Re: [PATCH] mmc: mmci: Add new VE MMCI variant

Russell King - ARM Linux
2012-12-14T17:11:24Z

On Fri, Dec 14, 2012 at 03:38:46PM +0000, Pawel Moll wrote:
> The Versatile Express IOFPGA as shipped on VECD 5.0 (bitfiles v108/208
> and v116/216) contains a modified version of the PL180 MMCI, with
> PeriphID Configuration value changed to 0x2.
>
> This version adds an optional "hardware flow control" feature. When
> enabled MMC card clock will be automatically disabled when FIFO is
> about to over/underflow and re-enabled once the host retrieved some
> data. This makes the controller immune to over/underrun errors caused
> by big interrupt handling latencies.

Wrong. It doesn't make it "immune", it just makes it less likely to
occur - you just need a heavier workload to provoke it.

"This makes the controller more immune to over/underrun errors caused
by longer interrupt handling latencies" would be a more accurate
statement.