)
+		return tqmx86_setup_i2c_machxo2(dev, label, i2c_base, clock_khz,
+						irq);
 
 	return 0;
 }
-- 
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