linux-kernel - Re: [PATCH] m68k/mac: Replace macide driver with generic platform driver

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Message-ID: <10a08764-c138-9fe5-966c-ce68349b9b6@nippy.intranet>
Date:   Mon, 26 Apr 2021 17:37:22 +1000 (AEST)
From:   Finn Thain <fthain@...tmail.com.au>
To:     John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de>
cc:     Finn Thain <fthain@...egraphics.com.au>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Michael Schmitz <schmitzmic@...il.com>,
        Christoph Hellwig <hch@....de>,
        Joshua Thompson <funaho@...ai.org>,
        "David S. Miller" <davem@...emloft.net>,
        linux-m68k@...ts.linux-m68k.org, linux-kernel@...r.kernel.org,
        linux-ide@...r.kernel.org
Subject: Re: [PATCH] m68k/mac: Replace macide driver with generic platform
 driver

On Sun, 25 Apr 2021, John Paul Adrian Glaubitz wrote:

> On 4/25/21 11:06 AM, Finn Thain wrote:
> > This was tested on my Quadra 630. I haven't tested it on my PowerBook 150
> > because I don't have a RAM adapter board for it.
> > 
> > Apparently, the hardware I tested doesn't need macide_clear_irq() or
> > macide_test_irq() -- if it did, the generic driver would not have worked.
> > It's possible that those routines are needed for the PowerBook 150 but
> > we can cross that bridge if and when we come to it.
> > 
> > BTW, macide_clear_irq() appears to suffer from a race condition. The write
> > to the interrupt flags register could easily have unintended side effects
> > as it may alter other flag bits. Fortunately, all of the other bits are
> > unused by Linux. Moreover, when tested on my Quadra 630, that assignment
> > (*ide_ifr &= ~0x20) was observed to have no effect on bit 5.
> 
> Shouldn't we switch to a libata driver instead with legacy IDE been slated
> for removal from the Linux kernel?
> 

This patch means that the Quadra 630/580 config will work the same as the 
Powerbook 190 config. Please see commit 50c5feeea0af ("ide/macide: Convert 
Mac IDE driver to platform driver") for some background.

This patch also means that the kernel/drivers/ide/macide.ko driver module 
will disappear completely. The module that will replace it is up to you.

If you enable CONFIG_IDE and CONFIG_BLK_DEV_PLATFORM, Quadras and 
Powerbooks will use the kernel/drivers/ide/ide_platform.ko module.

If you enable CONFIG_ATA and CONFIG_PATA_PLATFORM, Quadras and
Powerbooks will use the kernel/drivers/ata/pata_platform.ko module.

(If you enable all of the above, you may need to use a blacklist to ensure 
that the preferred driver module gets loaded.)

Was macide the only IDE driver in Debian/m68k kernels without a libata 
alternative? If so, this patch would allow you to finally drop CONFIG_IDE.

> Adrian
> 
> -- 
>  .''`.  John Paul Adrian Glaubitz
> : :' :  Debian Developer - glaubitz@...ian.org
> `. `'   Freie Universitaet Berlin - glaubitz@...sik.fu-berlin.de
>   `-    GPG: 62FF 8A75 84E0 2956 9546  0006 7426 3B37 F5B5 F913
>