From: Finn Thain <fthain@telegraphics.com.au>
To: Kars de Jong <jongk@linux-m68k.org>
Cc: "James E.J. Bottomley" <jejb@linux.ibm.com>,
"Martin K. Petersen" <martin.petersen@oracle.com>,
Michael Schmitz <schmitzmic@gmail.com>,
linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] esp_scsi: Clear Transfer Count registers before PIO transfers
Date: Mon, 18 Nov 2019 10:26:47 +1100 (AEDT) [thread overview]
Message-ID: <alpine.LNX.2.21.1.1911181019110.75@nippy.intranet> (raw)
In-Reply-To: <alpine.LNX.2.21.1.1911180947020.8@nippy.intranet>
On Mon, 18 Nov 2019, Finn Thain wrote:
> On Sun, 17 Nov 2019, Kars de Jong wrote:
>
> > The only [time when] the driver reads these registers is after a data
> > transfer. These are done using DMA on all Zorro boards, so I don't
> > think there's a risk of stale values from a PIO transfer there.
> >
>
> I'm not entirely sure that the chip is unaffected by stale counter
> values.
>
> (Stale transfer counter values are distinct from stale transfer count
> register values. Both are addressed by the patch.)
>
Sorry -- I should have said, "both were _intended_ to be addressed by the
patch". But, as Michael pointed out, the DMA NOP command was missing from
the v1 patch. Please see revised patch below.
diff --git a/drivers/scsi/esp_scsi.c b/drivers/scsi/esp_scsi.c
index bb88995a12c7..82d49f0f09df 100644
--- a/drivers/scsi/esp_scsi.c
+++ b/drivers/scsi/esp_scsi.c
@@ -2835,6 +2835,10 @@ void esp_send_pio_cmd(struct esp *esp, u32 addr, u32 esp_count,
cmd &= ~ESP_CMD_DMA;
esp->send_cmd_error = 0;
+ esp_write8(0, ESP_TCLOW);
+ esp_write8(0, ESP_TCMED);
+ scsi_esp_cmd(esp, ESP_CMD_NULL | ESP_CMD_DMA);
+
if (write) {
u8 *dst = (u8 *)addr;
u8 mask = ~(phase == ESP_MIP ? ESP_INTR_FDONE : ESP_INTR_BSERV);
diff --git a/drivers/scsi/mac_esp.c b/drivers/scsi/mac_esp.c
index 1c78bc10c790..797579247e47 100644
--- a/drivers/scsi/mac_esp.c
+++ b/drivers/scsi/mac_esp.c
@@ -361,8 +361,6 @@ static int esp_mac_probe(struct platform_device *dev)
esp->flags = ESP_FLAG_NO_DMA_MAP;
if (mep->pdma_io == NULL) {
printk(KERN_INFO PFX "using PIO for controller %d\n", dev->id);
- esp_write8(0, ESP_TCLOW);
- esp_write8(0, ESP_TCMED);
esp->flags |= ESP_FLAG_DISABLE_SYNC;
mac_esp_ops.send_dma_cmd = esp_send_pio_cmd;
} else {
next prev parent reply other threads:[~2019-11-17 23:26 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-16 3:36 [PATCH] esp_scsi: Clear Transfer Count registers before PIO transfers Finn Thain
2019-11-16 4:30 ` Michael Schmitz
2019-11-16 23:02 ` Finn Thain
2019-11-17 6:26 ` Kars de Jong
2019-11-17 6:29 ` Kars de Jong
2019-11-17 23:13 ` Finn Thain
2019-11-17 23:26 ` Finn Thain [this message]
2019-11-18 8:13 ` Kars de Jong
2019-11-18 23:04 ` Finn Thain
2019-11-19 23:12 ` Finn Thain
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