[PATCH 4.9 053/141] scsi: esp_scsi: Track residual for PIO transfers

[Greg Kroah-Hartman]

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Finn Thain <fthain@xxxxxxxxxxxxxxxxxxx>

[ Upstream commit fd47d919d0c336e7c22862b51ee94927ffea227a ]

If a target disconnects during a PIO data transfer the command may fail
when the target reconnects:

scsi host1: DMA length is zero!
scsi host1: cur adr[04380000] len[00000000]

The scsi bus is then reset. This happens because the residual reached
zero before the transfer was completed.

The usual residual calculation relies on the Transfer Count registers.
That works for DMA transfers but not for PIO transfers. Fix the problem
by storing the PIO transfer residual and using that to correctly
calculate bytes_sent.

Fixes: 6fe07aaffbf0 ("[SCSI] m68k: new mac_esp scsi driver")
Tested-by: Stan Johnson <userm57@xxxxxxxxx>
Signed-off-by: Finn Thain <fthain@xxxxxxxxxxxxxxxxxxx>
Tested-by: Michael Schmitz <schmitzmic@xxxxxxxxx>
Signed-off-by: Martin K. Petersen <martin.petersen@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 drivers/scsi/esp_scsi.c |    1 +
 drivers/scsi/esp_scsi.h |    2 ++
 drivers/scsi/mac_esp.c  |    2 ++
 3 files changed, 5 insertions(+)

--- a/drivers/scsi/esp_scsi.c
+++ b/drivers/scsi/esp_scsi.c
@@ -1349,6 +1349,7 @@ static int esp_data_bytes_sent(struct es
 
 	bytes_sent = esp->data_dma_len;
 	bytes_sent -= ecount;
+	bytes_sent -= esp->send_cmd_residual;
 
 	/*
 	 * The am53c974 has a DMA 'pecularity'. The doc states:
--- a/drivers/scsi/esp_scsi.h
+++ b/drivers/scsi/esp_scsi.h
@@ -540,6 +540,8 @@ struct esp {
 
 	void			*dma;
 	int			dmarev;
+
+	u32			send_cmd_residual;
 };
 
 /* A front-end driver for the ESP chip should do the following in
--- a/drivers/scsi/mac_esp.c
+++ b/drivers/scsi/mac_esp.c
@@ -426,6 +426,8 @@ static void mac_esp_send_pio_cmd(struct
 			scsi_esp_cmd(esp, ESP_CMD_TI);
 		}
 	}
+
+	esp->send_cmd_residual = esp_count;
 }
 
 static int mac_esp_irq_pending(struct esp *esp)