Re: [PATCH 2/2] Revert "iommu/arm-smmu-v3: Don't reserve implementation defined register space"

[Robin Murphy <robin.murphy@arm.com>]

On 2021-01-21 02:04, Leizhen (ThunderTown) wrote:
> 
> 
> On 2021/1/20 23:02, Robin Murphy wrote:
>> On 2021-01-19 01:59, Zhen Lei wrote:
>>> This reverts commit 52f3fab0067d6fa9e99c1b7f63265dd48ca76046.
>>>
>>> This problem has been fixed by another patch. The original method had side
>>> effects, it was not mapped to the user-specified resource size. The code
>>> will become more complex when ECMDQ is supported later.
>>
>> FWIW I don't think that's a significant issue either way - there could be any number of imp-def pages between SMMU page 0 and the ECMDQ control pages, so it will still be logical to map them as another separate thing anyway.
> 
> Yes, so now I'm thinking of preserving the SMMUv3 resources and eliminating the imp-def area. Then use another devm_ioremap() to cover the entire resource，assign it to smmu->base.
> Otherwise, a base pointer needs to be defined for each separated register space，or call a function to convert each time.

But we'll almost certainly want to maintain a pointer to start of the 
ECMDQ control page block anyway, since that's not fixed relative to 
smmu->base. Therefore what's the harm in handling that via a dedicated 
mapping, once we've determined that we *do* intend to use ECMDQs? 
Otherwise we end up with in the complicated dance of trying to map 
"everything" up-front in order to be able to read the ID registers to 
determine what the actual extent of "everything" is supposed to be.

(also this reminds me that I was going to remove arm_smmu_page1_fixup() 
entirely - I'd totally forgotten about that...)

Robin.

>>> Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
>>> ---
>>>    drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 32 ++++-------------------------
>>>    drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h |  3 ---
>>>    2 files changed, 4 insertions(+), 31 deletions(-)
>>>
>>> diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
>>> index 8ca7415d785d9bf..477f473842e5272 100644
>>> --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
>>> +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
>>> @@ -91,8 +91,9 @@ struct arm_smmu_option_prop {
>>>    static inline void __iomem *arm_smmu_page1_fixup(unsigned long offset,
>>>                             struct arm_smmu_device *smmu)
>>>    {
>>> -    if (offset > SZ_64K)
>>> -        return smmu->page1 + offset - SZ_64K;
>>> +    if ((offset > SZ_64K) &&
>>> +        (smmu->options & ARM_SMMU_OPT_PAGE0_REGS_ONLY))
>>> +        offset -= SZ_64K;
>>>          return smmu->base + offset;
>>>    }
>>> @@ -3486,18 +3487,6 @@ static int arm_smmu_set_bus_ops(struct iommu_ops *ops)
>>>        return err;
>>>    }
>>>    -static void __iomem *arm_smmu_ioremap(struct device *dev, resource_size_t start,
>>> -                      resource_size_t size)
>>> -{
>>> -    struct resource res = {
>>> -        .flags = IORESOURCE_MEM,
>>> -        .start = start,
>>> -        .end = start + size - 1,
>>> -    };
>>> -
>>> -    return devm_ioremap_resource(dev, &res);
>>> -}
>>> -
>>>    static int arm_smmu_device_probe(struct platform_device *pdev)
>>>    {
>>>        int irq, ret;
>>> @@ -3533,23 +3522,10 @@ static int arm_smmu_device_probe(struct platform_device *pdev)
>>>        }
>>>        ioaddr = res->start;
>>>    -    /*
>>> -     * Don't map the IMPLEMENTATION DEFINED regions, since they may contain
>>> -     * the PMCG registers which are reserved by the PMU driver.
>>> -     */
>>> -    smmu->base = arm_smmu_ioremap(dev, ioaddr, ARM_SMMU_REG_SZ);
>>> +    smmu->base = devm_ioremap_resource(dev, res);
>>>        if (IS_ERR(smmu->base))
>>>            return PTR_ERR(smmu->base);
>>>    -    if (arm_smmu_resource_size(smmu) > SZ_64K) {
>>> -        smmu->page1 = arm_smmu_ioremap(dev, ioaddr + SZ_64K,
>>> -                           ARM_SMMU_REG_SZ);
>>> -        if (IS_ERR(smmu->page1))
>>> -            return PTR_ERR(smmu->page1);
>>> -    } else {
>>> -        smmu->page1 = smmu->base;
>>> -    }
>>> -
>>>        /* Interrupt lines */
>>>          irq = platform_get_irq_byname_optional(pdev, "combined");
>>> diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
>>> index 96c2e9565e00282..0c3090c60840c22 100644
>>> --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
>>> +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
>>> @@ -152,8 +152,6 @@
>>>    #define ARM_SMMU_PRIQ_IRQ_CFG1        0xd8
>>>    #define ARM_SMMU_PRIQ_IRQ_CFG2        0xdc
>>>    -#define ARM_SMMU_REG_SZ            0xe00
>>> -
>>>    /* Common MSI config fields */
>>>    #define MSI_CFG0_ADDR_MASK        GENMASK_ULL(51, 2)
>>>    #define MSI_CFG2_SH            GENMASK(5, 4)
>>> @@ -584,7 +582,6 @@ struct arm_smmu_strtab_cfg {
>>>    struct arm_smmu_device {
>>>        struct device            *dev;
>>>        void __iomem            *base;
>>> -    void __iomem            *page1;
>>>      #define ARM_SMMU_FEAT_2_LVL_STRTAB    (1 << 0)
>>>    #define ARM_SMMU_FEAT_2_LVL_CDTAB    (1 << 1)
>>>
>>
>> .
>>
>