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

[Heikki Krogerus <heikki.krogerus@linux.intel.com>]

Hi,

On Tue, Oct 23, 2018 at 06:56:59PM +0000, Ajay Gupta wrote:
> > > +	/* 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.

I still didn't understand why can't this just be taken care of in your
I2C host driver? Why can't you just read 4 bytes at a time in your
master_xfer hook until you have received as much as the message is
asking, and only after that return?

> > > +		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--);

Doesn't that condition break out of the loop immediately?

>         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@nvidia.com>");
> > > +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.

OK, got it.


thanks,