linux-kernel - Re: [PATCH v7 19/21] iommu/mediatek: Rename enable_4GB to dram_is

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Message-ID: <d932ded6-2e1c-f2d1-d3cf-8cb0cdbdbb0d@gmail.com>
Date:   Fri, 21 Jun 2019 12:10:00 +0200
From:   Matthias Brugger <matthias.bgg@...il.com>
To:     Yong Wu <yong.wu@...iatek.com>
Cc:     Joerg Roedel <joro@...tes.org>,
        Robin Murphy <robin.murphy@....com>,
        Rob Herring <robh+dt@...nel.org>,
        Evan Green <evgreen@...omium.org>,
        Tomasz Figa <tfiga@...gle.com>,
        Will Deacon <will.deacon@....com>,
        linux-mediatek@...ts.infradead.org, srv_heupstream@...iatek.com,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        iommu@...ts.linux-foundation.org, yingjoe.chen@...iatek.com,
        youlin.pei@...iatek.com, Nicolas Boichat <drinkcat@...omium.org>,
        anan.sun@...iatek.com, Matthias Kaehlcke <mka@...omium.org>
Subject: Re: [PATCH v7 19/21] iommu/mediatek: Rename enable_4GB to dram_is_4gb



On 20/06/2019 15:59, Yong Wu wrote:
> On Tue, 2019-06-18 at 18:06 +0200, Matthias Brugger wrote:
>>
>> On 10/06/2019 14:17, Yong Wu wrote:
>>> This patch only rename the variable name from enable_4GB to
>>> dram_is_4gb for readable.
>>
>> From my understanding this is true when available RAM > 4GB so I think the name
>> should be something like dram_bigger_4gb otherwise it may create confusion again.
> 
> Strictly, It is not "dram_bigger_4gb". actually if the dram size is over
> 3GB (the first 1GB is the register space), the "4GB mode" will be
> enabled. then how about the name "dram_enable_32bit"?(the PA 32bit will
> be enabled in the 4GB mode.)

Ok I think dram_is_4gb is ok then. But I'd suggest to add an explanation above
the struct mtk_iommu_data to explain exactly what this means.

>      
> There is another option, please see the last part in [1] suggested by
> Evan, something like below:
> ----
> data->enable_4GB = !!(max_pfn > (BIT_ULL(32) >> PAGE_SHIFT));
> if (!data->plat_data->has_4gb_mode)
>     data->enable_4GB = false;
> Then mtk_iommu_map would only have:
>     if (data->enable_4GB)
>          paddr |= BIT_ULL(32);
> ----

I think that's a nicer way to handle it.

Regards,
Matthias

> 
> Which one do you prefer?      
>       
> [1] https://lore.kernel.org/patchwork/patch/1028421/
> 
>>
>> Also from my point of view this patch should be done before
>> "[PATCH 06/21] iommu/io-pgtable-arm-v7s: Extend MediaTek 4GB Mode"
> 
> OK.
> 
>>
>> Regards,
>> Matthias
>>
>>>
>>> Signed-off-by: Yong Wu <yong.wu@...iatek.com>
>>> Reviewed-by: Evan Green <evgreen@...omium.org>
>>> ---
>>>  drivers/iommu/mtk_iommu.c | 10 +++++-----
>>>  drivers/iommu/mtk_iommu.h |  2 +-
>>>  2 files changed, 6 insertions(+), 6 deletions(-)
>>>
>>> diff --git a/drivers/iommu/mtk_iommu.c b/drivers/iommu/mtk_iommu.c
>>> index 86158d8..67cab2d 100644
>>> --- a/drivers/iommu/mtk_iommu.c
>>> +++ b/drivers/iommu/mtk_iommu.c
>>> @@ -382,7 +382,7 @@ static int mtk_iommu_map(struct iommu_domain *domain, unsigned long iova,
>>>  	int ret;
>>>  
>>>  	/* The "4GB mode" M4U physically can not use the lower remap of Dram. */
>>> -	if (data->plat_data->has_4gb_mode && data->enable_4GB)
>>> +	if (data->plat_data->has_4gb_mode && data->dram_is_4gb)
>>>  		paddr |= BIT_ULL(32);
>>>  
>>>  	spin_lock_irqsave(&dom->pgtlock, flags);
>>> @@ -554,13 +554,13 @@ static int mtk_iommu_hw_init(const struct mtk_iommu_data *data)
>>>  	writel_relaxed(regval, data->base + REG_MMU_INT_MAIN_CONTROL);
>>>  
>>>  	if (data->plat_data->m4u_plat == M4U_MT8173)
>>> -		regval = (data->protect_base >> 1) | (data->enable_4GB << 31);
>>> +		regval = (data->protect_base >> 1) | (data->dram_is_4gb << 31);
>>>  	else
>>>  		regval = lower_32_bits(data->protect_base) |
>>>  			 upper_32_bits(data->protect_base);
>>>  	writel_relaxed(regval, data->base + REG_MMU_IVRP_PADDR);
>>>  
>>> -	if (data->enable_4GB && data->plat_data->has_vld_pa_rng) {
>>> +	if (data->dram_is_4gb && data->plat_data->has_vld_pa_rng) {
>>>  		/*
>>>  		 * If 4GB mode is enabled, the validate PA range is from
>>>  		 * 0x1_0000_0000 to 0x1_ffff_ffff. here record bit[32:30].
>>> @@ -611,8 +611,8 @@ static int mtk_iommu_probe(struct platform_device *pdev)
>>>  		return -ENOMEM;
>>>  	data->protect_base = ALIGN(virt_to_phys(protect), MTK_PROTECT_PA_ALIGN);
>>>  
>>> -	/* Whether the current dram is over 4GB */
>>> -	data->enable_4GB = !!(max_pfn > (BIT_ULL(32) >> PAGE_SHIFT));
>>> +	/* Whether the current dram is 4GB. */
>>> +	data->dram_is_4gb = !!(max_pfn > (BIT_ULL(32) >> PAGE_SHIFT));
>>>  
>>>  	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
>>>  	data->base = devm_ioremap_resource(dev, res);
>>> diff --git a/drivers/iommu/mtk_iommu.h b/drivers/iommu/mtk_iommu.h
>>> index 753266b..e8114b2 100644
>>> --- a/drivers/iommu/mtk_iommu.h
>>> +++ b/drivers/iommu/mtk_iommu.h
>>> @@ -65,7 +65,7 @@ struct mtk_iommu_data {
>>>  	struct mtk_iommu_domain		*m4u_dom;
>>>  	struct iommu_group		*m4u_group;
>>>  	struct mtk_smi_iommu		smi_imu;      /* SMI larb iommu info */
>>> -	bool                            enable_4GB;
>>> +	bool                            dram_is_4gb;
>>>  	bool				tlb_flush_active;
>>>  
>>>  	struct iommu_device		iommu;
>>>
> 
>