The am53c974 has an design issue where a single byte might be left in the SCSI FIFO after a DMA transfer. As the handling code is currently untested add a WARN_ON() statement here.
Signed-off-by: Hannes Reinecke <[email protected]> --- drivers/scsi/am53c974.c | 6 ++++++ drivers/scsi/esp_scsi.c | 29 +++++++++++++++++++++++++++++ drivers/scsi/esp_scsi.h | 1 + 3 files changed, 36 insertions(+) diff --git a/drivers/scsi/am53c974.c b/drivers/scsi/am53c974.c index 86c4c42..1c1312f 100644 --- a/drivers/scsi/am53c974.c +++ b/drivers/scsi/am53c974.c @@ -197,6 +197,12 @@ static void pci_esp_dma_drain(struct esp *esp) shost_printk(KERN_INFO, esp->host, "DMA blast done (%d tries, %d bytes left)\n", lim, resid); #endif + /* BLAST residual handling is currently untested */ + if (WARN_ON_ONCE(resid == 1)) { + struct esp_cmd_entry *ent = esp->active_cmd; + + ent->flags |= ESP_CMD_FLAG_RESIDUAL; + } } static void pci_esp_dma_invalidate(struct esp *esp) diff --git a/drivers/scsi/esp_scsi.c b/drivers/scsi/esp_scsi.c index 2a3277d..07b4d93 100644 --- a/drivers/scsi/esp_scsi.c +++ b/drivers/scsi/esp_scsi.c @@ -1334,6 +1334,35 @@ static int esp_data_bytes_sent(struct esp *esp, struct esp_cmd_entry *ent, bytes_sent = esp->data_dma_len; bytes_sent -= ecount; + /* + * The am53c974 has a DMA 'pecularity'. The doc states: + * In some odd byte conditions, one residual byte will + * be left in the SCSI FIFO, and the FIFO Flags will + * never count to '0 '. When this happens, the residual + * byte should be retrieved via PIO following completion + * of the BLAST operation. + */ + if (fifo_cnt == 1 && ent->flags & ESP_CMD_FLAG_RESIDUAL) { + size_t count = 1; + size_t offset = bytes_sent; + u8 bval = esp_read8(ESP_FDATA); + + if (ent->flags & ESP_CMD_FLAG_AUTOSENSE) + ent->sense_ptr[bytes_sent] = bval; + else { + struct esp_cmd_priv *p = ESP_CMD_PRIV(cmd); + u8 *ptr; + + ptr = scsi_kmap_atomic_sg(p->cur_sg, p->u.num_sg, + &offset, &count); + if (likely(ptr)) { + *(ptr + offset) = bval; + scsi_kunmap_atomic_sg(ptr); + } + } + bytes_sent += fifo_cnt; + ent->flags &= ~ESP_CMD_FLAG_RESIDUAL; + } if (!(ent->flags & ESP_CMD_FLAG_WRITE)) bytes_sent -= fifo_cnt; diff --git a/drivers/scsi/esp_scsi.h b/drivers/scsi/esp_scsi.h index 27dcaf8..5fa456c 100644 --- a/drivers/scsi/esp_scsi.h +++ b/drivers/scsi/esp_scsi.h @@ -269,6 +269,7 @@ struct esp_cmd_entry { #define ESP_CMD_FLAG_WRITE 0x01 /* DMA is a write */ #define ESP_CMD_FLAG_ABORT 0x02 /* being aborted */ #define ESP_CMD_FLAG_AUTOSENSE 0x04 /* Doing automatic REQUEST_SENSE */ +#define ESP_CMD_FLAG_RESIDUAL 0x08 /* AM53c974 BLAST residual */ u8 tag[2]; u8 orig_tag[2]; -- 1.8.5.2 -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
