Interrupt Handler and Command Completion

The interrupt handler must check the status of the device to be sure the device is generating the interrupt in question. The interrupt handler must also check for any errors that have occurred and service any interrupts generated by the device.

If data is transferred, the hardware should be checked to determine how much data was actually transferred. The pkt_resid field in the scsi_pkt(9S) structure should be set to the residual of the transfer.

Commands that are marked with the PKT_CONSISTENT flag when DMA resources are allocated through tran_init_pkt(9E) take special handling. The HBA driver must ensure that the data transfer for the command is correctly synchronized before the target driver's command completion callback is performed.

Once a command has completed, you need to act on two requirements:

• If a new command is queued up, start the command on the hardware as quickly as possible.

• Call the command completion callback. The callback has been set up in the scsi_pkt(9S) structure by the target driver to notify the target driver when the command is complete.

Start a new command on the hardware, if possible, before calling the PKT_COMP command completion callback. The command completion handling can take considerable time. Typically, the target driver calls functions such as biodone(9F) and possibly scsi_transport(9F) to begin a new command.

The interrupt handler must return DDI_INTR_CLAIMED if this interrupt is claimed by this driver. Otherwise, the handler returns DDI_INTR_UNCLAIMED.

The following example shows an interrupt handler for the SCSI HBA isp driver. The caddr_t parameter is set up when the interrupt handler is added in attach(9E). This parameter is typically a pointer to the state structure, which is allocated on a per instance basis.

Example 18–9 HBA Driver Interrupt Handler

static u_int
isp_intr(caddr_t arg)
{
    struct isp_cmd         *sp;
    struct isp_cmd         *head, *tail;
    u_short                response_in;
    struct isp_response    *resp;
    struct isp             *isp = (struct isp *)arg;
    struct isp_slot        *isp_slot;
    int                    n;

    if (ISP_INT_PENDING(isp) == 0) {
        return (DDI_INTR_UNCLAIMED);
    }

    do {
again:
        /*
         * head list collects completed packets for callback later
         */
        head = tail = NULL;
        /*
         * Assume no mailbox events (e.g., mailbox cmds, asynch
         * events, and isp dma errors) as common case.
         */
        if (ISP_CHECK_SEMAPHORE_LOCK(isp) == 0) {
            mutex_enter(ISP_RESP_MUTEX(isp));
            /*
             * Loop through completion response queue and post
             * completed pkts.  Check response queue again
             * afterwards in case there are more.
             */
            isp->isp_response_in =
            response_in = ISP_GET_RESPONSE_IN(isp);
            /*
             * Calculate the number of requests in the queue
             */
            n = response_in - isp->isp_response_out;
            if (n < 0) {
                n = ISP_MAX_REQUESTS -
                isp->isp_response_out + response_in;
            }
            while (n-- > 0) {
                ISP_GET_NEXT_RESPONSE_OUT(isp, resp);
                sp = (struct isp_cmd *)resp->resp_token;
                /*
                 * Copy over response packet in sp
                 */
                isp_i_get_response(isp, resp, sp);
            }
            if (head) {
                tail->cmd_forw = sp;
                tail = sp;
                tail->cmd_forw = NULL;
            } else {
                tail = head = sp;
                sp->cmd_forw = NULL;
            }
            ISP_SET_RESPONSE_OUT(isp);
            ISP_CLEAR_RISC_INT(isp);
            mutex_exit(ISP_RESP_MUTEX(isp));

            if (head) {
                isp_i_call_pkt_comp(isp, head);
            }
        } else {
            if (isp_i_handle_mbox_cmd(isp) != ISP_AEN_SUCCESS) {
                return (DDI_INTR_CLAIMED);
            }
            /*
             * if there was a reset then check the response
             * queue again
             */
            goto again;    
        }

    } while (ISP_INT_PENDING(isp));

    return (DDI_INTR_CLAIMED);
}

static void
isp_i_call_pkt_comp(
    struct isp             *isp,
    struct isp_cmd         *head)
{
    struct isp             *isp;
    struct isp_cmd         *sp;
    struct scsi_pkt        *pkt;
    struct isp_response    *resp;
    u_char                 status;

    while (head) {
        sp = head;
        pkt = sp->cmd_pkt;
        head = sp->cmd_forw;

        ASSERT(sp->cmd_flags & CFLAG_FINISHED);

        resp = &sp->cmd_isp_response;

        pkt->pkt_scbp[0] = (u_char)resp->resp_scb;
        pkt->pkt_state = ISP_GET_PKT_STATE(resp->resp_state);
        pkt->pkt_statistics = (u_long)
            ISP_GET_PKT_STATS(resp->resp_status_flags);
        pkt->pkt_resid = (long)resp->resp_resid;
        /*
         * If data was xferred and this is a consistent pkt,
         * do a dma sync
         */
        if ((sp->cmd_flags & CFLAG_CMDIOPB) &&
            (pkt->pkt_state & STATE_XFERRED_DATA)) {
                (void) ddi_dma_sync(sp->cmd_dmahandle,
                sp->cmd_dma_offset, sp->cmd_dma_len,
                DDI_DMA_SYNC_FORCPU);
        }

        sp->cmd_flags = (sp->cmd_flags & ~CFLAG_IN_TRANSPORT) |
            CFLAG_COMPLETED;
        /*
         * Call packet completion routine if FLAG_NOINTR is not set.
         */
        if (((pkt->pkt_flags & FLAG_NOINTR) == 0) &&
            pkt->pkt_comp) {
                (*pkt->pkt_comp)(pkt);
        }
    }
}