linux-kernel - Re: [RFC/PATCH 5/9] of: dma: Split of_configure

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Date:	Thu, 28 May 2015 14:01:19 +0100
From:	Will Deacon <will.deacon@....com>
To:	Laurent Pinchart <laurent.pinchart+renesas@...asonboard.com>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
	Laura Abbott <lauraa@...eaurora.org>,
	Arnd Bergmann <arnd@...db.de>,
	Mitchel Humpherys <mitchelh@...eaurora.org>,
	Joreg Roedel <joro@...tes.org>,
	"grant.likely@...aro.org" <grant.likely@...aro.org>,
	Robin Murphy <Robin.Murphy@....com>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	Thierry Reding <thierry.reding@...il.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [RFC/PATCH 5/9] of: dma: Split of_configure_dma() into mask and
 ops configuration

On Fri, May 15, 2015 at 12:00:06AM +0100, Laurent Pinchart wrote:
> The of_configure_dma() function configures both the DMA masks and ops.
> Moving DMA ops configuration to probe time would thus also delay
> configuration of the DMA masks, which might not be safe. To avoid issues
> split the configuration in two to allow keeping masks configuration at
> device add time and move ops configuration to device probe time.
> 
> Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@...asonboard.com>
> ---
>  drivers/of/device.c       | 48 ++++++++++++++++++++++++++++++++++-------------
>  drivers/of/of_pci.c       |  3 ++-
>  drivers/of/platform.c     |  6 ++++--
>  include/linux/of_device.h | 11 +++++++++--
>  4 files changed, 50 insertions(+), 18 deletions(-)
> 
> diff --git a/drivers/of/device.c b/drivers/of/device.c
> index f1b84f464fe1..3cb3f78a6d13 100644
> --- a/drivers/of/device.c
> +++ b/drivers/of/device.c
> @@ -70,7 +70,7 @@ int of_device_add(struct platform_device *ofdev)
>  }
>  
>  /**
> - * of_dma_configure - Setup DMA configuration
> + * of_dma_configure - Setup DMA masks and offset
>   * @dev:	Device to apply DMA configuration
>   * @np:		Pointer to OF node having DMA configuration
>   *
> @@ -81,13 +81,11 @@ int of_device_add(struct platform_device *ofdev)
>   * can use a platform bus notifier and handle BUS_NOTIFY_ADD_DEVICE events
>   * to fix up DMA configuration.
>   */
> -void of_dma_configure(struct device *dev, struct device_node *np)
> +void of_dma_configure_masks(struct device *dev, struct device_node *np)
>  {
> -	u64 dma_addr, paddr, size;
> -	int ret;
> -	bool coherent;
> +	u64 dma_addr, paddr, size, range_mask;
>  	unsigned long offset;
> -	struct iommu_ops *iommu;
> +	int ret;
>  
>  	/*
>  	 * Set default coherent_dma_mask to 32 bit.  Drivers are expected to
> @@ -105,9 +103,10 @@ void of_dma_configure(struct device *dev, struct device_node *np)
>  
>  	ret = of_dma_get_range(np, &dma_addr, &paddr, &size);
>  	if (ret < 0) {
> -		dma_addr = offset = 0;
> -		size = dev->coherent_dma_mask + 1;
> +		range_mask = dev->coherent_dma_mask + 1;

Hmm, do we still want this '+ 1'...

> +		offset = 0;
>  	} else {
> +		range_mask = DMA_BIT_MASK(ilog2(dma_addr + size));
>  		offset = PFN_DOWN(paddr - dma_addr);
>  		dev_dbg(dev, "dma_pfn_offset(%#08lx)\n", offset);
>  	}
> @@ -118,10 +117,31 @@ void of_dma_configure(struct device *dev, struct device_node *np)
>  	 * Limit coherent and dma mask based on size and default mask
>  	 * set by the driver.
>  	 */
> -	dev->coherent_dma_mask = min(dev->coherent_dma_mask,
> -				     DMA_BIT_MASK(ilog2(dma_addr + size)));
> -	*dev->dma_mask = min((*dev->dma_mask),
> -			     DMA_BIT_MASK(ilog2(dma_addr + size)));
> +	dev->coherent_dma_mask = min(dev->coherent_dma_mask, range_mask);

... if we now compare directly with the mask here? In fact, this setting
of the coherent_dma_mask could just belong in the else clause, no?

> +	*dev->dma_mask = min((*dev->dma_mask), range_mask);

Similar comment here, but we need to do this for both cases I guess.

> +}
> +EXPORT_SYMBOL_GPL(of_dma_configure_masks);
> +
> +/**
> + * of_dma_configure_ops - Setup DMA operations
> + * @dev:	Device to apply DMA configuration
> + * @np:		Pointer to OF node having DMA configuration
> + *
> + * Try to get devices's DMA configuration from DT and update it

Weird spelling.

Will
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