Commit 2fd5cf35 authored by Raviteja Narayanam's avatar Raviteja Narayanam Committed by Wolfram Sang
Browse files

i2c: xiic: Switch to Xiic standard mode for i2c-read 



Xilinx I2C IP has two modes of operation, both of which implement
I2C transactions. The only difference from sw perspective is the
programming sequence for these modes.
Dynamic mode  -> Simple to program, less number of steps in sequence.
Standard mode -> Gives flexibility, more number of steps in sequence.

In dynamic mode, during the i2c-read transactions, if there is a
delay(> 200us) between the register writes (address & byte count),
read transaction fails. On a system with load, this scenario is
occurring frequently.
To avoid this, switch to standard mode if there is a read request.

Added a quirk to identify the IP version effected by this and follow
the standard mode.

Signed-off-by: default avatarRaviteja Narayanam <raviteja.narayanam@xilinx.com>
Signed-off-by: default avatarManikanta Guntupalli <manikanta.guntupalli@amd.com>
Acked-by: default avatarMichal Simek <michal.simek@amd.com>
Signed-off-by: default avatarWolfram Sang <wsa@kernel.org>
parent 813eac4f

drivers/i2c/busses/i2c-xiic.c

+57 −39
Original line number Diff line number Diff line
@@ -32,6 +32,7 @@ 
#include <linux/pm_runtime.h>



#define DRIVER_NAME "xiic-i2c"

#define DYNAMIC_MODE_READ_BROKEN_BIT	BIT(0)



enum xilinx_i2c_state {

	STATE_DONE,
@@ -62,6 +63,7 @@ enum xiic_endian { 
 * @singlemaster: Indicates bus is single master

 * @dynamic: Mode of controller

 * @prev_msg_tx: Previous message is Tx

 * @quirks: To hold platform specific bug info

 */

struct xiic_i2c {

	struct device *dev;
@@ -80,6 +82,11 @@ struct xiic_i2c { 
	bool singlemaster;

	bool dynamic;

	bool prev_msg_tx;

	u32 quirks;

};



struct xiic_version_data {

	u32 quirks;

};



#define XIIC_MSB_OFFSET 0
@@ -878,7 +885,8 @@ static void __xiic_start_xfer(struct xiic_i2c *i2c) 


static int xiic_start_xfer(struct xiic_i2c *i2c, struct i2c_msg *msgs, int num)

{

	int ret;

	bool broken_read, max_read_len, smbus_blk_read;

	int ret, count;



	mutex_lock(&i2c->lock);
@@ -891,6 +899,34 @@ static int xiic_start_xfer(struct xiic_i2c *i2c, struct i2c_msg *msgs, int num) 
	i2c->nmsgs = num;

	init_completion(&i2c->completion);



	/* Decide standard mode or Dynamic mode */

	i2c->dynamic = true;



	/* Initialize prev message type */

	i2c->prev_msg_tx = false;



	/*

	 * Scan through nmsgs, use dynamic mode when none of the below three

	 * conditions occur. We need standard mode even if one condition holds

	 * true in the entire array of messages in a single transfer.

	 * If read transaction as dynamic mode is broken for delayed reads

	 * in xlnx,axi-iic-2.0 / xlnx,xps-iic-2.00.a IP versions.

	 * If read length is > 255 bytes.

	 * If smbus_block_read transaction.

	 */

	for (count = 0; count < i2c->nmsgs; count++) {

		broken_read = (i2c->quirks & DYNAMIC_MODE_READ_BROKEN_BIT) &&

				(i2c->tx_msg[count].flags & I2C_M_RD);

		max_read_len = (i2c->tx_msg[count].flags & I2C_M_RD) &&

				(i2c->tx_msg[count].len > MAX_READ_LENGTH_DYNAMIC);

		smbus_blk_read = (i2c->tx_msg[count].flags & I2C_M_RECV_LEN);



		if (broken_read || max_read_len || smbus_blk_read) {

			i2c->dynamic = false;

			break;

		}

	}



	ret = xiic_reinit(i2c);

	if (!ret)

		__xiic_start_xfer(i2c);
@@ -913,36 +949,6 @@ static int xiic_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num) 
	if (err < 0)

		return err;



	/* Decide standard mode or Dynamic mode */

	i2c->dynamic = true;



	/* Initialize prev message type */

	i2c->prev_msg_tx = false;



	/*

	 * If number of messages is 1 and read length is > 255 bytes,

	 * enter standard mode

	 */



	if (i2c->nmsgs == 1 && (i2c->tx_msg->flags & I2C_M_RD) &&

	    i2c->tx_msg->len > MAX_READ_LENGTH_DYNAMIC) {

		i2c->dynamic = false;

	} else if (i2c->nmsgs > 1) {

		int count;



		/*

		 * If number of messages is more than 1 and one of them is

		 * a read message, enter standard mode. Since repeated start

		 * operation in dynamic mode read is not happenning

		 */

		for (count = 0; count < i2c->nmsgs; count++) {

			if (i2c->tx_msg[count].flags & I2C_M_RD) {

				i2c->dynamic = false;

				break;

			}

		}

	}



	err = xiic_start_xfer(i2c, msgs, num);

	if (err < 0) {

		dev_err(adap->dev.parent, "Error xiic_start_xfer\n");
@@ -985,10 +991,23 @@ static const struct i2c_adapter xiic_adapter = { 
	.algo = &xiic_algorithm,

};



static const struct xiic_version_data xiic_2_00 = {

	.quirks = DYNAMIC_MODE_READ_BROKEN_BIT,

};



#if defined(CONFIG_OF)

static const struct of_device_id xiic_of_match[] = {

	{ .compatible = "xlnx,xps-iic-2.00.a", .data = &xiic_2_00 },

	{},

};

MODULE_DEVICE_TABLE(of, xiic_of_match);

#endif



static int xiic_i2c_probe(struct platform_device *pdev)

{

	struct xiic_i2c *i2c;

	struct xiic_i2c_platform_data *pdata;

	const struct of_device_id *match;

	struct resource *res;

	int ret, irq;

	u8 i;
@@ -998,6 +1017,13 @@ static int xiic_i2c_probe(struct platform_device *pdev) 
	if (!i2c)

		return -ENOMEM;



	match = of_match_node(xiic_of_match, pdev->dev.of_node);

	if (match && match->data) {

		const struct xiic_version_data *data = match->data;



		i2c->quirks = data->quirks;

	}



	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);

	i2c->base = devm_ioremap_resource(&pdev->dev, res);

	if (IS_ERR(i2c->base))
@@ -1112,14 +1138,6 @@ static int xiic_i2c_remove(struct platform_device *pdev) 
	return 0;

}



#if defined(CONFIG_OF)

static const struct of_device_id xiic_of_match[] = {

	{ .compatible = "xlnx,xps-iic-2.00.a", },

	{},

};

MODULE_DEVICE_TABLE(of, xiic_of_match);

#endif



static int __maybe_unused xiic_i2c_runtime_suspend(struct device *dev)

{

	struct xiic_i2c *i2c = dev_get_drvdata(dev);