[PATCH V4 15/17] i3c: mipi-i3c-hci: Base timeouts on actual transfer start time
Frank Li
Frank.li at nxp.com
Tue Jun 2 09:47:19 PDT 2026
On Fri, May 15, 2026 at 07:26:19PM +0300, Adrian Hunter wrote:
> Transfer timeouts are currently measured from the point where a transfer
> list is queued to the controller. This can cause transfers to time out
> before they have actually started, if earlier queued transfers consume
> the timeout interval.
>
> Fix this by recording when a transfer reaches the head of the queue and
> adjusting the timeout calculation to start from that point. The existing
> low-overhead completion-based timeout mechanism is preserved, but care is
> taken to ensure the transfer start time is consistently recorded for both
> PIO and DMA paths.
>
> This prevents premature timeouts while retaining efficient timeout
> handling.
>
> Signed-off-by: Adrian Hunter <adrian.hunter at intel.com>
> ---
Reviewed-by: Frank Li <Frank.Li at nxp.com>
>
>
> Changes in V4:
>
> Rename start_time to start_jiffies
>
> Changes in V3:
>
> None
>
> Changes in V2:
> Do not flag the next transfer as started when there is an error
> which halts the controller
> Instead flag it started at the end of hci_dma_dequeue_xfer()
> Use hci_start_xfer() in pio.c
>
>
> drivers/i3c/master/mipi-i3c-hci/core.c | 19 ++++++++++++++++++-
> drivers/i3c/master/mipi-i3c-hci/dma.c | 19 ++++++++++++++++++-
> drivers/i3c/master/mipi-i3c-hci/hci.h | 11 +++++++++++
> drivers/i3c/master/mipi-i3c-hci/pio.c | 1 +
> 4 files changed, 48 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/i3c/master/mipi-i3c-hci/core.c b/drivers/i3c/master/mipi-i3c-hci/core.c
> index 69dcf5dad3a5..c6edbbedfdd7 100644
> --- a/drivers/i3c/master/mipi-i3c-hci/core.c
> +++ b/drivers/i3c/master/mipi-i3c-hci/core.c
> @@ -275,13 +275,30 @@ int i3c_hci_process_xfer(struct i3c_hci *hci, struct hci_xfer *xfer, int n)
> {
> struct completion *done = xfer[n - 1].completion;
> unsigned long timeout = xfer[n - 1].timeout;
> + unsigned long remaining_timeout = timeout;
> + long time_taken;
> + bool started;
> int ret;
>
> + xfer[0].started = false;
> +
> ret = hci->io->queue_xfer(hci, xfer, n);
> if (ret)
> return ret;
>
> - if (!wait_for_completion_timeout(done, timeout)) {
> + while (!wait_for_completion_timeout(done, remaining_timeout)) {
> + scoped_guard(spinlock_irqsave, &hci->lock) {
> + started = xfer[0].started;
> + time_taken = jiffies - xfer[0].start_jiffies;
> + }
> + /* Keep waiting if xfer has not started */
> + if (!started)
> + continue;
> + /* Recalculate timeout based on actual start time */
> + if (time_taken < timeout) {
> + remaining_timeout = timeout - time_taken;
> + continue;
> + }
> if (hci->io->dequeue_xfer(hci, xfer, n)) {
> dev_err(&hci->master.dev, "%s: timeout error\n", __func__);
> return -ETIMEDOUT;
> diff --git a/drivers/i3c/master/mipi-i3c-hci/dma.c b/drivers/i3c/master/mipi-i3c-hci/dma.c
> index 0fd56bbb84ef..9a01c740760f 100644
> --- a/drivers/i3c/master/mipi-i3c-hci/dma.c
> +++ b/drivers/i3c/master/mipi-i3c-hci/dma.c
> @@ -543,6 +543,9 @@ static int hci_dma_queue_xfer(struct i3c_hci *hci,
> enqueue_ptr = (enqueue_ptr + 1) % rh->xfer_entries;
> }
>
> + if (rh->xfer_space == rh->xfer_entries)
> + hci_start_xfer(xfer_list);
> +
> rh->xfer_space -= n;
>
> op1_val &= ~RING_OP1_CR_ENQ_PTR;
> @@ -558,6 +561,7 @@ static void hci_dma_xfer_done(struct i3c_hci *hci, struct hci_rh_data *rh)
> u32 op1_val, op2_val, resp, *ring_resp;
> unsigned int tid, done_ptr = rh->done_ptr;
> unsigned int done_cnt = 0;
> + bool start_next = false;
> struct hci_xfer *xfer;
>
> for (;;) {
> @@ -588,8 +592,14 @@ static void hci_dma_xfer_done(struct i3c_hci *hci, struct hci_rh_data *rh)
> xfer->response = resp;
> if (xfer == xfer->final_xfer || RESP_STATUS(resp))
> complete(xfer->final_xfer->completion);
> - if (RESP_STATUS(resp))
> + else
> + hci_start_xfer(xfer);
> + if (RESP_STATUS(resp)) {
> hci->enqueue_blocked = true;
> + start_next = false;
> + } else {
> + start_next = true;
> + }
> }
>
> done_ptr = (done_ptr + 1) % rh->xfer_entries;
> @@ -598,6 +608,10 @@ static void hci_dma_xfer_done(struct i3c_hci *hci, struct hci_rh_data *rh)
> }
>
> rh->xfer_space += done_cnt;
> + if (start_next && rh->xfer_space < rh->xfer_entries) {
> + xfer = rh->src_xfers[done_ptr];
> + hci_start_xfer(xfer);
> + }
> op1_val = rh_reg_read(RING_OPERATION1);
> op1_val &= ~RING_OP1_CR_SW_DEQ_PTR;
> op1_val |= FIELD_PREP(RING_OP1_CR_SW_DEQ_PTR, done_ptr);
> @@ -810,6 +824,9 @@ static bool hci_dma_dequeue_xfer(struct i3c_hci *hci,
>
> hci_dma_unblock_enqueue(hci);
>
> + if (rh->xfer_space < rh->xfer_entries)
> + hci_start_xfer(rh->src_xfers[rh->done_ptr]);
> +
> spin_unlock_irq(&hci->lock);
>
> wait_for_completion_timeout(&rh->op_done, HZ);
> diff --git a/drivers/i3c/master/mipi-i3c-hci/hci.h b/drivers/i3c/master/mipi-i3c-hci/hci.h
> index 4bf2c66c97b4..30297823ca85 100644
> --- a/drivers/i3c/master/mipi-i3c-hci/hci.h
> +++ b/drivers/i3c/master/mipi-i3c-hci/hci.h
> @@ -11,6 +11,7 @@
> #define HCI_H
>
> #include <linux/io.h>
> +#include <linux/jiffies.h>
>
> /* 32-bit word aware bit and mask macros */
> #define W0_MASK(h, l) GENMASK((h) - 0, (l) - 0)
> @@ -88,11 +89,13 @@ struct hci_xfer {
> u32 cmd_desc[4];
> u32 response;
> bool rnw;
> + bool started;
> void *data;
> unsigned int data_len;
> unsigned int cmd_tid;
> struct completion *completion;
> unsigned long timeout;
> + unsigned long start_jiffies;
> union {
> struct {
> /* PIO specific */
> @@ -123,6 +126,14 @@ static inline void hci_free_xfer(struct hci_xfer *xfer, unsigned int n)
> kfree(xfer);
> }
>
> +static inline void hci_start_xfer(struct hci_xfer *xfer)
> +{
> + if (!xfer->started) {
> + xfer->started = true;
> + xfer->start_jiffies = jiffies;
> + }
> +}
> +
> /* This abstracts PIO vs DMA operations */
> struct hci_io_ops {
> bool (*irq_handler)(struct i3c_hci *hci);
> diff --git a/drivers/i3c/master/mipi-i3c-hci/pio.c b/drivers/i3c/master/mipi-i3c-hci/pio.c
> index 8f48a81e65ab..6b8cc5f2b4d2 100644
> --- a/drivers/i3c/master/mipi-i3c-hci/pio.c
> +++ b/drivers/i3c/master/mipi-i3c-hci/pio.c
> @@ -605,6 +605,7 @@ static bool hci_pio_process_cmd(struct i3c_hci *hci, struct hci_pio_data *pio)
> * Finally send the command.
> */
> hci_pio_write_cmd(hci, pio->curr_xfer);
> + hci_start_xfer(pio->curr_xfer);
> /*
> * And move on.
> */
> --
> 2.51.0
>
More information about the linux-i3c
mailing list