On 21/11/2014 13:41, Hannes Reinecke wrote: > 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]; >
Reviewed-by: Paolo Bonzini <[email protected]> -- 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
