[PATCH AUTOSEL 4.4 20/32] scsi: esp_scsi: Track residual for PIO transfers

Sasha Levin
2018-10-31T23:11:25Z

From: Finn Thain <fthain@telegraphics.com.au>

[ 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@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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
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 71cb05b1c3eb..60be0742e2c8 100644
--- a/drivers/scsi/esp_scsi.c
+++ b/drivers/scsi/esp_scsi.c
@@ -1349,6 +1349,7 @@ 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 84dcbe4a6268..55be43fe7667 100644
--- 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
diff --git a/drivers/scsi/mac_esp.c b/drivers/scsi/mac_esp.c
index 26c67c42985c..1002124bd8bf 100644
--- a/drivers/scsi/mac_esp.c
+++ b/drivers/scsi/mac_esp.c
@@ -426,6 +426,8 @@ 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)
--
2.17.1