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Subject: Re: [PATCH v7 19/21] iommu/mediatek: Rename enable_4GB to
 dram_is_4gb
From:   Yong Wu <yong.wu@mediatek.com>
To:     Matthias Brugger <matthias.bgg@gmail.com>
CC:     Joerg Roedel <joro@8bytes.org>,
        Robin Murphy <robin.murphy@arm.com>,
        "Rob Herring" <robh+dt@kernel.org>,
        Evan Green <evgreen@chromium.org>,
        "Tomasz Figa" <tfiga@google.com>,
        Will Deacon <will.deacon@arm.com>,
        <linux-mediatek@lists.infradead.org>,
        <srv_heupstream@mediatek.com>, <devicetree@vger.kernel.org>,
        <linux-kernel@vger.kernel.org>,
        <linux-arm-kernel@lists.infradead.org>,
        <iommu@lists.linux-foundation.org>, <yingjoe.chen@mediatek.com>,
        <youlin.pei@mediatek.com>, Nicolas Boichat <drinkcat@chromium.org>,
        <anan.sun@mediatek.com>, Matthias Kaehlcke <mka@chromium.org>
Date:   Thu, 20 Jun 2019 21:59:52 +0800
In-Reply-To: <9bf13c22-0c73-2950-2204-23d577976b03@gmail.com>
References: <1560169080-27134-1-git-send-email-yong.wu@mediatek.com>
         <1560169080-27134-20-git-send-email-yong.wu@mediatek.com>
         <9bf13c22-0c73-2950-2204-23d577976b03@gmail.com>
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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.)
     
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);
----

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@mediatek.com>
> > Reviewed-by: Evan Green <evgreen@chromium.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;
> >