Re: PATCH: (For review) Teach libata to tune master/slave seperately

[Bartlomiej Zolnierkiewicz]

Hi,

Patch looks fine some comments below:

On 1/17/06, Alan Cox <alan@xxxxxxxxxxxxxxxxxxx> wrote:
> This also adds a filter hook which allows drives to veto modes by drive
> specific detail. This is preferable to the more obvious 'have the driver
> change the speed itself' approach because we have a combination of
> constraints some known by the driver and some (such as PHY limits) by
> the core code. We don't want drivers overriding constraints due to lack
> of knowledge and setting unsafe/invalid modes.

Yep.

> The core logic is unchanged, it's merely had a re-order and the mode

The core logic is changed (in the positive way): ata_pio_modes()
is finally used for obtaining PIO mask to be used.

Please update the patch description or make it a separate change.

The other functional change is the ordering of programming host/devices:

previously:
* program PIO for device 0 [host]
* program PIO for device 1 [host]
* program DMA for device 0 [host]
* program DMA for device 1 [host]
* program xfer mode for device 0 [device]
* program xfer mode for device 1 [device]

now:
* program PIO for device 0 [host]
* program DMA for device 0 [host]
* program xfer mode for device 0 [device]
* program PIO for device 1 [host]
* program DMA for device 1 [host]
* program xfer mode for device 0 [device]

This change is OK but I wonder what is the reason for it?

> decision is made twice instead of once only. Another important change in
> the re-order which makes driver writers life much easier for PATA is
> that both drive speeds decisions are made *before* the driver is called.
>
> This is essential to your sanity when programming the many controllers
> that do not use the device select bit to switch between address setup
> times.
>
> Tested in my patches for a while and seems to work for the combinations
> I have. Introduces no new bugs I've found but obviously piix secondary
> slave doesn't reliably work with or without this change because of the
> current piix driver bug.

I thought it was merged already (it is obviously correct)?

Thanks,
Bartlomiej
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/