Re: [PATCH] ACPI: SPCR: Use access width to determine mmio usage

From: Jon Masters
Date: Sat May 06 2017 - 18:40:10 EST

On 05/04/2017 11:05 AM, Jon Mason wrote:
> The current SPCR code does not check the access width of the mmio, and
> uses a default of 8bit register accesses. This prevents devices that
> only do 16 or 32bit register accesses from working. By simply checking
> this field and setting the mmio string appropriately, this issue can be
> corrected. To prevent any legacy issues, the code will default to 8bit
> accesses if the value is anything but 16 or 32.

Thanks for this. Just as an FYI I've a running discussion with Microsoft
about defining additional UART subtypes in the DBG2 for special case
UARTs. Specifically, I want to address AppliedMicro's special 8250 dw IP
that also has a non-standard clock. At this time, there is general
agreement to use the access width for some cases rather than defining
yet more subtypes - so your patch is good.

Loc/Applied: please track this thread, incorporate feedback, and also
track the other general recent discussions of 8250 dw from this week.


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