Re: [PATCH] libata: IORDY handling, quiet handling

[Sergei Shtylyov <sshtylyov@ru.mvista.com>]

Alan wrote:
> For further review

> Turn on the IORDY handling logic.

> If a controller doesnt support IORDY don't try and use it

> If a device doesn't support IORDY don't try and use it

    Looks like we shouldn't change it default PIO mode at all in this case. 
See below why...

> Otherwise use it whenever possible.
> Always use IORDY for PIO3 and higher (it's mandatory)

> Send the correct set_features command if operating without IORDY

> Signed-off-by: Alan Cox <alan@redhat.com>
> 
> 
> diff -u --new-file --recursive --exclude-from /usr/src/exclude linux.vanilla-2.6.20-rc6-mm3/drivers/ata/libata-core.c linux-2.6.20-rc6-mm3/drivers/ata/libata-core.c
> --- linux.vanilla-2.6.20-rc6-mm3/drivers/ata/libata-core.c	2007-01-31 14:20:39.000000000 +0000
> +++ linux-2.6.20-rc6-mm3/drivers/ata/libata-core.c	2007-02-01 16:14:01.000000000 +0000
> @@ -1404,30 +1446,44 @@
>   *	Check if the current speed of the device requires IORDY. Used
>   *	by various controllers for chip configuration.
>   */
> -
> + 
>  unsigned int ata_pio_need_iordy(const struct ata_device *adev)
>  {
> -	int pio;
> -	int speed = adev->pio_mode - XFER_PIO_0;
> -
> -	if (speed < 2)
> +	/* Controller doesn't support  IORDY. Probably a pointless check
> +	   as the caller should know this */
> +	if (adev->ap->flags & ATA_FLAG_NO_IORDY)
>  		return 0;
> -	if (speed > 2)
> +	/* PIO3 and higher it is mandatory */
> +	if (adev->pio_mode > XFER_PIO_2)
>  		return 1;
> +	/* We turn it on when possible */
> +	if (ata_id_has_iordy(adev->id))
> +		return 1;
> +	return 0;
> +}
>  
> +/**
> + *	ata_pio_mask_no_iordy	-	Return the non IORDY mask
> + *	@adev: ATA device
> + *
> + *	Compute the highest mode possible if we are not using iordy. Return
> + *	-1 if no iordy mode is available.
> + */
> + 
> +static u32 ata_pio_mask_no_iordy(const struct ata_device *adev)
> +{
>  	/* If we have no drive specific rule, then PIO 2 is non IORDY */
> -
>  	if (adev->id[ATA_ID_FIELD_VALID] & 2) {	/* EIDE */
> -		pio = adev->id[ATA_ID_EIDE_PIO];
> +		u16 pio = adev->id[ATA_ID_EIDE_PIO];
>  		/* Is the speed faster than the drive allows non IORDY ? */
>  		if (pio) {
>  			/* This is cycle times not frequency - watch the logic! */
>  			if (pio > 240)	/* PIO2 is 240nS per cycle */
> -				return 1;
> -			return 0;
> +				return 3 << ATA_SHIFT_PIO;
> +			return 7 << ATA_SHIFT_PIO;
>  		}
>  	}
> -	return 0;
> +	return 3 << ATA_SHIFT_PIO;
>  }

    Well, after looking into ATA-1, it seems that the logic may have been and 
may be still is somewhat wrong here.  There was PIO2 already defined but no 
EIDE fields yet (and yet optional IORDY line already here).  We probably 
should always consider PIO2 non-IORDY indeed (unless told not to by the word 
67) but go figure... :-)

> @@ -3466,8 +3529,18 @@
>  	tf.command = ATA_CMD_SET_FEATURES;
>  	tf.feature = SETFEATURES_XFER;
>  	tf.flags |= ATA_TFLAG_ISADDR | ATA_TFLAG_DEVICE;
> +
> +	/* Older CFA may not support this command */
> +	if (ata_id_is_cfa(dev->id))
> +        	tf.flags |= ATA_TFLAG_QUIET;
> +
>  	tf.protocol = ATA_PROT_NODATA;
> -	tf.nsect = dev->xfer_mode;
> +
> +	/* Ancient devices may need us to avoid IORDY */
> +	if (ata_pio_need_iordy(dev))
> +		tf.nsect = dev->xfer_mode;
> +	else
> +		tf.nsect = 0x01;

    Note that ATA-1 did *not* yet define this subcode (only 0 for "block 
transfer"). I think that we should not change the PIO modes at all on 
non-IORDY drives, otherwise it's becoming pointless and messy -- you're not 
setting what you're told here and force the drive's default mode instead... 
why then change it at all?

MBR, Sergei