Re: [PATCH v2 1/3] i2c: cadence: Handle > 252 byte transfers

From: rajeev kumar
Date: Fri Dec 05 2014 - 00:42:08 EST

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In reply to: Harini Katakam: "Re: [PATCH v2 1/3] i2c: cadence: Handle > 252 byte transfers"
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On Wed, Dec 3, 2014 at 6:05 PM, Harini Katakam <harinik@xxxxxxxxxx> wrote:
> The I2C controller sends a NACK to the slave when transfer size register
> reaches zero, irrespective of the hold bit. So, in order to handle transfers
> greater than 252 bytes, the transfer size register has to be maintained at a
> value >= 1. This patch implements the same.

Why 252 Bytes ? Is it word allign or what ?

> The interrupt status is cleared at the beginning of the isr instead of
> the end, to avoid missing any interrupts - this is in sync with the new
> transfer handling.
>

No need to write this, actually this is the correct way of handling interrupt.

> Signed-off-by: Harini Katakam <harinik@xxxxxxxxxx>
> ---
>
> v2:
> No changes
>
> ---
> drivers/i2c/busses/i2c-cadence.c | 156 ++++++++++++++++++++------------------
> 1 file changed, 81 insertions(+), 75 deletions(-)
>
> diff --git a/drivers/i2c/busses/i2c-cadence.c b/drivers/i2c/busses/i2c-cadence.c
> index 63f3f03..e54899e 100644
> --- a/drivers/i2c/busses/i2c-cadence.c
> +++ b/drivers/i2c/busses/i2c-cadence.c
> @@ -126,6 +126,7 @@
> * @suspended: Flag holding the device's PM status
> * @send_count: Number of bytes still expected to send
> * @recv_count: Number of bytes still expected to receive
> + * @curr_recv_count: Number of bytes to be received in current transfer

Please do the alignment properly

> * @irq: IRQ number
> * @input_clk: Input clock to I2C controller
> * @i2c_clk: Maximum I2C clock speed
> @@ -144,6 +145,7 @@ struct cdns_i2c {
> u8 suspended;
> unsigned int send_count;
> unsigned int recv_count;
> + unsigned int curr_recv_count;

same here..

> int irq;
> unsigned long input_clk;
> unsigned int i2c_clk;
> @@ -180,14 +182,15 @@ static void cdns_i2c_clear_bus_hold(struct cdns_i2c *id)
> */
> static irqreturn_t cdns_i2c_isr(int irq, void *ptr)
> {
> - unsigned int isr_status, avail_bytes;
> - unsigned int bytes_to_recv, bytes_to_send;
> + unsigned int isr_status, avail_bytes, updatetx;
> + unsigned int bytes_to_send;

why you are mixing tab and space..

> struct cdns_i2c *id = ptr;
> /* Signal completion only after everything is updated */
> int done_flag = 0;
> irqreturn_t status = IRQ_NONE;
>
> isr_status = cdns_i2c_readreg(CDNS_I2C_ISR_OFFSET);
> + cdns_i2c_writereg(isr_status, CDNS_I2C_ISR_OFFSET);
>
> /* Handling nack and arbitration lost interrupt */
> if (isr_status & (CDNS_I2C_IXR_NACK | CDNS_I2C_IXR_ARB_LOST)) {
> @@ -195,89 +198,91 @@ static irqreturn_t cdns_i2c_isr(int irq, void *ptr)
> status = IRQ_HANDLED;
> }
>
> - /* Handling Data interrupt */
> - if ((isr_status & CDNS_I2C_IXR_DATA) &&
> - (id->recv_count >= CDNS_I2C_DATA_INTR_DEPTH)) {
> - /* Always read data interrupt threshold bytes */
> - bytes_to_recv = CDNS_I2C_DATA_INTR_DEPTH;
> - id->recv_count -= CDNS_I2C_DATA_INTR_DEPTH;
> - avail_bytes = cdns_i2c_readreg(CDNS_I2C_XFER_SIZE_OFFSET);
> -
> - /*
> - * if the tranfer size register value is zero, then
> - * check for the remaining bytes and update the
> - * transfer size register.
> - */
> - if (!avail_bytes) {
> - if (id->recv_count > CDNS_I2C_TRANSFER_SIZE)
> - cdns_i2c_writereg(CDNS_I2C_TRANSFER_SIZE,
> - CDNS_I2C_XFER_SIZE_OFFSET);
> - else
> - cdns_i2c_writereg(id->recv_count,
> - CDNS_I2C_XFER_SIZE_OFFSET);
> - }
> + updatetx = 0;
> + if (id->recv_count > id->curr_recv_count)
> + updatetx = 1;
> +
> + /* When receiving, handle data and transfer complete interrupts */

Breaking statement

> + if (id->p_recv_buf &&
> + ((isr_status & CDNS_I2C_IXR_COMP) ||
> + (isr_status & CDNS_I2C_IXR_DATA))) {
> + while (cdns_i2c_readreg(CDNS_I2C_SR_OFFSET) &
> + CDNS_I2C_SR_RXDV) {
> + if ((id->recv_count < CDNS_I2C_FIFO_DEPTH) &&
> + !id->bus_hold_flag)
> + cdns_i2c_clear_bus_hold(id);

make it simple. you can use extra variables also.

>
> - /* Process the data received */
> - while (bytes_to_recv--)
> *(id->p_recv_buf)++ =
> cdns_i2c_readreg(CDNS_I2C_DATA_OFFSET);
> + id->recv_count--;
> + id->curr_recv_count--;
>
> - if (!id->bus_hold_flag &&
> - (id->recv_count <= CDNS_I2C_FIFO_DEPTH))
> - cdns_i2c_clear_bus_hold(id);
> + if (updatetx &&
> + (id->curr_recv_count == CDNS_I2C_FIFO_DEPTH + 1))
> + break;
> + }
>
> - status = IRQ_HANDLED;
> - }
> + if (updatetx &&
> + (id->curr_recv_count == CDNS_I2C_FIFO_DEPTH + 1)) {
> + /* wait while fifo is full */

Not convinced with the implementation . you are waiting in ISR.. You
can move this part in transfer function,

> + while (cdns_i2c_readreg(CDNS_I2C_XFER_SIZE_OFFSET) !=
> + (id->curr_recv_count - CDNS_I2C_FIFO_DEPTH))
> + ;
>
> - /* Handling Transfer Complete interrupt */
> - if (isr_status & CDNS_I2C_IXR_COMP) {
> - if (!id->p_recv_buf) {
> - /*
> - * If the device is sending data If there is further
> - * data to be sent. Calculate the available space
> - * in FIFO and fill the FIFO with that many bytes.
> - */
> - if (id->send_count) {
> - avail_bytes = CDNS_I2C_FIFO_DEPTH -
> - cdns_i2c_readreg(CDNS_I2C_XFER_SIZE_OFFSET);
> - if (id->send_count > avail_bytes)
> - bytes_to_send = avail_bytes;
> - else
> - bytes_to_send = id->send_count;
> -
> - while (bytes_to_send--) {
> - cdns_i2c_writereg(
> - (*(id->p_send_buf)++),
> - CDNS_I2C_DATA_OFFSET);
> - id->send_count--;
> - }
> + if (((int)(id->recv_count) - CDNS_I2C_FIFO_DEPTH) >
> + CDNS_I2C_TRANSFER_SIZE) {
> + cdns_i2c_writereg(CDNS_I2C_TRANSFER_SIZE,
> + CDNS_I2C_XFER_SIZE_OFFSET);
> + id->curr_recv_count = CDNS_I2C_TRANSFER_SIZE +
> + CDNS_I2C_FIFO_DEPTH;
> } else {
> - /*
> - * Signal the completion of transaction and
> - * clear the hold bus bit if there are no
> - * further messages to be processed.
> - */
> - done_flag = 1;
> + cdns_i2c_writereg(id->recv_count -
> + CDNS_I2C_FIFO_DEPTH,
> + CDNS_I2C_XFER_SIZE_OFFSET);
> + id->curr_recv_count = id->recv_count;
> }
> - if (!id->send_count && !id->bus_hold_flag)
> - cdns_i2c_clear_bus_hold(id);
> - } else {
> + }
> +
> + if ((isr_status & CDNS_I2C_IXR_COMP) && !id->recv_count) {
> if (!id->bus_hold_flag)
> cdns_i2c_clear_bus_hold(id);
> + done_flag = 1;
> + }
> +
> + status = IRQ_HANDLED;
> + }
> +
> + /* When sending, handle transfer complete interrupt */
> + if ((isr_status & CDNS_I2C_IXR_COMP) && !id->p_recv_buf) {
> + /*
> + * If the device is sending data If there is further
> + * data to be sent. Calculate the available space
> + * in FIFO and fill the FIFO with that many bytes.
> + */
> + if (id->send_count) {
> + avail_bytes = CDNS_I2C_FIFO_DEPTH -
> + cdns_i2c_readreg(CDNS_I2C_XFER_SIZE_OFFSET);
> + if (id->send_count > avail_bytes)
> + bytes_to_send = avail_bytes;
> + else
> + bytes_to_send = id->send_count;
> +
> + while (bytes_to_send--) {
> + cdns_i2c_writereg(
> + (*(id->p_send_buf)++),
> + CDNS_I2C_DATA_OFFSET);
> + id->send_count--;
> + }
> + } else {
> /*
> - * If the device is receiving data, then signal
> - * the completion of transaction and read the data
> - * present in the FIFO. Signal the completion of
> - * transaction.
> + * Signal the completion of transaction and
> + * clear the hold bus bit if there are no
> + * further messages to be processed.
> */
> - while (cdns_i2c_readreg(CDNS_I2C_SR_OFFSET) &
> - CDNS_I2C_SR_RXDV) {
> - *(id->p_recv_buf)++ =
> - cdns_i2c_readreg(CDNS_I2C_DATA_OFFSET);
> - id->recv_count--;
> - }
> done_flag = 1;
> }
> + if (!id->send_count && !id->bus_hold_flag)
> + cdns_i2c_clear_bus_hold(id);
>
> status = IRQ_HANDLED;
> }
> @@ -287,8 +292,6 @@ static irqreturn_t cdns_i2c_isr(int irq, void *ptr)
> if (id->err_status)
> status = IRQ_HANDLED;
>
> - cdns_i2c_writereg(isr_status, CDNS_I2C_ISR_OFFSET);
> -
> if (done_flag)
> complete(&id->xfer_done);
>
> @@ -314,6 +317,8 @@ static void cdns_i2c_mrecv(struct cdns_i2c *id)
> if (id->p_msg->flags & I2C_M_RECV_LEN)
> id->recv_count = I2C_SMBUS_BLOCK_MAX + 1;
>
> + id->curr_recv_count = id->recv_count;
> +
> /*
> * Check for the message size against FIFO depth and set the
> * 'hold bus' bit if it is greater than FIFO depth.
> @@ -333,10 +338,11 @@ static void cdns_i2c_mrecv(struct cdns_i2c *id)
> * receive if it is less than transfer size and transfer size if
> * it is more. Enable the interrupts.
> */
> - if (id->recv_count > CDNS_I2C_TRANSFER_SIZE)
> + if (id->recv_count > CDNS_I2C_TRANSFER_SIZE) {
> cdns_i2c_writereg(CDNS_I2C_TRANSFER_SIZE,
> CDNS_I2C_XFER_SIZE_OFFSET);
> - else
> + id->curr_recv_count = CDNS_I2C_TRANSFER_SIZE;
> + } else
> cdns_i2c_writereg(id->recv_count, CDNS_I2C_XFER_SIZE_OFFSET);
> /* Clear the bus hold flag if bytes to receive is less than FIFO size */
> if (!id->bus_hold_flag &&
> --
> 1.7.9.5

Overall I think it is required to re-write isr.

~Rajeev

>
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Next message: æé: "Re: [PATCH v2 0/2] mmc: rtsx: add support for sdio card"
Previous message: Masami Hiramatsu: "Re: [PATCH 2/2] ftracetest: Add --verbose option for showing echo output"
In reply to: Harini Katakam: "Re: [PATCH v2 1/3] i2c: cadence: Handle > 252 byte transfers"
Next in thread: Harini Katakam: "Re: [PATCH v2 1/3] i2c: cadence: Handle > 252 byte transfers"
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