From: Mark Lord <liml@rtr.ca>
To: Tejun Heo <htejun@gmail.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>,
jeff@garzik.org, linux-ide@vger.kernel.org, albertl@mail.com,
jens.axboe@oracle.com
Subject: Re: [PATCH 13/13] libata: use PIO for misc ATAPI commands
Date: Tue, 27 Nov 2007 18:34:43 -0500 [thread overview]
Message-ID: <474CA993.3080703@rtr.ca> (raw)
In-Reply-To: <474CA8DD.3040004@rtr.ca>
Mark Lord wrote:
> Tejun Heo wrote:
>> Alan Cox wrote:
> ..
>> Because we can't use DMA uniformly, I went the other way and tried to
>> use PIO uniformly. Another important point is that the other OS which
>> is probably the only platform most ATAPI device vendors test against use
>> PIO for these commands.
>>
>>> - Control over the DMA/PIO strategy belongs with the driver. If we mess
>>> that up it will cost us dearly later.
>>
>> And I don't get what we'll lose. Care to deliberate?
> ..
>
> Mmmm.. so what happens with the various controllers that can do PIO
> using host-DMA and host-queuing ? Dropping to *real* PIO mode can
> be quite expensive on those, especially when the channel is shared
> with a hard disk.
..
Or, for that matter, shared with a port multiplier and several other devices ?
next prev parent reply other threads:[~2007-11-27 23:34 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-11-27 15:13 [PATCHSET] libata: improve ATAPI data transfer handling Tejun Heo
2007-11-27 15:13 ` [PATCH 01/13] libata: update atapi_eh_request_sense() such that lbam/lbah contains buffer size Tejun Heo
2007-11-27 15:13 ` [PATCH 02/13] cdrom: add more GPCMD_* constants Tejun Heo
2007-11-27 15:13 ` [PATCH 03/13] libata: rename ATA_PROT_ATAPI_* to ATAPI_PROT_* Tejun Heo
2007-11-27 15:13 ` [PATCH 04/13] libata: add ATAPI_* cmd types and implement atapi_cmd_type() Tejun Heo
2007-11-27 15:13 ` [PATCH 05/13] libata: improve ATAPI draining Tejun Heo
2007-11-29 6:28 ` Albert Lee
2007-11-29 7:26 ` Tejun Heo
2007-11-29 14:34 ` Tejun Heo
2007-11-27 15:13 ` [PATCH 06/13] libata: make atapi_request_sense() use sg Tejun Heo
2007-11-27 15:13 ` [PATCH 07/13] libata: kill non-sg DMA interface Tejun Heo
2007-11-27 15:13 ` [PATCH 08/13] libata: change ATA_QCFLAG_DMAMAP semantics Tejun Heo
2007-11-27 15:13 ` [PATCH 09/13] libata: convert to chained sg Tejun Heo
2007-11-27 15:13 ` [PATCH 10/13] libata: add qc->dma_nbytes Tejun Heo
2007-11-27 17:20 ` Alan Cox
2007-11-27 15:13 ` [PATCH 11/13] libata: implement ATAPI drain buffer Tejun Heo
2007-11-27 15:13 ` [PATCH 12/13] libata: implement ATAPI per-command-type DMA horkages Tejun Heo
2007-11-27 15:13 ` [PATCH 13/13] libata: use PIO for misc ATAPI commands Tejun Heo
2007-11-27 16:56 ` Alan Cox
2007-11-27 23:01 ` Tejun Heo
2007-11-27 23:31 ` Mark Lord
2007-11-27 23:34 ` Mark Lord [this message]
2007-11-27 23:37 ` Tejun Heo
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