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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)
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)
> 

  parent 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                           ` [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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