linux-kernel - Re: [PATCH linux v3 3/6] hwmon: occ: Add I2C transport implementation for SCOM operations

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Date:   Sat, 21 Jan 2017 10:11:21 -0800
From:   Guenter Roeck <linux@...ck-us.net>
To:     eajames.ibm@...il.com
Cc:     devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-hwmon@...r.kernel.org, linux-doc@...r.kernel.org,
        jdelvare@...e.com, corbet@....net, mark.rutland@....com,
        robh+dt@...nel.org, wsa@...-dreams.de, andrew@...id.au,
        joel@....id.au, benh@...nel.crashing.org,
        "Edward A. James" <eajames@...ibm.com>
Subject: Re: [PATCH linux v3 3/6] hwmon: occ: Add I2C transport implementation
 for SCOM operations

On 01/16/2017 01:13 PM, eajames.ibm@...il.com wrote:
> From: "Edward A. James" <eajames@...ibm.com>
>
> Add functions to send SCOM operations over I2C bus. The BMC can
> communicate with the Power8 host processor over I2C, but needs to use SCOM
> operations in order to access the OCC register space.
>
> Signed-off-by: Edward A. James <eajames@...ibm.com>
> Signed-off-by: Andrew Jeffery <andrew@...id.au>
> ---
>  drivers/hwmon/occ/occ_scom_i2c.c | 72 ++++++++++++++++++++++++++++++++++++++++
>  drivers/hwmon/occ/occ_scom_i2c.h | 26 +++++++++++++++
>  2 files changed, 98 insertions(+)
>  create mode 100644 drivers/hwmon/occ/occ_scom_i2c.c
>  create mode 100644 drivers/hwmon/occ/occ_scom_i2c.h
>
> diff --git a/drivers/hwmon/occ/occ_scom_i2c.c b/drivers/hwmon/occ/occ_scom_i2c.c
> new file mode 100644
> index 0000000..8b4ca13
> --- /dev/null
> +++ b/drivers/hwmon/occ/occ_scom_i2c.c
> @@ -0,0 +1,72 @@
> +/*
> + * occ_scom_i2c.c - hwmon OCC driver
> + *
> + * This file contains the functions for performing SCOM operations over I2C bus
> + * to access the OCC.
> + *
> + * Copyright 2016 IBM Corp.
> + *
> + * 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.
> + */
> +
> +#include <linux/i2c.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include "occ_scom_i2c.h"
> +#include "scom.h"
> +
> +int occ_i2c_getscom(void *bus, u32 address, u64 *data)
> +{
> +	ssize_t rc;
> +	u64 buf;
> +	struct i2c_client *client = bus;
> +
> +	rc = i2c_master_send(client, (const char *)&address, sizeof(u32));
> +	if (rc < 0)
> +		return rc;
> +	else if (rc != sizeof(u32))
> +		return -EIO;
> +
> +	rc = i2c_master_recv(client, (char *)&buf, sizeof(u64));
> +	if (rc < 0)
> +		return rc;
> +	else if (rc != sizeof(u64))
> +		return -EIO;
> +
> +	*data = be64_to_cpu(buf);
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL(occ_i2c_getscom);
> +
> +int occ_i2c_putscom(void *bus, u32 address, u32 data0, u32 data1)
> +{
> +	u32 buf[3];
> +	ssize_t rc;
> +	struct i2c_client *client = bus;
> +
> +	buf[0] = address;
> +	buf[1] = data1;
> +	buf[2] = data0;
> +

Receive data is converted from be64 to host byte order, transmit data is sent as-is.
Yet, if I recall correctly, some of the calling code passes in constants. Are you sure
this works on both little and big endian systems ?

> +	rc = i2c_master_send(client, (const char *)buf, sizeof(u32) * 3);
> +	if (rc < 0)
> +		return rc;
> +	else if (rc != sizeof(u32) * 3)
> +		return -EIO;
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL(occ_i2c_putscom);
> +
> +MODULE_AUTHOR("Eddie James <eajames@...ibm.com>");
> +MODULE_DESCRIPTION("I2C OCC SCOM transport");
> +MODULE_LICENSE("GPL");
> diff --git a/drivers/hwmon/occ/occ_scom_i2c.h b/drivers/hwmon/occ/occ_scom_i2c.h
> new file mode 100644
> index 0000000..945739c
> --- /dev/null
> +++ b/drivers/hwmon/occ/occ_scom_i2c.h
> @@ -0,0 +1,26 @@
> +/*
> + * occ_scom_i2c.h - hwmon OCC driver
> + *
> + * This file contains function protoypes for peforming SCOM operations over I2C
> + * bus to access the OCC.
> + *
> + * Copyright 2016 IBM Corp.
> + *
> + * 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.
> + */
> +
> +#ifndef __OCC_SCOM_I2C_H__
> +#define __OCC_SCOM_I2C_H__
> +
> +int occ_i2c_getscom(void *bus, u32 address, u64 *data);
> +int occ_i2c_putscom(void *bus, u32 address, u32 data0, u32 data1);
> +
> +#endif /* __OCC_SCOM_I2C_H__ */
>