[PATCH V4 3/9] i2c: xiic: Switch to Xiic standard mode for i2c-read

Manikanta Guntupalli
2023-02-02T09:44:20Z

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: Raviteja Narayanam <raviteja.narayanam@xilinx.com>
Signed-off-by: Manikanta Guntupalli <manikanta.guntupalli@amd.com>
Acked-by: Michal Simek <michal.simek@amd.com>
---
drivers/i2c/busses/i2c-xiic.c | 96 +++++++++++++++++++++--------------
1 file changed, 57 insertions(+), 39 deletions(-)

diff --git a/drivers/i2c/busses/i2c-xiic.c b/drivers/i2c/busses/i2c-xiic.c
index 86da622e060c..edc64b79e293 100644
--- a/drivers/i2c/busses/i2c-xiic.c
+++ b/drivers/i2c/busses/i2c-xiic.c
@@ -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);
--
2.25.1