[U-Boot] [PATCH 1/2] mtd: vf610_nfc: mark page as dirty on block erase

[Scott Wood]

On Tue, 2015-03-31 at 11:02 -0400, Bill Pringlemeir wrote:
> On 2015-03-31 00:15, Scott Wood wrote:
> 
> > Especially since you'd be doing one write rather than four full-page
> > "partial" writes.  Surely the bottleneck here is the NAND chip itself,
> > not copying data to the buffer?
> 
> The AHB bus that the NFC controller is on is relatively slow.  Here are
> some numbers from 'AN4947-vybrid-bus-architechure',
> 
> Vybrid Cortex A5 to DDR (in CPU clocks 400/500MHz),
> 
>    First read     Subsequent
>    285            8              all caches on
>    345            269            no cache, mmu
>    437            371            no cache, no mmu
> 
> The NFC is on an AHB bus 32bit, 66MHz (not AXI 64bit, 133-166MHz like
> DDR).  The AHB will be about four times slower.  Also the reads and
> writes to the physical NAND must take place serially.  Here are the
> program page steps.
> 
>   1. Issue controller Read full page to NFC buffer.
>   2. Copy update partial page from DDR to NFC buffer.
>   3. Issue write NAND page.

Why is any sort of read part of the write process?

If this controller can't handle subpage writes properly, then disable
them.

-Scott