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SubjectRe: use generic DMA mapping code in powerpc V4
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Hi Christoph,

Thanks a lot for your fast reply.

On 30 November 2018 at 11:53AM, Christoph Hellwig wrote:
> Hi Christian,
>
> for such a diverse architecture like powerpc we'll have to rely on
> users / non core developers like you to help with testing.
I see. I will help as good as I can.
>
> Can you try the patch below for he cyrus config?
Yes, of course. I patched your Git kernel and after that I compiled it
again. U-Boot loads the kernel and the dtb file. Then the kernel starts
but it doesn't find any hard disks (partitions).

@All
Could you please also test Christoph's kernel on your PASEMI and NXP
boards? Download: 'git clone git://git.infradead.org/users/hch/misc.git
-b powerpc-dma.4 a'
*PLEASE*
>
> For the nemo one I have no idea yet,
We had some problems with the PASEMI ethernet and DMA two years ago. I
had to deactivate the option PASEMI_IOMMU_DMA_FORCE.

commit 416f37d0816b powerpc/pasemi: Fix coherent_dma_mask for dma engine:

Commit 817820b0 ("powerpc/iommu: Support "hybrid" iommu/direct DMA
ops for coherent_mask < dma_mask) adds a check of coherent_dma_mask for
dma allocations.

Unfortunately current PASemi code does not set this value for the DMA
engine, which ends up with the default value of 0xffffffff, the result
is on a PASemi system with >2Gb ram and iommu enabled the onboard
ethernet stops working due to an inability to allocate memory. Add an
initialisation to pci_dma_dev_setup_pasemi().
Signed-off-by: Darren Stevens <darren@stevens-zone.net>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

Links:
https://lists.ozlabs.org/pipermail/linuxppc-dev/2016-July/146701.html
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=416f37d0816b9720b8227953e55954d81456f991

FYI: DMA handling has been rewritten in 2015. We had some problems with
the new DMA code in 2015. I had to revert the commit ' [RFC/PATCH,v2]
powerpc/iommu: Support "hybrid" iommu/direct DMA ops for coherent_mask <
dma_mask' in 2015.

Link: https://patchwork.ozlabs.org/patch/472535/

I had to create a patch in 2015:

    diff -rupN linux-4.4/arch/powerpc/Kconfig
linux-4.4-nemo/arch/powerpc/Kconfig
    --- linux-4.4/arch/powerpc/Kconfig    2015-12-07 00:43:12.000000000
+0100
    +++ linux-4.4-nemo/arch/powerpc/Kconfig    2015-12-07
14:48:23.371987988 +0100
    @@ -158,8 +155,6 @@ config PPC
         select HAVE_PERF_EVENTS_NMI if PPC64
         select EDAC_SUPPORT
         select EDAC_ATOMIC_SCRUB
    -    select ARCH_HAS_DMA_SET_COHERENT_MASK
    -    select HAVE_ARCH_SECCOMP_FILTER

     config GENERIC_CSUM
         def_bool CPU_LITTLE_ENDIAN
    @@ -419,8 +414,7 @@ config PPC64_SUPPORTS_MEMORY_FAILURE

     config KEXEC
         bool "kexec system call"
    -    depends on (PPC_BOOK3S || FSL_BOOKE || (44x && !SMP)) ||
PPC_BOOK3E
    -    select KEXEC_CORE
    +    depends on (PPC_BOOK3S || FSL_BOOKE || (44x && !SMP))
         help
           kexec is a system call that implements the ability to
shutdown your
           current kernel, and to start another kernel.  It is like a
reboot
    diff -rupN linux-4.4/arch/powerpc/kernel/dma.c
linux-4.4-nemo/arch/powerpc/kernel/dma.c
    --- linux-4.4/arch/powerpc/kernel/dma.c    2015-12-07
00:43:12.000000000 +0100
    +++ linux-4.4-nemo/arch/powerpc/kernel/dma.c    2015-12-07
14:49:38.098286892 +0100
    @@ -40,31 +39,9 @@ static u64 __maybe_unused get_pfn_limit(
         return pfn;
     }

    -static int dma_direct_dma_supported(struct device *dev, u64 mask)
    -{
    -#ifdef CONFIG_PPC64
    -    u64 limit = get_dma_offset(dev) + (memblock_end_of_DRAM() - 1);
    -
    -    /* Limit fits in the mask, we are good */
    -    if (mask >= limit)
    -        return 1;
    -
    -#ifdef CONFIG_FSL_SOC
    -    /* Freescale gets another chance via ZONE_DMA/ZONE_DMA32, however
    -     * that will have to be refined if/when they support iommus
    -     */
    -    return 1;
    -#endif
    -    /* Sorry ... */
    -    return 0;
    -#else
    -    return 1;
    -#endif
    -}
    -
    -void *__dma_direct_alloc_coherent(struct device *dev, size_t size,
    -                  dma_addr_t *dma_handle, gfp_t flag,
    -                  struct dma_attrs *attrs)
    +void *dma_direct_alloc_coherent(struct device *dev, size_t size,
    +                dma_addr_t *dma_handle, gfp_t flag,
    +                struct dma_attrs *attrs)
     {
         void *ret;
     #ifdef CONFIG_NOT_COHERENT_CACHE
    @@ -119,9 +96,9 @@ void *__dma_direct_alloc_coherent(struct
     #endif
     }

    -void __dma_direct_free_coherent(struct device *dev, size_t size,
    -                void *vaddr, dma_addr_t dma_handle,
    -                struct dma_attrs *attrs)
    +void dma_direct_free_coherent(struct device *dev, size_t size,
    +                  void *vaddr, dma_addr_t dma_handle,
    +                  struct dma_attrs *attrs)
     {
     #ifdef CONFIG_NOT_COHERENT_CACHE
         __dma_free_coherent(size, vaddr);
    @@ -130,51 +107,6 @@ void __dma_direct_free_coherent(struct d
     #endif
     }

    -static void *dma_direct_alloc_coherent(struct device *dev, size_t
size,
    -                       dma_addr_t *dma_handle, gfp_t flag,
    -                       struct dma_attrs *attrs)
    -{
    -    struct iommu_table *iommu;
    -
    -    /* The coherent mask may be smaller than the real mask, check if
    -     * we can really use the direct ops
    -     */
    -    if (dma_direct_dma_supported(dev, dev->coherent_dma_mask))
    -        return __dma_direct_alloc_coherent(dev, size, dma_handle,
    -                           flag, attrs);
    -
    -    /* Ok we can't ... do we have an iommu ? If not, fail */
    -    iommu = get_iommu_table_base(dev);
    -    if (!iommu)
    -        return NULL;
    -
    -    /* Try to use the iommu */
    -    return iommu_alloc_coherent(dev, iommu, size, dma_handle,
    -                    dev->coherent_dma_mask, flag,
    -                    dev_to_node(dev));
    -}
    -
    -static void dma_direct_free_coherent(struct device *dev, size_t size,
    -                     void *vaddr, dma_addr_t dma_handle,
    -                     struct dma_attrs *attrs)
    -{
    -    struct iommu_table *iommu;
    -
    -    /* See comments in dma_direct_alloc_coherent() */
    -    if (dma_direct_dma_supported(dev, dev->coherent_dma_mask))
    -        return __dma_direct_free_coherent(dev, size, vaddr,
dma_handle,
    -                          attrs);
    -    /* Maybe we used an iommu ... */
    -    iommu = get_iommu_table_base(dev);
    -
    -    /* If we hit that we should have never allocated in the first
    -     * place so how come we are freeing ?
    -     */
    -    if (WARN_ON(!iommu))
    -        return;
    -    iommu_free_coherent(iommu, size, vaddr, dma_handle);
    -}
    -
     int dma_direct_mmap_coherent(struct device *dev, struct
vm_area_struct *vma,
                      void *cpu_addr, dma_addr_t handle, size_t size,
                      struct dma_attrs *attrs)
    @@ -215,6 +147,18 @@ static void dma_direct_unmap_sg(struct d
     {
     }

    +static int dma_direct_dma_supported(struct device *dev, u64 mask)
    +{
    +#ifdef CONFIG_PPC64
    +    /* Could be improved so platforms can set the limit in case
    +     * they have limited DMA windows
    +     */
    +    return mask >= get_dma_offset(dev) + (memblock_end_of_DRAM() - 1);
    +#else
    +    return 1;
    +#endif
    +}
    +
     static u64 dma_direct_get_required_mask(struct device *dev)
     {
         u64 end, mask;
    @@ -286,25 +230,6 @@ struct dma_map_ops dma_direct_ops = {
     };
     EXPORT_SYMBOL(dma_direct_ops);

    -int dma_set_coherent_mask(struct device *dev, u64 mask)
    -{
    -    if (!dma_supported(dev, mask)) {
    -        /*
    -         * We need to special case the direct DMA ops which can
    -         * support a fallback for coherent allocations. There
    -         * is no dma_op->set_coherent_mask() so we have to do
    -         * things the hard way:
    -         */
    -        if (get_dma_ops(dev) != &dma_direct_ops ||
    -            get_iommu_table_base(dev) == NULL ||
    -            !dma_iommu_dma_supported(dev, mask))
    -            return -EIO;
    -    }
    -    dev->coherent_dma_mask = mask;
    -    return 0;
    -}
    -EXPORT_SYMBOL(dma_set_coherent_mask);
    -
     #define PREALLOC_DMA_DEBUG_ENTRIES (1 << 16)

     int __dma_set_mask(struct device *dev, u64 dma_mask)
Interesting PASEMI ethernet files:

arch/powerpc/platforms/pasemi/iommu.c
drivers/net/ethernet/pasemi/pasemi_mac.c
drivers/net/ethernet/pasemi/pasemi_mac.h
drivers/net/ethernet/pasemi/pasemi_mac_ethtool.c
drivers/net/ethernet/pasemi/Makefile
drivers/net/ethernet/pasemi/Kconfig

I know this is a lot of information but I hope it helps.

Thanks,
Christian

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