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Commit 6df388f2 authored by Hannes Reinecke's avatar Hannes Reinecke Committed by Christoph Hellwig
Browse files

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: default avatarPaolo Bonzini <pbonzini@redhat.com>
Acked-by: default avatarDavid S. Miller <davem@davemloft.net>
Signed-off-by: default avatarHannes Reinecke <hare@suse.de>
Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
parent 3a7e7be2

drivers/scsi/am53c974.c

+6 −0
Original line number Diff line number Diff line
@@ -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)

drivers/scsi/esp_scsi.c

+29 −0
Original line number Diff line number Diff line
@@ -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;

drivers/scsi/esp_scsi.h

+1 −0
Original line number Diff line number Diff line
@@ -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];