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From: Kars de Jong <jongk@linux-m68k.org>
To: "James E.J. Bottomley" <jejb@linux.ibm.com>
Cc: linux-scsi@vger.kernel.org, linux-m68k@vger.kernel.org,
	"Martin K. Petersen" <martin.petersen@oracle.com>,
	schmitzmic@gmail.com, fthain@telegraphics.com.au,
	Kars de Jong <jongk@linux-m68k.org>
Subject: [PATCH v2] zorro_esp: Limit DMA transfers to 65536 bytes (except on Fastlane)
Date: Tue, 12 Nov 2019 18:55:23 +0100
Message-ID: <20191112175523.23145-1-jongk@linux-m68k.org> (raw)
In-Reply-To: <1573414513.3230.4.camel@linux.ibm.com>

When using this driver on a Blizzard 1260, there were failures whenever
DMA transfers from the SCSI bus to memory of 65535 bytes were followed by a
DMA transfer of 1 byte. This caused the byte at offset 65535 to be
overwritten with 0xff. The Blizzard hardware can't handle single byte DMA
transfers.

Besides this issue, limiting the DMA length to something that is not a
multiple of the page size is very inefficient on most file systems.

It seems this limit was chosen because the DMA transfer counter of the ESP
by default is 16 bits wide, thus limiting the length to 65535 bytes.
However, the value 0 means 65536 bytes, which is handled by the ESP and the
Blizzard just fine. It is also the default maximum used by esp_scsi when
drivers don't provide their own dma_length_limit() function.

The limit of 65536 bytes can be used by all boards except the Fastlane. The
old driver used a limit of 65532 bytes (0xfffc), which is reintroduced in
this patch.

Fixes: b7ded0e8b0d1 ("scsi: zorro_esp: Limit DMA transfers to 65535 bytes")
Signed-off-by: Kars de Jong <jongk@linux-m68k.org>
---
 drivers/scsi/zorro_esp.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/drivers/scsi/zorro_esp.c b/drivers/scsi/zorro_esp.c
index ca8e3abeb2c7..a23a8e5794f5 100644
--- a/drivers/scsi/zorro_esp.c
+++ b/drivers/scsi/zorro_esp.c
@@ -218,7 +218,14 @@ static int fastlane_esp_irq_pending(struct esp *esp)
 static u32 zorro_esp_dma_length_limit(struct esp *esp, u32 dma_addr,
 					u32 dma_len)
 {
-	return dma_len > 0xFFFF ? 0xFFFF : dma_len;
+	return dma_len > (1U << 16) ? (1U << 16) : dma_len;
+}
+
+static u32 fastlane_esp_dma_length_limit(struct esp *esp, u32 dma_addr,
+					u32 dma_len)
+{
+	/* The old driver used 0xfffc as limit, so do that here too */
+	return dma_len > 0xfffc ? 0xfffc : dma_len;
 }
 
 static void zorro_esp_reset_dma(struct esp *esp)
@@ -604,7 +611,7 @@ static const struct esp_driver_ops fastlane_esp_ops = {
 	.esp_write8		= zorro_esp_write8,
 	.esp_read8		= zorro_esp_read8,
 	.irq_pending		= fastlane_esp_irq_pending,
-	.dma_length_limit	= zorro_esp_dma_length_limit,
+	.dma_length_limit	= fastlane_esp_dma_length_limit,
 	.reset_dma		= zorro_esp_reset_dma,
 	.dma_drain		= zorro_esp_dma_drain,
 	.dma_invalidate		= fastlane_esp_dma_invalidate,
-- 
2.17.1


  reply index

Thread overview: 74+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-24 20:56 Amiga PCMCIA network card support Andreas 'count' Kotes
2019-10-25  7:25 ` Kars de Jong
2019-10-25 11:49   ` Andreas 'count' Kotes
2019-10-28  9:19     ` Kars de Jong
2019-10-28 11:08       ` John Paul Adrian Glaubitz
2019-10-28 13:00         ` Kars de Jong
2019-10-28 13:20           ` John Paul Adrian Glaubitz
2019-10-28 15:39             ` ESP SCSI driver (was: Amiga PCMCIA network card support) Kars de Jong
2019-10-28 18:32               ` Michael Schmitz
2019-10-29  9:37                 ` Kars de Jong
2019-10-29 20:20                   ` ESP SCSI driver Michael Schmitz
2019-10-29 22:05                   ` [PATCH] esp_scsi: Add support for FSC chip Kars de Jong
2019-10-30  0:23                     ` Michael Schmitz
2019-10-30  7:11                       ` Kars de Jong
2019-10-30 18:42                         ` Michael Schmitz
2019-10-30  0:31                     ` Finn Thain
2019-10-30  1:06                       ` Michael Schmitz
2019-10-30  7:25                         ` Kars de Jong
2019-10-30  8:45                           ` Geert Uytterhoeven
2019-10-30  9:08                             ` Kars de Jong
2019-10-30 18:34                               ` Michael Schmitz
2019-10-30 18:52                             ` Brad Boyer
2019-10-30  7:22                       ` Kars de Jong
2019-10-30 23:15                         ` Finn Thain
2019-11-12 18:57                     ` [PATCH 0/2] Some esp_scsi updates Kars de Jong
2019-11-12 18:57                       ` [PATCH 1/2] esp_scsi: Correct ordering of PCSCSI definition in esp_rev enum Kars de Jong
2019-11-12 23:07                         ` Finn Thain
2019-11-13  8:00                           ` Kars de Jong
2019-11-13 22:25                             ` Finn Thain
2019-11-13 14:22                         ` Christoph Hellwig
2019-11-13 15:03                           ` Kars de Jong
2019-11-12 18:57                       ` [PATCH 2/2] esp_scsi: Add support for FSC chip Kars de Jong
2019-11-12 23:18                         ` Finn Thain
2019-11-12 23:57                           ` Finn Thain
2019-11-13  9:30                           ` Kars de Jong
2019-11-13 22:24                             ` Finn Thain
2019-11-14 21:59                       ` [PATCH v2 0/2] Some esp_scsi updates Kars de Jong
2019-11-14 21:59                         ` [PATCH 1/2] esp_scsi: Correct ordering of PCSCSI definition in esp_rev enum Kars de Jong
2019-11-14 22:06                           ` Kars de Jong
2019-11-14 21:59                         ` [PATCH 2/2] esp_scsi: Add support for FSC chip Kars de Jong
2019-11-14 22:07                           ` Kars de Jong
2019-11-14 22:25                         ` [PATCH v3 0/2] Some esp_scsi updates Kars de Jong
2019-11-14 22:25                           ` [PATCH v2 1/2] esp_scsi: Correct ordering of PCSCSI definition in esp_rev enum Kars de Jong
2019-11-15  2:13                             ` Finn Thain
2019-11-15  7:04                               ` Kars de Jong
2019-11-14 22:25                           ` [PATCH v3 2/2] esp_scsi: Add support for FSC chip Kars de Jong
2019-11-15  2:09                             ` Finn Thain
2019-11-18 13:27                               ` Kars de Jong
2019-11-09 19:14                   ` [PATCH] zorro_esp: increase maximum dma length to 65536 bytes Kars de Jong
2019-11-09 20:12                     ` James Bottomley
2019-11-10  2:36                       ` Michael Schmitz
2019-11-10  9:01                         ` Kars de Jong
2019-11-10 19:26                           ` Michael Schmitz
2019-11-11  8:47                             ` Kars de Jong
2019-11-10 19:35                         ` James Bottomley
2019-11-12 17:55                           ` Kars de Jong [this message]
2019-11-12 22:46                             ` [PATCH v2] zorro_esp: Limit DMA transfers to 65536 bytes (except on Fastlane) Finn Thain
2019-11-13  2:27                             ` Martin K. Petersen
2019-11-12  9:34                         ` [PATCH] zorro_esp: increase maximum dma length to 65536 bytes Kars de Jong
2019-11-09 22:53                     ` Finn Thain
2019-11-10  9:06                       ` Kars de Jong
2019-10-28 23:38               ` ESP SCSI driver (was: Amiga PCMCIA network card support) Finn Thain
2019-10-29 11:52                 ` Kars de Jong
2019-10-29 20:16                   ` ESP SCSI driver Michael Schmitz
2019-10-28 22:31           ` Amiga PCMCIA network card support Finn Thain
2019-10-29  8:56           ` FOSDEM (was: Re: Amiga PCMCIA network card support) Geert Uytterhoeven
2019-10-29  9:13             ` John Paul Adrian Glaubitz
2019-10-28 22:08       ` Amiga PCMCIA network card support Finn Thain
2019-10-29  9:00       ` Geert Uytterhoeven
2019-10-29  9:12         ` John Paul Adrian Glaubitz
2019-10-29  9:14           ` Geert Uytterhoeven
2019-10-29  9:20             ` John Paul Adrian Glaubitz
2019-10-29  9:40         ` Kars de Jong
2019-10-28  6:57   ` Michael Schmitz

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