Re: [PATCH 2/2] dw_dmac: return proper residue value

[Viresh Kumar]

On 23 January 2013 14:42, Andy Shevchenko
<andriy.shevchenko@xxxxxxxxxxxxxxx> wrote:
> Ah, you mean the dma_cookie_status returns DMA_SUCCESS in case
> active_list is empty, don't you?

Bingo!!

> Yesterday I spent in testing of different approaches. First of all, the
> calculation of the sent amount is nicer when ctlhi/ctllo is used and it
> works fine. But the approach, when we substract length of sent
> descriptors, is losing data. Namely, we have no information how big is
> the master descriptor (it has total length of the entire chain). So, I'm
> thinking how to solve this one. Otherwise it seems simpler than mine
> first idea.

I was planning to give you another review comment which i thought i will
give later :)

It looks to be a bit wrong to have individual lengths in all descriptors leaving
the first one :)

This is the descriptor struct:

struct dw_desc {
	/* FIRST values the hardware uses */
	struct dw_lli			lli;

	/* THEN values for driver housekeeping */
	struct list_head		desc_node;
	struct list_head		tx_list;
	struct dma_async_tx_descriptor	txd;
	size_t				len;
};

Firstly i believe we can have a union of both list_heads as only one is used
at any time. Can you patch it down?

Second to solve your problem, you can add another field here: total_len.
I know it will consume 4 bytes per desc but i think that's the drawback we need
to accept.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/