linux-kernel - Re: [PATCH] mfd: inherit coherent_dma

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Message-ID: <20140924101452.GF19999@lee--X1>
Date:	Wed, 24 Sep 2014 11:14:52 +0100
From:	Lee Jones <lee.jones@...aro.org>
To:	Boris BREZILLON <boris.brezillon@...e-electrons.com>
Cc:	Samuel Ortiz <sameo@...ux.intel.com>,
	Arnd Bergmann <arnd@...db.de>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mfd: inherit coherent_dma_mask from parent device

On Mon, 22 Sep 2014, Boris BREZILLON wrote:

> dma_mask and dma_parms are already inherited from the parent device but
> dma_coherent_mask was left uninitialized (set to zero thanks to kzalloc).
> Set sub-device coherent_dma_mask to its parent value to simplify
> sub-drivers making use of dma coherent helper functions (those drivers
> currently have to explicitly set the dma coherent mask using
> dma_set_coherent_mask function).
> 
> Signed-off-by: Boris BREZILLON <boris.brezillon@...e-electrons.com>

Applied with Arnd's Ack.

> ---
> 
> Hi,
> 
> This patch is follow-up of a discussion we had on a KMS driver thread [1].
> This patch is only copying the parent device coherent_dma_mask to avoid
> calling specific dma_set_coherent_mask in case the coherent mask is the
> default one.
> 
> I'm a bit surprised this hasn't been done earlier while other dma fields
> (mask and parms) are already inherited from the parent device, so please
> tell me if there already was an attempt to do the same, and if so, what
> was the reson for rejecting it :-).
> 
> Best Regards,
> 
> Boris
> 
> [1]https://lkml.org/lkml/2014/9/22/392
> 
>  drivers/mfd/mfd-core.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/mfd/mfd-core.c b/drivers/mfd/mfd-core.c
> index 892d343..5d0fbe1 100644
> --- a/drivers/mfd/mfd-core.c
> +++ b/drivers/mfd/mfd-core.c
> @@ -101,6 +101,7 @@ static int mfd_add_device(struct device *parent, int id,
>  	pdev->dev.type = &mfd_dev_type;
>  	pdev->dev.dma_mask = parent->dma_mask;
>  	pdev->dev.dma_parms = parent->dma_parms;
> +	pdev->dev.coherent_dma_mask = parent->coherent_dma_mask;
>  
>  	ret = regulator_bulk_register_supply_alias(
>  			&pdev->dev, cell->parent_supplies,

-- 
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
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