linux-kernel - Re: Kernel 2.6.37 erroneously limiting to UDMA/33

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Message-ID: <4D25DFDA.8010909@earthlink.net>
Date:	Thu, 06 Jan 2011 10:29:30 -0500
From:	Stephen Clark <sclark46@...thlink.net>
To:	Andreas Mohr <andi@...as.de>
CC:	Robert Hancock <hancockrwd@...il.com>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	ide <linux-ide@...r.kernel.org>
Subject: Re: Kernel 2.6.37 erroneously limiting to UDMA/33

On 01/06/2011 05:30 AM, Andreas Mohr wrote:
> Hi,
>
> Robert Hancock wrote:
>    
>> On 01/05/2011 12:33 PM, Stephen Clark wrote:
>>      
>>> Hello,
>>>
>>> Why is the kernel limiting me to udma/33 when the device says it can do
>>> ata2.01: CFA: TRANSCEND, 20070831, max UDMA/66
>>>
>>> There is no cable the compact flash is a socket on the motherboard!
>>>        
>> The kernel has no way to know that, and presumably the board isn't
>> connecting the signal for IDE pin 34 to ground in order to properly
>> signal that an 80-wire cable (or equivalent) is connected so that speeds
>> over UDMA33 can be used.
>>
>> You should be able to use the libata.force=80c option on the kernel
>> command line to override the cable detection.
>>      
> Further comments for the OP:
>
> If 80c happens to be correct for this machine (since it's soldered
> it's quite obvious) and the machine is quite wide-spread, perhaps one needs
> to add overrides within drivers/ata/pata_via.c/via_cable_detect() functionality,
> analogous to the ata_piix.c/ich_pata_cable_detect() case where it uses
> an entire ich_laptop device list to match against,
> to detect special 80c compatible cases.
>
> But since pata_via.c has the insightful comment
> "Perform cable detection. Actually for the VIA case the BIOS
>   already did this for us."
> it looks like your BIOS might be considered "broken"
> due to not indicating 80c for such a solder job
> -->  BIOS upgrade available?
>
>    
Will check. The machine is an Acrosser AR-M0898B micro box, for use such as
a firewall, vpn appliance, etc.
> And perhaps better avoid mentioning a specific kernel in the subject
> line unless it's a regression (which likely isn't the case here),
> or write it like "..... (on 2.6.XXX)".
>
>    
Good point.

> Andreas Mohr
>
>    


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