Re: [PATCH 2/2] MIPS: Add custom serial.h with BASE_BAUD override for generic kernel

[Matt Redfearn]

On 28/11/17 14:35, Greg Kroah-Hartman wrote:
> On Wed, Nov 22, 2017 at 09:57:29AM +0000, Matt Redfearn wrote:
> > Add a custom serial.h header for MIPS, allowing platforms to override
> > the asm-generic version if required.
> >
> > The generic platform uses this header to set BASE_BAUD to 0. The
> > generic platform supports multiple boards, which may have different
> > UART clocks. Also one of the boards supported is the Boston FPGA board,
> > where the UART clock depends on the loaded FPGA bitfile. As such there
> > is no way that the generic kernel can set a compile time default
> > BASE_BAUD.
> >
> > Commit 31cb9a8575ca ("earlycon: initialise baud field of earlycon device
> > structure") changed the behavior of of_setup_earlycon such that any baud
> > rate set in the device tree is now set in the earlycon structure. The
> > UART driver will then calculate a divisor based on BASE_BAUD and set it.
> > With MIPS generic kernels this resulted in garbage output due to the
> > incorrect uart clock rate being used to calculate a divisor. This
> > commit, combined with "serial: 8250_early: Only set divisor if valid clk
> > & baud" prevents the earlycon code setting a bad divisor and restores
> > earlycon output.
> >
> > Fixes: 31cb9a8575ca ("earlycon: initialise baud field of earlycon device structure")
> > Cc: stable <stable@xxxxxxxxxxxxxxx> # 4.14
> > Signed-off-by: Matt Redfearn <matt.redfearn@xxxxxxxx>
> >
> > ---
> >
> >   arch/mips/include/asm/Kbuild   |  1 -
> >   arch/mips/include/asm/serial.h | 21 +++++++++++++++++++++
> >   2 files changed, 21 insertions(+), 1 deletion(-)
> >   create mode 100644 arch/mips/include/asm/serial.h
> >
> > diff --git a/arch/mips/include/asm/Kbuild b/arch/mips/include/asm/Kbuild
> > index 7c8aab23bce8..b1f66699677d 100644
> > --- a/arch/mips/include/asm/Kbuild
> > +++ b/arch/mips/include/asm/Kbuild
> > @@ -16,7 +16,6 @@ generic-y += qrwlock.h
> >   generic-y += qspinlock.h
> >   generic-y += sections.h
> >   generic-y += segment.h
> > -generic-y += serial.h
> >   generic-y += trace_clock.h
> >   generic-y += unaligned.h
> >   generic-y += user.h
> > diff --git a/arch/mips/include/asm/serial.h b/arch/mips/include/asm/serial.h
> > new file mode 100644
> > index 000000000000..30be5cd8efdb
> > --- /dev/null
> > +++ b/arch/mips/include/asm/serial.h
> > @@ -0,0 +1,21 @@
> > +/*
> > + * This file is subject to the terms and conditions of the GNU General Public
> > + * License.  See the file "COPYING" in the main directory of this archive
> > + * for more details.
>
> Which version of the GPL?  As it is, this means "GPL v1 and all others".
>
> I doubt you want that :)

Good point - thanks!

Matt

> thanks,
>
> greg k-h