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Re: [Xen-devel] [PATCH 3/3 v3] xen: Fix 16550 UART console for HP Moonshot (Aarch64) platform



+ Graeme

On 27/11/17 10:06, Jan Beulich wrote:
On 24.11.17 at 12:39, <bhupinder.thakur@xxxxxxxxxx> wrote:
--- a/xen/drivers/char/ns16550.c
+++ b/xen/drivers/char/ns16550.c
@@ -1571,6 +1571,30 @@ DT_DEVICE_END
  #endif /* HAS_DEVICE_TREE */
#if defined(CONFIG_ACPI) && defined(CONFIG_ARM)
+/*
+ * APM X-Gene v1 and v2 UART hardware is an 16550 like device but has its
+ * register aligned to 32-bit. In addition, the BIOS also encoded the
+ * access width to be 8 bits. This function detects this errata condition.
+ */
+static bool xgene_8250_erratum_present(struct acpi_table_spcr *tb)

Is this really to be considered an erratum? From the description it
doesn't sound like this couldn't have been a deliberate decision.
IOW - does their behavior contradict any spec? (ACPI not providing
information in field and access width looks suspicious too - GAS fields
exist for both.)

I believe the problem here is the firmware table does not describe correctly the hardware. I have CCed Graeme which might be able to confirm.

Cheers,

--
Julien Grall

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