linux-kernel - Re: [PATCH] pata_it821x: sync with IDE it821x driver

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Message-ID: <466B830B.5020007@gmail.com>
Date:	Sun, 10 Jun 2007 13:50:19 +0900
From:	Tejun Heo <htejun@...il.com>
To:	Bartlomiej Zolnierkiewicz <bzolnier@...il.com>
CC:	Jeff Garzik <jeff@...zik.org>, Alan Cox <alan@...rguk.ukuu.org.uk>,
	linux-ide@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] pata_it821x: sync with IDE it821x driver

Bartlomiej Zolnierkiewicz wrote:
>>> @@ -258,8 +259,14 @@ static void it821x_passthru_set_piomode(
>>>  	static const u8 pio_want[]    = { ATA_66, ATA_66, ATA_66, ATA_66, ATA_ANY };
>>>  
>>>  	struct it821x_dev *itdev = ap->private_data;
>>> +	struct ata_device *pair = ata_dev_pair(adev);
>>>  	int unit = adev->devno;
>>> -	int mode_wanted = adev->pio_mode - XFER_PIO_0;
>>> +	int mode_wanted = adev->pio_mode;
>>> +
>>> +	if (pair && adev->pio_mode > pair->pio_mode)
>>> +		mode_wanted = pair->pio_mode;
>>> +
>>> +	mode_wanted -= XFER_PIO_0;
>> I think this is better done by mode_filter callback which is guaranteed
>> to be called before any actual mode configuration is performed and in
>> device order (master then slave).
> 
> I was thinking about using ->mode_filter but since all other PATA host
> drivers are doing PIO filtering in ->set_piomode methods and also since it
> seemed that using ->mode_filter method would result in slightly more complex
> code I opted for coherency / simplicity.  However if you (or somebody else)
> want to make a follow-up change to this driver (and preferably other PATA
> host drivers ie. pata_sil680) to use ->mode_filter I'm also fine with that.

Hmmm... indeed.  Alan, is there any reason we do that in ->set_piomode
not ->mode_filter?  We end up with mismatching configuration between the
controller and the higher speed drive.

-- 
tejun
-
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