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    SubjectRe: [PATCH v4 3/6] of: fix size when dma-range is not used
    On 01/28/2015 12:30 PM, Catalin Marinas wrote:
    > On Wed, Jan 28, 2015 at 03:55:57PM +0000, Robin Murphy wrote:
    >> On 28/01/15 11:05, Catalin Marinas 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;
    >>> } 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!
    >
    > Well, we could simply ignore the is_power_of_2() check but without
    > incrementing size as we don't know what arch_setup_dma_ops() does with
    > it.
    >
    > I think we can remove this check altogether (we leaved without it for a
    > while) but we need to add 1 when calculating the mask:
    >
    > dev->coherent_dma_mask = min(DMA_BIT_MASK(32),
    > DMA_BIT_MASK(ilog2(size + 1)));
    >
    For Keystone, the dma_addr is to be taken care as well to determine the
    mask. The above will not work.

    Based on the discussion so far, this is the function I have come up with
    incorporating the suggestions. Please review this and see if I have
    missed out any. This works fine on Keystone.

    void of_dma_configure(struct device *dev, struct device_node *np)
    {
    u64 dma_addr = 0, paddr, size;
    int ret;
    bool coherent;
    unsigned long offset = 0;
    struct iommu_ops *iommu;

    /*
    * Set default size to cover the 32-bit. Drivers are expected to setup
    * the correct size and dma_mask.
    */
    size = 1ULL << 32;

    ret = of_dma_get_range(np, &dma_addr, &paddr, &size);
    if (!ret) {
    offset = PFN_DOWN(paddr - dma_addr);
    if (!size) {
    dev_err(dev, "Invalid size (%llx)\n",
    size);
    return;
    }
    if (size & 1) {
    size = size + 1;
    dev_warn(dev, "Incorrect usage of size (%llx)\n",
    size);
    }
    dev_dbg(dev, "dma_pfn_offset(%#08lx)\n", offset);
    }
    dev->dma_pfn_offset = offset;

    /*
    * 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(dma_addr + size)));
    /*
    * Set dma_mask to coherent_dma_mask by default if the architecture
    * code has not set it.
    */
    if (!dev->dma_mask)
    dev->dma_mask = &dev->coherent_dma_mask;

    coherent = of_dma_is_coherent(np);
    dev_dbg(dev, "device is%sdma coherent\n",
    coherent ? " " : " not ");

    iommu = of_iommu_configure(dev, np);
    dev_dbg(dev, "device is%sbehind an iommu\n",
    iommu ? " " : " not ");

    arch_setup_dma_ops(dev, dma_addr, size, iommu, coherent);
    }


    --
    Murali Karicheri
    Linux Kernel, Texas Instruments


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