am53c974: BLAST residual handling

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.

Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Acked-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Christoph Hellwig <hch@lst.de>

1 files changed, 6 insertions, 0 deletions

diff --git a/drivers/scsi/am53c974.c b/drivers/scsi/am53c974.c
index a16c9cf0f0a2..a42e8db057a4 100644
--- a/drivers/scsi/am53c974.c
+++ b/drivers/scsi/am53c974.c
@@ -200,6 +200,12 @@ static void pci_esp_dma_drain(struct esp *esp)
         }
         pci_esp_write8(esp, ESP_DMA_CMD_DIR | ESP_DMA_CMD_IDLE, ESP_DMA_CMD);
         esp_dma_log("DMA blast done (%d tries, %d bytes left)\n", lim, resid);
+        /* 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)