linux-kernel - Re: [PATCH] DW: Read "is_memcpy" and "is

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Message-ID: <1471617566.4887.184.camel@linux.intel.com>
Date:   Fri, 19 Aug 2016 17:39:26 +0300
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Eugeniy Paltsev <Eugeniy.Paltsev@...opsys.com>,
        dmaengine@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, viresh.kumar@...aro.org,
        Nelson.Pereira@...opsys.com, vinod.koul@...el.com,
        linux-snps-arc@...ts.infradead.org, Rob Herring <robh@...nel.org>
Subject: Re: [PATCH] DW: Read "is_memcpy" and "is_nollp" property from
 device tree.

On Tue, 2016-08-16 at 14:31 +0300, Eugeniy Paltsev wrote:
> DW DMAC on ARC SDP became broken after df5c7386 ("dmaengine: dw: some
> Intel
> devices has no memcpy support") and 30cb2639 ("dmaengine: dw: don't
> override
> platform data with autocfg") commits.

I'm not sure that word 'broken' is a correct one here. Is the platform
code using this driver in the upstream already? If so, where is it
located?

> 
> * After df5c7386 commit "DMA_MEMCPY" capability option doesn't get set
> correctly in platform driver version.
> * After 30cb2639 commit "nollp" parameters don't get set correctly in
> platform driver version.

> 
> This happens because in old driver version there are three sources of
> parameters: pdata, device tree and autoconfig hardware registers. Some
> parameters were read from pdata and others from autoconfig hardware
> registers. If pdata was absent some pdata structure fields were filled
> with parameters from device tree.


> But 30cb2639 commit disabled overriding pdata with autocfg, so if we
> use platform driver version without pdata some parameters will not be
> set.
> This leads to inoperability of DW DMAC.

My suggestion is still the same, i.e. split platform data to actual
hardware properties and platform quirks. We might be able to use quirks
even in case of auto configuration.

> 
> This patch adds reading missed parameters from device tree.
> 
> Note there's a prerequisite http://www.spinics.net/lists/dmaengine/msg
> 10682.html
> 
> Signed-off-by: Eugeniy Paltsev <Eugeniy.Paltsev@...opsys.com>
> ---
>  drivers/dma/dw/platform.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/dma/dw/platform.c b/drivers/dma/dw/platform.c
> index 5bda0eb..2712602 100644
> --- a/drivers/dma/dw/platform.c
> +++ b/drivers/dma/dw/platform.c
> @@ -129,6 +129,12 @@ dw_dma_parse_dt(struct platform_device *pdev)
>  	if (of_property_read_bool(np, "is_private"))
>  		pdata->is_private = true;
>  
> +	if (of_property_read_bool(np, "is_memcpy"))
> +		pdata->is_memcpy = true;
> +
> +	if (of_property_read_bool(np, "is_nollp"))
> +		pdata->is_nollp = true;

I'm pretty sure this one (besides that fact that it misses documentation
update and '-' instead of '_' as ordered by DT policy) is unacceptable
in DT since it represents *OS related* quirks. (Btw, is_private is also
should not be there in the first place)

Rob Herring (Cc'ed) might shed a light how to proceed in this case.

> +
>  	if (!of_property_read_u32(np, "chan_allocation_order", &tmp))
>  		pdata->chan_allocation_order = (unsigned char)tmp;
>  

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