[i2c] [PATCH] AT91 I2C bus driver
Mark M. Hoffman
mhoffman at lightlink.com
Thu Oct 26 12:55:44 CEST 2006
Hi Andrew:
Thanks for your patience with my reviews.
* Andrew Victor <andrew at sanpeople.com> [2006-10-25 10:46:59 +0200]:
> hi Mark,
>
> Here is an updated patch that fixes the last points you raised:
> - Line length
> - Common error path in at91_i2c_probe().
>
>
> Signed-off-by: Andrew Victor <andrew at sanpeople.com>
>
Signed-off-by: Mark M. Hoffman <mhoffman at lightlink.com>
>
>
> diff -urN linux-2.6.19-rc3.orig/drivers/i2c/busses/Kconfig linux-2.6.19-rc3/drivers/i2c/busses/Kconfig
> --- linux-2.6.19-rc3.orig/drivers/i2c/busses/Kconfig Wed Oct 25 09:35:52 2006
> +++ linux-2.6.19-rc3/drivers/i2c/busses/Kconfig Wed Oct 25 09:46:15 2006
> @@ -74,6 +74,13 @@
> This driver can also be built as a module. If so, the module
> will be called i2c-amd8111.
>
> +config I2C_AT91
> + tristate "Atmel AT91 I2C Two-Wire interface (TWI)"
> + depends on I2C && ARCH_AT91 && EXPERIMENTAL
> + help
> + This supports the use of the I2C interface on Atmel AT91
> + processors.
> +
> config I2C_AU1550
> tristate "Au1550/Au1200 SMBus interface"
> depends on I2C && (SOC_AU1550 || SOC_AU1200)
> diff -urN linux-2.6.19-rc3.orig/drivers/i2c/busses/Makefile linux-2.6.19-rc3/drivers/i2c/busses/Makefile
> --- linux-2.6.19-rc3.orig/drivers/i2c/busses/Makefile Wed Oct 25 09:35:52 2006
> +++ linux-2.6.19-rc3/drivers/i2c/busses/Makefile Wed Oct 25 09:46:15 2006
> @@ -8,6 +8,7 @@
> obj-$(CONFIG_I2C_AMD756) += i2c-amd756.o
> obj-$(CONFIG_I2C_AMD756_S4882) += i2c-amd756-s4882.o
> obj-$(CONFIG_I2C_AMD8111) += i2c-amd8111.o
> +obj-$(CONFIG_I2C_AT91) += i2c-at91.o
> obj-$(CONFIG_I2C_AU1550) += i2c-au1550.o
> obj-$(CONFIG_I2C_ELEKTOR) += i2c-elektor.o
> obj-$(CONFIG_I2C_HYDRA) += i2c-hydra.o
> diff -urN linux-2.6.19-rc3.orig/drivers/i2c/busses/i2c-at91.c linux-2.6.19-rc3/drivers/i2c/busses/i2c-at91.c
> --- linux-2.6.19-rc3.orig/drivers/i2c/busses/i2c-at91.c Thu Jan 1 02:00:00 1970
> +++ linux-2.6.19-rc3/drivers/i2c/busses/i2c-at91.c Wed Oct 25 10:08:57 2006
> @@ -0,0 +1,325 @@
> +/*
> + i2c Support for Atmel's AT91 Two-Wire Interface (TWI)
> +
> + Copyright (C) 2004 Rick Bronson
> + Converted to 2.6 by Andrew Victor <andrew at sanpeople.com>
> +
> + Borrowed heavily from original work by:
> + Copyright (C) 2000 Philip Edelbrock <phil at stimpy.netroedge.com>
> +
> + 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.
> +*/
> +
> +#include <linux/module.h>
> +#include <linux/version.h>
> +#include <linux/kernel.h>
> +#include <linux/slab.h>
> +#include <linux/pci.h>
> +#include <linux/types.h>
> +#include <linux/delay.h>
> +#include <linux/i2c.h>
> +#include <linux/init.h>
> +#include <linux/clk.h>
> +#include <linux/platform_device.h>
> +
> +#include <asm/io.h>
> +
> +#include <asm/arch/at91rm9200_twi.h>
> +#include <asm/arch/board.h>
> +#include <asm/arch/system.h>
> +
> +#define TWI_CLOCK 100000 /* Hz. max 400 Kbits/sec */
> +
> +
> +static struct clk *twi_clk;
> +static void __iomem *twi_base;
> +
> +#define at91_twi_read(reg) __raw_readl(twi_base + (reg))
> +#define at91_twi_write(reg, val) __raw_writel((val), twi_base + (reg))
> +
> +
> +/*
> + * Initialize the TWI hardware registers.
> + */
> +static void __devinit at91_twi_hwinit(void)
> +{
> + unsigned long cdiv, ckdiv;
> +
> + at91_twi_write(AT91_TWI_IDR, 0xffffffff); /* Disable all interrupts */
> + at91_twi_write(AT91_TWI_CR, AT91_TWI_SWRST); /* Reset peripheral */
> + at91_twi_write(AT91_TWI_CR, AT91_TWI_MSEN); /* Set Master mode */
> +
> + /* Calcuate clock dividers */
> + cdiv = (clk_get_rate(twi_clk) / (2 * TWI_CLOCK)) - 3;
> + cdiv = cdiv + 1; /* round up */
> + ckdiv = 0;
> + while (cdiv > 255) {
> + ckdiv++;
> + cdiv = cdiv >> 1;
> + }
> +
> + if (arch_identify() == ARCH_ID_AT91RM9200) { /* AT91RM9200 Errata #22 */
> + if (ckdiv > 5) {
> + printk(KERN_ERR "AT91 I2C: Invalid TWI_CLOCK value!\n");
> + ckdiv = 5;
> + }
> + }
> +
> + at91_twi_write(AT91_TWI_CWGR, (ckdiv << 16) | (cdiv << 8) | cdiv);
> +}
> +
> +/*
> + * Poll the i2c status register until the specified bit is set.
> + * Returns 0 if timed out (100 msec).
> + */
> +static short at91_poll_status(unsigned long bit)
> +{
> + int loop_cntr = 10000;
> +
> + do {
> + udelay(10);
> + } while (!(at91_twi_read(AT91_TWI_SR) & bit) && (--loop_cntr > 0));
> +
> + return (loop_cntr > 0);
> +}
> +
> +static int xfer_read(struct i2c_adapter *adap, unsigned char *buf, int length)
> +{
> + /* Send Start */
> + at91_twi_write(AT91_TWI_CR, AT91_TWI_START);
> +
> + /* Read data */
> + while (length--) {
> + if (!length) /* need to send Stop before reading last byte */
> + at91_twi_write(AT91_TWI_CR, AT91_TWI_STOP);
> + if (!at91_poll_status(AT91_TWI_RXRDY)) {
> + dev_dbg(&adap->dev, "RXRDY timeout\n");
> + return -ETIMEDOUT;
> + }
> + *buf++ = (at91_twi_read(AT91_TWI_RHR) & 0xff);
> + }
> +
> + return 0;
> +}
> +
> +static int xfer_write(struct i2c_adapter *adap, unsigned char *buf, int length)
> +{
> + /* Load first byte into transmitter */
> + at91_twi_write(AT91_TWI_THR, *buf++);
> +
> + /* Send Start */
> + at91_twi_write(AT91_TWI_CR, AT91_TWI_START);
> +
> + do {
> + if (!at91_poll_status(AT91_TWI_TXRDY)) {
> + dev_dbg(&adap->dev, "TXRDY timeout\n");
> + return -ETIMEDOUT;
> + }
> +
> + length--; /* byte was transmitted */
> +
> + if (length > 0) /* more data to send? */
> + at91_twi_write(AT91_TWI_THR, *buf++);
> + } while (length);
> +
> + /* Send Stop */
> + at91_twi_write(AT91_TWI_CR, AT91_TWI_STOP);
> +
> + return 0;
> +}
> +
> +/*
> + * Generic i2c master transfer entrypoint.
> + *
> + * Note: We do not use Atmel's feature of storing the "internal device address".
> + * Instead the "internal device address" has to be written using a seperate
> + * i2c message.
> + * http://lists.arm.linux.org.uk/pipermail/linux-arm-kernel/2004-September/024411.html
> + */
> +static int at91_xfer(struct i2c_adapter *adap, struct i2c_msg *pmsg, int num)
> +{
> + int i, ret;
> +
> + dev_dbg(&adap->dev, "at91_xfer: processing %d messages:\n", num);
> +
> + for (i = 0; i < num; i++) {
> + dev_dbg(&adap->dev, " #%d: %sing %d byte%s %s 0x%02x\n", i,
> + pmsg->flags & I2C_M_RD ? "read" : "writ",
> + pmsg->len, pmsg->len > 1 ? "s" : "",
> + pmsg->flags & I2C_M_RD ? "from" : "to", pmsg->addr);
> +
> + at91_twi_write(AT91_TWI_MMR, (pmsg->addr << 16)
> + | ((pmsg->flags & I2C_M_RD) ? AT91_TWI_MREAD : 0));
> +
> + if (pmsg->len && pmsg->buf) { /* sanity check */
> + if (pmsg->flags & I2C_M_RD)
> + ret = xfer_read(adap, pmsg->buf, pmsg->len);
> + else
> + ret = xfer_write(adap, pmsg->buf, pmsg->len);
> +
> + if (ret)
> + return ret;
> +
> + /* Wait until transfer is finished */
> + if (!at91_poll_status(AT91_TWI_TXCOMP)) {
> + dev_dbg(&adap->dev, "TXCOMP timeout\n");
> + return -ETIMEDOUT;
> + }
> + }
> + dev_dbg(&adap->dev, "transfer complete\n");
> + pmsg++; /* next message */
> + }
> + return i;
> +}
> +
> +/*
> + * Return list of supported functionality.
> + */
> +static u32 at91_func(struct i2c_adapter *adapter)
> +{
> + return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
> +}
> +
> +static struct i2c_algorithm at91_algorithm = {
> + .master_xfer = at91_xfer,
> + .functionality = at91_func,
> +};
> +
> +/*
> + * Main initialization routine.
> + */
> +static int __devinit at91_i2c_probe(struct platform_device *pdev)
> +{
> + struct i2c_adapter *adapter;
> + struct resource *res;
> + int rc;
> +
> + res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> + if (!res)
> + return -ENXIO;
> +
> + if (!request_mem_region(res->start, res->end - res->start + 1, "at91_i2c"))
> + return -EBUSY;
> +
> + twi_base = ioremap(res->start, res->end - res->start + 1);
> + if (!twi_base) {
> + rc = -ENOMEM;
> + goto fail0;
> + }
> +
> + twi_clk = clk_get(NULL, "twi_clk");
> + if (IS_ERR(twi_clk)) {
> + dev_err(&pdev->dev, "no clock defined\n");
> + rc = -ENODEV;
> + goto fail1;
> + }
> +
> + adapter = kzalloc(sizeof(struct i2c_adapter), GFP_KERNEL);
> + if (adapter == NULL) {
> + dev_err(&pdev->dev, "can't allocate inteface!\n");
> + rc = -ENOMEM;
> + goto fail2;
> + }
> + sprintf(adapter->name, "AT91");
> + adapter->algo = &at91_algorithm;
> + adapter->class = I2C_CLASS_HWMON;
> + adapter->dev.parent = &pdev->dev;
> +
> + platform_set_drvdata(pdev, adapter);
> +
> + clk_enable(twi_clk); /* enable peripheral clock */
> + at91_twi_hwinit(); /* initialize TWI controller */
> +
> + rc = i2c_add_adapter(adapter);
> + if (rc) {
> + dev_err(&pdev->dev, "Adapter %s registration failed\n",
> + adapter->name);
> + goto fail3;
> + }
> +
> + dev_info(&pdev->dev, "AT91 i2c bus driver.\n");
> + return 0;
> +
> +fail3:
> + clk_disable(twi_clk);
> + platform_set_drvdata(pdev, NULL);
> + kfree(adapter);
> +fail2:
> + clk_put(twi_clk);
> +fail1:
> + iounmap(twi_base);
> +fail0:
> + release_mem_region(res->start, res->end - res->start + 1);
> +
> + return rc;
> +}
> +
> +static int __devexit at91_i2c_remove(struct platform_device *pdev)
> +{
> + struct i2c_adapter *adapter = platform_get_drvdata(pdev);
> + struct resource *res;
> + int rc;
> +
> + rc = i2c_del_adapter(adapter);
> + platform_set_drvdata(pdev, NULL);
> +
> + res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> + iounmap(twi_base);
> + release_mem_region(res->start, res->end - res->start + 1);
> +
> + clk_disable(twi_clk); /* disable peripheral clock */
> + clk_put(twi_clk);
> +
> + return rc;
> +}
> +
> +#ifdef CONFIG_PM
> +
> +/* NOTE: could save a few mA by keeping clock off outside of at91_xfer... */
> +
> +static int at91_i2c_suspend(struct platform_device *pdev, pm_message_t mesg)
> +{
> + clk_disable(twi_clk);
> + return 0;
> +}
> +
> +static int at91_i2c_resume(struct platform_device *pdev)
> +{
> + return clk_enable(twi_clk);
> +}
> +
> +#else
> +#define at91_i2c_suspend NULL
> +#define at91_i2c_resume NULL
> +#endif
> +
> +static struct platform_driver at91_i2c_driver = {
> + .probe = at91_i2c_probe,
> + .remove = __devexit_p(at91_i2c_remove),
> + .suspend = at91_i2c_suspend,
> + .resume = at91_i2c_resume,
> + .driver = {
> + .name = "at91_i2c",
> + .owner = THIS_MODULE,
> + },
> +};
> +
> +static int __init at91_i2c_init(void)
> +{
> + return platform_driver_register(&at91_i2c_driver);
> +}
> +
> +static void __exit at91_i2c_exit(void)
> +{
> + platform_driver_unregister(&at91_i2c_driver);
> +}
> +
> +module_init(at91_i2c_init);
> +module_exit(at91_i2c_exit);
> +
> +MODULE_AUTHOR("Rick Bronson");
> +MODULE_DESCRIPTION("I2C (TWI) driver for Atmel AT91");
> +MODULE_LICENSE("GPL");
>
>
--
Mark M. Hoffman
mhoffman at lightlink.com
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