linux-kernel - Re: [PATCH] i2c: Single-wire Serial Bus Interface for Qualcomm MSM chipsets

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Message-ID: <4C49E041.8070009@codeaurora.org>
Date:	Fri, 23 Jul 2010 12:32:33 -0600
From:	Kenneth Heitke <kheitke@...eaurora.org>
To:	Daniel Glöckner <dg@...ix.com>
CC:	khali@...ux-fr.org, ben-linux@...ff.org,
	linux-arm-msm@...r.kernel.org, sdharia@...eaurora.org,
	Crane Cai <crane.cai@....com>,
	Samuel Ortiz <sameo@...ux.intel.com>,
	Linus Walleij <linus.walleij@...ricsson.com>,
	Ralf Baechle <ralf@...ux-mips.org>,
	srinidhi kasagar <srinidhi.kasagar@...ricsson.com>,
	linux-i2c@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] i2c: Single-wire Serial Bus Interface for Qualcomm MSM
 chipsets

Daniel Glöckner wrote:
> On 07/21/2010 07:52 PM, Kenneth Heitke wrote:
>> Unlike I2C, SSBI is a point-to-point connection, and therefore there is no
>> need to specify a slave device address. The SSBI implementation
>> overrides the slave device address to be a device register address
>> instead.  This restricts the client drivers from using the SMBus
>> communication APIs unless they update the address field (addr) of the
>> i2c_client structure prior to every SMBus function call.
> 
> 
>> +static int
>> +i2c_ssbi_write_bytes(struct i2c_ssbi_dev *ssbi, struct i2c_msg *msg)
>> +{
>> +	int ret = 0;
>> +	u8 *buf = msg->buf;
>> +	u16 len = msg->len;
>> +	u16 addr = msg->addr;
>> +
>> +	if (ssbi->controller_type == MSM_SBI_CTRL_SSBI2) {
>> +		u32 mode2 = readl(ssbi->base + SSBI2_MODE2);
>> +		writel(SSBI_MODE2_REG_ADDR_15_8(mode2, addr),
>> +				ssbi->base + SSBI2_MODE2);
>> +	}
>> +
>> +	while (len) {
> 
> Where do you set the address if controller_type == MSM_SBI_CTRL_SSBI?
> 
>   Daniel
> 
> 

The SSBI_MODE2_REG_ADDR register contains the upper 8-bits of the 
address which is only supported by SSBI 2.0.  The lower 8 address bits 
are written as part of the SSBI_CMD_WRITE macro which is common for both 
of the controller types.

-- 
Sent by an employee of the Qualcomm Innovation Center, Inc.
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum.
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