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

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Message-ID: <1561171339.4850.6.camel@mhfsdcap03>
Date:   Sat, 22 Jun 2019 10:42:19 +0800
From:   Yong Wu <yong.wu@...iatek.com>
To:     Matthias Brugger <matthias.bgg@...il.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 Fri, 2019-06-21 at 12:10 +0200, Matthias Brugger wrote:
> 
> 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.

Thanks your feedback. then I will use this way.

> 
> 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;
> >>>
> > 
> >