From: Finn Thain <fthain@telegraphics.com.au>
Date: Tue, 16 Oct 2018 16:31:25 +1100
Subject: scsi: esp_scsi: Track residual for PIO transfers
Git-commit: fd47d919d0c336e7c22862b51ee94927ffea227a
Patch-mainline: v4.20-rc1
References: git-fixes

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@yahoo.com>
Signed-off-by: Finn Thain <fthain@telegraphics.com.au>
Tested-by: Michael Schmitz <schmitzmic@gmail.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Acked-by: Lee Duncan <lduncan@suse.com>
---
 drivers/scsi/esp_scsi.c | 1 +
 drivers/scsi/esp_scsi.h | 2 ++
 drivers/scsi/mac_esp.c  | 2 ++
 3 files changed, 5 insertions(+)

diff --git a/drivers/scsi/esp_scsi.c b/drivers/scsi/esp_scsi.c
index 5cd97d2e9105..cba58cf612e2 100644
--- a/drivers/scsi/esp_scsi.c
+++ b/drivers/scsi/esp_scsi.c
@@ -1352,6 +1352,7 @@ static int esp_data_bytes_sent(struct esp *esp, struct esp_cmd_entry *ent,
 
 	bytes_sent = esp->data_dma_len;
 	bytes_sent -= ecount;
+	bytes_sent -= esp->send_cmd_residual;
 
 	/*
 	 * The am53c974 has a DMA 'pecularity'. The doc states:
diff --git a/drivers/scsi/esp_scsi.h b/drivers/scsi/esp_scsi.h
index 3b1b501e76f9..8062b536cbff 100644
--- a/drivers/scsi/esp_scsi.h
+++ b/drivers/scsi/esp_scsi.h
@@ -524,6 +524,8 @@ struct esp {
 
 	void			*dma;
 	int			dmarev;
+
+	u32			send_cmd_residual;
 };
 
 /* A front-end driver for the ESP chip should do the following in
diff --git a/drivers/scsi/mac_esp.c b/drivers/scsi/mac_esp.c
index 2769df5acc07..c92b6c1e02ee 100644
--- a/drivers/scsi/mac_esp.c
+++ b/drivers/scsi/mac_esp.c
@@ -394,6 +394,8 @@ static void mac_esp_send_pio_cmd(struct esp *esp, u32 addr, u32 esp_count,
 			scsi_esp_cmd(esp, ESP_CMD_TI);
 		}
 	}
+
+	esp->send_cmd_residual = esp_count;
 }
 
 static int mac_esp_irq_pending(struct esp *esp)