[alsa-devel] [PATCH 1/2][RFC] dmaengine: rcar-audmapp: calculate chcr via src/dst addr

[Geert Uytterhoeven]

On Thu, Jan 29, 2015 at 10:15 AM, Arnd Bergmann <arnd at arndb.de> wrote:
> On Thursday 29 January 2015 01:24:06 Kuninori Morimoto wrote:
>> Current rcar-audmapp is assuming that CHCR value are specified
>> from platform data or DTS bindings. but, it is possible to
>> calculate CHCR settings from src/dst address.
>> DTS bindings node can be reduced by this patch.
>>
>> Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx at renesas.com>
>
> The intention definitely looks good, but I'm worried that the
> table you add here might be too SoC specific.
>
>> +struct id_addr_table {
>> +     u8  id;
>> +     u16 addr;
>> +};
>> +
>> +static u32 audmapp_addr_to_id(struct device *dev, u32 addr)
>> +{
>> +     struct id_addr_table ssi_id_table[] = {

static const, so they don't get copied to the stack on every invocation.

>> +             {0x00, 0x0000}, /* SSI00 */
>> +             {0x01, 0x0400}, /* SSI01 */
>> +             {0x02, 0x0800}, /* SSI02 */
>> +             {0x03, 0x0C00}, /* SSI03 */
>> +             {0x04, 0x1000}, /* SSI10 */
>> +             {0x05, 0x1400}, /* SSI11 */
>> +             {0x06, 0x1800}, /* SSI12 */
>> +             {0x07, 0x1C00}, /* SSI13 */
>> +             {0x08, 0x2000}, /* SSI20 */
>
> Isn't the address part here the physical address of the FIFO,

Yes they are.

> which can be different for each implementation that contains
> an audmapp device?

Fortunately they're identical for all (current) members of the R-Car Gen2
family.

Morimoto-san: Are the base addresses configured in DT?
I did a quick search for 0xec300000, 0xec320000, 0xec40000,
0xec420000, and 0xec000000,  and couldn't find them in DT, only in
source code (comments). They must come from somewhere?
Note that I didn't follow the sound binding discussions that closely.

Thanks!

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert at linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds