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Message-ID: <20260108115548.GF302752@google.com>
Date: Thu, 8 Jan 2026 11:55:48 +0000
From: Lee Jones <lee@...nel.org>
To: Matthias Schiffer <matthias.schiffer@...tq-group.com>
Cc: Andi Shyti <andi.shyti@...nel.org>, linux-i2c@...r.kernel.org,
linux-kernel@...r.kernel.org, linux@...tq-group.com
Subject: Re: [PATCH v4 4/4] mfd: tqmx86: add detection for MachXO2 I2C
controller
On Wed, 10 Dec 2025, Matthias Schiffer wrote:
> 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) {
What is 0xff? No magic numbers - please define.
> 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) {
As above - 0x00 means nothing to me.
> + 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;
> }
>
> --
> TQ-Systems GmbH | Mühlstraße 2, Gut Delling | 82229 Seefeld, Germany
> Amtsgericht München, HRB 105018
> Geschäftsführer: Detlef Schneider, Rüdiger Stahl, Stefan Schneider
> https://www.tq-group.com/
>
--
Lee Jones [李琼斯]
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