[PATCH 1/2] tty: pl011: Work around QDF2400 E44 stuck BUSY bit
Timur Tabi
timur at codeaurora.org
Wed Feb 8 15:04:57 PST 2017
On 02/08/2017 04:22 PM, Christopher Covington wrote:
>>> >> - while (pl011_read(uap, REG_FR) & uap->vendor->fr_busy)
>>> >> + while ((pl011_read(uap, REG_FR) ^ uap->vendor->inv_fr)
>>> >> + & uap->vendor->fr_busy)
>> >
>> > I really think the XOR logic needs to be documented wherever it's
>> > used. It's just too confusing.
> References such as the following for basic bit operations like
> setting, clearing, and toggling are easy enough to come by.
>
> http://stackoverflow.com/questions/47981/how-do-you-set-clear-and-toggle-a-single-bit-in-c-c
I know what XOR does. I was thinking a more high-level comment would be
appropriate. With E44, we want to ignore the BUSY bit and use TXFE instead.
So was hoping to a comment that says that:
/* Normally, we poll until BUSY=0, but E44 says we should poll until TXFE=1
instead. So with E44, we set fr_busy to TXFE, but we have to invert it. */
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