Re: [PATCH V3 14/16] i3c: mipi-i3c-hci: Base timeouts on actual transfer start time

[Frank Li]

On Mon, May 04, 2026 at 02:33:50PM +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@xxxxxxxxx>
> ---
>
>
> 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(-)
>
...
>
>  #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_time;

it'd better to add unit for start_time

Frank
>  	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_time = 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
>