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SubjectRe: [PATCH 1/3] serial: 8250_early: Add earlycon support for AMD Carrizo / Stoneyridge
Hi Ricardo,

On Wed, Mar 14, 2018 at 4:54 AM Ricardo Ribalda Delgado <> wrote:

> Hi Daniel

> On Wed, Mar 14, 2018 at 1:36 AM, Daniel Kurtz <>
> >
> > AMD Carrizo / Stoneyridge use a DesignWare 8250 UART that uses a 48 MHz
> > input clock.
> >
> > Allow these platforms to set up this clock by specifying a kernel
> > line like:
> > earlycon=amdcz,mmio32,0xfedc6000,115200

> If the port and the mode (mmio32) is always fixed, couldn't we just
> add those two into
> early_amdcz_setup?

There are multiple memory mapped UARTs on at least the one chip I am aware
of, specifying the address here chooses which port to use as the early

In fact, the recommended way is to have firmware specify an ACPI SPCR table
with OEMID="AMDCZ " (see to
configure proper access and address. With an SPCR table in place, the
kernel command line just becomes "earlycon", with no parameters.


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