linux-kernel - Re: [PATCH v1] of: calculate masks of the device based on dma-range size

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Message-ID: <20150226002033.GR6220@google.com>
Date:	Wed, 25 Feb 2015 18:20:33 -0600
From:	Bjorn Helgaas <bhelgaas@...gle.com>
To:	Murali Karicheri <m-karicheri2@...com>
Cc:	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	devicetree@...r.kernel.org, linux-pci@...r.kernel.org,
	Joerg Roedel <joro@...tes.org>,
	Grant Likely <grant.likely@...aro.org>,
	Rob Herring <robh+dt@...nel.org>,
	Will Deacon <will.deacon@....com>,
	Russell King <linux@....linux.org.uk>,
	Arnd Bergmann <arnd@...db.de>,
	Suravee Suthikulpanit <Suravee.Suthikulpanit@....com>,
	Catalin Marinas <catalin.marinas@....com>
Subject: Re: [PATCH v1] of: calculate masks of the device based on dma-range
 size

[+cc Catalin]

On Wed, Feb 11, 2015 at 12:53:35PM -0500, Murali Karicheri wrote:
> This patch update of_dma_configure() API to calculate the
> masks (dma_mask and coherent_dma_mask) based on the dma-range
> values set in DT for the device. Also limit the mask to lower
> of the default mask and mask calculated.
> 
> Cc: Joerg Roedel <joro@...tes.org>
> Cc: Grant Likely <grant.likely@...aro.org>
> Cc: Rob Herring <robh+dt@...nel.org>
> Cc: Bjorn Helgaas <bhelgaas@...gle.com>
> Cc: Will Deacon <will.deacon@....com>
> Cc: Russell King <linux@....linux.org.uk>
> Cc: Arnd Bergmann <arnd@...db.de>
> Cc: Suravee Suthikulpanit <Suravee.Suthikulpanit@....com>
> 
> Signed-off-by: Murali Karicheri <m-karicheri2@...com>

Applied with Catalin's reviewed-by to pci/iommu for v4.1, thanks!

I agree with Catalin's comment about the "size = 1ULL << 32" line.
I don't see how that will make a difference, so I dropped it.  The
patch I merged is below.  Let me know if you think we do need that
line or any other tweaks.

Bjorn

commit a5a1dd69080dfcf53bfd6e179f3db68e824aeaae
Author: Murali Karicheri <m-karicheri2@...com>
Date:   Wed Feb 25 17:21:04 2015 -0600

    of: Calculate device DMA masks based on DT dma-range size
    
    Calculate the dma_mask and coherent_dma_mask based on the dma-range values
    set in DT for the device.
    
    Limit the mask to lower of the default mask and mask calculated.
    
    Signed-off-by: Murali Karicheri <m-karicheri2@...com>
    Signed-off-by: Bjorn Helgaas <bhelgaas@...gle.com>
    Reviewed-by: Catalin Marinas <catalin.marinas@....com>
    CC: Joerg Roedel <joro@...tes.org>
    CC: Grant Likely <grant.likely@...aro.org>
    CC: Rob Herring <robh+dt@...nel.org>
    CC: Will Deacon <will.deacon@....com>
    CC: Russell King <linux@....linux.org.uk>
    CC: Arnd Bergmann <arnd@...db.de>
    CC: Suravee Suthikulpanit <Suravee.Suthikulpanit@....com>

diff --git a/drivers/of/device.c b/drivers/of/device.c
index 28e743888402..20c1332a0018 100644
--- a/drivers/of/device.c
+++ b/drivers/of/device.c
@@ -90,10 +90,11 @@ void of_dma_configure(struct device *dev, struct device_node *np)
 	struct iommu_ops *iommu;
 
 	/*
-	 * Set default dma-mask to 32 bit.  Drivers are expected to setup
-	 * the correct supported dma_mask.
+	 * Set default coherent_dma_mask to 32 bit.  Drivers are expected to
+	 * setup the correct supported mask.
 	 */
-	dev->coherent_dma_mask = DMA_BIT_MASK(32);
+	if (!dev->coherent_dma_mask)
+		dev->coherent_dma_mask = DMA_BIT_MASK(32);
 
 	/*
 	 * Set it to coherent_dma_mask by default if the architecture
@@ -128,6 +129,15 @@ void of_dma_configure(struct device *dev, struct device_node *np)
 
 	dev->dma_pfn_offset = offset;
 
+	/*
+	 * 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)));
+
 	coherent = of_dma_is_coherent(np);
 	dev_dbg(dev, "device is%sdma coherent\n",
 		coherent ? " " : " not ");
--
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