[PATCH v2 3/6] i2c: i2c-stm32f7: Add initial SMBus protocols support

Pierre-Yves MORDRET
2018-03-21T16:48:57Z

This patch adds SMBus support for I2C controller embedded in STM32F7 Soc.
All SMBus protocols are implemented except SMBus-specific protocols.

Signed-off-by: M'boumba Cedric Madianga <cedric.madianga@gmail.com>
Signed-off-by: Pierre-Yves MORDRET <pierre-yves.mordret@st.com>
---
Version history:
v1:
* Initial
v2:
* fix Kbuild test robot issue (Unneeded semicolon)
---

fixup! i2c: i2c-stm32f7: Add initial SMBus protocols support
---
drivers/i2c/busses/i2c-stm32f7.c | 377 ++++++++++++++++++++++++++++++++++++++-
1 file changed, 368 insertions(+), 9 deletions(-)

diff --git a/drivers/i2c/busses/i2c-stm32f7.c b/drivers/i2c/busses/i2c-stm32f7.c
index 9bf676e..0b81b5d 100644
--- a/drivers/i2c/busses/i2c-stm32f7.c
+++ b/drivers/i2c/busses/i2c-stm32f7.c
@@ -37,6 +37,7 @@
#define STM32F7_I2C_CR2 0x04
#define STM32F7_I2C_OAR1 0x08
#define STM32F7_I2C_OAR2 0x0C
+#define STM32F7_I2C_PECR 0x20
#define STM32F7_I2C_TIMINGR 0x10
#define STM32F7_I2C_ISR 0x18
#define STM32F7_I2C_ICR 0x1C
@@ -44,6 +45,7 @@
#define STM32F7_I2C_TXDR 0x28

/* STM32F7 I2C control 1 */
+#define STM32F7_I2C_CR1_PECEN BIT(23)
#define STM32F7_I2C_CR1_SBC BIT(16)
#define STM32F7_I2C_CR1_ANFOFF BIT(12)
#define STM32F7_I2C_CR1_ERRIE BIT(7)
@@ -67,6 +69,7 @@
| STM32F7_I2C_CR1_TXIE)

/* STM32F7 I2C control 2 */
+#define STM32F7_I2C_CR2_PECBYTE BIT(26)
#define STM32F7_I2C_CR2_RELOAD BIT(24)
#define STM32F7_I2C_CR2_NBYTES_MASK GENMASK(23, 16)
#define STM32F7_I2C_CR2_NBYTES(n) (((n) & 0xff) << 16)
@@ -111,6 +114,7 @@
(((n) & STM32F7_I2C_ISR_ADDCODE_MASK) >> 17)
#define STM32F7_I2C_ISR_DIR BIT(16)
#define STM32F7_I2C_ISR_BUSY BIT(15)
+#define STM32F7_I2C_ISR_PECERR BIT(11)
#define STM32F7_I2C_ISR_ARLO BIT(9)
#define STM32F7_I2C_ISR_BERR BIT(8)
#define STM32F7_I2C_ISR_TCR BIT(7)
@@ -123,6 +127,7 @@
#define STM32F7_I2C_ISR_TXE BIT(0)

/* STM32F7 I2C Interrupt Clear */
+#define STM32F7_I2C_ICR_PECCF BIT(11)
#define STM32F7_I2C_ICR_ARLOCF BIT(9)
#define STM32F7_I2C_ICR_BERRCF BIT(8)
#define STM32F7_I2C_ICR_STOPCF BIT(5)
@@ -225,6 +230,14 @@ struct stm32f7_i2c_timings {
* @buf: data buffer
* @result: result of the transfer
* @stop: last I2C msg to be sent, i.e. STOP to be generated
+ * @smbus: boolean to know if the I2C IP is used in SMBus mode
+ * @size: type of SMBus protocol
+ * @read_write: direction of SMBus protocol
+ * SMBus block read and SMBus block write - block read process call protocols
+ * @smbus_buff: buffer to be used for SMBus protocol transfer. It will
+ * contain a maximum of 32 bytes of data + byte command + byte count + PEC
+ * This buffer has to be 32-bit aligned to be compliant with memory address
+ * register in DMA mode.
*/
struct stm32f7_i2c_msg {
u16 addr;
@@ -232,6 +245,10 @@ struct stm32f7_i2c_msg {
u8 *buf;
int result;
bool stop;
+ bool smbus;
+ int size;
+ char read_write;
+ u8 smbus_buf[I2C_SMBUS_BLOCK_MAX + 3] __aligned(4);
};

/**
@@ -649,6 +666,29 @@ static void stm32f7_i2c_reload(struct stm32f7_i2c_dev *i2c_dev)
writel_relaxed(cr2, i2c_dev->base + STM32F7_I2C_CR2);
}

+static void stm32f7_i2c_smbus_reload(struct stm32f7_i2c_dev *i2c_dev)
+{
+ struct stm32f7_i2c_msg *f7_msg = &i2c_dev->f7_msg;
+ u32 cr2;
+ u8 *val;
+
+ /*
+ * For I2C_SMBUS_BLOCK_DATA && I2C_SMBUS_BLOCK_PROC_CALL, the first
+ * data received inform us how many data will follow.
+ */
+ stm32f7_i2c_read_rx_data(i2c_dev);
+
+ /*
+ * Update NBYTES with the value read to continue the transfer
+ */
+ val = f7_msg->buf - sizeof(u8);
+ f7_msg->count = *val;
+ cr2 = readl_relaxed(i2c_dev->base + STM32F7_I2C_CR2);
+ cr2 &= ~(STM32F7_I2C_CR2_NBYTES_MASK | STM32F7_I2C_CR2_RELOAD);
+ cr2 |= STM32F7_I2C_CR2_NBYTES(f7_msg->count);
+ writel_relaxed(cr2, i2c_dev->base + STM32F7_I2C_CR2);
+}
+
static int stm32f7_i2c_wait_free_bus(struct stm32f7_i2c_dev *i2c_dev)
{
u32 status;
@@ -732,6 +772,237 @@ static void stm32f7_i2c_xfer_msg(struct stm32f7_i2c_dev *i2c_dev,
writel_relaxed(cr2, base + STM32F7_I2C_CR2);
}

+static int stm32f7_i2c_smbus_xfer_msg(struct stm32f7_i2c_dev *i2c_dev,
+ unsigned short flags, u8 command,
+ union i2c_smbus_data *data)
+{
+ struct stm32f7_i2c_msg *f7_msg = &i2c_dev->f7_msg;
+ struct device *dev = i2c_dev->dev;
+ void __iomem *base = i2c_dev->base;
+ u32 cr1, cr2;
+ int i;
+
+ f7_msg->result = 0;
+ reinit_completion(&i2c_dev->complete);
+
+ cr2 = readl_relaxed(base + STM32F7_I2C_CR2);
+ cr1 = readl_relaxed(base + STM32F7_I2C_CR1);
+
+ /* Set transfer direction */
+ cr2 &= ~STM32F7_I2C_CR2_RD_WRN;
+ if (f7_msg->read_write)
+ cr2 |= STM32F7_I2C_CR2_RD_WRN;
+
+ /* Set slave address */
+ cr2 &= ~(STM32F7_I2C_CR2_ADD10 | STM32F7_I2C_CR2_SADD7_MASK);
+ cr2 |= STM32F7_I2C_CR2_SADD7(f7_msg->addr);
+
+ f7_msg->smbus_buf[0] = command;
+ switch (f7_msg->size) {
+ case I2C_SMBUS_QUICK:
+ f7_msg->stop = true;
+ f7_msg->count = 0;
+ break;
+ case I2C_SMBUS_BYTE:
+ f7_msg->stop = true;
+ f7_msg->count = 1;
+ break;
+ case I2C_SMBUS_BYTE_DATA:
+ if (f7_msg->read_write) {
+ f7_msg->stop = false;
+ f7_msg->count = 1;
+ cr2 &= ~STM32F7_I2C_CR2_RD_WRN;
+ } else {
+ f7_msg->stop = true;
+ f7_msg->count = 2;
+ f7_msg->smbus_buf[1] = data->byte;
+ }
+ break;
+ case I2C_SMBUS_WORD_DATA:
+ if (f7_msg->read_write) {
+ f7_msg->stop = false;
+ f7_msg->count = 1;
+ cr2 &= ~STM32F7_I2C_CR2_RD_WRN;
+ } else {
+ f7_msg->stop = true;
+ f7_msg->count = 3;
+ f7_msg->smbus_buf[1] = data->word & 0xff;
+ f7_msg->smbus_buf[2] = data->word >> 8;
+ }
+ break;
+ case I2C_SMBUS_BLOCK_DATA:
+ if (f7_msg->read_write) {
+ f7_msg->stop = false;
+ f7_msg->count = 1;
+ cr2 &= ~STM32F7_I2C_CR2_RD_WRN;
+ } else {
+ f7_msg->stop = true;
+ if (data->block[0] > I2C_SMBUS_BLOCK_MAX ||
+ !data->block[0]) {
+ dev_err(dev, "Invalid block write size %d\n",
+ data->block[0]);
+ return -EINVAL;
+ }
+ f7_msg->count = data->block[0] + 2;
+ for (i = 1; i < f7_msg->count; i++)
+ f7_msg->smbus_buf[i] = data->block[i - 1];
+ }
+ break;
+ case I2C_SMBUS_PROC_CALL:
+ f7_msg->stop = false;
+ f7_msg->count = 3;
+ f7_msg->smbus_buf[1] = data->word & 0xff;
+ f7_msg->smbus_buf[2] = data->word >> 8;
+ cr2 &= ~STM32F7_I2C_CR2_RD_WRN;
+ f7_msg->read_write = I2C_SMBUS_READ;
+ break;
+ case I2C_SMBUS_BLOCK_PROC_CALL:
+ f7_msg->stop = false;
+ if (data->block[0] > I2C_SMBUS_BLOCK_MAX - 1) {
+ dev_err(dev, "Invalid block write size %d\n",
+ data->block[0]);
+ return -EINVAL;
+ }
+ f7_msg->count = data->block[0] + 2;
+ for (i = 1; i < f7_msg->count; i++)
+ f7_msg->smbus_buf[i] = data->block[i - 1];
+ cr2 &= ~STM32F7_I2C_CR2_RD_WRN;
+ f7_msg->read_write = I2C_SMBUS_READ;
+ break;
+ default:
+ dev_err(dev, "Unsupported smbus protocol %d\n", f7_msg->size);
+ return -EOPNOTSUPP;
+ }
+
+ f7_msg->buf = f7_msg->smbus_buf;
+
+ /* Configure PEC */
+ if ((flags & I2C_CLIENT_PEC) && f7_msg->size != I2C_SMBUS_QUICK) {
+ cr1 |= STM32F7_I2C_CR1_PECEN;
+ cr2 |= STM32F7_I2C_CR2_PECBYTE;
+ if (!f7_msg->read_write)
+ f7_msg->count++;
+ } else {
+ cr1 &= ~STM32F7_I2C_CR1_PECEN;
+ cr2 &= ~STM32F7_I2C_CR2_PECBYTE;
+ }
+
+ /* Set number of bytes to be transferred */
+ cr2 &= ~(STM32F7_I2C_CR2_NBYTES_MASK | STM32F7_I2C_CR2_RELOAD);
+ cr2 |= STM32F7_I2C_CR2_NBYTES(f7_msg->count);
+
+ /* Enable NACK, STOP, error and transfer complete interrupts */
+ cr1 |= STM32F7_I2C_CR1_ERRIE | STM32F7_I2C_CR1_TCIE |
+ STM32F7_I2C_CR1_STOPIE | STM32F7_I2C_CR1_NACKIE;
+
+ /* Clear TX/RX interrupt */
+ cr1 &= ~(STM32F7_I2C_CR1_RXIE | STM32F7_I2C_CR1_TXIE);
+
+ /* Enable RX/TX interrupt according to msg direction */
+ if (cr2 & STM32F7_I2C_CR2_RD_WRN)
+ cr1 |= STM32F7_I2C_CR1_RXIE;
+ else
+ cr1 |= STM32F7_I2C_CR1_TXIE;
+
+ /* Set Start bit */
+ cr2 |= STM32F7_I2C_CR2_START;
+
+ i2c_dev->master_mode = true;
+
+ /* Write configurations registers */
+ writel_relaxed(cr1, base + STM32F7_I2C_CR1);
+ writel_relaxed(cr2, base + STM32F7_I2C_CR2);
+
+ return 0;
+}
+
+static void stm32f7_i2c_smbus_rep_start(struct stm32f7_i2c_dev *i2c_dev)
+{
+ struct stm32f7_i2c_msg *f7_msg = &i2c_dev->f7_msg;
+ void __iomem *base = i2c_dev->base;
+ u32 cr1, cr2;
+
+ cr2 = readl_relaxed(base + STM32F7_I2C_CR2);
+ cr1 = readl_relaxed(base + STM32F7_I2C_CR1);
+
+ /* Set transfer direction */
+ cr2 |= STM32F7_I2C_CR2_RD_WRN;
+
+ switch (f7_msg->size) {
+ case I2C_SMBUS_BYTE_DATA:
+ f7_msg->count = 1;
+ break;
+ case I2C_SMBUS_WORD_DATA:
+ case I2C_SMBUS_PROC_CALL:
+ f7_msg->count = 2;
+ break;
+ case I2C_SMBUS_BLOCK_DATA:
+ case I2C_SMBUS_BLOCK_PROC_CALL:
+ f7_msg->count = 1;
+ cr2 |= STM32F7_I2C_CR2_RELOAD;
+ break;
+ }
+
+ f7_msg->buf = f7_msg->smbus_buf;
+ f7_msg->stop = true;
+
+ /* Add one byte for PEC if needed */
+ if (cr1 & STM32F7_I2C_CR1_PECEN)
+ f7_msg->count++;
+
+ /* Set number of bytes to be transferred */
+ cr2 &= ~(STM32F7_I2C_CR2_NBYTES_MASK);
+ cr2 |= STM32F7_I2C_CR2_NBYTES(f7_msg->count);
+
+ /*
+ * Configure RX/TX interrupt:
+ */
+ cr1 &= ~(STM32F7_I2C_CR1_RXIE | STM32F7_I2C_CR1_TXIE);
+ cr1 |= STM32F7_I2C_CR1_RXIE;
+
+ /* Configure Repeated Start */
+ cr2 |= STM32F7_I2C_CR2_START;
+
+ /* Write configurations registers */
+ writel_relaxed(cr1, base + STM32F7_I2C_CR1);
+ writel_relaxed(cr2, base + STM32F7_I2C_CR2);
+}
+
+static int stm32f7_i2c_smbus_check_pec(struct stm32f7_i2c_dev *i2c_dev)
+{
+ struct stm32f7_i2c_msg *f7_msg = &i2c_dev->f7_msg;
+ u8 count, internal_pec, received_pec;
+
+ internal_pec = readl_relaxed(i2c_dev->base + STM32F7_I2C_PECR);
+
+ switch (f7_msg->size) {
+ case I2C_SMBUS_BYTE:
+ case I2C_SMBUS_BYTE_DATA:
+ received_pec = f7_msg->smbus_buf[1];
+ break;
+ case I2C_SMBUS_WORD_DATA:
+ case I2C_SMBUS_PROC_CALL:
+ received_pec = f7_msg->smbus_buf[2];
+ break;
+ case I2C_SMBUS_BLOCK_DATA:
+ case I2C_SMBUS_BLOCK_PROC_CALL:
+ count = f7_msg->smbus_buf[0];
+ received_pec = f7_msg->smbus_buf[count];
+ break;
+ default:
+ dev_err(i2c_dev->dev, "Unsupported smbus protocol for PEC\n");
+ return -EINVAL;
+ }
+
+ if (internal_pec != received_pec) {
+ dev_err(i2c_dev->dev, "Bad PEC 0x%02x vs. 0x%02x\n",
+ internal_pec, received_pec);
+ return -EBADMSG;
+ }
+
+ return 0;
+}
+
static bool stm32f7_i2c_is_addr_match(struct i2c_client *slave, u32 addcode)
{
u32 addr;
@@ -1023,6 +1294,8 @@ static irqreturn_t stm32f7_i2c_isr_event(int irq, void *data)
if (f7_msg->stop) {
mask = STM32F7_I2C_CR2_STOP;
stm32f7_i2c_set_bits(base + STM32F7_I2C_CR2, mask);
+ } else if (f7_msg->smbus) {
+ stm32f7_i2c_smbus_rep_start(i2c_dev);
} else {
i2c_dev->msg_id++;
i2c_dev->msg++;
@@ -1030,13 +1303,12 @@ static irqreturn_t stm32f7_i2c_isr_event(int irq, void *data)
}
}

- /*
- * Transfer Complete Reload: 255 data bytes have been transferred
- * We have to prepare the I2C controller to transfer the remaining
- * data.
- */
- if (status & STM32F7_I2C_ISR_TCR)
- stm32f7_i2c_reload(i2c_dev);
+ if (status & STM32F7_I2C_ISR_TCR) {
+ if (f7_msg->smbus)
+ stm32f7_i2c_smbus_reload(i2c_dev);
+ else
+ stm32f7_i2c_reload(i2c_dev);
+ }

return IRQ_HANDLED;
}
@@ -1065,6 +1337,12 @@ static irqreturn_t stm32f7_i2c_isr_error(int irq, void *data)
f7_msg->result = -EAGAIN;
}

+ if (status & STM32F7_I2C_ISR_PECERR) {
+ dev_err(dev, "<%s>: PEC error in reception\n", __func__);
+ writel_relaxed(STM32F7_I2C_ICR_PECCF, base + STM32F7_I2C_ICR);
+ f7_msg->result = -EINVAL;
+ }
+
/* Disable interrupts */
if (stm32f7_i2c_is_slave_registered(i2c_dev))
mask = STM32F7_I2C_XFER_IRQ_MASK;
@@ -1089,6 +1367,7 @@ static int stm32f7_i2c_xfer(struct i2c_adapter *i2c_adap,
i2c_dev->msg = msgs;
i2c_dev->msg_num = num;
i2c_dev->msg_id = 0;
+ f7_msg->smbus = false;

ret = clk_enable(i2c_dev->clk);
if (ret) {
@@ -1118,6 +1397,82 @@ static int stm32f7_i2c_xfer(struct i2c_adapter *i2c_adap,
return (ret < 0) ? ret : num;
}

+static int stm32f7_i2c_smbus_xfer(struct i2c_adapter *adapter, u16 addr,
+ unsigned short flags, char read_write,
+ u8 command, int size,
+ union i2c_smbus_data *data)
+{
+ struct stm32f7_i2c_dev *i2c_dev = i2c_get_adapdata(adapter);
+ struct stm32f7_i2c_msg *f7_msg = &i2c_dev->f7_msg;
+ struct device *dev = i2c_dev->dev;
+ unsigned long timeout;
+ int i, ret;
+
+ f7_msg->addr = addr;
+ f7_msg->size = size;
+ f7_msg->read_write = read_write;
+ f7_msg->smbus = true;
+
+ ret = clk_enable(i2c_dev->clk);
+ if (ret) {
+ dev_err(i2c_dev->dev, "Failed to enable clock\n");
+ return ret;
+ }
+
+ ret = stm32f7_i2c_wait_free_bus(i2c_dev);
+ if (ret)
+ goto clk_free;
+
+ ret = stm32f7_i2c_smbus_xfer_msg(i2c_dev, flags, command, data);
+ if (ret)
+ goto clk_free;
+
+ timeout = wait_for_completion_timeout(&i2c_dev->complete,
+ i2c_dev->adap.timeout);
+ ret = f7_msg->result;
+ if (ret)
+ goto clk_free;
+
+ if (!timeout) {
+ dev_dbg(dev, "Access to slave 0x%x timed out\n", f7_msg->addr);
+ ret = -ETIMEDOUT;
+ goto clk_free;
+ }
+
+ /* Check PEC */
+ if ((flags & I2C_CLIENT_PEC) && size != I2C_SMBUS_QUICK && read_write) {
+ ret = stm32f7_i2c_smbus_check_pec(i2c_dev);
+ if (ret)
+ goto clk_free;
+ }
+
+ if (read_write && size != I2C_SMBUS_QUICK) {
+ switch (size) {
+ case I2C_SMBUS_BYTE:
+ case I2C_SMBUS_BYTE_DATA:
+ data->byte = f7_msg->smbus_buf[0];
+ break;
+ case I2C_SMBUS_WORD_DATA:
+ case I2C_SMBUS_PROC_CALL:
+ data->word = f7_msg->smbus_buf[0] |
+ (f7_msg->smbus_buf[1] << 8);
+ break;
+ case I2C_SMBUS_BLOCK_DATA:
+ case I2C_SMBUS_BLOCK_PROC_CALL:
+ for (i = 0; i <= f7_msg->smbus_buf[0]; i++)
+ data->block[i] = f7_msg->smbus_buf[i];
+ break;
+ default:
+ dev_err(dev, "Unsupported smbus transaction\n");
+ ret = -EINVAL;
+ }
+ }
+
+clk_free:
+ clk_disable(i2c_dev->clk);
+ return ret;
+}
+
static int stm32f7_i2c_reg_slave(struct i2c_client *slave)
{
struct stm32f7_i2c_dev *i2c_dev = i2c_get_adapdata(slave->adapter);
@@ -1229,12 +1584,16 @@ static int stm32f7_i2c_unreg_slave(struct i2c_client *slave)

static u32 stm32f7_i2c_func(struct i2c_adapter *adap)
{
- return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL | I2C_FUNC_10BIT_ADDR |
- I2C_FUNC_SLAVE;
+ return I2C_FUNC_I2C | I2C_FUNC_10BIT_ADDR | I2C_FUNC_SLAVE |
+ I2C_FUNC_SMBUS_QUICK | I2C_FUNC_SMBUS_BYTE |
+ I2C_FUNC_SMBUS_BYTE_DATA | I2C_FUNC_SMBUS_WORD_DATA |
+ I2C_FUNC_SMBUS_BLOCK_DATA | I2C_FUNC_SMBUS_BLOCK_PROC_CALL |
+ I2C_FUNC_SMBUS_PROC_CALL | I2C_FUNC_SMBUS_PEC;
}

static struct i2c_algorithm stm32f7_i2c_algo = {
.master_xfer = stm32f7_i2c_xfer,
+ .smbus_xfer = stm32f7_i2c_smbus_xfer,
.functionality = stm32f7_i2c_func,
.reg_slave = stm32f7_i2c_reg_slave,
.unreg_slave = stm32f7_i2c_unreg_slave,
--
2.7.4