2018-03-14 00:38:57

by Daniel Kurtz

Subject: [PATCH 2/3] ACPI: SPCR: Add support for AMD CT/SZ

AMD Carrizo / Stoneyridge use a DesignWare 8250 UART that uses a special
earlycon setup handler to configure its input clock in order to compute
baud rate divisor registers.
Detect them by examining the OEMID field in the SPCR header, and pass
then pass uart type amdcz to earlycon.

Signed-off-by: Daniel Kurtz <[email protected]>
---
drivers/acpi/spcr.c | 23 +++++++++++++++++++++++
1 file changed, 23 insertions(+)

diff --git a/drivers/acpi/spcr.c b/drivers/acpi/spcr.c
index 9d52743080a4..52d840d0e05b 100644
--- a/drivers/acpi/spcr.c
+++ b/drivers/acpi/spcr.c
@@ -73,6 +73,24 @@ static bool xgene_8250_erratum_present(struct acpi_table_spcr *tb)
return xgene_8250;
}

+/*
+ * AMD Carrizo / Stoneyridge use a DesignWare 8250 UART that uses a special
+ * earlycon setup handler to configure its input clock in order to compute
+ * baud rate divisor registers.
+ * Detect them by examining the OEM fields in the SPCR header.
+ */
+static bool amdcz_present(struct acpi_table_spcr *tb)
+{
+ if (memcmp(tb->header.oem_id, "AMDCZ ", ACPI_OEM_ID_SIZE))
+ return false;
+
+ if (memcmp(tb->header.oem_table_id, "AMDCZ ",
+ ACPI_OEM_TABLE_ID_SIZE))
+ return false;
+
+ return true;
+}
+
/**
* acpi_parse_spcr() - parse ACPI SPCR table and add preferred console
*
@@ -189,6 +207,11 @@ int __init acpi_parse_spcr(bool enable_earlycon, bool enable_console)
uart = "qdf2400_e44";
}

+ if (amdcz_present(table)) {
+ if (enable_earlycon)
+ uart = "amdcz";
+ }
+
if (xgene_8250_erratum_present(table)) {
iotype = "mmio32";

--
2.16.2.804.g6dcf76e118-goog

2018-03-14 10:38:20

by Andy Shevchenko

Subject: Re: [PATCH 2/3] ACPI: SPCR: Add support for AMD CT/SZ

On Wed, Mar 14, 2018 at 2:36 AM, Daniel Kurtz <[email protected]> wrote:
> AMD Carrizo / Stoneyridge use a DesignWare 8250 UART that uses a special
> earlycon setup handler to configure its input clock in order to compute
> baud rate divisor registers.
> Detect them by examining the OEMID field in the SPCR header, and pass
> then pass uart type amdcz to earlycon.

Thanks, this is what I meant.
Reviewed-by: Andy Shevchenko <[email protected]>

> Signed-off-by: Daniel Kurtz <[email protected]>
> ---
> drivers/acpi/spcr.c | 23 +++++++++++++++++++++++
> 1 file changed, 23 insertions(+)
>
> diff --git a/drivers/acpi/spcr.c b/drivers/acpi/spcr.c
> index 9d52743080a4..52d840d0e05b 100644
> --- a/drivers/acpi/spcr.c
> +++ b/drivers/acpi/spcr.c
> @@ -73,6 +73,24 @@ static bool xgene_8250_erratum_present(struct acpi_table_spcr *tb)
> return xgene_8250;
> }
>
> +/*
> + * AMD Carrizo / Stoneyridge use a DesignWare 8250 UART that uses a special
> + * earlycon setup handler to configure its input clock in order to compute
> + * baud rate divisor registers.
> + * Detect them by examining the OEM fields in the SPCR header.
> + */
> +static bool amdcz_present(struct acpi_table_spcr *tb)
> +{
> + if (memcmp(tb->header.oem_id, "AMDCZ ", ACPI_OEM_ID_SIZE))
> + return false;
> +
> + if (memcmp(tb->header.oem_table_id, "AMDCZ ",
> + ACPI_OEM_TABLE_ID_SIZE))
> + return false;
> +
> + return true;
> +}
> +
> /**
> * acpi_parse_spcr() - parse ACPI SPCR table and add preferred console
> *
> @@ -189,6 +207,11 @@ int __init acpi_parse_spcr(bool enable_earlycon, bool enable_console)
> uart = "qdf2400_e44";
> }
>
> + if (amdcz_present(table)) {
> + if (enable_earlycon)
> + uart = "amdcz";
> + }
> +
> if (xgene_8250_erratum_present(table)) {
> iotype = "mmio32";
>
> --
> 2.16.2.804.g6dcf76e118-goog
>



--
With Best Regards,
Andy Shevchenko

2018-04-17 00:45:18

by Jon Masters

Subject: Re: [PATCH 2/3] ACPI: SPCR: Add support for AMD CT/SZ

On 03/13/2018 08:36 PM, Daniel Kurtz wrote:
> AMD Carrizo / Stoneyridge use a DesignWare 8250 UART that uses a special
> earlycon setup handler to configure its input clock in order to compute
> baud rate divisor registers.
> Detect them by examining the OEMID field in the SPCR header, and pass
> then pass uart type amdcz to earlycon.

FYI I spoke with Microsoft some time ago about standardizing the ability
to convey non-standard baud rates in the SPCR. If you're interested in
driving, I can put you in touch with the right person over there.

Jon.

--
Computer Architect