On Tue, 10 Sep 2019, Andreas Schwab wrote:

> On Sep 10 2019, Christoph Hellwig <hch@lst.de> wrote:
> 
> > On Tue, Sep 10, 2019 at 08:57:37AM +0200, Andreas Schwab wrote:
> >> On Sep 10 2019, Christoph Hellwig <hch@lst.de> wrote:
> >> 
> >> > The sifive serial driver implements earlycon support,
> >> 
> >> It should probably be documented in admin-guide/kernel-parameters.txt.
> >
> > How so?  Wіth OF and a stdout path you just set earlycon on the
> > command line without any arguments and it will be found.
> 
> Doesn't work for me.
> 
> [    0.000000] Malformed early option 'earlycon'

Try:

    earlycon=sifive,0x10010000

If it works, you should see this message on the kernel console very early 
in the boot:

[    0.000000] earlycon: sifive0 at MMIO 0x0000000010010000 (options '')


- Paul