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am53c974: BLAST residual handling

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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>
This commit is contained in:
Hannes Reinecke
2014-11-24 15:37:26 +01:00
committed by Christoph Hellwig
parent 3a7e7be2a9
commit 6df388f2d5
3 changed files with 36 additions and 0 deletions
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drivers/scsi/esp_scsi.c
+29
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@@ -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;