Subject: Re: [PATCH v3] i2c: Driver to expose PowerNV platform i2c busses

From: Benjamin Herrenschmidt <[email-masked]>
Date: Tue, 09 Dec 2014 07:13:15 +1100

On Mon, 2014-12-08 at 12:06 +0530, Neelesh Gupta wrote:
> The patch exposes the available i2c busses on the PowerNV platform
> to the kernel and implements the bus driver to support i2c and
> smbus commands.
> The driver uses the platform device infrastructure to probe the busses
> on the platform and registers them with the i2c driver framework.

Wolfram, what are you remaining objections here ? We need that in
distros ASAP ...

I still maintain that it's not reasonable to hold driver for the
additions of multi-byte smbus offsets. This is a new feature that will
require changes to a number of existing bus and device drivers, so a
very pervasive change, and which will be visible to user space, which
means that drivers will need to continue supporting the "old" way at
least for a while anyway...

Ben.

> Signed-off-by: Neelesh Gupta <[email-masked]>
> Signed-off-by: Benjamin Herrenschmidt <[email-masked]>
> ---
> 
> v2 -> v3:
> - Added the device tree binding documentation for the driver.
> - Sorted the ordering of this new driver added in Makefile.
> - Removed populating the superfluous .owner field in 'struct driver'.
> 
>  Documentation/devicetree/bindings/i2c/i2c-opal.txt |   37 +++
>  arch/powerpc/include/asm/opal.h                    |   29 ++
>  arch/powerpc/platforms/powernv/opal-wrappers.S     |    1 
>  arch/powerpc/platforms/powernv/opal.c              |   11 +
>  drivers/i2c/busses/Kconfig                         |   11 +
>  drivers/i2c/busses/Makefile                        |    1 
>  drivers/i2c/busses/i2c-opal.c                      |  294 ++++++++++++++++++++
>  7 files changed, 384 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/i2c/i2c-opal.txt
>  create mode 100644 drivers/i2c/busses/i2c-opal.c
> 
> diff --git a/Documentation/devicetree/bindings/i2c/i2c-opal.txt b/Documentation/devicetree/bindings/i2c/i2c-opal.txt
> new file mode 100644
> index 0000000..12bc614
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/i2c/i2c-opal.txt
> @@ -0,0 +1,37 @@
> +Device-tree bindings for I2C OPAL driver
> +----------------------------------------
> +
> +Most of the device node and properties layout is specific to the firmware and
> +used by the firmware itself for configuring the port. From the linux
> +perspective, the properties of use are "ibm,port-name" and "ibm,opal-id".
> +
> +Required properties:
> +
> +- reg: Port-id within a given master
> +- compatible: must be "ibm,opal-i2c"
> +- ibm,opal-id: Refers to a specific bus and used to identify it when calling
> +	       the relevant OPAL functions.
> +- bus-frequency: Operating frequency of the i2c bus (in HZ). Informational for
> +		 linux, used by the FW though.
> +
> +Optional properties:
> +- ibm,port-name: Firmware provides this name that uniquely identifies the i2c
> +		 port.
> +
> +The node contains a number of other properties that are used by the FW itself
> +and depend on the specific hardware implementation. The example below depicts
> +a P8 on-chip bus.
> +
> +Example:
> +
> +i2c-bus@0 {
> +	reg = <0x0>;
> +	bus-frequency = <0x61a80>;
> +	compatible = "ibm,power8-i2c-port", "ibm,opal-i2c";
> +	ibm,opal-id = <0x1>;
> +	ibm,port-name = "p8_00000000_e1p0";
> +	#address-cells = <0x1>;
> +	phandle = <0x10000006>;
> +	#size-cells = <0x0>;
> +	linux,phandle = <0x10000006>;
> +};
> diff --git a/arch/powerpc/include/asm/opal.h b/arch/powerpc/include/asm/opal.h
> index 9124b0e..537807b 100644
> --- a/arch/powerpc/include/asm/opal.h
> +++ b/arch/powerpc/include/asm/opal.h
> @@ -56,6 +56,14 @@ struct opal_sg_list {
>  #define OPAL_HARDWARE_FROZEN	-13
>  #define OPAL_WRONG_STATE	-14
>  #define OPAL_ASYNC_COMPLETION	-15
> +#define OPAL_I2C_TIMEOUT	-17
> +#define OPAL_I2C_INVALID_CMD	-18
> +#define OPAL_I2C_LBUS_PARITY	-19
> +#define OPAL_I2C_BKEND_OVERRUN	-20
> +#define OPAL_I2C_BKEND_ACCESS	-21
> +#define OPAL_I2C_ARBT_LOST	-22
> +#define OPAL_I2C_NACK_RCVD	-23
> +#define OPAL_I2C_STOP_ERR	-24
>  
>  /* API Tokens (in r0) */
>  #define OPAL_INVALID_CALL			-1
> @@ -154,6 +162,7 @@ struct opal_sg_list {
>  #define OPAL_HANDLE_HMI				98
>  #define OPAL_REGISTER_DUMP_REGION		101
>  #define OPAL_UNREGISTER_DUMP_REGION		102
> +#define OPAL_I2C_REQUEST			109
>  
>  #ifndef __ASSEMBLY__
>  
> @@ -801,6 +810,24 @@ typedef struct oppanel_line {
>  	uint64_t 	line_len;
>  } oppanel_line_t;
>  
> +/* OPAL I2C request */
> +struct opal_i2c_request {
> +	uint8_t	type;
> +#define OPAL_I2C_RAW_READ	0
> +#define OPAL_I2C_RAW_WRITE	1
> +#define OPAL_I2C_SM_READ	2
> +#define OPAL_I2C_SM_WRITE	3
> +	uint8_t flags;
> +#define OPAL_I2C_ADDR_10	0x01	/* Not supported yet */
> +	uint8_t	subaddr_sz;		/* Max 4 */
> +	uint8_t reserved;
> +	__be16 addr;			/* 7 or 10 bit address */
> +	__be16 reserved2;
> +	__be32 subaddr;		/* Sub-address if any */
> +	__be32 size;			/* Data size */
> +	__be64 buffer_ra;		/* Buffer real address */
> +};
> +
>  /* /sys/firmware/opal */
>  extern struct kobject *opal_kobj;
>  
> @@ -963,6 +990,8 @@ int64_t opal_handle_hmi(void);
>  int64_t opal_register_dump_region(uint32_t id, uint64_t start, uint64_t end);
>  int64_t opal_unregister_dump_region(uint32_t id);
>  int64_t opal_pci_set_phb_cxl_mode(uint64_t phb_id, uint64_t mode, uint64_t pe_number);
> +int64_t opal_i2c_request(uint64_t async_token, uint32_t bus_id,
> +			 struct opal_i2c_request *oreq);
>  
>  /* Internal functions */
>  extern int early_init_dt_scan_opal(unsigned long node, const char *uname,
> diff --git a/arch/powerpc/platforms/powernv/opal-wrappers.S b/arch/powerpc/platforms/powernv/opal-wrappers.S
> index feb549a..4673c02 100644
> --- a/arch/powerpc/platforms/powernv/opal-wrappers.S
> +++ b/arch/powerpc/platforms/powernv/opal-wrappers.S
> @@ -250,3 +250,4 @@ OPAL_CALL(opal_handle_hmi,			OPAL_HANDLE_HMI);
>  OPAL_CALL(opal_register_dump_region,		OPAL_REGISTER_DUMP_REGION);
>  OPAL_CALL(opal_unregister_dump_region,		OPAL_UNREGISTER_DUMP_REGION);
>  OPAL_CALL(opal_pci_set_phb_cxl_mode,		OPAL_PCI_SET_PHB_CXL_MODE);
> +OPAL_CALL(opal_i2c_request,			OPAL_I2C_REQUEST);
> diff --git a/arch/powerpc/platforms/powernv/opal.c b/arch/powerpc/platforms/powernv/opal.c
> index bb90e6e..994975e 100644
> --- a/arch/powerpc/platforms/powernv/opal.c
> +++ b/arch/powerpc/platforms/powernv/opal.c
> @@ -667,6 +667,14 @@ static void opal_console_create_devs(void)
>  
>  }
>  
> +static void opal_i2c_create_devs(void)
> +{
> +	struct device_node *np;
> +
> +	for_each_compatible_node(np, NULL, "ibm,opal-i2c")
> +		of_platform_device_create(np, NULL, NULL);
> +}
> +
>  static void opal_request_interrupts(void)
>  {
>  	const __be32 *irqs;
> @@ -732,6 +740,9 @@ static int __init opal_init(void)
>  	/* Create console platform devices */
>  	opal_console_create_devs();
>  
> +	/* Create i2c platform devices */
> +	opal_i2c_create_devs();
> +
>  	/* Register OPAL interrupts */
>  	opal_request_interrupts();
>  
> diff --git a/drivers/i2c/busses/Kconfig b/drivers/i2c/busses/Kconfig
> index 917c358..71ad6e1 100644
> --- a/drivers/i2c/busses/Kconfig
> +++ b/drivers/i2c/busses/Kconfig
> @@ -1044,4 +1044,15 @@ config SCx200_ACB
>  	  This support is also available as a module.  If so, the module
>  	  will be called scx200_acb.
>  
> +config I2C_OPAL
> +	tristate "IBM OPAL I2C driver"
> +	depends on PPC_POWERNV
> +	default y
> +	help
> +	  This exposes the PowerNV platform i2c busses to the linux i2c layer,
> +	  the driver is based on the OPAL interfaces.
> +
> +	  This driver can also be built as a module. If so, the module will be
> +	  called as i2c-opal.
> +
>  endmenu
> diff --git a/drivers/i2c/busses/Makefile b/drivers/i2c/busses/Makefile
> index 78d56c5..e23ec81 100644
> --- a/drivers/i2c/busses/Makefile
> +++ b/drivers/i2c/busses/Makefile
> @@ -99,6 +99,7 @@ obj-$(CONFIG_I2C_ACORN)		+= i2c-acorn.o
>  obj-$(CONFIG_I2C_BCM_KONA)	+= i2c-bcm-kona.o
>  obj-$(CONFIG_I2C_CROS_EC_TUNNEL)	+= i2c-cros-ec-tunnel.o
>  obj-$(CONFIG_I2C_ELEKTOR)	+= i2c-elektor.o
> +obj-$(CONFIG_I2C_OPAL)		+= i2c-opal.o
>  obj-$(CONFIG_I2C_PCA_ISA)	+= i2c-pca-isa.o
>  obj-$(CONFIG_I2C_SIBYTE)	+= i2c-sibyte.o
>  obj-$(CONFIG_SCx200_ACB)	+= scx200_acb.o
> diff --git a/drivers/i2c/busses/i2c-opal.c b/drivers/i2c/busses/i2c-opal.c
> new file mode 100644
> index 0000000..16f90b1
> --- /dev/null
> +++ b/drivers/i2c/busses/i2c-opal.c
> @@ -0,0 +1,294 @@
> +/*
> + * IBM OPAL I2C driver
> + * Copyright (C) 2014 IBM
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License as published by
> + * the Free Software Foundation; either version 2 of the License, or
> + * (at your option) any later version.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
> + * GNU General Public License for more details.
> + *
> + * You should have received a copy of the GNU General Public License
> + * along with this program.
> + */
> +
> +#include <linux/device.h>
> +#include <linux/i2c.h>
> +#include <linux/kernel.h>
> +#include <linux/mm.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/platform_device.h>
> +#include <linux/slab.h>
> +
> +#include <asm/firmware.h>
> +#include <asm/opal.h>
> +
> +static int i2c_opal_translate_error(int rc)
> +{
> +	switch (rc) {
> +	case OPAL_NO_MEM:
> +		return -ENOMEM;
> +	case OPAL_PARAMETER:
> +		return -EINVAL;
> +	case OPAL_I2C_ARBT_LOST:
> +		return -EAGAIN;
> +	case OPAL_I2C_TIMEOUT:
> +		return -ETIMEDOUT;
> +	case OPAL_I2C_NACK_RCVD:
> +		return -ENXIO;
> +	case OPAL_I2C_STOP_ERR:
> +		return -EBUSY;
> +	default:
> +		return -EIO;
> +	}
> +}
> +
> +static int i2c_opal_send_request(u32 bus_id, struct opal_i2c_request *req)
> +{
> +	struct opal_msg msg;
> +	int token, rc;
> +
> +	token = opal_async_get_token_interruptible();
> +	if (token < 0) {
> +		if (token != -ERESTARTSYS)
> +			pr_err("Failed to get the async token\n");
> +
> +		return token;
> +	}
> +
> +	rc = opal_i2c_request(token, bus_id, req);
> +	if (rc != OPAL_ASYNC_COMPLETION) {
> +		rc = i2c_opal_translate_error(rc);
> +		goto exit;
> +	}
> +
> +	rc = opal_async_wait_response(token, &msg);
> +	if (rc)
> +		goto exit;
> +
> +	rc = be64_to_cpu(msg.params[1]);
> +	if (rc != OPAL_SUCCESS) {
> +		rc = i2c_opal_translate_error(rc);
> +		goto exit;
> +	}
> +
> +exit:
> +	opal_async_release_token(token);
> +	return rc;
> +}
> +
> +static int i2c_opal_master_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
> +				int num)
> +{
> +	unsigned long opal_id = (unsigned long)adap->algo_data;
> +	struct opal_i2c_request req;
> +	int rc, i;
> +
> +	/* We only support fairly simple combinations here of one
> +	 * or two messages
> +	 */
> +	memset(&req, 0, sizeof(req));
> +	switch(num) {
> +	case 0:
> +		return 0;
> +	case 1:
> +		req.type = (msgs[0].flags & I2C_M_RD) ?
> +			OPAL_I2C_RAW_READ : OPAL_I2C_RAW_WRITE;
> +		req.addr = cpu_to_be16(msgs[0].addr);
> +		req.size = cpu_to_be32(msgs[0].len);
> +		req.buffer_ra = cpu_to_be64(__pa(msgs[0].buf));
> +		break;
> +	case 2:
> +		/* For two messages, we basically support only simple
> +		 * smbus transactions of a write plus a read. We might
> +		 * want to allow also two writes but we'd have to bounce
> +		 * the data into a single buffer.
> +		 */
> +		if ((msgs[0].flags & I2C_M_RD) || !(msgs[1].flags & I2C_M_RD))
> +			return -EOPNOTSUPP;
> +		if (msgs[0].len > 4)
> +			return -EOPNOTSUPP;
> +		if (msgs[0].addr != msgs[1].addr)
> +			return -EOPNOTSUPP;
> +		req.type = OPAL_I2C_SM_READ;
> +		req.addr = cpu_to_be16(msgs[0].addr);
> +		req.subaddr_sz = msgs[0].len;
> +		for (i = 0; i < msgs[0].len; i++)
> +			req.subaddr = (req.subaddr << 8) | msgs[0].buf[i];
> +		req.subaddr = cpu_to_be32(req.subaddr);
> +		req.size = cpu_to_be32(msgs[1].len);
> +		req.buffer_ra = cpu_to_be64(__pa(msgs[1].buf));
> +		break;
> +	default:
> +		return -EOPNOTSUPP;
> +	}
> +
> +	rc = i2c_opal_send_request(opal_id, &req);
> +	if (rc)
> +		return rc;
> +
> +	return num;
> +}
> +
> +static int i2c_opal_smbus_xfer(struct i2c_adapter *adap, u16 addr,
> +			       unsigned short flags, char read_write,
> +			       u8 command, int size, union i2c_smbus_data *data)
> +{
> +	unsigned long opal_id = (unsigned long)adap->algo_data;
> +	struct opal_i2c_request req;
> +	u8 local[2];
> +	int rc;
> +
> +	memset(&req, 0, sizeof(req));
> +
> +	req.addr = cpu_to_be16(addr);
> +	switch (size) {
> +	case I2C_SMBUS_BYTE:
> +		req.buffer_ra = cpu_to_be64(__pa(&data->byte));
> +		req.size = cpu_to_be32(1);
> +		/* Fall through */
> +	case I2C_SMBUS_QUICK:
> +		req.type = (read_write == I2C_SMBUS_READ) ?
> +			OPAL_I2C_RAW_READ : OPAL_I2C_RAW_WRITE;
> +		break;
> +	case I2C_SMBUS_BYTE_DATA:
> +		req.buffer_ra = cpu_to_be64(__pa(&data->byte));
> +		req.size = cpu_to_be32(1);
> +		req.subaddr = cpu_to_be32(command);
> +		req.subaddr_sz = 1;
> +		req.type = (read_write == I2C_SMBUS_READ) ?
> +			OPAL_I2C_SM_READ : OPAL_I2C_SM_WRITE;
> +		break;
> +	case I2C_SMBUS_WORD_DATA:
> +		if (!read_write) {
> +			local[0] = data->word & 0xff;
> +			local[1] = (data->word >> 8) & 0xff;
> +		}
> +		req.buffer_ra = cpu_to_be64(__pa(local));
> +		req.size = cpu_to_be32(2);
> +		req.subaddr = cpu_to_be32(command);
> +		req.subaddr_sz = 1;
> +		req.type = (read_write == I2C_SMBUS_READ) ?
> +			OPAL_I2C_SM_READ : OPAL_I2C_SM_WRITE;
> +		break;
> +	case I2C_SMBUS_I2C_BLOCK_DATA:
> +		req.buffer_ra = cpu_to_be64(__pa(&data->block[1]));
> +		req.size = cpu_to_be32(data->block[0]);
> +		req.subaddr = cpu_to_be32(command);
> +		req.subaddr_sz = 1;
> +		req.type = (read_write == I2C_SMBUS_READ) ?
> +			OPAL_I2C_SM_READ : OPAL_I2C_SM_WRITE;
> +		break;
> +	default:
> +		return -EINVAL;
> +	}
> +
> +	rc = i2c_opal_send_request(opal_id, &req);
> +	if (!rc && read_write && size == I2C_SMBUS_WORD_DATA) {
> +		data->word = ((u16)local[1]) << 8;
> +		data->word |= local[0];
> +	}
> +
> +	return rc;
> +}
> +
> +static u32 i2c_opal_func(struct i2c_adapter *adapter)
> +{
> +	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_QUICK | I2C_FUNC_SMBUS_BYTE |
> +	       I2C_FUNC_SMBUS_BYTE_DATA | I2C_FUNC_SMBUS_WORD_DATA |
> +	       I2C_FUNC_SMBUS_I2C_BLOCK;
> +}
> +
> +static const struct i2c_algorithm i2c_opal_algo = {
> +	.master_xfer	= i2c_opal_master_xfer,
> +	.smbus_xfer	= i2c_opal_smbus_xfer,
> +	.functionality	= i2c_opal_func,
> +};
> +
> +static int i2c_opal_probe(struct platform_device *pdev)
> +{
> +	struct i2c_adapter	*adapter;
> +	const char		*pname;
> +	u32			opal_id;
> +	int			rc;
> +
> +	if (!pdev->dev.of_node)
> +		return -ENODEV;
> +
> +	rc = of_property_read_u32(pdev->dev.of_node, "ibm,opal-id", &opal_id);
> +	if (rc) {
> +		dev_err(&pdev->dev, "Missing ibm,opal-id property !\n");
> +		return -EIO;
> +	}
> +
> +	adapter = devm_kzalloc(&pdev->dev, sizeof(*adapter), GFP_KERNEL);
> +	if (!adapter)
> +		return -ENOMEM;
> +
> +	adapter->algo = &i2c_opal_algo;
> +	adapter->algo_data = (void *)(unsigned long)opal_id;
> +	adapter->dev.parent = &pdev->dev;
> +	adapter->dev.of_node = of_node_get(pdev->dev.of_node);
> +	pname = of_get_property(pdev->dev.of_node, "ibm,port-name", NULL);
> +	if (pname)
> +		strlcpy(adapter->name, pname, sizeof(adapter->name));
> +	else
> +		strlcpy(adapter->name, "opal", sizeof(adapter->name));
> +
> +	platform_set_drvdata(pdev, adapter);
> +	rc = i2c_add_adapter(adapter);
> +	if (rc)
> +		dev_err(&pdev->dev, "Failed to register the i2c adapter\n");
> +
> +	return rc;
> +}
> +
> +static int i2c_opal_remove(struct platform_device *pdev)
> +{
> +	struct i2c_adapter *adapter = platform_get_drvdata(pdev);
> +
> +	i2c_del_adapter(adapter);
> +
> +	return 0;
> +}
> +
> +static const struct of_device_id i2c_opal_of_match[] = {
> +	{
> +		.compatible = "ibm,opal-i2c",
> +	},
> +	{ }
> +};
> +MODULE_DEVICE_TABLE(of, i2c_opal_of_match);
> +
> +static struct platform_driver i2c_opal_driver = {
> +	.probe	= i2c_opal_probe,
> +	.remove	= i2c_opal_remove,
> +	.driver	= {
> +		.name		= "i2c-opal",
> +		.of_match_table	= i2c_opal_of_match,
> +	},
> +};
> +
> +static int __init i2c_opal_init(void)
> +{
> +	if (!firmware_has_feature(FW_FEATURE_OPAL))
> +		return -ENODEV;
> +
> +	return platform_driver_register(&i2c_opal_driver);
> +}
> +module_init(i2c_opal_init);
> +
> +static void __exit i2c_opal_exit(void)
> +{
> +	return platform_driver_unregister(&i2c_opal_driver);
> +}
> +module_exit(i2c_opal_exit);
> +
> +MODULE_AUTHOR("Neelesh Gupta <[email-masked]>");
> +MODULE_DESCRIPTION("IBM OPAL I2C driver");
> +MODULE_LICENSE("GPL");