Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::3:8 as permitted sender) client-ip=2620:137:e000::3:8;
From:   Chris Packham <chris.packham@alliedtelesis.co.nz>
To:     gregory.clement@bootlin.com, andi.shyti@kernel.org,
        robh+dt@kernel.org, krzysztof.kozlowski+dt@linaro.org,
        conor+dt@kernel.org
Cc:     linux-i2c@vger.kernel.org, devicetree@vger.kernel.org,
        linux-kernel@vger.kernel.org,
        Chris Packham <chris.packham@alliedtelesis.co.nz>
Subject: [PATCH v5 2/2] i2c: mv64xxx: add an optional bus-reset-gpios property
Date:   Fri, 27 Oct 2023 16:31:04 +1300
Message-ID: <20231027033104.1348921-3-chris.packham@alliedtelesis.co.nz>
In-Reply-To: <20231027033104.1348921-1-chris.packham@alliedtelesis.co.nz>
References: <20231027033104.1348921-1-chris.packham@alliedtelesis.co.nz>
MIME-Version: 1.0
Content-Transfer-Encoding: quoted-printable
Precedence: bulk

Some hardware designs have a GPIO used to control the reset of all the
devices on and I2C bus. It's not possible for every child node to
declare a reset-gpios property as only the first device probed would be
able to successfully request it (the others will get -EBUSY). Represent
this kind of hardware design by associating the bus-reset-gpios with the
parent I2C bus. The reset line will be released prior to the child I2C
devices being probed.

Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
---

Notes:
    Changes in v5:
    - Rename reset-gpios and reset-duration-us to bus-reset-gpios and
      bus-reset-duration-us as requested by Wolfram
    Changes in v4:
    - Add missing gpio/consumer.h
    - use fsleep() for enforcing reset-duration
    Changes in v3:
    - Rename reset-delay to reset-duration
    - Use reset-duration-us property to control the reset pulse rather th=
an
      delaying after the reset
    Changes in v2:
    - Add a property to cover the length of delay after releasing the res=
et
      GPIO
    - Use dev_err_probe() when requesing the GPIO fails

 drivers/i2c/busses/i2c-mv64xxx.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/drivers/i2c/busses/i2c-mv64xxx.c b/drivers/i2c/busses/i2c-mv=
64xxx.c
index efd28bbecf61..6e2762d22e5a 100644
--- a/drivers/i2c/busses/i2c-mv64xxx.c
+++ b/drivers/i2c/busses/i2c-mv64xxx.c
@@ -13,6 +13,7 @@
 #include <linux/slab.h>
 #include <linux/module.h>
 #include <linux/spinlock.h>
+#include <linux/gpio/consumer.h>
 #include <linux/i2c.h>
 #include <linux/interrupt.h>
 #include <linux/mv643xx_i2c.h>
@@ -160,6 +161,7 @@ struct mv64xxx_i2c_data {
 	bool			clk_n_base_0;
 	struct i2c_bus_recovery_info	rinfo;
 	bool			atomic;
+	struct gpio_desc	*reset_gpio;
 };
=20
 static struct mv64xxx_i2c_regs mv64xxx_i2c_regs_mv64xxx =3D {
@@ -1036,6 +1038,7 @@ mv64xxx_i2c_probe(struct platform_device *pd)
 	struct mv64xxx_i2c_data		*drv_data;
 	struct mv64xxx_i2c_pdata	*pdata =3D dev_get_platdata(&pd->dev);
 	struct resource *res;
+	u32	reset_duration;
 	int	rc;
=20
 	if ((!pdata && !pd->dev.of_node))
@@ -1083,6 +1086,14 @@ mv64xxx_i2c_probe(struct platform_device *pd)
 	if (drv_data->irq < 0)
 		return drv_data->irq;
=20
+	drv_data->reset_gpio =3D devm_gpiod_get_optional(&pd->dev, "bus-reset",=
 GPIOD_OUT_HIGH);
+	if (IS_ERR(drv_data->reset_gpio))
+		return dev_err_probe(&pd->dev, PTR_ERR(drv_data->reset_gpio),
+				     "Cannot get reset gpio\n");
+	rc =3D device_property_read_u32(&pd->dev, "bus-reset-duration-us", &res=
et_duration);
+	if (rc)
+		reset_duration =3D 1;
+
 	if (pdata) {
 		drv_data->freq_m =3D pdata->freq_m;
 		drv_data->freq_n =3D pdata->freq_n;
@@ -1121,6 +1132,11 @@ mv64xxx_i2c_probe(struct platform_device *pd)
 			goto exit_disable_pm;
 	}
=20
+	if (drv_data->reset_gpio) {
+		fsleep(reset_duration);
+		gpiod_set_value_cansleep(drv_data->reset_gpio, 0);
+	}
+
 	rc =3D request_irq(drv_data->irq, mv64xxx_i2c_intr, 0,
 			 MV64XXX_I2C_CTLR_NAME, drv_data);
 	if (rc) {
--=20
2.42.0