Re: [PATCH v1 07/10] powerpc/pseries/iommu: Allow DDW windows starting at 0x00

Alexey Kardashevskiy
2020-08-31T00:50:27Z

On 29/08/2020 00:04, Leonardo Bras wrote:
> On Mon, 2020-08-24 at 13:44 +1000, Alexey Kardashevskiy wrote:
>>
>>> On 18/08/2020 09:40, Leonardo Bras wrote:
>>> enable_ddw() currently returns the address of the DMA window, which is
>>> considered invalid if has the value 0x00.
>>>
>>> Also, it only considers valid an address returned from find_existing_ddw
>>> if it's not 0x00.
>>>
>>> Changing this behavior makes sense, given the users of enable_ddw() only
>>> need to know if direct mapping is possible. It can also allow a DMA window
>>> starting at 0x00 to be used.
>>>
>>> This will be helpful for using a DDW with indirect mapping, as the window
>>> address will be different than 0x00, but it will not map the whole
>>> partition.
>>>
>>> Signed-off-by: Leonardo Bras <leobras.c@gmail.com>
>>> ---
>>> arch/powerpc/platforms/pseries/iommu.c | 30 ++++++++++++--------------
>>> 1 file changed, 14 insertions(+), 16 deletions(-)
>>>
>>> diff --git a/arch/powerpc/platforms/pseries/iommu.c b/arch/powerpc/platforms/pseries/iommu.c
>>> index fcdefcc0f365..4031127c9537 100644
>>> --- a/arch/powerpc/platforms/pseries/iommu.c
>>> +++ b/arch/powerpc/platforms/pseries/iommu.c
>>> @@ -852,24 +852,25 @@ static void remove_ddw(struct device_node *np, bool remove_prop)
>>> np, ret);
>>> }
>>>>
>>> -static u64 find_existing_ddw(struct device_node *pdn)
>>> +static bool find_existing_ddw(struct device_node *pdn, u64 *dma_addr)
>>> {
>>> struct direct_window *window;
>>> const struct dynamic_dma_window_prop *direct64;
>>> - u64 dma_addr = 0;
>>> + bool found = false;
>>>
>>> spin_lock(&direct_window_list_lock);
>>> /* check if we already created a window and dupe that config if so */
>>> list_for_each_entry(window, &direct_window_list, list) {
>>> if (window->device == pdn) {
>>> direct64 = window->prop;
>>> - dma_addr = be64_to_cpu(direct64->dma_base);
>>> + *dma_addr = be64_to_cpu(direct64->dma_base);
>>> + found = true;
>>> break;
>>> }
>>> }
>>> spin_unlock(&direct_window_list_lock);
>>>
>>> - return dma_addr;
>>> + return found;
>>> }
>>>
>>> static struct direct_window *ddw_list_add(struct device_node *pdn,
>>> @@ -1131,15 +1132,15 @@ static void reset_dma_window(struct pci_dev *dev, struct device_node *par_dn)
>>> * pdn: the parent pe node with the ibm,dma_window property
>>> * Future: also check if we can remap the base window for our base page size
>>> *
>>> - * returns the dma offset for use by the direct mapped DMA code.
>>> + * returns true if can map all pages (direct mapping), false otherwise..
>>> */
>>> -static u64 enable_ddw(struct pci_dev *dev, struct device_node *pdn)
>>> +static bool enable_ddw(struct pci_dev *dev, struct device_node *pdn)
>>> {
>>> int len, ret;
>>> struct ddw_query_response query;
>>> struct ddw_create_response create;
>>> int page_shift;
>>> - u64 dma_addr, max_addr;
>>> + u64 max_addr;
>>> struct device_node *dn;
>>> u32 ddw_avail[DDW_APPLICABLE_SIZE];
>>> struct direct_window *window;
>>> @@ -1150,8 +1151,7 @@ static u64 enable_ddw(struct pci_dev *dev, struct device_node *pdn)
>>>
>>> mutex_lock(&direct_window_init_mutex);
>>>
>>> - dma_addr = find_existing_ddw(pdn);
>>> - if (dma_addr != 0)
>>> + if (find_existing_ddw(pdn, &dev->dev.archdata.dma_offset))
>>> goto out_unlock;
>>>
>>> /*
>>> @@ -1292,7 +1292,7 @@ static u64 enable_ddw(struct pci_dev *dev, struct device_node *pdn)
>>> goto out_free_window;
>>> }
>>>
>>> - dma_addr = be64_to_cpu(ddwprop->dma_base);
>>> + dev->dev.archdata.dma_offset = be64_to_cpu(ddwprop->dma_base);
>>
>> Do not you need the same chunk in the find_existing_ddw() case above as
>> well? Thanks,
>
> The new signature of find_existing_ddw() is
> static bool find_existing_ddw(struct device_node *pdn, u64 *dma_addr)
>
> And on enable_ddw(), we call
> find_existing_ddw(pdn, &dev->dev.archdata.dma_offset)
>
> And inside the function we do:
> *dma_addr = be64_to_cpu(direct64->dma_base);
>
> I think it's the same as the chunk before.
> Am I missing something?

ah no, sorry, you are not missing anything.

Reviewed-by: Alexey Kardashevskiy <aik@ozlabs.ru>

--
Alexey