[PATCH v4 0/2] i2c: mv64xxx: reset-gpios

[PATCH v4 0/2] i2c: mv64xxx: reset-gpios

[Chris Packham]

This series adds the ability to associate a gpio with an I2C bus so that
downstream devices can be brought out of reset when the host controller is
probed.

Chris Packham (2):
  dt-bindings: i2c: mv64xxx: add reset-gpios property
  i2c: mv64xxx: add an optional reset-gpios property

 .../bindings/i2c/marvell,mv64xxx-i2c.yaml        | 10 ++++++++++
 drivers/i2c/busses/i2c-mv64xxx.c                 | 16 ++++++++++++++++
 2 files changed, 26 insertions(+)

-- 
2.42.0

[PATCH v4 1/2] dt-bindings: i2c: mv64xxx: add reset-gpios property

[Chris Packham]

Add reset-gpios and reset-duration-us properties to the
marvell,mv64xxx-i2c binding. These can be used to describe hardware
where a common reset GPIO is connected to all downstream devices on and
I2C bus. This reset will be asserted then released before the downstream
devices on the bus are probed.

Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
---

Notes:
    Changes in v4:
    - Add r-by from Krzysztof
    Changes in v3:
    - Rename reset-delay-us to reset-duration-us to better reflect its
      purpose
    - Add default: for reset-duration-us
    - Add description: for reset-gpios
    Changes in v2:
    - Update commit message
    - Add reset-delay-us property

 .../devicetree/bindings/i2c/marvell,mv64xxx-i2c.yaml   | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/Documentation/devicetree/bindings/i2c/marvell,mv64xxx-i2c.yaml b/Documentation/devicetree/bindings/i2c/marvell,mv64xxx-i2c.yaml
index 461d1c9ee3f7..ecf5b279cfa4 100644
--- a/Documentation/devicetree/bindings/i2c/marvell,mv64xxx-i2c.yaml
+++ b/Documentation/devicetree/bindings/i2c/marvell,mv64xxx-i2c.yaml
@@ -70,6 +70,16 @@ properties:
   resets:
     maxItems: 1
 
+  reset-gpios:
+    description:
+      GPIO pin providing a common reset for all downstream devices. This GPIO
+      will be asserted then released before the downstream devices are probed.
+    maxItems: 1
+
+  reset-duration-us:
+    description: Reset duration in us.
+    default: 1
+
   dmas:
     items:
       - description: RX DMA Channel
-- 
2.42.0

Re: [PATCH v4 1/2] dt-bindings: i2c: mv64xxx: add reset-gpios property

[Andi Shyti]

Hi Chris,

On Wed, Oct 25, 2023 at 11:30:31AM +1300, Chris Packham wrote:
> Add reset-gpios and reset-duration-us properties to the
> marvell,mv64xxx-i2c binding. These can be used to describe hardware
> where a common reset GPIO is connected to all downstream devices on and
> I2C bus. This reset will be asserted then released before the downstream
> devices on the bus are probed.
> 
> Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
> Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>

Acked-by: Andi Shyti <andi.shyti@kernel.org>

Thanks,
Andi

Re: [PATCH v4 1/2] dt-bindings: i2c: mv64xxx: add reset-gpios property

[Wolfram Sang]

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> +  reset-gpios:
> +    description:
> +      GPIO pin providing a common reset for all downstream devices. This GPIO
> +      will be asserted then released before the downstream devices are probed.

How about renaming this to "bus-reset-gpios"?

Reason: When I read "reset-gpios", then I assume the device itself will
be reset. In this case, the Marvell I2C controller. Some I2C mux devices
and PCA9564 already use the property like I described.


[-- Attachment #2: signature.asc --]
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Re: [PATCH v4 1/2] dt-bindings: i2c: mv64xxx: add reset-gpios property

[Chris Packham]

(resend as plain text)


On 27/10/23 00:15, Wolfram Sang wrote:
>> +  reset-gpios:
>> +    description:
>> +      GPIO pin providing a common reset for all downstream devices. This GPIO
>> +      will be asserted then released before the downstream devices are probed.
> How about renaming this to "bus-reset-gpios"?
>
> Reason: When I read "reset-gpios", then I assume the device itself will
> be reset. In this case, the Marvell I2C controller. Some I2C mux devices
> and PCA9564 already use the property like I described.

I don't have an objection to "bus-reset-gpios" it would be trivial for 
me to spin a v5 with the naming changed if everyone is in agreement 
(given my timezone I might just send out a v5 with this change and then 
it can be argued whether to apply v4 or v5).

[PATCH v4 2/2] i2c: mv64xxx: add an optional reset-gpios property

[Chris Packham]

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 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 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 than
      delaying after the reset
    Changes in v2:
    - Add a property to cover the length of delay after releasing the reset
      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-mv64xxx.c
index efd28bbecf61..a7c6617655f7 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;
 };
 
 static struct mv64xxx_i2c_regs mv64xxx_i2c_regs_mv64xxx = {
@@ -1036,6 +1038,7 @@ mv64xxx_i2c_probe(struct platform_device *pd)
 	struct mv64xxx_i2c_data		*drv_data;
 	struct mv64xxx_i2c_pdata	*pdata = dev_get_platdata(&pd->dev);
 	struct resource *res;
+	u32	reset_duration;
 	int	rc;
 
 	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;
 
+	drv_data->reset_gpio = devm_gpiod_get_optional(&pd->dev, "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 = device_property_read_u32(&pd->dev, "reset-duration-us", &reset_duration);
+	if (rc)
+		reset_duration = 1;
+
 	if (pdata) {
 		drv_data->freq_m = pdata->freq_m;
 		drv_data->freq_n = pdata->freq_n;
@@ -1121,6 +1132,11 @@ mv64xxx_i2c_probe(struct platform_device *pd)
 			goto exit_disable_pm;
 	}
 
+	if (drv_data->reset_gpio) {
+		fsleep(reset_duration);
+		gpiod_set_value_cansleep(drv_data->reset_gpio, 0);
+	}
+
 	rc = request_irq(drv_data->irq, mv64xxx_i2c_intr, 0,
 			 MV64XXX_I2C_CTLR_NAME, drv_data);
 	if (rc) {
-- 
2.42.0

Re: [PATCH v4 2/2] i2c: mv64xxx: add an optional reset-gpios property

[Andi Shyti]

Hi Chris,

On Wed, Oct 25, 2023 at 11:30:32AM +1300, Chris Packham wrote:
> 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 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>

Reviewed-by: Andi Shyti <andi.shyti@kernel.org>

Thanks,
Andi