Commit 73371d5f authored by Codrin Ciubotariu's avatar Codrin Ciubotariu Committed by Wolfram Sang
Browse files

i2c: at91: Send bus clear command if SDA is down 



After a transfer timeout, some faulty I2C slave devices might hold down
the SDA pin. We can generate a bus clear command, hoping that the slave
might release the pins.
If the CLEAR command is not supported, we will use gpio recovery, if
available, to reset the bus.

Signed-off-by: default avatarCodrin Ciubotariu <codrin.ciubotariu@microchip.com>
Acked-by: default avatarLudovic Desroches <ludovic.desroches@microchip.com>
Signed-off-by: default avatarWolfram Sang <wsa@kernel.org>
parent e896be5a

drivers/i2c/busses/i2c-at91-core.c

+2 −0
Original line number Diff line number Diff line
@@ -131,6 +131,7 @@ static struct at91_twi_pdata sama5d2_config = { 
	.has_dig_filtr = true,

	.has_adv_dig_filtr = true,

	.has_ana_filtr = true,

	.has_clear_cmd = false,	/* due to errata, CLEAR cmd is not working */

};



static struct at91_twi_pdata sam9x60_config = {
@@ -142,6 +143,7 @@ static struct at91_twi_pdata sam9x60_config = { 
	.has_dig_filtr = true,

	.has_adv_dig_filtr = true,

	.has_ana_filtr = true,

	.has_clear_cmd = true,

};



static const struct of_device_id atmel_twi_dt_ids[] = {

drivers/i2c/busses/i2c-at91-master.c

+42 −7
Original line number Diff line number Diff line
@@ -480,7 +480,6 @@ static int at91_do_twi_transfer(struct at91_twi_dev *dev) 
	unsigned long time_left;

	bool has_unre_flag = dev->pdata->has_unre_flag;

	bool has_alt_cmd = dev->pdata->has_alt_cmd;

	struct i2c_bus_recovery_info *rinfo = &dev->rinfo;



	/*

	 * WARNING: the TXCOMP bit in the Status Register is NOT a clear on
@@ -641,11 +640,12 @@ static int at91_do_twi_transfer(struct at91_twi_dev *dev) 
			       AT91_TWI_THRCLR | AT91_TWI_LOCKCLR);

	}



	if (rinfo->get_sda && !(rinfo->get_sda(&dev->adapter))) {

		dev_dbg(dev->dev,

			"SDA is down; clear bus using gpio\n");

	/*

	 * some faulty I2C slave devices might hold SDA down;

	 * we can send a bus clear command, hoping that the pins will be

	 * released

	 */

	i2c_recover_bus(&dev->adapter);

	}



	return ret;

}
@@ -830,7 +830,7 @@ static void at91_unprepare_twi_recovery(struct i2c_adapter *adap) 
	pinctrl_select_state(dev->pinctrl, dev->pinctrl_pins_default);

}



static int at91_init_twi_recovery_info(struct platform_device *pdev,

static int at91_init_twi_recovery_gpio(struct platform_device *pdev,

				       struct at91_twi_dev *dev)

{

	struct i2c_bus_recovery_info *rinfo = &dev->rinfo;
@@ -880,6 +880,41 @@ static int at91_init_twi_recovery_info(struct platform_device *pdev, 
	return 0;

}



static int at91_twi_recover_bus_cmd(struct i2c_adapter *adap)

{

	struct at91_twi_dev *dev = i2c_get_adapdata(adap);



	dev->transfer_status |= at91_twi_read(dev, AT91_TWI_SR);

	if (!(dev->transfer_status & AT91_TWI_SDA)) {

		dev_dbg(dev->dev, "SDA is down; sending bus clear command\n");

		if (dev->use_alt_cmd) {

			unsigned int acr;



			acr = at91_twi_read(dev, AT91_TWI_ACR);

			acr &= ~AT91_TWI_ACR_DATAL_MASK;

			at91_twi_write(dev, AT91_TWI_ACR, acr);

		}

		at91_twi_write(dev, AT91_TWI_CR, AT91_TWI_CLEAR);

	}



	return 0;

}



static int at91_init_twi_recovery_info(struct platform_device *pdev,

				       struct at91_twi_dev *dev)

{

	struct i2c_bus_recovery_info *rinfo = &dev->rinfo;

	bool has_clear_cmd = dev->pdata->has_clear_cmd;



	if (!has_clear_cmd)

		return at91_init_twi_recovery_gpio(pdev, dev);



	rinfo->recover_bus = at91_twi_recover_bus_cmd;

	dev->adapter.bus_recovery_info = rinfo;



	return 0;

}



int at91_twi_probe_master(struct platform_device *pdev,

			  u32 phy_addr, struct at91_twi_dev *dev)

{

drivers/i2c/busses/i2c-at91.h

+6 −1
Original line number Diff line number Diff line
@@ -36,6 +36,7 @@ 
#define	AT91_TWI_SVDIS		BIT(5)	/* Slave Transfer Disable */

#define	AT91_TWI_QUICK		BIT(6)	/* SMBus quick command */

#define	AT91_TWI_SWRST		BIT(7)	/* Software Reset */

#define	AT91_TWI_CLEAR		BIT(15) /* Bus clear command */

#define	AT91_TWI_ACMEN		BIT(16) /* Alternative Command Mode Enable */

#define	AT91_TWI_ACMDIS		BIT(17) /* Alternative Command Mode Disable */

#define	AT91_TWI_THRCLR		BIT(24) /* Transmit Holding Register Clear */
@@ -69,6 +70,8 @@ 
#define	AT91_TWI_NACK		BIT(8)	/* Not Acknowledged */

#define	AT91_TWI_EOSACC		BIT(11)	/* End Of Slave Access */

#define	AT91_TWI_LOCK		BIT(23) /* TWI Lock due to Frame Errors */

#define	AT91_TWI_SCL		BIT(24) /* TWI SCL status */

#define	AT91_TWI_SDA		BIT(25) /* TWI SDA status */



#define	AT91_TWI_INT_MASK \

	(AT91_TWI_TXCOMP | AT91_TWI_RXRDY | AT91_TWI_TXRDY | AT91_TWI_NACK \
@@ -81,7 +84,8 @@ 
#define	AT91_TWI_THR		0x0034	/* Transmit Holding Register */



#define	AT91_TWI_ACR		0x0040	/* Alternative Command Register */

#define	AT91_TWI_ACR_DATAL(len)	((len) & 0xff)

#define	AT91_TWI_ACR_DATAL_MASK	GENMASK(15, 0)

#define	AT91_TWI_ACR_DATAL(len)	((len) & AT91_TWI_ACR_DATAL_MASK)

#define	AT91_TWI_ACR_DIR	BIT(8)



#define AT91_TWI_FILTR		0x0044
@@ -118,6 +122,7 @@ struct at91_twi_pdata { 
	bool has_dig_filtr;

	bool has_adv_dig_filtr;

	bool has_ana_filtr;

	bool has_clear_cmd;

	struct at_dma_slave dma_slave;

};