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commit 379dd1c5e0efd4860496ca6347005537498aa9e3 Author: Matteo Golin <[email protected]> AuthorDate: Sat Jun 20 12:53:50 2026 -0400 bcm2711/i2c: Support I2C_M_NOSTOP/I2C_M_NOSTART properly This commit adds support for I2C transfers spread across multiple messages using the I2C_M_NOSTOP/I2C_M_NOSTART. The approach greedily merges as many sequential I2C messages together as possible and considers them as a single transfer. Signed-off-by: Matteo Golin <[email protected]> --- arch/arm64/src/bcm2711/bcm2711_i2c.c | 245 +++++++++++++++++++++++++---------- 1 file changed, 175 insertions(+), 70 deletions(-) diff --git a/arch/arm64/src/bcm2711/bcm2711_i2c.c b/arch/arm64/src/bcm2711/bcm2711_i2c.c index 67208f8d588..ab9fb9d81bb 100644 --- a/arch/arm64/src/bcm2711/bcm2711_i2c.c +++ b/arch/arm64/src/bcm2711/bcm2711_i2c.c @@ -51,8 +51,6 @@ #include "chip.h" #include "hardware/bcm2711_bsc.h" -#if defined(CONFIG_BCM2711_I2C) - /**************************************************************************** * Pre-processor Definitions ****************************************************************************/ @@ -210,13 +208,13 @@ static int bcm2711_i2c_interrupted(struct bcm2711_i2cdev_s *priv); static void bcm2711_i2c_disable(struct bcm2711_i2cdev_s *priv); static void bcm2711_i2c_enable(struct bcm2711_i2cdev_s *priv); static size_t bcm2711_i2c_drainrxfifo(struct bcm2711_i2cdev_s *priv, - FAR uint8_t *buf, size_t n); + uint8_t *buf, size_t n); static size_t bcm2711_i2c_filltxfifo(struct bcm2711_i2cdev_s *priv, - FAR uint8_t *buf, size_t n); -static int bcm2711_i2c_send(struct bcm2711_i2cdev_s *priv, FAR void *buf, - size_t n); -static int bcm2711_i2c_receive(struct bcm2711_i2cdev_s *priv, FAR void *buf, - size_t n); + uint8_t *buf, size_t n); +static int bcm2711_i2c_send(struct bcm2711_i2cdev_s *priv, + struct i2c_msg_s *msgs, size_t n); +static int bcm2711_i2c_receive(struct bcm2711_i2cdev_s *priv, + struct i2c_msg_s *msgs, size_t n); static int bcm2711_i2c_secondary_handler(struct bcm2711_i2cdev_s *priv); static int bcm2711_i2c_transfer(struct i2c_master_s *dev, @@ -389,6 +387,77 @@ static struct bcm2711_i2cdev_s *g_i2c_devices[BCM_BSCS_NUM] = * Private Functions ****************************************************************************/ +/**************************************************************************** + * Name: merge_messages + * + * Description: + * The BCM2711 I2C interface does not natively support I2C_M_NOSTART and + * I2C_M_NOSTOP. However, the NuttX I2C driver requires that a message with + * the I2C_M_NOSTOP flag followed by a message with I2C_M_NOSTART should be + * sent as one, homogeneous message. + * + * This function greedily merges as many sequential I2C messages as + * possible that have these flags. This way, the I2C messages will be sent + * as one larger I2C message via the BCM2711. + * + * For two messages to be merged, they must: + * - Both have the same message type (READ/WRITE) + * - The first message must have the NOSTOP flag + * - The second message must have the NOSTART flag + * + * If we have three READ messages with the following flags: + * 1) NOSTOP + * 2) NOSTOP | NOSTART + * 3) NOSTART + * + * They will be merged as one message, with the size returned being their + * combined sizes. + * + * Input Parameters: + * msgs - A list of messages to try to merge, starting from the first + * message + * count - The number of messages in `msgs` (NOTE: assumed >= 1) + * + * Return Value: + * The total length (in bytes) of the full message (composed of + * fragments) starting from the first message component in `msg`. + * + ****************************************************************************/ + +static size_t merge_messages(struct i2c_msg_s *msgs, int count) +{ + const uint16_t type = msgs[0].flags & I2C_M_READ; + const uint16_t addr = msgs[0].addr; + const uint32_t freq = msgs[0].frequency; + size_t combined_size = msgs[0].length; + + for (int i = 1; i < count; i++) + { + /* Check that the message has the same core attributes or break */ + + if ((msgs[i].flags & I2C_M_READ) != type && msgs[i].addr != addr && + msgs[i].frequency != freq) + { + break; + } + + /* This message has the same core attributes as our merge. If it is + * NOSTART and the previous message was NOSTOP, add its length. + */ + + if (msgs[i].flags & I2C_M_NOSTART && msgs[i - 1].flags & I2C_M_NOSTOP) + { + combined_size += msgs[i].length; + } + else + { + break; /* We've reached the end of the merge */ + } + } + + return combined_size; +} + /**************************************************************************** * Name: bcm2711_i2c_clearfifos * @@ -559,7 +628,7 @@ static void bcm2711_i2c_enable(struct bcm2711_i2cdev_s *priv) ****************************************************************************/ static size_t bcm2711_i2c_drainrxfifo(struct bcm2711_i2cdev_s *priv, - FAR uint8_t *buf, size_t n) + uint8_t *buf, size_t n) { uint8_t to_read = n < FIFO_DEPTH ? n : FIFO_DEPTH; uint8_t i = 0; @@ -587,16 +656,17 @@ static size_t bcm2711_i2c_drainrxfifo(struct bcm2711_i2cdev_s *priv, * * Input Parameters: * dev - The I2C interface to receive on. - * buf - The buffer to receive into - * n - The buffer size in bytes - * stop - Whether to send a stop condition at the end of the transfer. + * buf - The I2C messages list + * n - The total transfer size in bytes ****************************************************************************/ -static int bcm2711_i2c_receive(struct bcm2711_i2cdev_s *priv, FAR void *buf, - size_t n) +static int bcm2711_i2c_receive(struct bcm2711_i2cdev_s *priv, + struct i2c_msg_s *msgs, size_t n) { - size_t remaining = n; + size_t total_remaining = n; size_t bread; + size_t msg_remaining = msgs->length; + void *buf = msgs->buffer; int ret = 0; /* Start transfer. */ @@ -607,7 +677,7 @@ static int bcm2711_i2c_receive(struct bcm2711_i2cdev_s *priv, FAR void *buf, * indicated as done. */ - while (remaining > 0 || !priv->done) + while (total_remaining > 0 || !priv->done) { /* Wait here for interrupt handler to signal that RX FIFO has data * (RXR). We can then continue reading. @@ -625,23 +695,38 @@ static int bcm2711_i2c_receive(struct bcm2711_i2cdev_s *priv, FAR void *buf, /* Check if we are done and there's no data left to read. */ - if (priv->done && remaining == 0) + if (priv->done && total_remaining == 0) { break; /* Leave loop and return */ } - /* The remaining message length is the current remainder minus how far - * into the message we are. We also move forward the buffer pointer by - * how many bytes were just read so it starts at the correct location - * next iteration. - * - * We still have to read this if we received the "DONE" indicator but - * have the tail-end of the data in the RX FIFO. + /* Drain as much as possible from the FIFO into the respective messages */ - bread = bcm2711_i2c_drainrxfifo(priv, buf, remaining); - remaining -= bread; - buf += bread; + do + { + if (msg_remaining == 0) + { + msgs++; + msg_remaining = msgs->length; + buf = msgs->buffer; + } + + /* The remaining message length is the current remainder minus how + * far into the message we are. We also move forward the buffer + * pointer by how many bytes were just read so it starts at the + * correct location next iteration. + * + * We still have to read this if we received the "DONE" indicator + * but have the tail-end of the data in the RX FIFO. + */ + + bread = bcm2711_i2c_drainrxfifo(priv, buf, msg_remaining); + msg_remaining -= bread; + total_remaining -= bread; + buf += bread; + } + while (msg_remaining == 0 && total_remaining > 0); } priv->done = false; /* Reset done indicator */ @@ -664,7 +749,7 @@ static int bcm2711_i2c_receive(struct bcm2711_i2cdev_s *priv, FAR void *buf, ****************************************************************************/ static size_t bcm2711_i2c_filltxfifo(struct bcm2711_i2cdev_s *priv, - FAR uint8_t *buf, size_t n) + uint8_t *buf, size_t n) { uint8_t to_send = n < FIFO_DEPTH ? n : FIFO_DEPTH; uint8_t i = 0; @@ -691,30 +776,67 @@ static size_t bcm2711_i2c_filltxfifo(struct bcm2711_i2cdev_s *priv, * * Input Parameters: * dev - The I2C interface to send on. - * buf - The buffer to send data from. - * n - The size of the buffer in bytes. - * stop - Whether to send a stop condition at the end of the transfer. + * msgs - The I2C messages list + * n - The total transfer size in bytes ****************************************************************************/ -static int bcm2711_i2c_send(struct bcm2711_i2cdev_s *priv, FAR void *buf, - size_t n) +static int bcm2711_i2c_send(struct bcm2711_i2cdev_s *priv, + struct i2c_msg_s *msgs, size_t n) { - size_t remaining = n; + size_t total_remaining = n; + size_t msg_remaining; size_t bwrote; + void *buf; int ret = OK; - DEBUGASSERT(buf != NULL || (buf == NULL && n == 0)); + DEBUGASSERT(msgs != NULL || (msgs == NULL && n == 0)); + + /* Populate vars with first message information */ - while (remaining > 0 || !priv->done) + msg_remaining = msgs->length; + buf = msgs->buffer; + + while (total_remaining > 0 || !priv->done) { - /* Write data to FIFO. The remaining message length is the total - * remaining before, minus how far into the message we are. The `buf` - * pointer is incremented to point to data that hasn't been sent yet. + /* Fill the TX FIFO as much as possible across all message components. + * + * This always executes for the first message. + * + * On subsequent messages, we continue to fill the FIFO with their data + * until we run out of space in the FIFO or data to send. + * + * Then, we start the transfer. If we need to send more data, after + * receiving the TXW interrupt we return here to complete the same + * process of maximally filling the FIFO. Otherwise, the transfer is + * done and we exit. */ - bwrote = bcm2711_i2c_filltxfifo(priv, buf, remaining); - remaining -= bwrote; - buf += bwrote; + do + { + /* Acquire the length and buffer of the next message if this one is + * done. + */ + + if (msg_remaining == 0) + { + msgs++; + msg_remaining = msgs->length; + buf = msgs->buffer; + } + + /* Write data to FIFO. The remaining message length is the total + * remaining before, minus how far into the message we are. The + * `buf` pointer is incremented to point to data that hasn't been + * sent yet. We also increment the `total_remaining` size of the + * overall transfer (could be multiple messages). + */ + + bwrote = bcm2711_i2c_filltxfifo(priv, buf, msg_remaining); + msg_remaining -= bwrote; + total_remaining -= bwrote; + buf += bwrote; + } + while (msg_remaining == 0 && total_remaining > 0); /* Start the transfer if it's not running already */ @@ -756,7 +878,7 @@ static int bcm2711_i2c_send(struct bcm2711_i2cdev_s *priv, FAR void *buf, * failure. */ - DEBUGASSERT(remaining == 0); + DEBUGASSERT(total_remaining == 0); break; } } @@ -783,7 +905,7 @@ static int bcm2711_i2c_transfer(struct i2c_master_s *dev, struct bcm2711_i2cdev_s *priv = (struct bcm2711_i2cdev_s *)dev; int i; int ret; - bool stop = true; + size_t transfer_size; DEBUGASSERT(dev != NULL); DEBUGASSERT(msgs != NULL); @@ -809,21 +931,14 @@ static int bcm2711_i2c_transfer(struct i2c_master_s *dev, bcm2711_i2c_clearfifos(priv); bcm2711_i2c_setfrequency(priv, msgs->frequency); bcm2711_i2c_setaddr(priv, msgs->addr); - putreg32(msgs->length, BCM_BSC_DLEN(priv->base)); /* Set transfer len */ - bcm2711_i2c_enable(priv); - /* TODO: do I need to support I2C_M_NOSTART? */ - - /* TODO: Support restart condition (no stop) */ + /* Try to merge as many sequential messages as possible to respect + * I2C_M_NOSTOP/I2C_M_NOSTART. + */ - if (msgs->flags & I2C_M_NOSTOP) - { - stop = false; - } - else - { - stop = true; - } + transfer_size = merge_messages(msgs, count); + putreg32(transfer_size, BCM_BSC_DLEN(priv->base)); /* Set transfer len */ + bcm2711_i2c_enable(priv); /* Perform the operation corresponding to whether the user wanted to * send or receive on this transfer. @@ -832,12 +947,12 @@ static int bcm2711_i2c_transfer(struct i2c_master_s *dev, if (msgs->flags & I2C_M_READ) { modreg32(BCM_BSC_C_READ, BCM_BSC_C_READ, BCM_BSC_C(priv->base)); - ret = bcm2711_i2c_receive(priv, msgs->buffer, msgs->length); + ret = bcm2711_i2c_receive(priv, msgs, transfer_size); } else { modreg32(0, BCM_BSC_C_READ, BCM_BSC_C(priv->base)); - ret = bcm2711_i2c_send(priv, msgs->buffer, msgs->length); + ret = bcm2711_i2c_send(priv, msgs, transfer_size); } /* Check if there was an error during the send/receive operation and @@ -856,15 +971,7 @@ static int bcm2711_i2c_transfer(struct i2c_master_s *dev, } } - /* If our last message had a stop condition, we can safely disable this I2C - * interface until it's used again. - */ - - if (stop) - { - bcm2711_i2c_disable(priv); - } - + bcm2711_i2c_disable(priv); /* Transfer done */ nxmutex_unlock(&priv->lock); return ret; } @@ -1170,5 +1277,3 @@ int bcm2711_i2cbus_uninitialize(struct i2c_master_s *dev) nxmutex_unlock(&priv->lock); return ret; } - -#endif // defined(CONFIG_BCM2711_I2C)
