[SLOF] [PATCH slof] pci-phb: Reimplement dma-map-in/out

[Alexey Kardashevskiy]

On 14/11/2019 22:47, Segher Boessenkool wrote:
> Hi!
> 
> On Thu, Nov 14, 2019 at 02:33:41PM +1100, Alexey Kardashevskiy wrote:
>> +: align-4k
>> +    fff not and
>> +;
> 
> This is aligning down.  "align" means "align upwards" normally.  The word
> "align" aligns the data space, while "aligned" aligns a pointer.  SLOF also
> has a utility word "#aligned" to align to some certain boundary.  So you
> would do
> 
> : align-4k  ( a - a ) 1000 #aligned ;
> 
> but that sligns *upwards*.
> 
> : trunc-4k  ( a - a ) -1000 and ;
> 
> if you want a lower address, instead (less often useful, btw).
> 
> (OF always is two's complement, you can write -1000 instead of fff invert).

I am really not used to "-1000" :-/

> 
>> +\ grub does not align allocated addresses to the size
>> +\ so when mapping in dma-map-in, sometime we call H_PUT_TCE more than
>> +\ bm-alloc allocated
>> +: dma-align ( virt size -- virt aligned-size )
>> +    over fff and + fff + fff not and
>> +;
> 
> : dma-align  ( virt size -- virt a-size )  over fff and +  1000 @aligned ;
> 
> fff + fff not and   is just  1000 #aligned  .
> 
> I don't understand why you are adding the low twelve bits of the address
> to the size as well?

Because everything from the beginning of 4K chunk need to be included
into the DMA mapping - the IOMMU pages are 4K aligned.


-- 
Alexey