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From: Catalin Marinas <catalin.marinas@arm.com>
To: Rob Herring <robherring2@gmail.com>
Cc: Murali Karicheri <m-karicheri2@ti.com>,
	Robin Murphy <Robin.Murphy@arm.com>,
	"devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
	Russell King <linux@arm.linux.org.uk>,
	Arnd Bergmann <arnd@arndb.de>,
	"linux-pci@vger.kernel.org" <linux-pci@vger.kernel.org>,
	Joerg Roedel <joro@8bytes.org>, Will Deacon <Will.Deacon@arm.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"grant.likely@linaro.org" <grant.likely@linaro.org>,
	"iommu@lists.linux-foundation.org"
	<iommu@lists.linux-foundation.org>,
	Rob Herring <robh+dt@kernel.org>,
	"suravee.suthikulpanit@amd.com" <suravee.suthikulpanit@amd.com>,
	Bjorn Helgaas <bhelgaas@google.com>,
	"linux-arm-kernel@lists.infradead.org" 
	<linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH v4 3/6] of: fix size when dma-range is not used
Date: Wed, 28 Jan 2015 17:23:31 +0000	[thread overview]
Message-ID: <20150128172330.GD31752@e104818-lin.cambridge.arm.com> (raw)
In-Reply-To: <CAL_JsqJiCKW0ny=_ueq=A7RH3octpEhN+KZuLZhbNEHusyjcig@mail.gmail.com>

On Wed, Jan 28, 2015 at 03:45:19PM +0000, Rob Herring wrote:
> On Wed, Jan 28, 2015 at 5:05 AM, Catalin Marinas
> <catalin.marinas@arm.com> wrote:
> > On Tue, Jan 27, 2015 at 06:55:15PM +0000, Murali Karicheri wrote:
> >> 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;
> 
> Are we assuming dma_addr, paddr and size are not touched on error? If
> so, we can get rid of this clause entirely.

We can if we initialise dma_addr and offset to 0 when declared in this
function. The dma_addr and size variables are later passed to the
arch_setup_dma_ops(), so they need to have some sane values independent
of the presence of dma-ranges in the DT.

> >         } 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;
> 
> As I mentioned, I think power of 2 is too restrictive (from a DT
> perspective even though the kernel may require a power of 2 here for
> the mask). Just checking bit0 set should be enough.

The power of 2 was mainly to cover the case where the size is wrongly
written as a mask in the DT. If the size is deliberately not a power of
two and not a full mask, the above check won't change it. With my
proposal, ilog2 gets rid of extra bits in size, only that if the size
was a mask because of DT error, we lose a bit in the coherent_dma_mask.

> Also, we need a WARN here so DTs get fixed.

I agree.

-- 
Catalin

  reply	other threads:[~2015-01-29  1:43 UTC|newest]

Thread overview: 45+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-01-23 22:32 [PATCH v4 0/6] PCI: get DMA configuration from parent device Murali Karicheri
2015-01-23 22:32 ` [PATCH v4 1/6] of: iommu: add ptr to OF node arg to of_iommu_configure() Murali Karicheri
2015-01-25 13:32   ` Laurent Pinchart
2015-01-26 18:49     ` Murali Karicheri
2015-01-28 11:33       ` Will Deacon
2015-01-28 12:23         ` Laurent Pinchart
2015-01-28 12:29           ` Will Deacon
2015-01-28 13:15             ` Laurent Pinchart
2015-01-28 13:32               ` Will Deacon
2015-01-28 15:21                 ` Murali Karicheri
2015-01-28 23:32                 ` Laurent Pinchart
2015-01-29 14:59                   ` Murali Karicheri
2015-01-29 16:49                   ` Rob Herring
2015-01-30  0:24                     ` Laurent Pinchart
2015-01-30 15:23                       ` Murali Karicheri
2015-01-23 22:32 ` [PATCH v4 2/6] of: move of_dma_configure() to device.c to help re-use Murali Karicheri
2015-01-23 22:32 ` [PATCH v4 3/6] of: fix size when dma-range is not used Murali Karicheri
2015-01-27 11:27   ` Robin Murphy
2015-01-27 15:44     ` Murali Karicheri
2015-01-27 18:55     ` Murali Karicheri
2015-01-28 11:05       ` Catalin Marinas
2015-01-28 15:45         ` Rob Herring
2015-01-28 17:23           ` Catalin Marinas [this message]
2015-01-28 17:34           ` Murali Karicheri
2015-01-28 15:55         ` Robin Murphy
2015-01-28 17:30           ` Catalin Marinas
2015-01-30 18:06             ` Murali Karicheri
2015-02-02 12:18               ` Catalin Marinas
2015-02-02 16:10                 ` Murali Karicheri
2015-02-05 21:42                 ` Murali Karicheri
2015-02-05 22:44                   ` Catalin Marinas
2015-01-23 22:32 ` [PATCH v4 4/6] of/pci: add of_pci_dma_configure() update dma configuration Murali Karicheri
2015-01-23 23:41   ` Bjorn Helgaas
2015-01-26 23:25     ` Murali Karicheri
2015-01-26 23:59       ` Bjorn Helgaas
2015-01-27 18:14         ` Murali Karicheri
2015-01-27 18:42           ` Bjorn Helgaas
2015-01-27 18:45             ` Murali Karicheri
2015-01-23 22:32 ` [PATCH v4 5/6] PCI: update dma configuration from DT Murali Karicheri
2015-01-23 23:27   ` Bjorn Helgaas
2015-01-26 23:28     ` Murali Karicheri
2015-01-23 22:32 ` [PATCH v4 6/6] arm: dma-mapping: updates to limit dma_mask and iommu mapping size Murali Karicheri
2015-01-27 11:12   ` Robin Murphy
2015-01-27 11:34     ` Catalin Marinas
2015-01-27 15:19       ` Murali Karicheri

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