linux-kernel - Re: [PATCH v5 3/8] of: fix size when dma-range is not used

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Date:	Tue, 27 Jan 2015 20:37:14 -0600
From:	Rob Herring <robherring2@...il.com>
To:	Murali Karicheri <m-karicheri2@...com>
Cc:	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Linux IOMMU <iommu@...ts.linux-foundation.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-pci@...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>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Will Deacon <will.deacon@....com>,
	Russell King <linux@....linux.org.uk>,
	Arnd Bergmann <arnd@...db.de>,
	Suravee Suthikulpanit <Suravee.Suthikulpanit@....com>
Subject: Re: [PATCH v5 3/8] of: fix size when dma-range is not used

On Tue, Jan 27, 2015 at 3:00 PM, Murali Karicheri <m-karicheri2@...com> 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. Also add
> code to check invalid values of size configured in DT and log error.
>
> 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>
> ---
>  drivers/of/device.c |    9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/of/device.c b/drivers/of/device.c
> index 2de320d..17504f4 100644
> --- a/drivers/of/device.c
> +++ b/drivers/of/device.c
> @@ -105,12 +105,19 @@ 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;

This is fine since coherent_dma_mask will always be 4G - 1 in this case.

>         } 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;

I think this is too restrictive. I think checking bit 0 is 1 is enough
to tell the size is a mask.

I would like it to be a WARN if detected and just add 1.

Rob
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