Re: [PATCH v2 6/6] nvme-apple: Add initial Apple SoC NVMe driver

Re: [PATCH v2 6/6] nvme-apple: Add initial Apple SoC NVMe driver

[Christoph Hellwig]

On Fri, Apr 15, 2022 at 04:20:55PM +0200, Sven Peter wrote:
> +++ b/drivers/nvme/host/apple.c
> @@ -0,0 +1,1597 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Apple ANS NVM Express device driver
> + * Copyright The Asahi Linux Contributors

Is that actually a valid legal entity?

> +#include <linux/io-64-nonatomic-lo-hi.h>

Does this controller still not support 64-bit MMIO accesses like
the old Apple PCIe controllers or is this just a leftover?

The rest of the code looks fine to me:

Reviewed-by: Christoph Hellwig <hch@lst.de>

Re: [PATCH v2 6/6] nvme-apple: Add initial Apple SoC NVMe driver

[Hector Martin]

On 19/04/2022 14.31, Christoph Hellwig wrote:
> On Fri, Apr 15, 2022 at 04:20:55PM +0200, Sven Peter wrote:
>> +++ b/drivers/nvme/host/apple.c
>> @@ -0,0 +1,1597 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +/*
>> + * Apple ANS NVM Express device driver
>> + * Copyright The Asahi Linux Contributors
> 
> Is that actually a valid legal entity?

It does not have to be. See here for the rationale behind this style of
copyright line:

https://www.linuxfoundation.org/blog/copyright-notices-in-open-source-software-projects/

TL;DR name- and year-ful copyright lines are basically useless, as they
become out of date almost immediately after they are applied. This way
we acknowledge that the files have multiple contributors (and that the
copyright line isn't trying to be an exhaustive list thereof). This
style is so far rare, but not unheard of, in the kernel; there is prior
art (e.g. grep for 'Chromium OS Authors').

(I get to re-tell this story every time we upstream to a new subsystem;
I think it's the sixth time or so :-) )

-- 
Hector Martin (marcan@marcan.st)
Public Key: https://mrcn.st/pub

Re: [PATCH v2 6/6] nvme-apple: Add initial Apple SoC NVMe driver

[Sven Peter]

On Tue, Apr 19, 2022, at 07:31, Christoph Hellwig wrote:
> On Fri, Apr 15, 2022 at 04:20:55PM +0200, Sven Peter wrote:
>> +++ b/drivers/nvme/host/apple.c
>> @@ -0,0 +1,1597 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +/*
>> + * Apple ANS NVM Express device driver
>> + * Copyright The Asahi Linux Contributors
>
> Is that actually a valid legal entity?
>
>> +#include <linux/io-64-nonatomic-lo-hi.h>
>
> Does this controller still not support 64-bit MMIO accesses like
> the old Apple PCIe controllers or is this just a leftover?

I just checked again and 64-bit accesses seem to work fine.
I'll remove the lo_hi_* calls and this include.

>
> The rest of the code looks fine to me:
>
> Reviewed-by: Christoph Hellwig <hch@lst.de>

Thanks!


Sven

Re: [PATCH v2 6/6] nvme-apple: Add initial Apple SoC NVMe driver

[Arnd Bergmann]

On Tue, Apr 19, 2022 at 11:47 AM Sven Peter <sven@svenpeter.dev> wrote:
> On Tue, Apr 19, 2022, at 07:31, Christoph Hellwig wrote:
> > On Fri, Apr 15, 2022 at 04:20:55PM +0200, Sven Peter wrote:
> >> +++ b/drivers/nvme/host/apple.c
> >> @@ -0,0 +1,1597 @@
> >> +// SPDX-License-Identifier: GPL-2.0
> >> +/*
> >> + * Apple ANS NVM Express device driver
> >> + * Copyright The Asahi Linux Contributors
> >
> > Is that actually a valid legal entity?
> >
> >> +#include <linux/io-64-nonatomic-lo-hi.h>
> >
> > Does this controller still not support 64-bit MMIO accesses like
> > the old Apple PCIe controllers or is this just a leftover?
>
> I just checked again and 64-bit accesses seem to work fine.
> I'll remove the lo_hi_* calls and this include.

If you remove the #include, it is no longer possible to compile-test
this on all 32-bit architectures, though that is probably fine as long
as the Kconfig file has the right dependencies, like

      depends on ARCH_APPLE || (COMPILE_TEST && 64BIT)

I'd prefer to keep the #include here, but I don't mind the dependency
if Christoph prefers it that way.

       Arnd

Re: [PATCH v2 6/6] nvme-apple: Add initial Apple SoC NVMe driver

[hch]

On Tue, Apr 19, 2022 at 11:52:15AM +0200, Arnd Bergmann wrote:
> > I just checked again and 64-bit accesses seem to work fine.
> > I'll remove the lo_hi_* calls and this include.
> 
> If you remove the #include, it is no longer possible to compile-test
> this on all 32-bit architectures, though that is probably fine as long
> as the Kconfig file has the right dependencies, like
> 
>       depends on ARCH_APPLE || (COMPILE_TEST && 64BIT)
> 
> I'd prefer to keep the #include here, but I don't mind the dependency
> if Christoph prefers it that way.

So thre's really two steps here:

 1) stop uing lo_hi_readq diretly which forces 32-bit access even on
    64-bit platforms
 2) stop using the io-64-nonatomic headers entirely

I definitively want 1) done if the hardware does not require it.  Trying
to cater to 32-bit build tests on hardware that has no chance of ever
being used there by including the header seems a bit silly, but if
it makes folks happy I can live with it.

> 
>        Arnd
---end quoted text---

Re: [PATCH v2 6/6] nvme-apple: Add initial Apple SoC NVMe driver

[Arnd Bergmann]

On Wed, Apr 20, 2022 at 6:34 AM hch@lst.de <hch@lst.de> wrote:
> On Tue, Apr 19, 2022 at 11:52:15AM +0200, Arnd Bergmann wrote:
> > > I just checked again and 64-bit accesses seem to work fine.
> > > I'll remove the lo_hi_* calls and this include.
> >
> > If you remove the #include, it is no longer possible to compile-test
> > this on all 32-bit architectures, though that is probably fine as long
> > as the Kconfig file has the right dependencies, like
> >
> >       depends on ARCH_APPLE || (COMPILE_TEST && 64BIT)
> >
> > I'd prefer to keep the #include here, but I don't mind the dependency
> > if Christoph prefers it that way.
>
> So thre's really two steps here:
>
>  1) stop uing lo_hi_readq diretly which forces 32-bit access even on
>     64-bit platforms
>  2) stop using the io-64-nonatomic headers entirely
>
> I definitively want 1) done if the hardware does not require it.

Yes, of cours.e

> Trying to cater to 32-bit build tests on hardware that has no chance of
> ever being used there by including the header seems a bit silly, but if
> it makes folks happy I can live with it.

As I said, I don't have a strong opinion either, it's either a trivial change
in Kconfig or a trivial header inclusion and I'd pick the header one because
it's more obvious what this is for without adding a comment.

      Arnd