Re: [PoC] arm: dma-mapping: direct: Apply dma_pfn_offset only when it is valid

[Peter Ujfalusi]

On 14/01/2020 20.19, Robin Murphy wrote:
> On 14/01/2020 4:43 pm, Peter Ujfalusi wrote:
>> The dma_pfn_offset should only be applied to an address which is
>> within the
>> dma-ranges range. Any address outside should have offset as 0.
> 
> No, that's wrong. If a non-empty dma-ranges is present, then addresses
> which do not fall within any specified range are invalid altogether.

It is not explicitly stated by the specification, but can be interpreted
like that and from a pow it does make sense to treat things like that.

> The current long-term plan is indeed to try to move to some sort of
> internal "DMA range descriptor" in order to properly cope with the kind
> of esoteric integrations which have multiple disjoint windows,
> potentially even with different offsets, but as you point out there are
> still many hurdles between now and that becoming reality. So although
> this patch does represent the "right" thing, it's for entirely the wrong
> reason. AFAICT for your case it basically just works out as a very
> baroque way to hack dma_direct_supported() again - we shouldn't need a
> special case to map a bogus physical address to valid DMA address, we
> should be fixing the source of the bogus PA in the first place.

DMA_BIT_MASK(32) is pretty clear: The DMA can handle addresses within
32bit space. DMA_BIT_MASK(24) is also clear: The DMA can handle
addresses within 24bit space.

dma-ranges does not change that. The DMA can still address the same
space. What dma-ranges will tell is that a physical address range 'X'
can be accessed on the bus under range 'Y'.
For the DMA within the bus the physical address within 'X' does not
matter. What matters is the matching address within 'Y'

We should do dma_pfn_offset conversion _only_ for the range it applies
to. Outside of it is not valid to apply it. The dma API will check
(without applying dma_pfn_offset) addresses outside of any range (only
one currently in Linux) and if it is not OK for the mask then it will fail.

> 
>> This is a proof of concept patch which works on k2g where we have
>> dma-ranges = <0x80000000 0x8 0x00000000 0x80000000>;
>> for the SoC.
> 
> TBH it's probably extra-confusing that you're on Keystone 2, where
> technically this ends up closer-to-OK than most, since IIRC the 0-2GB
> MMIO region is the same on all 3(?) interconnect maps. Thus the 100%
> honest description would really be:
> 
> dma-ranges = <0x0 0x0 0x0 0x80000000>,
> ÂÂÂÂÂÂÂÂ <0x80000000 0x8 0x00000000 0x80000000>;
> 
> but yeah, that would just go horribly wrong with Linux today.

It does ;) This was the first thing I have tried.

> The
> subtelty that dma_map_resource() ignores the pfn_offset happens to be a
> "feature" in this regard ;)

Right, but Keystone 2 is broken since 5.3-rc3 by commit
ad3c7b18c5b362be5dbd0f2c0bcf1fd5fd659315.

Can you propose a fix which we can use until things get sorted out?

Thanks,
- PÃter

> 
> Robin.
> 
>> Without this patch everything which tries to set DMA_BIT_MASK(32) or less
>> fails -> DMA and peripherals with built in DMA (SD with ADMA) will not
>> probe or fall back to PIO mode.
>>
>> With this patch EDMA probes, SD's ADMA is working.
>> Audio and dma-test is working just fine with EDMA, mmc accesses with ADMA
>> also operational.
>>
>> The patch does not tried to address the incomplete handling of dma-ranges
>> from DT and it is not fixing/updating arch code or drivers which uses
>> dma_pfn_offset.
>> Neither provides fallback support for kernel setting only
>> dma_pfn_offset to
>> arbitrary number without paddr/dma_addr/size.
>>
>> Signed-off-by: Peter Ujfalusi <peter.ujfalusi@xxxxxx>
>> ---
>> Hi Christoph, Robin,
>>
>> I know it is a bit more complicated, but with this patch k2g is
>> working fine...
>>
>> I wanted to test the concept I was describing and a patch speaks
>> better than
>> words.
>>
>> Kind regards,
>> Peter
>>
>> Â arch/arm/include/asm/dma-mapping.h | 25 ++++++++++++++++++++--
>> Â drivers/of/device.cÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ |Â 7 ++++++-
>> Â include/linux/device.hÂÂÂÂÂÂÂÂÂÂÂÂ |Â 8 ++++++++
>> Â include/linux/dma-direct.hÂÂÂÂÂÂÂÂ | 33 ++++++++++++++++++++++++++++--
>> Â kernel/dma/coherent.cÂÂÂÂÂÂÂÂÂÂÂÂÂ |Â 9 +++++---
>> Â 5 files changed, 74 insertions(+), 8 deletions(-)
>>
>> diff --git a/arch/arm/include/asm/dma-mapping.h
>> b/arch/arm/include/asm/dma-mapping.h
>> index bdd80ddbca34..9bff6ad2d8c8 100644
>> --- a/arch/arm/include/asm/dma-mapping.h
>> +++ b/arch/arm/include/asm/dma-mapping.h
>> @@ -33,10 +33,31 @@ static inline const struct dma_map_ops
>> *get_arch_dma_ops(struct bus_type *bus)
>> ÂÂ * addresses. They must not be used by drivers.
>> ÂÂ */
>> Â #ifndef __arch_pfn_to_dma
>> +
>> +static inline unsigned long __phys_to_dma_pfn_offset(struct device *dev,
>> +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ phys_addr_t paddr)
>> +{
>> +ÂÂÂ if (paddr >= dev->dma_ranges.paddr &&
>> +ÂÂÂÂÂÂÂ paddr <= (dev->dma_ranges.paddr + dev->dma_ranges.size))
>> +ÂÂÂÂÂÂÂ return dev->dma_ranges.pfn_offset;
>> +
>> +ÂÂÂ return 0;
>> +}
>> +
>> +static inline unsigned long __dma_to_phys_pfn_offset(struct device *dev,
>> +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ dma_addr_t dma_addr)
>> +{
>> +ÂÂÂ if (dma_addr >= dev->dma_ranges.dma_addr &&
>> +ÂÂÂÂÂÂÂ dma_addr <= (dev->dma_ranges.dma_addr + dev->dma_ranges.size))
>> +ÂÂÂÂÂÂÂ return dev->dma_ranges.pfn_offset;
>> +
>> +ÂÂÂ return 0;
>> +}
>> +
>> Â static inline dma_addr_t pfn_to_dma(struct device *dev, unsigned
>> long pfn)
>> Â {
>> ÂÂÂÂÂ if (dev)
>> -ÂÂÂÂÂÂÂ pfn -= dev->dma_pfn_offset;
>> +ÂÂÂÂÂÂÂ pfn -= __phys_to_dma_pfn_offset(dev, __pfn_to_phys(pfn));
>> ÂÂÂÂÂ return (dma_addr_t)__pfn_to_bus(pfn);
>> Â }
>> Â @@ -45,7 +66,7 @@ static inline unsigned long dma_to_pfn(struct
>> device *dev, dma_addr_t addr)
>> ÂÂÂÂÂ unsigned long pfn = __bus_to_pfn(addr);
>> Â ÂÂÂÂÂ if (dev)
>> -ÂÂÂÂÂÂÂ pfn += dev->dma_pfn_offset;
>> +ÂÂÂÂÂÂÂ pfn += __dma_to_phys_pfn_offset(dev, addr);
>> Â ÂÂÂÂÂ return pfn;
>> Â }
>> diff --git a/drivers/of/device.c b/drivers/of/device.c
>> index 27203bfd0b22..07a8cc1a7d7f 100644
>> --- a/drivers/of/device.c
>> +++ b/drivers/of/device.c
>> @@ -105,7 +105,7 @@ int of_dma_configure(struct device *dev, struct
>> device_node *np, bool force_dma)
>> ÂÂÂÂÂÂÂÂÂ if (!force_dma)
>> ÂÂÂÂÂÂÂÂÂÂÂÂÂ return ret == -ENODEV ? 0 : ret;
>> Â -ÂÂÂÂÂÂÂ dma_addr = offset = 0;
>> +ÂÂÂÂÂÂÂ dma_addr = offset = paddr = 0;
>> ÂÂÂÂÂ } else {
>> ÂÂÂÂÂÂÂÂÂ offset = PFN_DOWN(paddr - dma_addr);
>> Â @@ -144,6 +144,11 @@ int of_dma_configure(struct device *dev, struct
>> device_node *np, bool force_dma)
>> Â ÂÂÂÂÂ dev->dma_pfn_offset = offset;
>> Â +ÂÂÂ dev->dma_ranges.paddr = paddr;
>> +ÂÂÂ dev->dma_ranges.dma_addr = dma_addr;
>> +ÂÂÂ dev->dma_ranges.size = size;
>> +ÂÂÂ dev->dma_ranges.pfn_offset = offset;
>> +
>> ÂÂÂÂÂ /*
>> ÂÂÂÂÂÂ * Limit coherent and dma mask based on size and default mask
>> ÂÂÂÂÂÂ * set by the driver.
>> diff --git a/include/linux/device.h b/include/linux/device.h
>> index ce6db68c3f29..57006b51a989 100644
>> --- a/include/linux/device.h
>> +++ b/include/linux/device.h
>> @@ -293,6 +293,13 @@ struct device_dma_parameters {
>> ÂÂÂÂÂ unsigned long segment_boundary_mask;
>> Â };
>> Â +struct dma_ranges {
>> +ÂÂÂ u64 paddr;
>> +ÂÂÂ u64 dma_addr;
>> +ÂÂÂ u64 size;
>> +ÂÂÂ unsigned long pfn_offset;
>> +};
>> +
>> Â /**
>> ÂÂ * struct device_connection - Device Connection Descriptor
>> ÂÂ * @fwnode: The device node of the connected device
>> @@ -581,6 +588,7 @@ struct device {
>> ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ allocations such descriptors. */
>> ÂÂÂÂÂ u64ÂÂÂÂÂÂÂ bus_dma_limit;ÂÂÂ /* upstream dma constraint */
>> ÂÂÂÂÂ unsigned longÂÂÂ dma_pfn_offset;
>> +ÂÂÂ struct dma_ranges dma_ranges;
>> Â ÂÂÂÂÂ struct device_dma_parameters *dma_parms;
>> Â diff --git a/include/linux/dma-direct.h b/include/linux/dma-direct.h
>> index 24b8684aa21d..4a46a15945ea 100644
>> --- a/include/linux/dma-direct.h
>> +++ b/include/linux/dma-direct.h
>> @@ -11,18 +11,47 @@ extern unsigned int zone_dma_bits;
>> Â #ifdef CONFIG_ARCH_HAS_PHYS_TO_DMA
>> Â #include <asm/dma-direct.h>
>> Â #else
>> +
>> +static inline unsigned long __phys_to_dma_pfn_offset(struct device *dev,
>> +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ phys_addr_t paddr)
>> +{
>> +ÂÂÂ if (!dev)
>> +ÂÂÂÂÂÂÂ return 0;
>> +
>> +ÂÂÂ if (paddr >= dev->dma_ranges.paddr &&
>> +ÂÂÂÂÂÂÂ paddr <= (dev->dma_ranges.paddr + dev->dma_ranges.size))
>> +ÂÂÂÂÂÂÂ return dev->dma_ranges.pfn_offset
>> +
>> +ÂÂÂ return 0;
>> +}
>> +
>> +static inline unsigned long __dma_to_phys_pfn_offset(struct device *dev,
>> +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ dma_addr_t dma_addr)
>> +{
>> +ÂÂÂ if (!dev)
>> +ÂÂÂÂÂÂÂ return 0;
>> +
>> +ÂÂÂ if (dma_addr >= dev->dma_ranges.dma_addr &&
>> +ÂÂÂÂÂÂÂ dma_addr <= (dev->dma_ranges.dma_addr + dev->dma_ranges.size))
>> +ÂÂÂÂÂÂÂ return dev->dma_ranges.pfn_offset
>> +
>> +ÂÂÂ return 0;
>> +}
>> +
>> Â static inline dma_addr_t __phys_to_dma(struct device *dev,
>> phys_addr_t paddr)
>> Â {
>> ÂÂÂÂÂ dma_addr_t dev_addr = (dma_addr_t)paddr;
>> +ÂÂÂ unsigned long offset = __phys_to_dma_pfn_offset(dev, paddr);
>> Â -ÂÂÂ return dev_addr - ((dma_addr_t)dev->dma_pfn_offset << PAGE_SHIFT);
>> +ÂÂÂ return dev_addr - ((dma_addr_t)offset << PAGE_SHIFT);
>> Â }
>> Â Â static inline phys_addr_t __dma_to_phys(struct device *dev,
>> dma_addr_t dev_addr)
>> Â {
>> ÂÂÂÂÂ phys_addr_t paddr = (phys_addr_t)dev_addr;
>> +ÂÂÂ unsigned long offset = __dma_to_phys_pfn_offset(dev, dev_addr);
>> Â -ÂÂÂ return paddr + ((phys_addr_t)dev->dma_pfn_offset << PAGE_SHIFT);
>> +ÂÂÂ return paddr + ((phys_addr_t)offset << PAGE_SHIFT);
>> Â }
>> Â #endif /* !CONFIG_ARCH_HAS_PHYS_TO_DMA */
>> Â diff --git a/kernel/dma/coherent.c b/kernel/dma/coherent.c
>> index 551b0eb7028a..7a68fd09f5d0 100644
>> --- a/kernel/dma/coherent.c
>> +++ b/kernel/dma/coherent.c
>> @@ -31,10 +31,13 @@ static inline struct dma_coherent_mem
>> *dev_get_coherent_memory(struct device *de
>> Â static inline dma_addr_t dma_get_device_base(struct device *dev,
>> ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ struct dma_coherent_mem * mem)
>> Â {
>> -ÂÂÂ if (mem->use_dev_dma_pfn_offset)
>> -ÂÂÂÂÂÂÂ return (mem->pfn_base - dev->dma_pfn_offset) << PAGE_SHIFT;
>> -ÂÂÂ else
>> +ÂÂÂ if (mem->use_dev_dma_pfn_offset) {
>> +ÂÂÂÂÂÂÂ unsigned long offset = __phys_to_dma_pfn_offset(dev,
>> +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ __pfn_to_phys(mem->pfn_base));
>> +ÂÂÂÂÂÂÂ return (mem->pfn_base - offset) << PAGE_SHIFT;
>> +ÂÂÂ } else {
>> ÂÂÂÂÂÂÂÂÂ return mem->device_base;
>> +ÂÂÂ }
>> Â }
>> Â Â static int dma_init_coherent_memory(phys_addr_t phys_addr,
>>

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