linux-kernel - Re: [PATCH v6 03/10] iommu/mediatek: Use a u32 flags to describe different HW features

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Message-ID: <bce3e1e0-f0b0-8c77-d966-3b6e37b3b647@gmail.com>
Date:   Mon, 6 Jul 2020 17:17:03 +0200
From:   Matthias Brugger <matthias.bgg@...il.com>
To:     Yingjoe Chen <yingjoe.chen@...iatek.com>,
        Chao Hao <chao.hao@...iatek.com>
Cc:     Joerg Roedel <joro@...tes.org>, Rob Herring <robh+dt@...nel.org>,
        devicetree@...r.kernel.org, FY Yang <fy.yang@...iatek.com>,
        wsd_upstream@...iatek.com, linux-kernel@...r.kernel.org,
        iommu@...ts.linux-foundation.org, TH Yang <th.yang@...iatek.com>,
        linux-mediatek@...ts.infradead.org, Yong Wu <yong.wu@...iatek.com>,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v6 03/10] iommu/mediatek: Use a u32 flags to describe
 different HW features



On 04/07/2020 03:16, Yingjoe Chen wrote:
> On Fri, 2020-07-03 at 12:41 +0800, Chao Hao wrote:
>> Given the fact that we are adding more and more plat_data bool values,
>> it would make sense to use a u32 flags register and add the appropriate
>> macro definitions to set and check for a flag present.
>> No functional change.
>>
>> Cc: Yong Wu <yong.wu@...iatek.com>
>> Suggested-by: Matthias Brugger <matthias.bgg@...il.com>
>> Signed-off-by: Chao Hao <chao.hao@...iatek.com>
>> Reviewed-by: Matthias Brugger <matthias.bgg@...il.com>
>> ---
>>  drivers/iommu/mtk_iommu.c | 28 +++++++++++++++++-----------
>>  drivers/iommu/mtk_iommu.h |  7 +------
>>  2 files changed, 18 insertions(+), 17 deletions(-)
>>
>> diff --git a/drivers/iommu/mtk_iommu.c b/drivers/iommu/mtk_iommu.c
>> index 88d3df5b91c2..40ca564d97af 100644
>> --- a/drivers/iommu/mtk_iommu.c
>> +++ b/drivers/iommu/mtk_iommu.c
>> @@ -100,6 +100,15 @@
>>  #define MTK_M4U_TO_LARB(id)		(((id) >> 5) & 0xf)
>>  #define MTK_M4U_TO_PORT(id)		((id) & 0x1f)
>>  
>> +#define HAS_4GB_MODE			BIT(0)
>> +/* HW will use the EMI clock if there isn't the "bclk". */
>> +#define HAS_BCLK			BIT(1)
>> +#define HAS_VLD_PA_RNG			BIT(2)
>> +#define RESET_AXI			BIT(3)
>> +
>> +#define MTK_IOMMU_HAS_FLAG(pdata, _x) \
>> +		((((pdata)->flags) & (_x)) == (_x))
>> +
>>  struct mtk_iommu_domain {
>>  	struct io_pgtable_cfg		cfg;
>>  	struct io_pgtable_ops		*iop;
>> @@ -563,7 +572,8 @@ static int mtk_iommu_hw_init(const struct mtk_iommu_data *data)
>>  			 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->enable_4GB &&
>> +	    MTK_IOMMU_HAS_FLAG(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].
>> @@ -573,7 +583,7 @@ static int mtk_iommu_hw_init(const struct mtk_iommu_data *data)
>>  	}
>>  	writel_relaxed(0, data->base + REG_MMU_DCM_DIS);
>>  
>> -	if (data->plat_data->reset_axi) {
>> +	if (MTK_IOMMU_HAS_FLAG(data->plat_data, RESET_AXI)) {
>>  		/* The register is called STANDARD_AXI_MODE in this case */
>>  		writel_relaxed(0, data->base + REG_MMU_MISC_CTRL);
>>  	}
>> @@ -618,7 +628,7 @@ static int mtk_iommu_probe(struct platform_device *pdev)
>>  
>>  	/* Whether the current dram is over 4GB */
>>  	data->enable_4GB = !!(max_pfn > (BIT_ULL(32) >> PAGE_SHIFT));
>> -	if (!data->plat_data->has_4gb_mode)
>> +	if (!MTK_IOMMU_HAS_FLAG(data->plat_data, HAS_4GB_MODE))
>>  		data->enable_4GB = false;
>>  
>>  	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
>> @@ -631,7 +641,7 @@ static int mtk_iommu_probe(struct platform_device *pdev)
>>  	if (data->irq < 0)
>>  		return data->irq;
>>  
>> -	if (data->plat_data->has_bclk) {
>> +	if (MTK_IOMMU_HAS_FLAG(data->plat_data, HAS_BCLK)) {
>>  		data->bclk = devm_clk_get(dev, "bclk");
>>  		if (IS_ERR(data->bclk))
>>  			return PTR_ERR(data->bclk);
>> @@ -763,23 +773,19 @@ static const struct dev_pm_ops mtk_iommu_pm_ops = {
>>  
>>  static const struct mtk_iommu_plat_data mt2712_data = {
>>  	.m4u_plat     = M4U_MT2712,
>> -	.has_4gb_mode = true,
>> -	.has_bclk     = true,
>> -	.has_vld_pa_rng   = true,
>> +	.flags        = HAS_4GB_MODE | HAS_BCLK | HAS_VLD_PA_RNG,
>>  	.larbid_remap = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9},
>>  };
>>  
>>  static const struct mtk_iommu_plat_data mt8173_data = {
>>  	.m4u_plat     = M4U_MT8173,
>> -	.has_4gb_mode = true,
>> -	.has_bclk     = true,
>> -	.reset_axi    = true,
>> +	.flags	      = HAS_4GB_MODE | HAS_BCLK | RESET_AXI,
>>  	.larbid_remap = {0, 1, 2, 3, 4, 5}, /* Linear mapping. */
>>  };
>>  
>>  static const struct mtk_iommu_plat_data mt8183_data = {
>>  	.m4u_plat     = M4U_MT8183,
>> -	.reset_axi    = true,
>> +	.flags        = RESET_AXI,
>>  	.larbid_remap = {0, 4, 5, 6, 7, 2, 3, 1},
>>  };
>>  
>> diff --git a/drivers/iommu/mtk_iommu.h b/drivers/iommu/mtk_iommu.h
>> index 7212e6fcf982..5225a9170aaa 100644
>> --- a/drivers/iommu/mtk_iommu.h
>> +++ b/drivers/iommu/mtk_iommu.h
>> @@ -39,12 +39,7 @@ enum mtk_iommu_plat {
>>  
>>  struct mtk_iommu_plat_data {
>>  	enum mtk_iommu_plat m4u_plat;
>> -	bool                has_4gb_mode;
>> -
>> -	/* HW will use the EMI clock if there isn't the "bclk". */
>> -	bool                has_bclk;
>> -	bool                has_vld_pa_rng;
>> -	bool                reset_axi;
>> +	u32                 flags;
> 
> 
> How about using bit field instead? eg
> 
>   u32 has_bclk:1;
> 
> In this way, we don't need to change code.
> 

Actually I proposed to use the flag approach because I didn't want to bloat the
mtk_iommu_plat_data structure with new variables for every new feature, being it
a bit field or a bool.

Regards,
Matthias