On 21/05/14 21:14, Geert Uytterhoeven wrote:
> Hi Ben,
>
> On Tue, Apr 15, 2014 at 11:54 AM, Ben Dooks <ben.dooks@xxxxxxxxxxxxxxx> wrote:
>>>> static struct dma_chan *shdma_of_xlate(struct of_phandle_args
>>>> *dma_spec,
>>>> struct of_dma *ofdma)
>>>> {
>>>> + struct platform_device *pdev = ofdma->of_dma_data;
>>>> u32 id = dma_spec->args[0];
>>>> dma_cap_mask_t mask;
>>>> struct dma_chan *chan;
>>>>
>>>> - if (dma_spec->args_count != 1)
>>>> + if (dma_spec->args_count == 2) {
>>>> + struct shdma_of_state *state =
>>>> platform_get_drvdata(pdev);
>>>> + struct shdma_of_client *client;
>>>> +
>>>> + client = shdma_of_find_client(state, id);
>>>> + if (!client) {
>>>> + client = devm_kzalloc(&pdev->dev,
>>>> sizeof(*client),
>>>> + GFP_KERNEL);
>>>> + if (!client)
>>>> + return NULL;
>>>> +
>>>> + client->index =
>>>> atomic_inc_return(&of_slave_index);
>>>> + client->cfg.slave_id = id;
>>>> + client->cfg.mid_rid = id;
>>>> + client->cfg.chcr = dma_spec->args[1];
>>>
>>>
>>> Can you explain the purpose of setting the chcr in DT? For all I can
>>> tell, this should come from the device driver when that calls the
>>> dma_slave_config function, unlike the mid_rid value.
>>
>>
>> See previous note about transfer-widths and register-sizes not always
>> matching. I also do not have any idea about other SoCs in the series
>> if there are any differences between channel settings.
>
> If you look for sh_dmae_slave_config in arch/arm arch/sh, you find the values
> for the existing board support.
>
> The same device always seem to use the same value, i.e. MMC always uses
> 32-bit, SCIF uses 8-bit, SDHI uses 16-bit. So I think it could be hardcoded
> in the device driver (passed via enum dma_slave_buswidth {src,dst}_addr_width
> in dma_slave_config?), and you can drop the field in the bindings.
>
> Notes:
> - RSPI is special: on SH, it's 16-bit, while QSPI on R-Car uses 8-bit.
> - SDHI uses 32-bit according to the R-Car docs, but the (working) code
> uses 16-bit?
I will move to using the configuration passed when the slave is used
instead of the one in the slave table.
--
Ben Dooks http://www.codethink.co.uk/
Senior Engineer Codethink - Providing Genius
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