RE: [PATCH v13 2/2] usb: typec: ucsi: add support for Cypress CCGx

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Hi Heikki,

> I still have a few more comments below..
Thanks for reviewing. 
 
> On Wed, Oct 03, 2018 at 11:27:28AM -0700, Ajay Gupta wrote:
> > Latest NVIDIA GPU cards have a Cypress CCGx Type-C controller over I2C
> > interface.
> >
> > This UCSI I2C driver uses I2C bus driver interface for communicating
> > with Type-C controller.
> >
> > Signed-off-by: Ajay Gupta <ajayg@xxxxxxxxxx>
> > Reviewed-by: Andy Shevchenko <andy.shevchenko@xxxxxxxxx>
> > Acked-by: Heikki Krogerus <heikki.krogerus@xxxxxxxxxxxxxxx>
> > ---
> > Changes from v1 -> v2
> > 	Fixed identation in drivers/usb/typec/ucsi/Kconfig Changes from v2 ->
> > v3
> > 	Fixed most of comments from Heikki
> > 	Rename ucsi_i2c_ccg.c -> ucsi_ccg.c
> > Changes from v3 -> v4
> > 	Fixed comments from Andy
> > Changes from v4 -> v5
> > 	Fixed comments from Andy
> > Changes from v5 -> v6
> > 	Fixed review comments from Greg
> > Changes from v6 -> v7
> > 	None
> > Changes from v7 -> v8
> > 	Fixed review comments from Peter
> > 	- Removed empty STOP message
> > 	- Using stack memory for i2c_transfer() Changes from v8 -> v9
> > 	None
> > Changes from v9 -> v10
> > 	Fixed review comments from Peter
> > 	- Use UCSI macros
> > 	- Cleanups
> > Changes from v10 -> v11
> > 	Fixed review comments from Peter
> > 	- Combined two writes into one
> > 	- Used offsetof() for ucsi_data struct Changes from v11 -> v12
> > 	- some cleanup
> > Changes from v12 -> v13
> > 	- changed "u8 buf[1]" -> "u8 data"
> >
> >  drivers/usb/typec/ucsi/Kconfig    |  10 ++
> >  drivers/usb/typec/ucsi/Makefile   |   2 +
> >  drivers/usb/typec/ucsi/ucsi_ccg.c | 305
> > ++++++++++++++++++++++++++++++++++++++
> >  3 files changed, 317 insertions(+)
> >  create mode 100644 drivers/usb/typec/ucsi/ucsi_ccg.c
> >
> > diff --git a/drivers/usb/typec/ucsi/Kconfig
> > b/drivers/usb/typec/ucsi/Kconfig index e36d6c7..7811888 100644
> > --- a/drivers/usb/typec/ucsi/Kconfig
> > +++ b/drivers/usb/typec/ucsi/Kconfig
> > @@ -23,6 +23,16 @@ config TYPEC_UCSI
> >
> >  if TYPEC_UCSI
> >
> > +config UCSI_CCG
> > +	tristate "UCSI Interface Driver for Cypress CCGx"
> > +	depends on I2C
> > +	help
> > +	  This driver enables UCSI support on platforms that expose a
> > +	  Cypress CCGx Type-C controller over I2C interface.
> > +
> > +	  To compile the driver as a module, choose M here: the module will
> be
> > +	  called ucsi_ccg.
> > +
> >  config UCSI_ACPI
> >  	tristate "UCSI ACPI Interface Driver"
> >  	depends on ACPI
> > diff --git a/drivers/usb/typec/ucsi/Makefile
> > b/drivers/usb/typec/ucsi/Makefile index 7afbea5..2f4900b 100644
> > --- a/drivers/usb/typec/ucsi/Makefile
> > +++ b/drivers/usb/typec/ucsi/Makefile
> > @@ -8,3 +8,5 @@ typec_ucsi-y			:= ucsi.o
> >  typec_ucsi-$(CONFIG_TRACING)	+= trace.o
> >
> >  obj-$(CONFIG_UCSI_ACPI)		+= ucsi_acpi.o
> > +
> > +obj-$(CONFIG_UCSI_CCG)		+= ucsi_ccg.o
> > diff --git a/drivers/usb/typec/ucsi/ucsi_ccg.c
> > b/drivers/usb/typec/ucsi/ucsi_ccg.c
> > new file mode 100644
> > index 0000000..0e0bac1
> > --- /dev/null
> > +++ b/drivers/usb/typec/ucsi/ucsi_ccg.c
> > @@ -0,0 +1,305 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +/*
> > + * UCSI driver for Cypress CCGx Type-C controller
> > + *
> > + * Copyright (C) 2017-2018 NVIDIA Corporation. All rights reserved.
> > + * Author: Ajay Gupta <ajayg@xxxxxxxxxx>
> > + *
> > + * Some code borrowed from drivers/usb/typec/ucsi/ucsi_acpi.c
> > + */
> > +#include <linux/acpi.h>
> > +#include <linux/delay.h>
> > +#include <linux/i2c.h>
> > +#include <linux/module.h>
> > +#include <linux/pci.h>
> > +#include <linux/platform_device.h>
> > +
> > +#include <asm/unaligned.h>
> > +#include "ucsi.h"
> > +
> > +struct ucsi_ccg {
> > +	struct device *dev;
> > +	struct ucsi *ucsi;
> > +	struct ucsi_ppm ppm;
> > +	struct i2c_client *client;
> > +	int irq;
> 
> That member is actually useless.
I will drop it in next revision.

> > +};
> > +
> > +#define CCGX_RAB_INTR_REG			0x06
> > +#define CCGX_RAB_UCSI_CONTROL			0x39
> > +#define CCGX_RAB_UCSI_CONTROL_START		BIT(0)
> > +#define CCGX_RAB_UCSI_CONTROL_STOP		BIT(1)
> > +#define CCGX_RAB_UCSI_DATA_BLOCK(offset)	(0xf000 | ((offset) &
> 0xff))
> > +
> > +static int ccg_read(struct ucsi_ccg *uc, u16 rab, u8 *data, u32 len)
> > +{
> > +	struct i2c_client *client = uc->client;
> > +	unsigned char buf[2];
> > +	struct i2c_msg msgs[] = {
> > +		{
> > +			.addr	= client->addr,
> > +			.flags  = 0x0,
> > +			.len	= sizeof(buf),
> > +			.buf	= buf,
> > +		},
> > +		{
> > +			.addr	= client->addr,
> > +			.flags  = I2C_M_RD,
> > +			.buf	= data,
> > +		},
> > +	};
> > +	u32 rlen, rem_len = len;
> > +	int status;
> > +
> > +	/* i2c adapter (ccgx-ucsi) can read 4 byte max */
> 
> By "i2c adapter" do you mean this Cypress CCGx controller, or the NVIDIA I2C
> host adapter?
It mean NVIDIA I2C host adapter with name "ccgx-ucsi"
 
> > +	while (rem_len > 0) {
> > +		msgs[1].buf = &data[len - rem_len];
> > +		rlen = min_t(u16, rem_len, 4);
> 
> I guess this is where you check for that 4 bytes.
> 
> I'm guessing this limitation is for the NVIDIA I2C host adapter.
Correct

> If that is the case than this driver really should not care about it.
I got your point but need to handle this case gracefully.

I think best way to handle this is to add a runtime check to find 
I2C adapter's quirk and use quirks->max_read_len of the adapter.
How does below look?

@@ -247,6 +247,7 @@ struct ucsi_ccg {
 static int ccg_read(struct ucsi_ccg *uc, u16 rab, u8 *data, u32 len)
 {
        struct i2c_client *client = uc->client;
+       const struct i2c_adapter_quirks *quirks = client->adapter->quirks;
        unsigned char buf[2];
        struct i2c_msg msgs[] = {
                {
@@ -261,13 +262,16 @@ static int ccg_read(struct ucsi_ccg *uc, u16 rab, u8 *data, u32 len)
                        .buf    = data,
                },
        };
-       u32 rlen, rem_len = len;
+       u32 rlen, rem_len = len, max_read_len = len;
        int status;

-       /* i2c adapter (ccgx-ucsi) can read 4 byte max */
+       /* check any max_read_len limitation on i2c adapter */
+       if (quirks && quirks->max_read_len)
+               max_read_len = quirks->max_read_len;
+
        while (rem_len > 0) {
                msgs[1].buf = &data[len - rem_len];
-               rlen = min_t(u16, rem_len, 4);
+               rlen = min_t(u16, rem_len, max_read_len);
                msgs[1].len = rlen;
                put_unaligned_le16(rab, buf);
                status = i2c_transfer(client->adapter, msgs, ARRAY_SIZE(msgs));

> We most likely need to use this driver on other platforms as well
> where the I2C host is something else.
Correct and above solution would not impact other I2C host.

> 
> > +		msgs[1].len = rlen;
> > +		put_unaligned_le16(rab, buf);
> > +		status = i2c_transfer(client->adapter, msgs,
> ARRAY_SIZE(msgs));
> > +		if (status < 0) {
> > +			dev_err(uc->dev, "i2c_transfer failed %d\n", status);
> > +			return status;
> > +		}
> > +		rab += rlen;
> > +		rem_len -= rlen;
> > +	}
> > +
> > +	return 0;
> > +}
> > +
> > +static int ccg_write(struct ucsi_ccg *uc, u16 rab, u8 *data, u32 len)
> > +{
> > +	struct i2c_client *client = uc->client;
> > +	unsigned char *buf;
> > +	struct i2c_msg msgs[] = {
> > +		{
> > +			.addr	= client->addr,
> > +			.flags  = 0x0,
> > +		}
> > +	};
> > +	int status;
> > +
> > +	buf = kzalloc(len + sizeof(rab), GFP_KERNEL);
> > +	if (!buf)
> > +		return -ENOMEM;
> > +
> > +	put_unaligned_le16(rab, buf);
> > +	memcpy(buf + sizeof(rab), data, len);
> > +
> > +	msgs[0].len = len + sizeof(rab);
> > +	msgs[0].buf = buf;
> > +
> > +	status = i2c_transfer(client->adapter, msgs, ARRAY_SIZE(msgs));
> > +	if (status < 0) {
> > +		dev_err(uc->dev, "i2c_transfer failed %d\n", status);
> > +		kfree(buf);
> > +		return status;
> > +	}
> > +
> > +	kfree(buf);
> > +	return 0;
> > +}
> > +
> > +static int ucsi_ccg_init(struct ucsi_ccg *uc) {
> > +	unsigned int count = 10;
> > +	u8 data;
> > +	int status;
> > +
> > +	data = CCGX_RAB_UCSI_CONTROL_STOP;
> > +	status = ccg_write(uc, CCGX_RAB_UCSI_CONTROL, &data,
> sizeof(data));
> > +	if (status < 0)
> > +		return status;
> > +
> > +	data = CCGX_RAB_UCSI_CONTROL_START;
> > +	status = ccg_write(uc, CCGX_RAB_UCSI_CONTROL, &data,
> sizeof(data));
> > +	if (status < 0)
> > +		return status;
> > +
> > +	/*
> > +	 * Flush CCGx RESPONSE queue by acking interrupts. Above ucsi
> control
> > +	 * register write will push response which must be cleared.
> > +	 */
> > +	status = ccg_read(uc, CCGX_RAB_INTR_REG, &data, sizeof(data));
> > +	if (status < 0)
> > +		return status;
> > +	do {
> > +		status = ccg_write(uc, CCGX_RAB_INTR_REG, &data,
> sizeof(data));
> > +		if (status < 0)
> > +			return status;
> > +
> > +		usleep_range(10000, 11000);
> > +
> > +		status = ccg_read(uc, CCGX_RAB_INTR_REG, &data,
> sizeof(data));
> > +		if (status < 0)
> > +			return status;
> > +	} while ((data != 0x00) && count--);
> 
> What's the significance of that count?
It is like a retry count to clear interrupt status.

> Shouldn't you return -ETIMEDOUT if count == 0?
Yes. Good catch. Does the below fix looks ok?

        do {
                status = ccg_write(uc, CCGX_RAB_INTR_REG, &data, sizeof(data));
                if (status < 0)
                        return status;

                usleep_range(10000, 11000);

                status = ccg_read(uc, CCGX_RAB_INTR_REG, &data, sizeof(data));
                if (status < 0)
                        return status;

                if (!data)
                        return 0;
        } while (data && count--);

        return -ETIMEDOUT;
 
> Something like:
> 
>         ...
>         while (count--)
> 		status = ccg_read(uc, CCGX_RAB_INTR_REG, &data,
> sizeof(data));
> 		if (status < 0)
> 			return status;
>                 if (!data)
>                         return 0;
> 	}
> 
>         return -ETIMEDOUT;
> 
> Or does the count of 10 have some specific meaning?
> 
> > +}
> > +
> > +static int ucsi_ccg_send_data(struct ucsi_ccg *uc) {
> > +	u8 *ppm = (u8 *)uc->ppm.data;
> > +	int status;
> > +	u16 rab;
> > +
> > +	rab = CCGX_RAB_UCSI_DATA_BLOCK(offsetof(struct ucsi_data,
> message_out));
> > +	status = ccg_write(uc, rab, ppm +
> > +			   offsetof(struct ucsi_data, message_out),
> > +			   sizeof(uc->ppm.data->message_out));
> > +	if (status < 0)
> > +		return status;
> > +
> > +	rab = CCGX_RAB_UCSI_DATA_BLOCK(offsetof(struct ucsi_data, ctrl));
> > +	return ccg_write(uc, rab, ppm + offsetof(struct ucsi_data, ctrl),
> > +			 sizeof(uc->ppm.data->ctrl));
> > +}
> > +
> > +static int ucsi_ccg_recv_data(struct ucsi_ccg *uc) {
> > +	u8 *ppm = (u8 *)uc->ppm.data;
> > +	int status;
> > +	u16 rab;
> > +
> > +	rab = CCGX_RAB_UCSI_DATA_BLOCK(offsetof(struct ucsi_data, cci));
> > +	status = ccg_read(uc, rab, ppm + offsetof(struct ucsi_data, cci),
> > +			  sizeof(uc->ppm.data->cci));
> > +	if (status < 0)
> > +		return status;
> > +
> > +	rab = CCGX_RAB_UCSI_DATA_BLOCK(offsetof(struct ucsi_data,
> message_in));
> > +	return ccg_read(uc, rab, ppm + offsetof(struct ucsi_data, message_in),
> > +			sizeof(uc->ppm.data->message_in));
> > +}
> > +
> > +static int ucsi_ccg_ack_interrupt(struct ucsi_ccg *uc) {
> > +	int status;
> > +	unsigned char data;
> > +
> > +	status = ccg_read(uc, CCGX_RAB_INTR_REG, &data, sizeof(data));
> > +	if (status < 0)
> > +		return status;
> > +
> > +	return ccg_write(uc, CCGX_RAB_INTR_REG, &data, sizeof(data)); }
> > +
> > +static int ucsi_ccg_sync(struct ucsi_ppm *ppm) {
> > +	struct ucsi_ccg *uc = container_of(ppm, struct ucsi_ccg, ppm);
> > +	int status;
> > +
> > +	status = ucsi_ccg_recv_data(uc);
> > +	if (status < 0)
> > +		return status;
> > +
> > +	/* ack interrupt to allow next command to run */
> > +	return ucsi_ccg_ack_interrupt(uc);
> > +}
> > +
> > +static int ucsi_ccg_cmd(struct ucsi_ppm *ppm, struct ucsi_control
> > +*ctrl) {
> > +	struct ucsi_ccg *uc = container_of(ppm, struct ucsi_ccg, ppm);
> > +
> > +	ppm->data->ctrl.raw_cmd = ctrl->raw_cmd;
> > +	return ucsi_ccg_send_data(uc);
> > +}
> > +
> > +static irqreturn_t ccg_irq_handler(int irq, void *data) {
> > +	struct ucsi_ccg *uc = data;
> > +
> > +	ucsi_notify(uc->ucsi);
> > +
> > +	return IRQ_HANDLED;
> > +}
> > +
> > +static int ucsi_ccg_probe(struct i2c_client *client,
> > +			  const struct i2c_device_id *id)
> > +{
> > +	struct device *dev = &client->dev;
> > +	struct ucsi_ccg *uc;
> > +	int status;
> > +	u16 rab;
> > +
> > +	uc = devm_kzalloc(dev, sizeof(*uc), GFP_KERNEL);
> > +	if (!uc)
> > +		return -ENOMEM;
> > +
> > +	uc->ppm.data = devm_kzalloc(dev, sizeof(struct ucsi_data),
> GFP_KERNEL);
> > +	if (!uc->ppm.data)
> > +		return -ENOMEM;
> > +
> > +	uc->ppm.cmd = ucsi_ccg_cmd;
> > +	uc->ppm.sync = ucsi_ccg_sync;
> > +	uc->dev = dev;
> > +	uc->client = client;
> > +
> > +	/* reset ccg device and initialize ucsi */
> > +	status = ucsi_ccg_init(uc);
> > +	if (status < 0) {
> > +		dev_err(uc->dev, "ucsi_ccg_init failed - %d\n", status);
> > +		return status;
> > +	}
> > +
> > +	uc->irq = client->irq;
> > +
> > +	status = devm_request_threaded_irq(dev, uc->irq, NULL,
> ccg_irq_handler,
> > +					   IRQF_ONESHOT |
> IRQF_TRIGGER_HIGH,
> > +					   dev_name(dev), uc);
> > +	if (status < 0) {
> > +		dev_err(uc->dev, "request_threaded_irq failed - %d\n",
> status);
> > +		return status;
> > +	}
> > +
> > +	uc->ucsi = ucsi_register_ppm(dev, &uc->ppm);
> > +	if (IS_ERR(uc->ucsi)) {
> > +		dev_err(uc->dev, "ucsi_register_ppm failed\n");
> > +		return PTR_ERR(uc->ucsi);
> > +	}
> > +
> > +	rab = CCGX_RAB_UCSI_DATA_BLOCK(offsetof(struct ucsi_data,
> version));
> > +	status = ccg_read(uc, rab, (u8 *)(uc->ppm.data) +
> > +			  offsetof(struct ucsi_data, version),
> > +			  sizeof(uc->ppm.data->version));
> > +	if (status < 0) {
> > +		ucsi_unregister_ppm(uc->ucsi);
> > +		return status;
> > +	}
> > +
> > +	i2c_set_clientdata(client, uc);
> > +	return 0;
> > +}
> > +
> > +static int ucsi_ccg_remove(struct i2c_client *client) {
> > +	struct ucsi_ccg *uc = i2c_get_clientdata(client);
> > +
> > +	ucsi_unregister_ppm(uc->ucsi);
> > +
> > +	return 0;
> > +}
> > +
> > +static const struct i2c_device_id ucsi_ccg_device_id[] = {
> > +	{"ccgx-ucsi", 0},
> > +	{}
> > +};
> > +MODULE_DEVICE_TABLE(i2c, ucsi_ccg_device_id);
> > +
> > +static struct i2c_driver ucsi_ccg_driver = {
> > +	.driver = {
> > +		.name = "ucsi_ccg",
> > +	},
> > +	.probe = ucsi_ccg_probe,
> > +	.remove = ucsi_ccg_remove,
> > +	.id_table = ucsi_ccg_device_id,
> > +};
> > +
> > +module_i2c_driver(ucsi_ccg_driver);
> > +
> > +MODULE_AUTHOR("Ajay Gupta <ajayg@xxxxxxxxxx>");
> > +MODULE_DESCRIPTION("UCSI driver for Cypress CCGx Type-C controller");
> > +MODULE_LICENSE("GPL v2");
> 
> I'm still worried about how this driver works on other platforms. It just looks
> like you have written ccg_read/write() functions for only your I2C host.
> 
> I would feel much more comfortable with this if you for example used those
> i2c_smbus_read/write*() helpers instead of raw i2c_transfer().
> I would expect them to force you to write your i2c host driver, as well as this
> driver, in a more generic fashion.

I2c_smbus_read/write*() will not work with Cypress CCGx controller since CCGx
requires 2 byte of command for any read/write transaction. 
I2c_smbus_read/write*() APIs support only 1 byte of command.

Thanks
Ajay
--nvpublic
> 
> 
> Thanks,
> 
> --
> heikki




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