Re: [PATCH v4 3/4] memory: mtk-smi: Add enable IOMMU SMC command for MM master

[Chengci.Xu <chengci.xu@mediatek.com>]

On Tue, 2022-08-09 at 13:58 +0800, Yong Wu wrote:
> On Mon, 2022-08-01 at 10:18 +0800, Chengci.Xu wrote:
> > For concerns about security, the register to enable/disable IOMMU
> > of
> > SMI LARB should only be configured in secure world. Thus, we add
> > some
> > SMC command for multimedia master to enable/disable MM IOMMU in ATF
> > by
> > setting the register of SMI LARB. This function is prepared for
> > MT8188.
> > 
> > Signed-off-by: Chengci.Xu <chengci.xu@mediatek.com>
> > ---
> >  drivers/memory/mtk-smi.c                 | 19 +++++++++++++++++++
> >  include/linux/soc/mediatek/mtk_sip_svc.h |  3 +++
> >  include/soc/mediatek/smi.h               |  5 +++++
> >  3 files changed, 27 insertions(+)
> > 
> > diff --git a/drivers/memory/mtk-smi.c b/drivers/memory/mtk-smi.c
> > index 08c1668d47bf..28e1123f9d76 100644
> > --- a/drivers/memory/mtk-smi.c
> > +++ b/drivers/memory/mtk-smi.c
> > @@ -3,6 +3,7 @@
> >   * Copyright (c) 2015-2016 MediaTek Inc.
> >   * Author: Yong Wu <yong.wu@mediatek.com>
> >   */
> > +#include <linux/arm-smccc.h>
> >  #include <linux/clk.h>
> >  #include <linux/component.h>
> >  #include <linux/device.h>
> > @@ -14,6 +15,7 @@
> >  #include <linux/of_platform.h>
> >  #include <linux/platform_device.h>
> >  #include <linux/pm_runtime.h>
> > +#include <linux/soc/mediatek/mtk_sip_svc.h>
> >  #include <soc/mediatek/smi.h>
> >  #include <dt-bindings/memory/mt2701-larb-port.h>
> >  #include <dt-bindings/memory/mtk-memory-port.h>
> > @@ -89,6 +91,7 @@
> >  #define MTK_SMI_FLAG_THRT_UPDATE	BIT(0)
> >  #define MTK_SMI_FLAG_SW_FLAG		BIT(1)
> >  #define MTK_SMI_FLAG_SLEEP_CTL		BIT(2)
> > +#define MTK_SMI_FLAG_CFG_PORT_SEC_CTL	BIT(3)
> >  #define MTK_SMI_CAPS(flags, _x)		(!!((flags) & (_x)))
> >  
> >  struct mtk_smi_reg_pair {
> > @@ -238,6 +241,7 @@ static int
> > mtk_smi_larb_config_port_gen2_general(struct device *dev)
> >  	struct mtk_smi_larb *larb = dev_get_drvdata(dev);
> >  	u32 reg, flags_general = larb->larb_gen->flags_general;
> >  	const u8 *larbostd = larb->larb_gen->ostd ? larb->larb_gen-
> > > ostd[larb->larbid] : NULL;
> > 
> > +	struct arm_smccc_res res;
> >  	int i;
> >  
> >  	if (BIT(larb->larbid) & larb->larb_gen-
> > > larb_direct_to_common_mask)
> > 
> > @@ -262,6 +266,21 @@ static int
> > mtk_smi_larb_config_port_gen2_general(struct device *dev)
> >  		reg |= BANK_SEL(larb->bank[i]);
> >  		writel(reg, larb->base + SMI_LARB_NONSEC_CON(i));
> >  	}
> > +
> > +	/*
> > +	 * We still need to write above NONSEC_CON register for bank
> > selection
> > +	 * even if enabling IOMMU is failed by SMC call. Otherwise, all
> > master
> > +	 * will be configured to bank 0 with a state of IOMMU enable
> > due to the
> > +	 * HW default value of register.
> 
> I don't understand this. Does bankX(X!=0) make sense if SMC fail? 
> 
> I guess the below segment should be before SMI_LARB_NONSEC_CON. It
> means we shouldn't touch bank_sel while SMC fail.

If SMC call failed, we do have no need to configure bank_sel. All we
can do is stop following step and report an error. So it is a good
choice to put the code about MTK_SMI_FLAG_CFG_PORT_SEC_CTL in front of
SMI_LARB_NONSEC_CON. I will do it in next version.

> 
> Just add a comment like:
> /* When mmu_en bits are in security world, the bank_sel still is in
> the
> LARB_NONSEC_CON below. and the mmu_en of LARB_NONSEC_CON have no
> effect
> in this case. */

OK, got it, thanks.

> 
> > +	 */
> > +	if (MTK_SMI_CAPS(flags_general, MTK_SMI_FLAG_CFG_PORT_SEC_CTL))
> > {
> > +		arm_smccc_smc(MTK_SIP_KERNEL_IOMMU_CONTROL,
> > IOMMU_ATF_CMD_CONFIG_SMI_LARB,
> > +			      larb->larbid, (u32)(*larb->mmu), 0, 0, 0,
> 
> The type of mmu is "u32", no need the "(u32)".
> 
> > 0, &res);
> > +		if (res.a0 != 0) {
> > +			dev_err(dev, "Enable iommu fail, ret %ld\n",
> > res.a0);
> > +			return -EINVAL;
> > +		}
> > +	}
> >  	return 0;
> >  }
> >  
> > diff --git a/include/linux/soc/mediatek/mtk_sip_svc.h
> > b/include/linux/soc/mediatek/mtk_sip_svc.h
> > index 082398e0cfb1..0761128b4354 100644
> > --- a/include/linux/soc/mediatek/mtk_sip_svc.h
> > +++ b/include/linux/soc/mediatek/mtk_sip_svc.h
> > @@ -22,4 +22,7 @@
> >  	ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL, MTK_SIP_SMC_CONVENTION,
> > \
> >  			   ARM_SMCCC_OWNER_SIP, fn_id)
> >  
> > +/* IOMMU related SMC call */
> > +#define MTK_SIP_KERNEL_IOMMU_CONTROL	MTK_SIP_SMC_CMD(0x514)
> > +
> >  #endif
> > diff --git a/include/soc/mediatek/smi.h
> > b/include/soc/mediatek/smi.h
> > index 11f7d6b59642..dfd8efca5e60 100644
> > --- a/include/soc/mediatek/smi.h
> > +++ b/include/soc/mediatek/smi.h
> > @@ -11,6 +11,11 @@
> >  
> >  #if IS_ENABLED(CONFIG_MTK_SMI)
> >  
> > +enum iommu_atf_cmd {
> > +	IOMMU_ATF_CMD_CONFIG_SMI_LARB,		/* For mm master to
> > en/disable iommu */
> > +	IOMMU_ATF_CMD_MAX,
> > +};
> > +
> >  #define MTK_SMI_MMU_EN(port)	BIT(port)
> >  
> >  struct mtk_smi_larb_iommu {
> 
> 


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