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>,
linux-scsi@vger.kernel.org, linux-m68k@vger.kernel.org
Subject: Re: [PATCH] zorro_esp: increase maximum dma length to 65536 bytes
Date: Sun, 10 Nov 2019 09:53:33 +1100 (AEDT) [thread overview]
Message-ID: <alpine.LNX.2.21.1.1911100936080.8@nippy.intranet> (raw)
In-Reply-To: <20191109191400.8999-1-jongk@linux-m68k.org>
On Sat, 9 Nov 2019, Kars de Jong wrote:
> 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.
>
Makes sense. You may want to add,
Fixes: b7ded0e8b0d1 ("scsi: zorro_esp: Limit DMA transfers to 65535 bytes")
> 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.
>
> Signed-off-by: Kars de Jong <jongk@linux-m68k.org>
> ---
> drivers/scsi/zorro_esp.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/scsi/zorro_esp.c b/drivers/scsi/zorro_esp.c
> index ca8e3abeb2c7..4448567c495d 100644
> --- a/drivers/scsi/zorro_esp.c
> +++ b/drivers/scsi/zorro_esp.c
> @@ -218,7 +218,7 @@ 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;
> }
>
Would it be safer to simply remove this code and leave
esp_driver_ops.dma_length_limit == NULL for all board types?
--
> static void zorro_esp_reset_dma(struct esp *esp)
>
next prev parent reply other threads:[~2019-11-09 22:53 UTC|newest]
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 ` [PATCH v2] zorro_esp: Limit DMA transfers to 65536 bytes (except on Fastlane) Kars de Jong
2019-11-12 22:46 ` 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 [this message]
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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