linux-kernel - Re: [PATCH v6 31/34] iommu/mediatek: Get the proper bankid for multi banks

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Date:   Sun, 1 May 2022 10:33:30 +0800
From:   Yong Wu <yong.wu@...iatek.com>
To:     Matthias Brugger <matthias.bgg@...il.com>,
        Joerg Roedel <joro@...tes.org>,
        Rob Herring <robh+dt@...nel.org>, Will Deacon <will@...nel.org>
CC:     Robin Murphy <robin.murphy@....com>,
        Krzysztof Kozlowski <krzysztof.kozlowski@...onical.com>,
        Tomasz Figa <tfiga@...omium.org>,
        <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>,
        Hsin-Yi Wang <hsinyi@...omium.org>, <youlin.pei@...iatek.com>,
        <anan.sun@...iatek.com>, <xueqi.zhang@...iatek.com>,
        <yen-chang.chen@...iatek.com>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>,
        <mingyuan.ma@...iatek.com>, <yf.wang@...iatek.com>,
        <libo.kang@...iatek.com>, <chengci.xu@...iatek.com>
Subject: Re: [PATCH v6 31/34] iommu/mediatek: Get the proper bankid for
 multi banks

Hi Matthias,

Thanks very much for reviewing.

On Thu, 2022-04-28 at 16:14 +0200, Matthias Brugger wrote:
> 
> On 07/04/2022 09:57, Yong Wu wrote:
> > We preassign some ports in a special bank via the new defined
> > banks_portmsk. Put it in the plat_data means it is not expected to
> > be
> > adjusted dynamically.
> > 
> > If the iommu id in the iommu consumer's dtsi node is inside this
> > banks_portmsk, then we switch it to this special iommu bank, and
> > initialise the IOMMU bank HW.
> > 
> > Each a bank has the independent pgtable(4GB iova range). Each a
> > bank
> > is a independent iommu domain/group. Currently we don't separate
> > different
> > iova ranges inside a bank.
> > 
> > Signed-off-by: Yong Wu <yong.wu@...iatek.com>
> > Reviewed-by: AngeloGioacchino Del Regno <
> > angelogioacchino.delregno@...labora.com>
> > ---
> >   drivers/iommu/mtk_iommu.c | 39
> > ++++++++++++++++++++++++++++++++++++---
> >   1 file changed, 36 insertions(+), 3 deletions(-)
> > 
> > diff --git a/drivers/iommu/mtk_iommu.c b/drivers/iommu/mtk_iommu.c
> > index 0828cff97625..d42b3d35a36e 100644
> > --- a/drivers/iommu/mtk_iommu.c
> > +++ b/drivers/iommu/mtk_iommu.c

[snip]

> > @@ -802,6 +828,7 @@ static struct iommu_group
> > *mtk_iommu_device_group(struct device *dev)
> >   	struct mtk_iommu_data *c_data = dev_iommu_priv_get(dev), *data;
> >   	struct list_head *hw_list = c_data->hw_list;
> >   	struct iommu_group *group;
> > +	unsigned int bankid, groupid;
> >   	int regionid;
> >   
> >   	data = mtk_iommu_get_frst_data(hw_list);
> > @@ -812,12 +839,18 @@ static struct iommu_group
> > *mtk_iommu_device_group(struct device *dev)
> >   	if (regionid < 0)
> >   		return ERR_PTR(regionid);
> >   
> > +	bankid = mtk_iommu_get_bank_id(dev, data->plat_data);
> 
> I think code readability would be improved if we add a new function
> like 
> mtk_iommu_get_id which call mtk_iommu_get_bankid and if necessary 
> mtk_iommu_get_regionid.

OK, I will define a new function, like mtk_iommu_get_group_id for the
readability.

> 
> >   	mutex_lock(&data->mutex);
> > -	group = data->m4u_group[regionid];
> > +	/*
> > +	 * If the bank function is enabled, each a bank is a iommu
> > group/domain.
> > +	 * otherwise, each a iova region is a iommu group/domain.
> 
> While at it:
> "If the bank function is enabled, each bank is a iommu group/domain.
> Otherwise, 
> each iova region is a iommu group/domain."

And move this comment into the new funtion.

Also of course, I will fix the other two comments and send v7.

Thanks.

> 
> Regards,
> Matthias
> 
> > +	 */
> > +	groupid = bankid ? bankid : regionid;
> > +	group = data->m4u_group[groupid];
> >   	if (!group) {
> >   		group = iommu_group_alloc();
> >   		if (!IS_ERR(group))
> > -			data->m4u_group[regionid] = group;
> > +			data->m4u_group[groupid] = group;
> >   	} else {
> >   		iommu_group_ref_get(group);
> >   	}