linux-kernel - Re: [PATCH v3 2/4] of: move of_dma_configure() to device,c to help re-use

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Message-ID: <54AED9EC.1020703@ti.com>
Date:	Thu, 8 Jan 2015 14:26:36 -0500
From:	Murali Karicheri <m-karicheri2@...com>
To:	Arnd Bergmann <arnd@...db.de>
CC:	Rob Herring <robherring2@...il.com>,
	Joerg Roedel <joro@...tes.org>,
	Grant Likely <grant.likely@...aro.org>,
	Rob Herring <robh+dt@...nel.org>,
	Linux IOMMU <iommu@...ts.linux-foundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Will Deacon <will.deacon@....com>,
	Russell King - ARM Linux <linux@....linux.org.uk>
Subject: Re: [PATCH v3 2/4] of: move of_dma_configure() to device,c to help
 re-use

On 01/08/2015 03:40 AM, Arnd Bergmann wrote:
> On Wednesday 07 January 2015 17:37:56 Rob Herring wrote:
>> On Wed, Jan 7, 2015 at 12:49 PM, Murali Karicheri<m-karicheri2@...com>  wrote:
>>
>>> +       ret = of_dma_get_range(np,&dma_addr,&paddr,&size);
>>> +       if (ret<  0) {
>>> +               dma_addr = offset = 0;
>>> +               size = dev->coherent_dma_mask + 1;
>>
>> If coherent_dma_mask is DMA_BIT_MASK(64), then you will overflow and
>> have a size of 0. There may also be a problem when the mask is only
>> 32-bit type.
>
> The mask is always a 64-bit type, it's not optional. But you are right,
> the 64-bit mask case is broken, so I guess we have to fix it differently
> by always passing the smaller value into arch_setup_dma_ops and
> adapting that function instead.
Arnd,

What is the smaller value you are referring to in the below code? 
between *dev->dma_mask and size from DT? But overflow can still happen 
when size is to be calculated in arch_setup_dma_ops() for Non DT case or 
when DT size is configured to be equivalent of DMA_BIT_MASK(64) + 1. Can 
we discuss the code change you have in mind when you get a chance?

Murali
>
> 	Arnd


-- 
Murali Karicheri
Linux Kernel, Texas Instruments
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