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: Raviteja Narayanam <raviteja.narayanam@xilinx.com>
Signed-off-by: Manikanta Guntupalli <manikanta.guntupalli@amd.com>
Acked-by: Michal Simek <michal.simek@amd.com>
Signed-off-by: Wolfram Sang <wsa@kernel.org>

diff --git a/drivers/i2c/busses/i2c-xiic.c b/drivers/i2c/busses/i2c-xiic.c
index 86da622..edc64b7 100644 (file)
--- 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);