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Re: [PATCH 03/10] fpga: allow to compile-test Altera FPGA bridge drivers

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  Re: [PATCH 03/10] fpga: allow to compile-test Altera FPGA bridge  drivers Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-06-09 11:50 +0200
    Re: [PATCH 03/10] fpga: allow to compile-test Altera FPGA bridge  drivers Tobias Klauser <tklauser@distanz.ch> - 2017-06-09 15:50 +0200
      Re: [PATCH 03/10] fpga: allow to compile-test Altera FPGA bridge drivers Alan Tull <atull@kernel.org> - 2017-06-10 06:00 +0200

#1662200 — Re: [PATCH 03/10] fpga: allow to compile-test Altera FPGA bridge drivers

On Mon, Jun 05, 2017 at 02:07:34PM -0500, Alan Tull wrote:
> From: Tobias Klauser <tklauser@distanz.ch>
> 
> Add COMPILE_TEST to the Kconfig entry for the Altera SoCFPGA FPGA
> Bridge. The Altera FPGA Freeze Bridge can also be used on Altera PEIe
> FPGAs, so the driver shouldn't depend on ARCH_SOCFPGA in the first place.
> This allows test-compiling the drivers on other architectures to catch
> compiler errors/warnings, e.g. due to API/header changes earlier on.
> 
> Signed-off-by: Tobias Klauser <tklauser@distanz.ch>
> Signed-off-by: Alan Tull <atull@kernel.org>
> ---
>  drivers/fpga/Kconfig | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)

I'll drop this patch from the series, as kbuild reports errors with it
:(

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#1662431

On 2017-06-09 at 11:49:02 +0200, Greg Kroah-Hartman <gregkh@linuxfoundation.org> wrote:
> On Mon, Jun 05, 2017 at 02:07:34PM -0500, Alan Tull wrote:
> > From: Tobias Klauser <tklauser@distanz.ch>
> > 
> > Add COMPILE_TEST to the Kconfig entry for the Altera SoCFPGA FPGA
> > Bridge. The Altera FPGA Freeze Bridge can also be used on Altera PEIe
> > FPGAs, so the driver shouldn't depend on ARCH_SOCFPGA in the first place.
> > This allows test-compiling the drivers on other architectures to catch
> > compiler errors/warnings, e.g. due to API/header changes earlier on.
> > 
> > Signed-off-by: Tobias Klauser <tklauser@distanz.ch>
> > Signed-off-by: Alan Tull <atull@kernel.org>
> > ---
> >  drivers/fpga/Kconfig | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> I'll drop this patch from the series, as kbuild reports errors with it
> :(

These are warnings from the m32r cross compiler, not errors. They are
due to the way readl() is defined on m32r (returning unsigned long
instead of u32, as all other architectures do, see [1]). On all other
architectures the patch doesn't cause any issues. There are also other
cases which are already in mainline where this issue appers, so I'd say
this patch rather uncovers the symptom of a problem rather than causing
it ;)

[1] https://marc.info/?l=linux-kernel&m=149252925326414

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#1662872 — Re: [PATCH 03/10] fpga: allow to compile-test Altera FPGA bridge drivers

On Fri, Jun 9, 2017 at 8:44 AM, Tobias Klauser <tklauser@distanz.ch> wrote:
> On 2017-06-09 at 11:49:02 +0200, Greg Kroah-Hartman <gregkh@linuxfoundation.org> wrote:
>> On Mon, Jun 05, 2017 at 02:07:34PM -0500, Alan Tull wrote:
>> > From: Tobias Klauser <tklauser@distanz.ch>
>> >
>> > Add COMPILE_TEST to the Kconfig entry for the Altera SoCFPGA FPGA
>> > Bridge. The Altera FPGA Freeze Bridge can also be used on Altera PEIe
>> > FPGAs, so the driver shouldn't depend on ARCH_SOCFPGA in the first place.
>> > This allows test-compiling the drivers on other architectures to catch
>> > compiler errors/warnings, e.g. due to API/header changes earlier on.
>> >
>> > Signed-off-by: Tobias Klauser <tklauser@distanz.ch>
>> > Signed-off-by: Alan Tull <atull@kernel.org>
>> > ---
>> >  drivers/fpga/Kconfig | 4 ++--
>> >  1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> I'll drop this patch from the series, as kbuild reports errors with it
>> :(
>
> These are warnings from the m32r cross compiler, not errors. They are
> due to the way readl() is defined on m32r (returning unsigned long
> instead of u32, as all other architectures do, see [1]). On all other
> architectures the patch doesn't cause any issues. There are also other
> cases which are already in mainline where this issue appers, so I'd say
> this patch rather uncovers the symptom of a problem rather than causing
> it ;)
>
> [1] https://marc.info/?l=linux-kernel&m=149252925326414

Yes the issue is the way m32r defines readl().  Tobias has pointed out
[2] other kernel patches cause the same warning.  There is a trivial
suggested workaround in [1] above (declare a local u32 to take the
readl() value).  Doing that would be effort to mask a known issue that
lies in the m32r code though.

Alan

[2] https://marc.info/?l=linux-kernel&m=149260369012554&w=2

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