linux-kernel - [PATCH v4 4/4] mfd: tqmx86: add detection for MachXO2 I2C controller

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Message-ID: <8d275757b7544fe81e5cec4a1a5d4524e9b6967b.1765373900.git.matthias.schiffer@ew.tq-group.com>
Date: Wed, 10 Dec 2025 14:52:53 +0100
From: Matthias Schiffer <matthias.schiffer@...tq-group.com>
To: Andi Shyti <andi.shyti@...nel.org>,
	Lee Jones <lee@...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 v4 4/4] mfd: tqmx86: add detection for MachXO2 I2C controller

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

Signed-off-by: Matthias Schiffer <matthias.schiffer@...tq-group.com>
---

v2: no changes

v3: no changes

v4:
- Reorder patch (was 3/4) - the new order makes more sense with the changed (less generic) approach
- Platform data and mfd_cell are toplevel variables now
- With the new less generic approach i2c-machxo2 detection is only done for the secondary I2C controller
  (as the primary one is always i2c-ocores anyways)


 drivers/mfd/tqmx86.c | 44 +++++++++++++++++++++++++++++++++++++++-----
 1 file changed, 39 insertions(+), 5 deletions(-)

diff --git a/drivers/mfd/tqmx86.c b/drivers/mfd/tqmx86.c
index 708b33c3e5724..a4e3ecfccb8ab 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>
 
@@ -61,6 +62,8 @@
 #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)");
@@ -130,6 +133,8 @@ static const struct mfd_cell tqmx86_i2c1_dev_ocores = {
 	.num_resources = ARRAY_SIZE(tqmx_i2c1_resources),
 };
 
+/* Only one of the tqmx86_i2c2_* instances is registered, depending on which is detected */
+
 static struct ocores_i2c_platform_data tqmx86_i2c2_platform_data_ocores = {};
 
 static const struct mfd_cell tqmx86_i2c2_dev_ocores = {
@@ -140,6 +145,18 @@ static const struct mfd_cell tqmx86_i2c2_dev_ocores = {
 	.num_resources = ARRAY_SIZE(tqmx_i2c2_resources),
 };
 
+struct machxo2_i2c_platform_data tqmx86_i2c2_platform_data_machxo2 = {
+	.bus_khz = 100,
+};
+
+static const struct mfd_cell tqmx86_i2c2_dev_machxo2 = {
+	.name = "i2c-machxo2",
+	.platform_data = &tqmx86_i2c2_platform_data_machxo2,
+	.pdata_size = sizeof(tqmx86_i2c2_platform_data_machxo2),
+	.resources = tqmx_i2c2_resources,
+	.num_resources = ARRAY_SIZE(tqmx_i2c2_resources),
+};
+
 static const struct mfd_cell tqmx86_devs[] = {
 	{
 		.name = "tqmx86-wdt",
@@ -282,9 +299,9 @@ static int tqmx86_detect_i2c1(struct device *dev, void __iomem *io_base, int clo
 	}
 
 	/*
-	 * 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.
 	 */
 	i2c_det = inb(TQMX86_IOBASE_I2C1 + TQMX86_REG_I2C_DETECT);
 
@@ -300,7 +317,7 @@ static int tqmx86_detect_i2c1(struct device *dev, void __iomem *io_base, int clo
 
 static int tqmx86_detect_i2c2(struct device *dev, void __iomem *io_base, int clock_khz)
 {
-	u8 i2c_det;
+	u8 i2c_det, i2c_ien;
 
 	if (i2c2_irq) {
 		if (!tqmx86_setup_irq(dev, "I2C2", i2c2_irq, io_base,
@@ -312,16 +329,33 @@ static int tqmx86_detect_i2c2(struct device *dev, void __iomem *io_base, int clo
 	 * 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.
+	 *
+	 * There are 3 cases to distinguish for the secondary controller:
+	 *
+	 * - 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(TQMX86_IOBASE_I2C2 + TQMX86_REG_I2C_DETECT);
+	i2c_ien = inb(TQMX86_IOBASE_I2C2 + TQMX86_REG_I2C_IEN);
 
-	if (i2c_det == TQMX86_REG_I2C_DETECT_OCORES) {
+	if (i2c_det == TQMX86_REG_I2C_DETECT_OCORES && i2c_ien == 0xff) {
 		tqmx86_i2c2_platform_data_ocores.clock_khz = clock_khz;
 		return devm_mfd_add_devices(dev, PLATFORM_DEVID_NONE,
 					    &tqmx86_i2c2_dev_ocores, 1, NULL, 0,
 					    NULL);
+	} else if ((i2c_ien & 0xf0) == 0x00) {
+		tqmx86_i2c2_platform_data_machxo2.clock_khz = clock_khz;
+		return devm_mfd_add_devices(dev, PLATFORM_DEVID_NONE,
+					    &tqmx86_i2c2_dev_machxo2, 1, NULL, 0,
+					    NULL);
 	}
 
+
 	return 0;
 }
 
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