linux-kernel - Re: [PATCH 2/3] dmaengine: dw_dmac: Enhance device tree support

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Message-ID: <1350052912.10584.167.camel@smile>
Date:	Fri, 12 Oct 2012 14:41:55 +0000
From:	"Shevchenko, Andriy" <andriy.shevchenko@...el.com>
To:	Viresh Kumar <viresh.kumar@...aro.org>
CC:	"Koul, Vinod" <vinod.koul@...el.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"spear-devel@...t.st.com" <spear-devel@...t.st.com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	devicetree-discuss <devicetree-discuss@...ts.ozlabs.org>
Subject: Re: [PATCH 2/3] dmaengine: dw_dmac: Enhance device tree support

On Fri, 2012-10-12 at 19:36 +0530, Viresh Kumar wrote: 
> On 12 October 2012 18:58, Shevchenko, Andriy
> <andriy.shevchenko@...el.com> wrote:
> > On Fri, 2012-10-12 at 11:14 +0530, Viresh Kumar wrote:
> 
> >> +     if (!of_property_read_u32(np, "nr_masters", &val)) {
> >> +             if (val > 4)
> > I thought once that we might introduce constant like #define
> > DW_MAX_AHB_MASTERS 4. It seems a bit useless because hw is designed for
> > that number anyway, but maybe you have another opinion.
> 
> Not everyone have four masters in there SoC configurations. So its better
> to export correct values.
I meant is to use that constant instead of hard coding 4 everywhere.
It's a maximum value, not the SoC specific.

> >> +     if (!of_property_read_u32_array(np, "data_width", arr,
> >> +                             pdata->nr_masters))
> >> +             for (count = 0; count < pdata->nr_masters; count++)
> >> +                     pdata->data_width[count] = arr[count];
> > Ah, it would be nice to have of_property_read_u8_array and so on...
> 
> :)
> Maybe yes. I don't want to do it with this patchset, as that will take more
> time to go through maintainers.
Agreed, the comment just for future. I don't know if there any other
users of *_u8/u16_array().

> > it will probably require to split this part in a separate function and
> > calculate count of slave_info children before pdata memory allocation.
> 
> Liked the idea partially. Check my new implementation in fixup for all
> these comments:
Let me see.

> diff --git a/drivers/dma/dw_dmac.c b/drivers/dma/dw_dmac.c

> @@ -1516,7 +1516,7 @@ __devinit dw_dma_parse_dt(struct platform_device *pdev)
>  	struct device_node *sn, *cn, *np = pdev->dev.of_node;
>  	struct dw_dma_platform_data *pdata;
>  	struct dw_dma_slave *sd;
> -	u32 count, val, arr[4];
> +	u32 val, arr[4];
what about to use tmp name instead of val? It's really minor, but I
think val name is little bit unrelated to a loop counter.

> @@ -1533,63 +1533,57 @@ __devinit dw_dma_parse_dt(struct platform_device *pdev)

> -	count = 0;
> +	pdata->sd = sd;
> +	pdata->sd_count = val;
> +
>  	for_each_child_of_node(sn, cn) {
> -		of_property_read_string(cn, "bus_id", &sd[count].bus_id);
> -		of_property_read_u32(cn, "cfg_hi", &sd[count].cfg_hi);
> -		of_property_read_u32(cn, "cfg_lo", &sd[count].cfg_lo);
> +		sd->dma_dev = &pdev->dev;
> +		of_property_read_string(cn, "bus_id", &sd->bus_id);
> +		of_property_read_u32(cn, "cfg_hi", &sd->cfg_hi);
> +		of_property_read_u32(cn, "cfg_lo", &sd->cfg_lo);
>  		if (!of_property_read_u32(cn, "src_master", &val))
> -			sd[count].src_master = (u8)val;
> +			sd->src_master = val;
> 
>  		if (!of_property_read_u32(cn, "dst_master", &val))
> -			sd[count].dst_master = (u8)val;
> -
> -		sd[count].dma_dev = &pdev->dev;
> -		count++;
> +			sd->dst_master = val;
> +		sd++;
>  	}
This looks good.

-- 
Andy Shevchenko <andriy.shevchenko@...el.com>
Intel Finland Oy
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