From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754932AbbA1U4k (ORCPT ); Wed, 28 Jan 2015 15:56:40 -0500 Received: from service88.mimecast.com ([195.130.217.12]:34044 "EHLO service88.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754761AbbA1U42 convert rfc822-to-8bit (ORCPT ); Wed, 28 Jan 2015 15:56:28 -0500 Message-ID: <54C9068D.8050701@arm.com> Date: Wed, 28 Jan 2015 15:55:57 +0000 From: Robin Murphy User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.4.0 MIME-Version: 1.0 To: Catalin Marinas , Murali Karicheri CC: "devicetree@vger.kernel.org" , Russell King , Arnd Bergmann , "linux-pci@vger.kernel.org" , Joerg Roedel , Will Deacon , "linux-kernel@vger.kernel.org" , "grant.likely@linaro.org" , "iommu@lists.linux-foundation.org" , Rob Herring , "suravee.suthikulpanit@amd.com" , Bjorn Helgaas , "linux-arm-kernel@lists.infradead.org" Subject: Re: [PATCH v4 3/6] of: fix size when dma-range is not used References: <1422052359-12384-1-git-send-email-m-karicheri2@ti.com> <1422052359-12384-4-git-send-email-m-karicheri2@ti.com> <54C77616.80301@arm.com> <54C7DF13.20402@ti.com> <20150128110523.GC6646@e104818-lin.cambridge.arm.com> In-Reply-To: <20150128110523.GC6646@e104818-lin.cambridge.arm.com> X-OriginalArrivalTime: 28 Jan 2015 15:55:57.0868 (UTC) FILETIME=[E7D4D6C0:01D03B12] X-MC-Unique: 115012815560001101 Content-Type: text/plain; charset=WINDOWS-1252; format=flowed Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 28/01/15 11:05, Catalin Marinas wrote: > On Tue, Jan 27, 2015 at 06:55:15PM +0000, Murali Karicheri wrote: >> On 01/27/2015 06:27 AM, Robin Murphy wrote: >>> On 23/01/15 22:32, Murali Karicheri wrote: >>>> Fix the dma-range size when the DT attribute is missing. i.e set size to >>>> dev->coherent_dma_mask + 1 instead of dev->coherent_dma_mask. To detect >>>> overflow when mask is set to max of u64, add a check, log error and >>>> return. >>>> Some platform use mask format for size in DTS. So add a work around to >>>> catch this and fix. >>>> >>>> Cc: Joerg Roedel >>>> Cc: Grant Likely >>>> Cc: Rob Herring >>>> Cc: Bjorn Helgaas >>>> Cc: Will Deacon >>>> Cc: Russell King >>>> Cc: Arnd Bergmann >>>> Cc: Suravee Suthikulpanit >>>> >>>> Signed-off-by: Murali Karicheri >>>> --- >>>> drivers/of/device.c | 14 +++++++++++++- >>>> 1 file changed, 13 insertions(+), 1 deletion(-) >>>> >>>> diff --git a/drivers/of/device.c b/drivers/of/device.c >>>> index 2de320d..0a5ff54 100644 >>>> --- a/drivers/of/device.c >>>> +++ b/drivers/of/device.c >>>> @@ -105,12 +105,24 @@ 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; >>>> + size = dev->coherent_dma_mask + 1; >>>> } else { >>>> offset = PFN_DOWN(paddr - dma_addr); >>>> + /* >>>> + * Add a work around to treat the size as mask + 1 in case >>>> + * it is defined in DT as a mask. >>>> + */ >>>> + if (size & 1) >>>> + size = size + 1; >>>> dev_dbg(dev, "dma_pfn_offset(%#08lx)\n", offset); >>>> } >>>> >>>> + /* if size is 0, we have an overflow of u64 */ >>>> + if (!size) { >>>> + dev_err(dev, "invalid size\n"); >>>> + return; >>>> + } >>>> + >>> >>> This seems potentially fragile to dodgy DTs given that we might also be >>> using size to make a mask later. Would it make sense to double-up a >>> sanity check as mask-format detection? Something like: >>> >>> if is_power_of_2(size) >>> // use size >>> else if is_power_of_2(size + 1) >>> // use size + 1 >>> else >>> // cry >> >> How about having the logic like this? >> >> ret = of_dma_get_range(np, &dma_addr, &paddr, &size); >> if (ret < 0) { >> dma_addr = offset = 0; >> size = dev->coherent_dma_mask + 1; >> } else { >> offset = PFN_DOWN(paddr - dma_addr); >> dev_dbg(dev, "dma_pfn_offset(%#08lx)\n", offset); >> } >> >> if (is_power_of_2(size + 1)) >> size = size + 1; >> else if (!is_power_of_2(size)) >> { >> dev_err(dev, "invalid size\n"); >> return; >> } > > In of_dma_configure(), we currently assume that the default coherent > mask is 32-bit. In this thread: > > http://article.gmane.org/gmane.linux.kernel/1835096 > > we talked about setting the coherent mask based on size automatically. > I'm not sure about the size but I think we can assume is 32-bit mask + 1 > if it is not specified in the DT. Instead of just assuming a default > mask, let's assume a default size and create the mask based on this > (untested): > > diff --git a/drivers/of/platform.c b/drivers/of/platform.c > index 5b33c6a21807..9ff8d1286b44 100644 > --- a/drivers/of/platform.c > +++ b/drivers/of/platform.c > @@ -170,10 +170,10 @@ static void of_dma_configure(struct device *dev) > struct iommu_ops *iommu; > > /* > - * Set default dma-mask to 32 bit. Drivers are expected to setup > - * the correct supported dma_mask. > + * Set default size to cover the 32-bit. Drivers are expected to setup > + * the correct size and dma_mask. > */ > - dev->coherent_dma_mask = DMA_BIT_MASK(32); > + size = 1ULL << 32; > > /* > * Set it to coherent_dma_mask by default if the architecture > @@ -185,13 +185,24 @@ static void of_dma_configure(struct device *dev) > ret = of_dma_get_range(dev->of_node, &dma_addr, &paddr, &size); > if (ret < 0) { > dma_addr = offset = 0; > - size = dev->coherent_dma_mask; > } else { > offset = PFN_DOWN(paddr - dma_addr); > dev_dbg(dev, "dma_pfn_offset(%#08lx)\n", dev->dma_pfn_offset); > } > dev->dma_pfn_offset = offset; > > + /* > + * Workaround for DTs setting the size to a mask or 0. > + */ > + if (is_power_of_2(size + 1)) > + size += 1; In fact, since the ilog2 below ends up effectively rounding down, we might as well do away with this check as well and just add 1 unconditionally. The only time it makes any difference is when we want it to anyway! I like this approach, it ends up looking a lot neater. Robin. > + > + /* > + * Coherent DMA masks larger than 32-bit must be explicitly set by the > + * driver. > + */ > + dev->coherent_dma_mask = min(DMA_BIT_MASK(32), DMA_BIT_MASK(ilog2(size))); > + > coherent = of_dma_is_coherent(dev->of_node); > dev_dbg(dev, "device is%sdma coherent\n", > coherent ? " " : " not "); > From mboxrd@z Thu Jan 1 00:00:00 1970 From: Robin Murphy Subject: Re: [PATCH v4 3/6] of: fix size when dma-range is not used Date: Wed, 28 Jan 2015 15:55:57 +0000 Message-ID: <54C9068D.8050701@arm.com> References: <1422052359-12384-1-git-send-email-m-karicheri2@ti.com> <1422052359-12384-4-git-send-email-m-karicheri2@ti.com> <54C77616.80301@arm.com> <54C7DF13.20402@ti.com> <20150128110523.GC6646@e104818-lin.cambridge.arm.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20150128110523.GC6646-M2fw3Uu6cmfZROr8t4l/smS4ubULX0JqMm0uRHvK7Nw@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org Errors-To: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org To: Catalin Marinas , Murali Karicheri Cc: "devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , Russell King , Arnd Bergmann , "linux-pci-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , Will Deacon , "linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , Bjorn Helgaas , "iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org" , Rob Herring , "grant.likely-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org" , "linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org" List-Id: devicetree@vger.kernel.org On 28/01/15 11:05, Catalin Marinas wrote: > On Tue, Jan 27, 2015 at 06:55:15PM +0000, Murali Karicheri wrote: >> On 01/27/2015 06:27 AM, Robin Murphy wrote: >>> On 23/01/15 22:32, Murali Karicheri wrote: >>>> Fix the dma-range size when the DT attribute is missing. i.e set size to >>>> dev->coherent_dma_mask + 1 instead of dev->coherent_dma_mask. To detect >>>> overflow when mask is set to max of u64, add a check, log error and >>>> return. >>>> Some platform use mask format for size in DTS. So add a work around to >>>> catch this and fix. >>>> >>>> Cc: Joerg Roedel >>>> Cc: Grant Likely >>>> Cc: Rob Herring >>>> Cc: Bjorn Helgaas >>>> Cc: Will Deacon >>>> Cc: Russell King >>>> Cc: Arnd Bergmann >>>> Cc: Suravee Suthikulpanit >>>> >>>> Signed-off-by: Murali Karicheri >>>> --- >>>> drivers/of/device.c | 14 +++++++++++++- >>>> 1 file changed, 13 insertions(+), 1 deletion(-) >>>> >>>> diff --git a/drivers/of/device.c b/drivers/of/device.c >>>> index 2de320d..0a5ff54 100644 >>>> --- a/drivers/of/device.c >>>> +++ b/drivers/of/device.c >>>> @@ -105,12 +105,24 @@ 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; >>>> + size = dev->coherent_dma_mask + 1; >>>> } else { >>>> offset = PFN_DOWN(paddr - dma_addr); >>>> + /* >>>> + * Add a work around to treat the size as mask + 1 in case >>>> + * it is defined in DT as a mask. >>>> + */ >>>> + if (size & 1) >>>> + size = size + 1; >>>> dev_dbg(dev, "dma_pfn_offset(%#08lx)\n", offset); >>>> } >>>> >>>> + /* if size is 0, we have an overflow of u64 */ >>>> + if (!size) { >>>> + dev_err(dev, "invalid size\n"); >>>> + return; >>>> + } >>>> + >>> >>> This seems potentially fragile to dodgy DTs given that we might also be >>> using size to make a mask later. Would it make sense to double-up a >>> sanity check as mask-format detection? Something like: >>> >>> if is_power_of_2(size) >>> // use size >>> else if is_power_of_2(size + 1) >>> // use size + 1 >>> else >>> // cry >> >> How about having the logic like this? >> >> ret = of_dma_get_range(np, &dma_addr, &paddr, &size); >> if (ret < 0) { >> dma_addr = offset = 0; >> size = dev->coherent_dma_mask + 1; >> } else { >> offset = PFN_DOWN(paddr - dma_addr); >> dev_dbg(dev, "dma_pfn_offset(%#08lx)\n", offset); >> } >> >> if (is_power_of_2(size + 1)) >> size = size + 1; >> else if (!is_power_of_2(size)) >> { >> dev_err(dev, "invalid size\n"); >> return; >> } > > In of_dma_configure(), we currently assume that the default coherent > mask is 32-bit. In this thread: > > http://article.gmane.org/gmane.linux.kernel/1835096 > > we talked about setting the coherent mask based on size automatically. > I'm not sure about the size but I think we can assume is 32-bit mask + 1 > if it is not specified in the DT. Instead of just assuming a default > mask, let's assume a default size and create the mask based on this > (untested): > > diff --git a/drivers/of/platform.c b/drivers/of/platform.c > index 5b33c6a21807..9ff8d1286b44 100644 > --- a/drivers/of/platform.c > +++ b/drivers/of/platform.c > @@ -170,10 +170,10 @@ static void of_dma_configure(struct device *dev) > struct iommu_ops *iommu; > > /* > - * Set default dma-mask to 32 bit. Drivers are expected to setup > - * the correct supported dma_mask. > + * Set default size to cover the 32-bit. Drivers are expected to setup > + * the correct size and dma_mask. > */ > - dev->coherent_dma_mask = DMA_BIT_MASK(32); > + size = 1ULL << 32; > > /* > * Set it to coherent_dma_mask by default if the architecture > @@ -185,13 +185,24 @@ static void of_dma_configure(struct device *dev) > ret = of_dma_get_range(dev->of_node, &dma_addr, &paddr, &size); > if (ret < 0) { > dma_addr = offset = 0; > - size = dev->coherent_dma_mask; > } else { > offset = PFN_DOWN(paddr - dma_addr); > dev_dbg(dev, "dma_pfn_offset(%#08lx)\n", dev->dma_pfn_offset); > } > dev->dma_pfn_offset = offset; > > + /* > + * Workaround for DTs setting the size to a mask or 0. > + */ > + if (is_power_of_2(size + 1)) > + size += 1; In fact, since the ilog2 below ends up effectively rounding down, we might as well do away with this check as well and just add 1 unconditionally. The only time it makes any difference is when we want it to anyway! I like this approach, it ends up looking a lot neater. Robin. > + > + /* > + * Coherent DMA masks larger than 32-bit must be explicitly set by the > + * driver. > + */ > + dev->coherent_dma_mask = min(DMA_BIT_MASK(32), DMA_BIT_MASK(ilog2(size))); > + > coherent = of_dma_is_coherent(dev->of_node); > dev_dbg(dev, "device is%sdma coherent\n", > coherent ? " " : " not "); > From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from service88.mimecast.com ([195.130.217.12]:34043 "EHLO service88.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754769AbbA1U42 convert rfc822-to-8bit (ORCPT ); Wed, 28 Jan 2015 15:56:28 -0500 Message-ID: <54C9068D.8050701@arm.com> Date: Wed, 28 Jan 2015 15:55:57 +0000 From: Robin Murphy MIME-Version: 1.0 To: Catalin Marinas , Murali Karicheri CC: "devicetree@vger.kernel.org" , Russell King , Arnd Bergmann , "linux-pci@vger.kernel.org" , Joerg Roedel , Will Deacon , "linux-kernel@vger.kernel.org" , "grant.likely@linaro.org" , "iommu@lists.linux-foundation.org" , Rob Herring , "suravee.suthikulpanit@amd.com" , Bjorn Helgaas , "linux-arm-kernel@lists.infradead.org" Subject: Re: [PATCH v4 3/6] of: fix size when dma-range is not used References: <1422052359-12384-1-git-send-email-m-karicheri2@ti.com> <1422052359-12384-4-git-send-email-m-karicheri2@ti.com> <54C77616.80301@arm.com> <54C7DF13.20402@ti.com> <20150128110523.GC6646@e104818-lin.cambridge.arm.com> In-Reply-To: <20150128110523.GC6646@e104818-lin.cambridge.arm.com> Content-Type: text/plain; charset=WINDOWS-1252; format=flowed Sender: linux-pci-owner@vger.kernel.org List-ID: On 28/01/15 11:05, Catalin Marinas wrote: > On Tue, Jan 27, 2015 at 06:55:15PM +0000, Murali Karicheri wrote: >> On 01/27/2015 06:27 AM, Robin Murphy wrote: >>> On 23/01/15 22:32, Murali Karicheri wrote: >>>> Fix the dma-range size when the DT attribute is missing. i.e set size to >>>> dev->coherent_dma_mask + 1 instead of dev->coherent_dma_mask. To detect >>>> overflow when mask is set to max of u64, add a check, log error and >>>> return. >>>> Some platform use mask format for size in DTS. So add a work around to >>>> catch this and fix. >>>> >>>> Cc: Joerg Roedel >>>> Cc: Grant Likely >>>> Cc: Rob Herring >>>> Cc: Bjorn Helgaas >>>> Cc: Will Deacon >>>> Cc: Russell King >>>> Cc: Arnd Bergmann >>>> Cc: Suravee Suthikulpanit >>>> >>>> Signed-off-by: Murali Karicheri >>>> --- >>>> drivers/of/device.c | 14 +++++++++++++- >>>> 1 file changed, 13 insertions(+), 1 deletion(-) >>>> >>>> diff --git a/drivers/of/device.c b/drivers/of/device.c >>>> index 2de320d..0a5ff54 100644 >>>> --- a/drivers/of/device.c >>>> +++ b/drivers/of/device.c >>>> @@ -105,12 +105,24 @@ 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; >>>> + size = dev->coherent_dma_mask + 1; >>>> } else { >>>> offset = PFN_DOWN(paddr - dma_addr); >>>> + /* >>>> + * Add a work around to treat the size as mask + 1 in case >>>> + * it is defined in DT as a mask. >>>> + */ >>>> + if (size & 1) >>>> + size = size + 1; >>>> dev_dbg(dev, "dma_pfn_offset(%#08lx)\n", offset); >>>> } >>>> >>>> + /* if size is 0, we have an overflow of u64 */ >>>> + if (!size) { >>>> + dev_err(dev, "invalid size\n"); >>>> + return; >>>> + } >>>> + >>> >>> This seems potentially fragile to dodgy DTs given that we might also be >>> using size to make a mask later. Would it make sense to double-up a >>> sanity check as mask-format detection? Something like: >>> >>> if is_power_of_2(size) >>> // use size >>> else if is_power_of_2(size + 1) >>> // use size + 1 >>> else >>> // cry >> >> How about having the logic like this? >> >> ret = of_dma_get_range(np, &dma_addr, &paddr, &size); >> if (ret < 0) { >> dma_addr = offset = 0; >> size = dev->coherent_dma_mask + 1; >> } else { >> offset = PFN_DOWN(paddr - dma_addr); >> dev_dbg(dev, "dma_pfn_offset(%#08lx)\n", offset); >> } >> >> if (is_power_of_2(size + 1)) >> size = size + 1; >> else if (!is_power_of_2(size)) >> { >> dev_err(dev, "invalid size\n"); >> return; >> } > > In of_dma_configure(), we currently assume that the default coherent > mask is 32-bit. In this thread: > > http://article.gmane.org/gmane.linux.kernel/1835096 > > we talked about setting the coherent mask based on size automatically. > I'm not sure about the size but I think we can assume is 32-bit mask + 1 > if it is not specified in the DT. Instead of just assuming a default > mask, let's assume a default size and create the mask based on this > (untested): > > diff --git a/drivers/of/platform.c b/drivers/of/platform.c > index 5b33c6a21807..9ff8d1286b44 100644 > --- a/drivers/of/platform.c > +++ b/drivers/of/platform.c > @@ -170,10 +170,10 @@ static void of_dma_configure(struct device *dev) > struct iommu_ops *iommu; > > /* > - * Set default dma-mask to 32 bit. Drivers are expected to setup > - * the correct supported dma_mask. > + * Set default size to cover the 32-bit. Drivers are expected to setup > + * the correct size and dma_mask. > */ > - dev->coherent_dma_mask = DMA_BIT_MASK(32); > + size = 1ULL << 32; > > /* > * Set it to coherent_dma_mask by default if the architecture > @@ -185,13 +185,24 @@ static void of_dma_configure(struct device *dev) > ret = of_dma_get_range(dev->of_node, &dma_addr, &paddr, &size); > if (ret < 0) { > dma_addr = offset = 0; > - size = dev->coherent_dma_mask; > } else { > offset = PFN_DOWN(paddr - dma_addr); > dev_dbg(dev, "dma_pfn_offset(%#08lx)\n", dev->dma_pfn_offset); > } > dev->dma_pfn_offset = offset; > > + /* > + * Workaround for DTs setting the size to a mask or 0. > + */ > + if (is_power_of_2(size + 1)) > + size += 1; In fact, since the ilog2 below ends up effectively rounding down, we might as well do away with this check as well and just add 1 unconditionally. The only time it makes any difference is when we want it to anyway! I like this approach, it ends up looking a lot neater. Robin. > + > + /* > + * Coherent DMA masks larger than 32-bit must be explicitly set by the > + * driver. > + */ > + dev->coherent_dma_mask = min(DMA_BIT_MASK(32), DMA_BIT_MASK(ilog2(size))); > + > coherent = of_dma_is_coherent(dev->of_node); > dev_dbg(dev, "device is%sdma coherent\n", > coherent ? " " : " not "); > From mboxrd@z Thu Jan 1 00:00:00 1970 From: robin.murphy@arm.com (Robin Murphy) Date: Wed, 28 Jan 2015 15:55:57 +0000 Subject: [PATCH v4 3/6] of: fix size when dma-range is not used In-Reply-To: <20150128110523.GC6646@e104818-lin.cambridge.arm.com> References: <1422052359-12384-1-git-send-email-m-karicheri2@ti.com> <1422052359-12384-4-git-send-email-m-karicheri2@ti.com> <54C77616.80301@arm.com> <54C7DF13.20402@ti.com> <20150128110523.GC6646@e104818-lin.cambridge.arm.com> Message-ID: <54C9068D.8050701@arm.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On 28/01/15 11:05, Catalin Marinas wrote: > On Tue, Jan 27, 2015 at 06:55:15PM +0000, Murali Karicheri wrote: >> On 01/27/2015 06:27 AM, Robin Murphy wrote: >>> On 23/01/15 22:32, Murali Karicheri wrote: >>>> Fix the dma-range size when the DT attribute is missing. i.e set size to >>>> dev->coherent_dma_mask + 1 instead of dev->coherent_dma_mask. To detect >>>> overflow when mask is set to max of u64, add a check, log error and >>>> return. >>>> Some platform use mask format for size in DTS. So add a work around to >>>> catch this and fix. >>>> >>>> Cc: Joerg Roedel >>>> Cc: Grant Likely >>>> Cc: Rob Herring >>>> Cc: Bjorn Helgaas >>>> Cc: Will Deacon >>>> Cc: Russell King >>>> Cc: Arnd Bergmann >>>> Cc: Suravee Suthikulpanit >>>> >>>> Signed-off-by: Murali Karicheri >>>> --- >>>> drivers/of/device.c | 14 +++++++++++++- >>>> 1 file changed, 13 insertions(+), 1 deletion(-) >>>> >>>> diff --git a/drivers/of/device.c b/drivers/of/device.c >>>> index 2de320d..0a5ff54 100644 >>>> --- a/drivers/of/device.c >>>> +++ b/drivers/of/device.c >>>> @@ -105,12 +105,24 @@ 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; >>>> + size = dev->coherent_dma_mask + 1; >>>> } else { >>>> offset = PFN_DOWN(paddr - dma_addr); >>>> + /* >>>> + * Add a work around to treat the size as mask + 1 in case >>>> + * it is defined in DT as a mask. >>>> + */ >>>> + if (size & 1) >>>> + size = size + 1; >>>> dev_dbg(dev, "dma_pfn_offset(%#08lx)\n", offset); >>>> } >>>> >>>> + /* if size is 0, we have an overflow of u64 */ >>>> + if (!size) { >>>> + dev_err(dev, "invalid size\n"); >>>> + return; >>>> + } >>>> + >>> >>> This seems potentially fragile to dodgy DTs given that we might also be >>> using size to make a mask later. Would it make sense to double-up a >>> sanity check as mask-format detection? Something like: >>> >>> if is_power_of_2(size) >>> // use size >>> else if is_power_of_2(size + 1) >>> // use size + 1 >>> else >>> // cry >> >> How about having the logic like this? >> >> ret = of_dma_get_range(np, &dma_addr, &paddr, &size); >> if (ret < 0) { >> dma_addr = offset = 0; >> size = dev->coherent_dma_mask + 1; >> } else { >> offset = PFN_DOWN(paddr - dma_addr); >> dev_dbg(dev, "dma_pfn_offset(%#08lx)\n", offset); >> } >> >> if (is_power_of_2(size + 1)) >> size = size + 1; >> else if (!is_power_of_2(size)) >> { >> dev_err(dev, "invalid size\n"); >> return; >> } > > In of_dma_configure(), we currently assume that the default coherent > mask is 32-bit. In this thread: > > http://article.gmane.org/gmane.linux.kernel/1835096 > > we talked about setting the coherent mask based on size automatically. > I'm not sure about the size but I think we can assume is 32-bit mask + 1 > if it is not specified in the DT. Instead of just assuming a default > mask, let's assume a default size and create the mask based on this > (untested): > > diff --git a/drivers/of/platform.c b/drivers/of/platform.c > index 5b33c6a21807..9ff8d1286b44 100644 > --- a/drivers/of/platform.c > +++ b/drivers/of/platform.c > @@ -170,10 +170,10 @@ static void of_dma_configure(struct device *dev) > struct iommu_ops *iommu; > > /* > - * Set default dma-mask to 32 bit. Drivers are expected to setup > - * the correct supported dma_mask. > + * Set default size to cover the 32-bit. Drivers are expected to setup > + * the correct size and dma_mask. > */ > - dev->coherent_dma_mask = DMA_BIT_MASK(32); > + size = 1ULL << 32; > > /* > * Set it to coherent_dma_mask by default if the architecture > @@ -185,13 +185,24 @@ static void of_dma_configure(struct device *dev) > ret = of_dma_get_range(dev->of_node, &dma_addr, &paddr, &size); > if (ret < 0) { > dma_addr = offset = 0; > - size = dev->coherent_dma_mask; > } else { > offset = PFN_DOWN(paddr - dma_addr); > dev_dbg(dev, "dma_pfn_offset(%#08lx)\n", dev->dma_pfn_offset); > } > dev->dma_pfn_offset = offset; > > + /* > + * Workaround for DTs setting the size to a mask or 0. > + */ > + if (is_power_of_2(size + 1)) > + size += 1; In fact, since the ilog2 below ends up effectively rounding down, we might as well do away with this check as well and just add 1 unconditionally. The only time it makes any difference is when we want it to anyway! I like this approach, it ends up looking a lot neater. Robin. > + > + /* > + * Coherent DMA masks larger than 32-bit must be explicitly set by the > + * driver. > + */ > + dev->coherent_dma_mask = min(DMA_BIT_MASK(32), DMA_BIT_MASK(ilog2(size))); > + > coherent = of_dma_is_coherent(dev->of_node); > dev_dbg(dev, "device is%sdma coherent\n", > coherent ? " " : " not "); >