[PATCH 2/2] i2c: xiic: Add atomic transfer support

Manikanta Guntupalli
2024-10-11T10:47:22Z

Rework the read and write code paths in the driver to support operation
in atomic contexts.

Similar changes have been implemented in other drivers, including:
commit 3a5ee18d2a32 ("i2c: imx: implement master_xfer_atomic callback")
commit 445094c8a9fb ("i2c: exynos5: add support for atomic transfers")
commit ede2299f7101 ("i2c: tegra: Support atomic transfers")
commit fe402bd09049 ("i2c: meson: implement the master_xfer_atomic
callback")

Signed-off-by: Manikanta Guntupalli <manikanta.guntupalli@amd.com>
---
drivers/i2c/busses/i2c-xiic.c | 245 +++++++++++++++++++++++++++++-----
1 file changed, 212 insertions(+), 33 deletions(-)

diff --git a/drivers/i2c/busses/i2c-xiic.c b/drivers/i2c/busses/i2c-xiic.c
index 052bae4fc664..e5e9a4993bd4 100644
--- a/drivers/i2c/busses/i2c-xiic.c
+++ b/drivers/i2c/busses/i2c-xiic.c
@@ -30,6 +30,8 @@
#include <linux/of.h>
#include <linux/clk.h>
#include <linux/pm_runtime.h>
+#include <linux/iopoll.h>
+#include <linux/spinlock.h>

#define DRIVER_NAME "xiic-i2c"
#define DYNAMIC_MODE_READ_BROKEN_BIT BIT(0)
@@ -74,6 +76,9 @@ enum i2c_scl_freq {
* @smbus_block_read: Flag to handle block read
* @input_clk: Input clock to I2C controller
* @i2c_clk: I2C SCL frequency
+ * @atomic: Mode of transfer
+ * @atomic_lock: Lock for atomic transfer mode
+ * @atomic_xfer_state: See STATE_
*/
struct xiic_i2c {
struct device *dev;
@@ -96,6 +101,9 @@ struct xiic_i2c {
bool smbus_block_read;
unsigned long input_clk;
unsigned int i2c_clk;
+ bool atomic;
+ spinlock_t atomic_lock; /* Lock for atomic transfer mode */
+ enum xilinx_i2c_state atomic_xfer_state;
};

struct xiic_version_data {
@@ -224,6 +232,8 @@ static const struct timing_regs timing_reg_values[] = {
#define XIIC_I2C_TIMEOUT (msecs_to_jiffies(1000))
/* timeout waiting for the controller finish transfers */
#define XIIC_XFER_TIMEOUT (msecs_to_jiffies(10000))
+/* timeout waiting for the controller finish transfers in micro seconds */
+#define XIIC_XFER_TIMEOUT_US 10000000

/*
* The following constant is used for the device global interrupt enable
@@ -238,7 +248,7 @@ static const struct timing_regs timing_reg_values[] = {
static int xiic_start_xfer(struct xiic_i2c *i2c, struct i2c_msg *msgs, int num);
static void __xiic_start_xfer(struct xiic_i2c *i2c);

-static int __maybe_unused xiic_i2c_runtime_suspend(struct device *dev)
+static int xiic_i2c_runtime_suspend(struct device *dev)
{
struct xiic_i2c *i2c = dev_get_drvdata(dev);

@@ -247,7 +257,7 @@ static int __maybe_unused xiic_i2c_runtime_suspend(struct device *dev)
return 0;
}

-static int __maybe_unused xiic_i2c_runtime_resume(struct device *dev)
+static int xiic_i2c_runtime_resume(struct device *dev)
{
struct xiic_i2c *i2c = dev_get_drvdata(dev);
int ret;
@@ -397,9 +407,10 @@ static int xiic_setclk(struct xiic_i2c *i2c)
unsigned int index = 0;
u32 reg_val;

- dev_dbg(i2c->adap.dev.parent,
- "%s entry, i2c->input_clk: %ld, i2c->i2c_clk: %d\n",
- __func__, i2c->input_clk, i2c->i2c_clk);
+ if (!i2c->atomic)
+ dev_dbg(i2c->adap.dev.parent,
+ "%s entry, i2c->input_clk: %ld, i2c->i2c_clk: %d\n",
+ __func__, i2c->input_clk, i2c->i2c_clk);

/* If not specified in DT, do not configure in SW. Rely only on Vivado design */
if (!i2c->i2c_clk || !i2c->input_clk)
@@ -490,7 +501,8 @@ static int xiic_reinit(struct xiic_i2c *i2c)
return ret;

/* Enable interrupts */
- xiic_setreg32(i2c, XIIC_DGIER_OFFSET, XIIC_GINTR_ENABLE_MASK);
+ if (!i2c->atomic)
+ xiic_setreg32(i2c, XIIC_DGIER_OFFSET, XIIC_GINTR_ENABLE_MASK);

xiic_irq_clr_en(i2c, XIIC_INTR_ARB_LOST_MASK);

@@ -572,11 +584,12 @@ static void xiic_read_rx(struct xiic_i2c *i2c)

bytes_in_fifo = xiic_getreg8(i2c, XIIC_RFO_REG_OFFSET) + 1;

- dev_dbg(i2c->adap.dev.parent,
- "%s entry, bytes in fifo: %d, rem: %d, SR: 0x%x, CR: 0x%x\n",
- __func__, bytes_in_fifo, xiic_rx_space(i2c),
- xiic_getreg8(i2c, XIIC_SR_REG_OFFSET),
- xiic_getreg8(i2c, XIIC_CR_REG_OFFSET));
+ if (!i2c->atomic)
+ dev_dbg(i2c->adap.dev.parent,
+ "%s entry, bytes in fifo: %d, rem: %d, SR: 0x%x, CR: 0x%x\n",
+ __func__, bytes_in_fifo, xiic_rx_space(i2c),
+ xiic_getreg8(i2c, XIIC_SR_REG_OFFSET),
+ xiic_getreg8(i2c, XIIC_CR_REG_OFFSET));

if (bytes_in_fifo > xiic_rx_space(i2c))
bytes_in_fifo = xiic_rx_space(i2c);
@@ -635,6 +648,26 @@ static void xiic_read_rx(struct xiic_i2c *i2c)
}
}

+static bool xiic_error_check(struct xiic_i2c *i2c)
+{
+ bool status = false;
+ u32 pend, isr, ier;
+
+ isr = xiic_getreg32(i2c, XIIC_IISR_OFFSET);
+ ier = xiic_getreg32(i2c, XIIC_IIER_OFFSET);
+ pend = isr & ier;
+
+ if ((pend & XIIC_INTR_ARB_LOST_MASK) ||
+ ((pend & XIIC_INTR_TX_ERROR_MASK) &&
+ !(pend & XIIC_INTR_RX_FULL_MASK))) {
+ xiic_reinit(i2c);
+ status = true;
+ if (i2c->tx_msg || i2c->rx_msg)
+ i2c->atomic_xfer_state = STATE_ERROR;
+ }
+ return status;
+}
+
static int xiic_tx_fifo_space(struct xiic_i2c *i2c)
{
/* return the actual space left in the FIFO */
@@ -648,8 +681,9 @@ static void xiic_fill_tx_fifo(struct xiic_i2c *i2c)

len = (len > fifo_space) ? fifo_space : len;

- dev_dbg(i2c->adap.dev.parent, "%s entry, len: %d, fifo space: %d\n",
- __func__, len, fifo_space);
+ if (!i2c->atomic)
+ dev_dbg(i2c->adap.dev.parent, "%s entry, len: %d, fifo space: %d\n",
+ __func__, len, fifo_space);

while (len--) {
u16 data = i2c->tx_msg->buf[i2c->tx_pos++];
@@ -672,9 +706,13 @@ static void xiic_fill_tx_fifo(struct xiic_i2c *i2c)
xiic_setreg8(i2c, XIIC_CR_REG_OFFSET, cr &
~XIIC_CR_MSMS_MASK);
}
- dev_dbg(i2c->adap.dev.parent, "%s TX STOP\n", __func__);
+ if (!i2c->atomic)
+ dev_dbg(i2c->adap.dev.parent, "%s TX STOP\n", __func__);
}
xiic_setreg16(i2c, XIIC_DTR_REG_OFFSET, data);
+
+ if (i2c->atomic && xiic_error_check(i2c))
+ return;
}
}

@@ -877,22 +915,55 @@ static int xiic_wait_not_busy(struct xiic_i2c *i2c)
*/
err = xiic_bus_busy(i2c);
while (err && tries--) {
- msleep(1);
+ if (i2c->atomic)
+ udelay(1000);
+ else
+ usleep_range(1000, 1100);
err = xiic_bus_busy(i2c);
}

return err;
}

+static void xiic_recv_atomic(struct xiic_i2c *i2c)
+{
+ while (xiic_rx_space(i2c)) {
+ if (xiic_getreg32(i2c, XIIC_IISR_OFFSET) & XIIC_INTR_RX_FULL_MASK) {
+ if (!i2c->rx_msg) {
+ xiic_clear_rx_fifo(i2c);
+ break;
+ }
+ xiic_read_rx(i2c);
+
+ /* Clear Rx full and Tx error interrupts. */
+ xiic_irq_clr_en(i2c, XIIC_INTR_RX_FULL_MASK |
+ XIIC_INTR_TX_ERROR_MASK);
+ }
+ if (xiic_error_check(i2c))
+ return;
+ }
+
+ i2c->rx_msg = NULL;
+ xiic_irq_clr_en(i2c, XIIC_INTR_TX_ERROR_MASK);
+
+ /* send next message if this wasn't the last. */
+ if (i2c->nmsgs > 1) {
+ i2c->nmsgs--;
+ i2c->tx_msg++;
+ __xiic_start_xfer(i2c);
+ }
+}
+
static void xiic_start_recv(struct xiic_i2c *i2c)
{
u16 rx_watermark;
u8 cr = 0, rfd_set = 0;
struct i2c_msg *msg = i2c->rx_msg = i2c->tx_msg;

- dev_dbg(i2c->adap.dev.parent, "%s entry, ISR: 0x%x, CR: 0x%x\n",
- __func__, xiic_getreg32(i2c, XIIC_IISR_OFFSET),
- xiic_getreg8(i2c, XIIC_CR_REG_OFFSET));
+ if (!i2c->atomic)
+ dev_dbg(i2c->adap.dev.parent, "%s entry, ISR: 0x%x, CR: 0x%x\n",
+ __func__, xiic_getreg32(i2c, XIIC_IISR_OFFSET),
+ xiic_getreg8(i2c, XIIC_CR_REG_OFFSET));

/* Disable Tx interrupts */
xiic_irq_dis(i2c, XIIC_INTR_TX_HALF_MASK | XIIC_INTR_TX_EMPTY_MASK);
@@ -990,9 +1061,10 @@ static void xiic_start_recv(struct xiic_i2c *i2c)
XIIC_CR_MSMS_MASK)
& ~(XIIC_CR_DIR_IS_TX_MASK));
}
- dev_dbg(i2c->adap.dev.parent, "%s end, ISR: 0x%x, CR: 0x%x\n",
- __func__, xiic_getreg32(i2c, XIIC_IISR_OFFSET),
- xiic_getreg8(i2c, XIIC_CR_REG_OFFSET));
+ if (!i2c->atomic)
+ dev_dbg(i2c->adap.dev.parent, "%s end, ISR: 0x%x, CR: 0x%x\n",
+ __func__, xiic_getreg32(i2c, XIIC_IISR_OFFSET),
+ xiic_getreg8(i2c, XIIC_CR_REG_OFFSET));
}

if (i2c->nmsgs == 1)
@@ -1002,10 +1074,57 @@ static void xiic_start_recv(struct xiic_i2c *i2c)
/* the message is tx:ed */
i2c->tx_pos = msg->len;

+ i2c->prev_msg_tx = false;
+
/* Enable interrupts */
- xiic_setreg32(i2c, XIIC_DGIER_OFFSET, XIIC_GINTR_ENABLE_MASK);
+ if (!i2c->atomic)
+ xiic_setreg32(i2c, XIIC_DGIER_OFFSET, XIIC_GINTR_ENABLE_MASK);
+ else
+ xiic_recv_atomic(i2c);
+}

- i2c->prev_msg_tx = false;
+static void xiic_send_rem_atomic(struct xiic_i2c *i2c)
+{
+ if (!i2c->tx_msg)
+ goto send_atomic_out;
+ while (xiic_tx_space(i2c)) {
+ if (xiic_tx_fifo_space(i2c)) {
+ u16 data;
+
+ data = i2c->tx_msg->buf[i2c->tx_pos];
+ i2c->tx_pos++;
+ if (!xiic_tx_space(i2c) && i2c->nmsgs == 1) {
+ /* last message in transfer -> STOP */
+ if (i2c->dynamic) {
+ data |= XIIC_TX_DYN_STOP_MASK;
+ } else {
+ u8 cr;
+ int status;
+
+ /* Wait till FIFO is empty so STOP is sent last */
+ status = xiic_wait_tx_empty(i2c);
+ if (status)
+ return;
+
+ /* Write to CR to stop */
+ cr = xiic_getreg8(i2c, XIIC_CR_REG_OFFSET);
+ xiic_setreg8(i2c, XIIC_CR_REG_OFFSET, cr &
+ ~XIIC_CR_MSMS_MASK);
+ }
+ }
+ xiic_setreg16(i2c, XIIC_DTR_REG_OFFSET, data);
+ }
+ if (xiic_error_check(i2c))
+ return;
+ }
+send_atomic_out:
+ if (i2c->nmsgs > 1) {
+ i2c->nmsgs--;
+ i2c->tx_msg++;
+ __xiic_start_xfer(i2c);
+ } else {
+ xiic_irq_dis(i2c, XIIC_INTR_TX_HALF_MASK);
+ }
}

static void xiic_start_send(struct xiic_i2c *i2c)
@@ -1014,11 +1133,13 @@ static void xiic_start_send(struct xiic_i2c *i2c)
u16 data;
struct i2c_msg *msg = i2c->tx_msg;

- dev_dbg(i2c->adap.dev.parent, "%s entry, msg: %p, len: %d",
- __func__, msg, msg->len);
- dev_dbg(i2c->adap.dev.parent, "%s entry, ISR: 0x%x, CR: 0x%x\n",
- __func__, xiic_getreg32(i2c, XIIC_IISR_OFFSET),
- xiic_getreg8(i2c, XIIC_CR_REG_OFFSET));
+ if (!i2c->atomic) {
+ dev_dbg(i2c->adap.dev.parent, "%s entry, msg: %p, len: %d",
+ __func__, msg, msg->len);
+ dev_dbg(i2c->adap.dev.parent, "%s entry, ISR: 0x%x, CR: 0x%x\n",
+ __func__, xiic_getreg32(i2c, XIIC_IISR_OFFSET),
+ xiic_getreg8(i2c, XIIC_CR_REG_OFFSET));
+ }

if (i2c->dynamic) {
/* write the address */
@@ -1083,19 +1204,27 @@ static void xiic_start_send(struct xiic_i2c *i2c)
XIIC_INTR_TX_ERROR_MASK |
XIIC_INTR_BNB_MASK);
}
+
i2c->prev_msg_tx = true;
+
+ if (i2c->atomic && !i2c->atomic_xfer_state)
+ xiic_send_rem_atomic(i2c);
}

static void __xiic_start_xfer(struct xiic_i2c *i2c)
{
int fifo_space = xiic_tx_fifo_space(i2c);

- dev_dbg(i2c->adap.dev.parent, "%s entry, msg: %p, fifos space: %d\n",
- __func__, i2c->tx_msg, fifo_space);
+ if (!i2c->atomic)
+ dev_dbg(i2c->adap.dev.parent, "%s entry, msg: %p, fifos space: %d\n",
+ __func__, i2c->tx_msg, fifo_space);

if (!i2c->tx_msg)
return;

+ if (i2c->atomic && xiic_error_check(i2c))
+ return;
+
i2c->rx_pos = 0;
i2c->tx_pos = 0;
i2c->state = STATE_START;
@@ -1112,7 +1241,10 @@ static int xiic_start_xfer(struct xiic_i2c *i2c, struct i2c_msg *msgs, int num)
bool broken_read, max_read_len, smbus_blk_read;
int ret, count;

- mutex_lock(&i2c->lock);
+ if (i2c->atomic)
+ spin_lock(&i2c->atomic_lock);
+ else
+ mutex_lock(&i2c->lock);

if (i2c->tx_msg || i2c->rx_msg) {
dev_err(i2c->adap.dev.parent,
@@ -1121,6 +1253,8 @@ static int xiic_start_xfer(struct xiic_i2c *i2c, struct i2c_msg *msgs, int num)
goto out;
}

+ i2c->atomic_xfer_state = STATE_DONE;
+
/* In single master mode bus can only be busy, when in use by this
* driver. If the register indicates bus being busy for some reason we
* should ignore it, since bus will never be released and i2c will be
@@ -1147,7 +1281,9 @@ static int xiic_start_xfer(struct xiic_i2c *i2c, struct i2c_msg *msgs, int num)
i2c->tx_msg = msgs;
i2c->rx_msg = NULL;
i2c->nmsgs = num;
- init_completion(&i2c->completion);
+
+ if (!i2c->atomic)
+ init_completion(&i2c->completion);

/* Decide standard mode or Dynamic mode */
i2c->dynamic = true;
@@ -1182,7 +1318,10 @@ static int xiic_start_xfer(struct xiic_i2c *i2c, struct i2c_msg *msgs, int num)
__xiic_start_xfer(i2c);

out:
- mutex_unlock(&i2c->lock);
+ if (i2c->atomic)
+ spin_unlock(&i2c->atomic_lock);
+ else
+ mutex_unlock(&i2c->lock);

return ret;
}
@@ -1221,6 +1360,44 @@ static int xiic_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num)
return err;
}

+static int xiic_xfer_atomic(struct i2c_adapter *adap, struct i2c_msg *msgs, int num)
+{
+ struct xiic_i2c *i2c = i2c_get_adapdata(adap);
+ u32 status_reg;
+ int err;
+
+ err = xiic_i2c_runtime_resume(i2c->dev);
+ if (err)
+ return err;
+
+ i2c->atomic = true;
+ err = xiic_start_xfer(i2c, msgs, num);
+ if (err < 0)
+ return err;
+
+ err = readl_poll_timeout_atomic(i2c->base + XIIC_SR_REG_OFFSET,
+ status_reg, !(status_reg & XIIC_SR_BUS_BUSY_MASK),
+ 1, XIIC_XFER_TIMEOUT_US);
+
+ if (err) /* Timeout */
+ err = -ETIMEDOUT;
+
+ spin_lock(&i2c->atomic_lock);
+ if (err || i2c->state) {
+ i2c->tx_msg = NULL;
+ i2c->rx_msg = NULL;
+ i2c->nmsgs = 0;
+ }
+
+ err = (i2c->atomic_xfer_state == STATE_DONE) ? num : -EIO;
+ spin_unlock(&i2c->atomic_lock);
+
+ i2c->atomic = false;
+ xiic_i2c_runtime_suspend(i2c->dev);
+
+ return err;
+}
+
static u32 xiic_func(struct i2c_adapter *adap)
{
return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL | I2C_FUNC_SMBUS_BLOCK_DATA;
@@ -1228,6 +1405,7 @@ static u32 xiic_func(struct i2c_adapter *adap)

static const struct i2c_algorithm xiic_algorithm = {
.master_xfer = xiic_xfer,
+ .master_xfer_atomic = xiic_xfer_atomic,
.functionality = xiic_func,
};

@@ -1291,6 +1469,7 @@ static int xiic_i2c_probe(struct platform_device *pdev)
DRIVER_NAME " %s", pdev->name);

mutex_init(&i2c->lock);
+ spin_lock_init(&i2c->atomic_lock);

i2c->clk = devm_clk_get_enabled(&pdev->dev, NULL);
if (IS_ERR(i2c->clk))
--
2.34.1