summaryrefslogtreecommitdiffstats
path: root/drivers/i2c
diff options
context:
space:
mode:
authorThomas Petazzoni <thomas.petazzoni@free-electrons.com>2014-12-11 17:33:46 +0100
committerWolfram Sang <wsa@the-dreams.de>2014-12-17 19:26:03 +0100
commit00d8689b85a7bb37cc57ba4c40bd46325f51ced4 (patch)
tree8621f9a761df85f67c14945aaf091b647d04f5f8 /drivers/i2c
parent12598695c26ff8fccea92bd36ee3617a6da9b0d0 (diff)
downloadlinux-00d8689b85a7bb37cc57ba4c40bd46325f51ced4.tar.bz2
i2c: mv64xxx: rework offload support to fix several problems
Originally, the I2C controller supported by the i2c-mv64xxx driver requires a lot of software support: an interrupt is generated at each step of an I2C transaction (after the start bit, after sending the address, etc.) and the driver is in charge of re-programming the I2C controller to do the next step of the I2C transaction. This explains the fairly complex state machine that the driver has. On Marvell Armada XP and later processors (Armada 375, 38x, etc.), the I2C controller was extended with a part called the "I2C Bridge", which allows to offload the I2C transaction completely to the hardware. Initial support for this mechanism was added in commit 930ab3d403a ("i2c: mv64xxx: Add I2C Transaction Generator support"). However, the implementation done in this commit has two related issues, which this commit fixes by completely changing how the offload implementation is done: * SMBus read transfers, where there is one write to select the register immediately followed in the same transaction by one read, were making the processor hang. This was easier visible on the Marvell Armada XP WRT1900AC platform using a driver for an I2C LED controller, or on other Armada XP platforms by using a simple 'i2cget' command to read an I2C EEPROM. * The implementation was based on the fact that the offload engine was re-programmed to transfer each message of an I2C xfer: this meant that each message sent with the offload engine was starting with a normal I2C start sequence. However, the I2C subsystem assumes that all messages belonging to the same xfer will use the so-called "repeated start" so that the entire I2C xfer is seen as one transfer by the I2C devices and cannot be interrupt by other I2C masters on the same bus. In fact, the "I2C Bridge" allows to offload three types of xfer: - xfer of one write message - xfer of one read message - xfer of one write message followed by one read message For all other situations, we have to fallback to not using the "I2C Bridge" in order to get proper I2C semantics. Therefore, this commit reworks the offload implementation to put it not at the message level, but at the xfer level: in the mv64xxx_i2c_xfer() function, we decide if the transaction can be offloaded (in which case it is handled by the mv64xxx_i2c_offload_xfer() function), or otherwise it is handled by the slow path (implemented in the existing mv64xxx_i2c_execute_msg()). This allows to simplify the state machine, which no longer needs to have any state related to the offload implementation: the offload implementation is now completely separated from the slow path (with the exception of the interrupt handler, of course). In summary: - mv64xxx_i2c_can_offload() will analyze an I2C xfer and decided of the "I2C Bridge" can be used to offload it or not. - mv64xxx_i2c_offload_xfer() will actually program the "I2C Bridge" to offload one xfer (of either one or two messages), and block using mv64xxx_i2c_wait_for_completion() until the xfer completes. - The interrupt handler mv64xxx_i2c_intr() is modified to push the offload related code to a separate function, mv64xxx_i2c_intr_offload(). It will take care of reading the received data if needed. This commit was tested on: - Armada XP OpenBlocks AX3-4 (EEPROM on I2C and RTC on I2C) - Armada XP WRT1900AC (LED controller on I2C) - Armada XP GP (EEPROM on I2C) Fixes: 930ab3d403ae ("i2c: mv64xxx: Add I2C Transaction Generator support") Cc: <stable@vger.kernel.org> # v3.12+ Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com> [wsa: fixed checkpatch warnings] Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
Diffstat (limited to 'drivers/i2c')
-rw-r--r--drivers/i2c/busses/i2c-mv64xxx.c306
1 files changed, 186 insertions, 120 deletions
diff --git a/drivers/i2c/busses/i2c-mv64xxx.c b/drivers/i2c/busses/i2c-mv64xxx.c
index eff108cbcd4c..30059c1df2a3 100644
--- a/drivers/i2c/busses/i2c-mv64xxx.c
+++ b/drivers/i2c/busses/i2c-mv64xxx.c
@@ -75,12 +75,10 @@
#define MV64XXX_I2C_BRIDGE_CONTROL_TX_SIZE_SHIFT 13
#define MV64XXX_I2C_BRIDGE_CONTROL_RX_SIZE_SHIFT 16
#define MV64XXX_I2C_BRIDGE_CONTROL_ENABLE BIT(19)
+#define MV64XXX_I2C_BRIDGE_CONTROL_REPEATED_START BIT(20)
/* Bridge Status values */
#define MV64XXX_I2C_BRIDGE_STATUS_ERROR BIT(0)
-#define MV64XXX_I2C_STATUS_OFFLOAD_ERROR 0xf0000001
-#define MV64XXX_I2C_STATUS_OFFLOAD_OK 0xf0000000
-
/* Driver states */
enum {
@@ -99,14 +97,12 @@ enum {
MV64XXX_I2C_ACTION_INVALID,
MV64XXX_I2C_ACTION_CONTINUE,
MV64XXX_I2C_ACTION_SEND_RESTART,
- MV64XXX_I2C_ACTION_OFFLOAD_RESTART,
MV64XXX_I2C_ACTION_SEND_ADDR_1,
MV64XXX_I2C_ACTION_SEND_ADDR_2,
MV64XXX_I2C_ACTION_SEND_DATA,
MV64XXX_I2C_ACTION_RCV_DATA,
MV64XXX_I2C_ACTION_RCV_DATA_STOP,
MV64XXX_I2C_ACTION_SEND_STOP,
- MV64XXX_I2C_ACTION_OFFLOAD_SEND_STOP,
};
struct mv64xxx_i2c_regs {
@@ -193,75 +189,6 @@ mv64xxx_i2c_prepare_for_io(struct mv64xxx_i2c_data *drv_data,
}
}
-static int mv64xxx_i2c_offload_msg(struct mv64xxx_i2c_data *drv_data)
-{
- unsigned long data_reg_hi = 0;
- unsigned long data_reg_lo = 0;
- unsigned long ctrl_reg;
- struct i2c_msg *msg = drv_data->msgs;
-
- if (!drv_data->offload_enabled)
- return -EOPNOTSUPP;
-
- /* Only regular transactions can be offloaded */
- if ((msg->flags & ~(I2C_M_TEN | I2C_M_RD)) != 0)
- return -EINVAL;
-
- /* Only 1-8 byte transfers can be offloaded */
- if (msg->len < 1 || msg->len > 8)
- return -EINVAL;
-
- /* Build transaction */
- ctrl_reg = MV64XXX_I2C_BRIDGE_CONTROL_ENABLE |
- (msg->addr << MV64XXX_I2C_BRIDGE_CONTROL_ADDR_SHIFT);
-
- if ((msg->flags & I2C_M_TEN) != 0)
- ctrl_reg |= MV64XXX_I2C_BRIDGE_CONTROL_ADDR_EXT;
-
- if ((msg->flags & I2C_M_RD) == 0) {
- u8 local_buf[8] = { 0 };
-
- memcpy(local_buf, msg->buf, msg->len);
- data_reg_lo = cpu_to_le32(*((u32 *)local_buf));
- data_reg_hi = cpu_to_le32(*((u32 *)(local_buf+4)));
-
- ctrl_reg |= MV64XXX_I2C_BRIDGE_CONTROL_WR |
- (msg->len - 1) << MV64XXX_I2C_BRIDGE_CONTROL_TX_SIZE_SHIFT;
-
- writel(data_reg_lo,
- drv_data->reg_base + MV64XXX_I2C_REG_TX_DATA_LO);
- writel(data_reg_hi,
- drv_data->reg_base + MV64XXX_I2C_REG_TX_DATA_HI);
-
- } else {
- ctrl_reg |= MV64XXX_I2C_BRIDGE_CONTROL_RD |
- (msg->len - 1) << MV64XXX_I2C_BRIDGE_CONTROL_RX_SIZE_SHIFT;
- }
-
- /* Execute transaction */
- writel(ctrl_reg, drv_data->reg_base + MV64XXX_I2C_REG_BRIDGE_CONTROL);
-
- return 0;
-}
-
-static void
-mv64xxx_i2c_update_offload_data(struct mv64xxx_i2c_data *drv_data)
-{
- struct i2c_msg *msg = drv_data->msg;
-
- if (msg->flags & I2C_M_RD) {
- u32 data_reg_lo = readl(drv_data->reg_base +
- MV64XXX_I2C_REG_RX_DATA_LO);
- u32 data_reg_hi = readl(drv_data->reg_base +
- MV64XXX_I2C_REG_RX_DATA_HI);
- u8 local_buf[8] = { 0 };
-
- *((u32 *)local_buf) = le32_to_cpu(data_reg_lo);
- *((u32 *)(local_buf+4)) = le32_to_cpu(data_reg_hi);
- memcpy(msg->buf, local_buf, msg->len);
- }
-
-}
/*
*****************************************************************************
*
@@ -389,16 +316,6 @@ mv64xxx_i2c_fsm(struct mv64xxx_i2c_data *drv_data, u32 status)
drv_data->rc = -ENXIO;
break;
- case MV64XXX_I2C_STATUS_OFFLOAD_OK:
- if (drv_data->send_stop || drv_data->aborting) {
- drv_data->action = MV64XXX_I2C_ACTION_OFFLOAD_SEND_STOP;
- drv_data->state = MV64XXX_I2C_STATE_IDLE;
- } else {
- drv_data->action = MV64XXX_I2C_ACTION_OFFLOAD_RESTART;
- drv_data->state = MV64XXX_I2C_STATE_WAITING_FOR_RESTART;
- }
- break;
-
default:
dev_err(&drv_data->adapter.dev,
"mv64xxx_i2c_fsm: Ctlr Error -- state: 0x%x, "
@@ -419,25 +336,15 @@ static void mv64xxx_i2c_send_start(struct mv64xxx_i2c_data *drv_data)
drv_data->aborting = 0;
drv_data->rc = 0;
- /* Can we offload this msg ? */
- if (mv64xxx_i2c_offload_msg(drv_data) < 0) {
- /* No, switch to standard path */
- mv64xxx_i2c_prepare_for_io(drv_data, drv_data->msgs);
- writel(drv_data->cntl_bits | MV64XXX_I2C_REG_CONTROL_START,
- drv_data->reg_base + drv_data->reg_offsets.control);
- }
+ mv64xxx_i2c_prepare_for_io(drv_data, drv_data->msgs);
+ writel(drv_data->cntl_bits | MV64XXX_I2C_REG_CONTROL_START,
+ drv_data->reg_base + drv_data->reg_offsets.control);
}
static void
mv64xxx_i2c_do_action(struct mv64xxx_i2c_data *drv_data)
{
switch(drv_data->action) {
- case MV64XXX_I2C_ACTION_OFFLOAD_RESTART:
- mv64xxx_i2c_update_offload_data(drv_data);
- writel(0, drv_data->reg_base + MV64XXX_I2C_REG_BRIDGE_CONTROL);
- writel(0, drv_data->reg_base +
- MV64XXX_I2C_REG_BRIDGE_INTR_CAUSE);
- /* FALLTHRU */
case MV64XXX_I2C_ACTION_SEND_RESTART:
/* We should only get here if we have further messages */
BUG_ON(drv_data->num_msgs == 0);
@@ -518,16 +425,71 @@ mv64xxx_i2c_do_action(struct mv64xxx_i2c_data *drv_data)
drv_data->block = 0;
wake_up(&drv_data->waitq);
break;
+ }
+}
- case MV64XXX_I2C_ACTION_OFFLOAD_SEND_STOP:
- mv64xxx_i2c_update_offload_data(drv_data);
- writel(0, drv_data->reg_base + MV64XXX_I2C_REG_BRIDGE_CONTROL);
- writel(0, drv_data->reg_base +
- MV64XXX_I2C_REG_BRIDGE_INTR_CAUSE);
- drv_data->block = 0;
- wake_up(&drv_data->waitq);
- break;
+static void
+mv64xxx_i2c_read_offload_rx_data(struct mv64xxx_i2c_data *drv_data,
+ struct i2c_msg *msg)
+{
+ u32 buf[2];
+
+ buf[0] = readl(drv_data->reg_base + MV64XXX_I2C_REG_RX_DATA_LO);
+ buf[1] = readl(drv_data->reg_base + MV64XXX_I2C_REG_RX_DATA_HI);
+
+ memcpy(msg->buf, buf, msg->len);
+}
+
+static int
+mv64xxx_i2c_intr_offload(struct mv64xxx_i2c_data *drv_data)
+{
+ u32 cause, status;
+
+ cause = readl(drv_data->reg_base +
+ MV64XXX_I2C_REG_BRIDGE_INTR_CAUSE);
+ if (!cause)
+ return IRQ_NONE;
+
+ status = readl(drv_data->reg_base +
+ MV64XXX_I2C_REG_BRIDGE_STATUS);
+
+ if (status & MV64XXX_I2C_BRIDGE_STATUS_ERROR) {
+ drv_data->rc = -EIO;
+ goto out;
+ }
+
+ drv_data->rc = 0;
+
+ /*
+ * Transaction is a one message read transaction, read data
+ * for this message.
+ */
+ if (drv_data->num_msgs == 1 && drv_data->msgs[0].flags & I2C_M_RD) {
+ mv64xxx_i2c_read_offload_rx_data(drv_data, drv_data->msgs);
+ drv_data->msgs++;
+ drv_data->num_msgs--;
+ }
+ /*
+ * Transaction is a two messages write/read transaction, read
+ * data for the second (read) message.
+ */
+ else if (drv_data->num_msgs == 2 &&
+ !(drv_data->msgs[0].flags & I2C_M_RD) &&
+ drv_data->msgs[1].flags & I2C_M_RD) {
+ mv64xxx_i2c_read_offload_rx_data(drv_data, drv_data->msgs + 1);
+ drv_data->msgs += 2;
+ drv_data->num_msgs -= 2;
}
+
+out:
+ writel(0, drv_data->reg_base + MV64XXX_I2C_REG_BRIDGE_CONTROL);
+ writel(0, drv_data->reg_base +
+ MV64XXX_I2C_REG_BRIDGE_INTR_CAUSE);
+ drv_data->block = 0;
+
+ wake_up(&drv_data->waitq);
+
+ return IRQ_HANDLED;
}
static irqreturn_t
@@ -540,20 +502,9 @@ mv64xxx_i2c_intr(int irq, void *dev_id)
spin_lock_irqsave(&drv_data->lock, flags);
- if (drv_data->offload_enabled) {
- while (readl(drv_data->reg_base +
- MV64XXX_I2C_REG_BRIDGE_INTR_CAUSE)) {
- int reg_status = readl(drv_data->reg_base +
- MV64XXX_I2C_REG_BRIDGE_STATUS);
- if (reg_status & MV64XXX_I2C_BRIDGE_STATUS_ERROR)
- status = MV64XXX_I2C_STATUS_OFFLOAD_ERROR;
- else
- status = MV64XXX_I2C_STATUS_OFFLOAD_OK;
- mv64xxx_i2c_fsm(drv_data, status);
- mv64xxx_i2c_do_action(drv_data);
- rc = IRQ_HANDLED;
- }
- }
+ if (drv_data->offload_enabled)
+ rc = mv64xxx_i2c_intr_offload(drv_data);
+
while (readl(drv_data->reg_base + drv_data->reg_offsets.control) &
MV64XXX_I2C_REG_CONTROL_IFLG) {
status = readl(drv_data->reg_base + drv_data->reg_offsets.status);
@@ -635,6 +586,117 @@ mv64xxx_i2c_execute_msg(struct mv64xxx_i2c_data *drv_data, struct i2c_msg *msg,
return drv_data->rc;
}
+static void
+mv64xxx_i2c_prepare_tx(struct mv64xxx_i2c_data *drv_data)
+{
+ struct i2c_msg *msg = drv_data->msgs;
+ u32 buf[2];
+
+ memcpy(buf, msg->buf, msg->len);
+
+ writel(buf[0], drv_data->reg_base + MV64XXX_I2C_REG_TX_DATA_LO);
+ writel(buf[1], drv_data->reg_base + MV64XXX_I2C_REG_TX_DATA_HI);
+}
+
+static int
+mv64xxx_i2c_offload_xfer(struct mv64xxx_i2c_data *drv_data)
+{
+ struct i2c_msg *msgs = drv_data->msgs;
+ int num = drv_data->num_msgs;
+ unsigned long ctrl_reg;
+ unsigned long flags;
+
+ spin_lock_irqsave(&drv_data->lock, flags);
+
+ /* Build transaction */
+ ctrl_reg = MV64XXX_I2C_BRIDGE_CONTROL_ENABLE |
+ (msgs[0].addr << MV64XXX_I2C_BRIDGE_CONTROL_ADDR_SHIFT);
+
+ if (msgs[0].flags & I2C_M_TEN)
+ ctrl_reg |= MV64XXX_I2C_BRIDGE_CONTROL_ADDR_EXT;
+
+ /* Single write message transaction */
+ if (num == 1 && !(msgs[0].flags & I2C_M_RD)) {
+ size_t len = msgs[0].len - 1;
+
+ ctrl_reg |= MV64XXX_I2C_BRIDGE_CONTROL_WR |
+ (len << MV64XXX_I2C_BRIDGE_CONTROL_TX_SIZE_SHIFT);
+ mv64xxx_i2c_prepare_tx(drv_data);
+ }
+ /* Single read message transaction */
+ else if (num == 1 && msgs[0].flags & I2C_M_RD) {
+ size_t len = msgs[0].len - 1;
+
+ ctrl_reg |= MV64XXX_I2C_BRIDGE_CONTROL_RD |
+ (len << MV64XXX_I2C_BRIDGE_CONTROL_RX_SIZE_SHIFT);
+ }
+ /*
+ * Transaction with one write and one read message. This is
+ * guaranteed by the mv64xx_i2c_can_offload() checks.
+ */
+ else if (num == 2) {
+ size_t lentx = msgs[0].len - 1;
+ size_t lenrx = msgs[1].len - 1;
+
+ ctrl_reg |=
+ MV64XXX_I2C_BRIDGE_CONTROL_RD |
+ MV64XXX_I2C_BRIDGE_CONTROL_WR |
+ (lentx << MV64XXX_I2C_BRIDGE_CONTROL_TX_SIZE_SHIFT) |
+ (lenrx << MV64XXX_I2C_BRIDGE_CONTROL_RX_SIZE_SHIFT) |
+ MV64XXX_I2C_BRIDGE_CONTROL_REPEATED_START;
+ mv64xxx_i2c_prepare_tx(drv_data);
+ }
+
+ /* Execute transaction */
+ drv_data->block = 1;
+ writel(ctrl_reg, drv_data->reg_base + MV64XXX_I2C_REG_BRIDGE_CONTROL);
+ spin_unlock_irqrestore(&drv_data->lock, flags);
+
+ mv64xxx_i2c_wait_for_completion(drv_data);
+
+ return drv_data->rc;
+}
+
+static bool
+mv64xxx_i2c_valid_offload_sz(struct i2c_msg *msg)
+{
+ return msg->len <= 8 && msg->len >= 1;
+}
+
+static bool
+mv64xxx_i2c_can_offload(struct mv64xxx_i2c_data *drv_data)
+{
+ struct i2c_msg *msgs = drv_data->msgs;
+ int num = drv_data->num_msgs;
+
+ return false;
+
+ if (!drv_data->offload_enabled)
+ return false;
+
+ /*
+ * We can offload a transaction consisting of a single
+ * message, as long as the message has a length between 1 and
+ * 8 bytes.
+ */
+ if (num == 1 && mv64xxx_i2c_valid_offload_sz(msgs))
+ return true;
+
+ /*
+ * We can offload a transaction consisting of two messages, if
+ * the first is a write and a second is a read, and both have
+ * a length between 1 and 8 bytes.
+ */
+ if (num == 2 &&
+ mv64xxx_i2c_valid_offload_sz(msgs) &&
+ mv64xxx_i2c_valid_offload_sz(msgs + 1) &&
+ !(msgs[0].flags & I2C_M_RD) &&
+ msgs[1].flags & I2C_M_RD)
+ return true;
+
+ return false;
+}
+
/*
*****************************************************************************
*
@@ -658,7 +720,11 @@ mv64xxx_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[], int num)
drv_data->msgs = msgs;
drv_data->num_msgs = num;
- rc = mv64xxx_i2c_execute_msg(drv_data, &msgs[0], num == 1);
+ if (mv64xxx_i2c_can_offload(drv_data))
+ rc = mv64xxx_i2c_offload_xfer(drv_data);
+ else
+ rc = mv64xxx_i2c_execute_msg(drv_data, &msgs[0], num == 1);
+
if (rc < 0)
ret = rc;