Re: [PATCH v1 12/12] serial: 8250_lpss: enable DMA on Intel Quark UART

[Bryan O'Donoghue]

On Tue, 2016-04-12 at 19:50 +0300, Andy Shevchenko wrote:
> > I haven't read your V2 yet but on this, I'd suggest raising the
> burst
> > size to 32 bytes for UART (no higher) we found during bringup that
> > larger sizes "fall-over and die" but, anything up to 32 bytes is OK
> -
> > and therefore you should be able to reduce the number of
> > bursts/interrupts etc.
> 
> It can't be more that FIFO size and recommendation as far as I know
> is
> FIFO/2, which is exactly 8 bytes.

Why not ?

We went as high as 32 bytes previously in the BSP with no obvious
errors.

At 8 bytes or 1/2 of the FIFO size I'd ask the question is DMA even
worth it i.e. does it take more time to setup and execute a DMA
transaction @ 1/2 FIFO size than just writing straight into the FIFO ?

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bod