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SubjectRe: [PATCH v5 07/10] iommu/mediatek: Add REG_MMU_WR_LEN register definition
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On 30/06/2020 12:59, chao hao wrote:
> On Mon, 2020-06-29 at 12:16 +0200, Matthias Brugger wrote:
>>
>> On 29/06/2020 09:13, Chao Hao wrote:
>>> Some platforms(ex: mt6779) need to improve performance by setting
>>> REG_MMU_WR_LEN register. And we can use WR_THROT_EN macro to control
>>> whether we need to set the register. If the register uses default value,
>>> iommu will send command to EMI without restriction, when the number of
>>> commands become more and more, it will drop the EMI performance. So when
>>> more than ten_commands(default value) don't be handled for EMI, iommu will
>>> stop send command to EMI for keeping EMI's performace by enabling write
>>> throttling mechanism(bit[5][21]=0) in MMU_WR_LEN_CTRL register.
>>>
>>> Cc: Matthias Brugger <matthias.bgg@gmail.com>
>>> Signed-off-by: Chao Hao <chao.hao@mediatek.com>
>>> ---
>>> drivers/iommu/mtk_iommu.c | 10 ++++++++++
>>> drivers/iommu/mtk_iommu.h | 2 ++
>>> 2 files changed, 12 insertions(+)
>>>
>>> diff --git a/drivers/iommu/mtk_iommu.c b/drivers/iommu/mtk_iommu.c
>>> index ec1f86913739..92316c4175a9 100644
>>> --- a/drivers/iommu/mtk_iommu.c
>>> +++ b/drivers/iommu/mtk_iommu.c
>>> @@ -46,6 +46,8 @@
>>> #define F_MMU_STANDARD_AXI_MODE_BIT (BIT(3) | BIT(19))
>>>
>>> #define REG_MMU_DCM_DIS 0x050
>>> +#define REG_MMU_WR_LEN 0x054
>>
>> The register name is confusing. For me it seems to describe the length of a
>> write but it is used for controlling the write throttling. Is this the name
>> that's used in the datasheet?
>>
>
> Thanks for your review carefully, we can name it to REG_MMU_WR_LEN_CTRL

Yes, that's mbetter, thanks.

>
>
>>> +#define F_MMU_WR_THROT_DIS_BIT (BIT(5) | BIT(21))
>>
>> There are two spaces between '|' and 'BIT(21)', should be one.
>>
>> Regarding the name of the define, what does the 'F_' statnds for?
>
> F_ is used to described some bits in register and doesn't have other
> meanings. The format is refer to other bits definition
>
>> Also I think
>> it should be called '_MASK' instead of '_BIT' as it defines a mask of bits.
>>
>
> Thanks for your advice.
> For F_MMU_WR_THROT_DIS_BIT:
> 1'b0: Enable write throttling mechanism
> 1'b1: Disable write throttling mechanism
> So I think we can name "F_MMU_WR_THROT_DIS BIT(5) | BIT(21)" directly,
> it maybe more clearer.
>

Is this what the datasheet names it? If not then I'd prefer F_MMU_WR_THROT_DIS_MASK.

Regards,
Matthias

>> Regards,
>> Matthias
>>
>>>
>>> #define REG_MMU_CTRL_REG 0x110
>>> #define F_MMU_TF_PROT_TO_PROGRAM_ADDR (2 << 4)
>>> @@ -582,6 +584,12 @@ static int mtk_iommu_hw_init(const struct mtk_iommu_data *data)
>>> writel_relaxed(regval, data->base + REG_MMU_VLD_PA_RNG);
>>> }
>>> writel_relaxed(0, data->base + REG_MMU_DCM_DIS);
>>> + if (MTK_IOMMU_HAS_FLAG(data->plat_data, WR_THROT_EN)) {
>>> + /* write command throttling mode */
>>> + regval = readl_relaxed(data->base + REG_MMU_WR_LEN);
>>> + regval &= ~F_MMU_WR_THROT_DIS_BIT;
>>> + writel_relaxed(regval, data->base + REG_MMU_WR_LEN);
>>> + }
>>>
>>> regval = readl_relaxed(data->base + REG_MMU_MISC_CTRL);
>>> if (MTK_IOMMU_HAS_FLAG(data->plat_data, RESET_AXI)) {
>>> @@ -737,6 +745,7 @@ static int __maybe_unused mtk_iommu_suspend(struct device *dev)
>>> struct mtk_iommu_suspend_reg *reg = &data->reg;
>>> void __iomem *base = data->base;
>>>
>>> + reg->wr_len = readl_relaxed(base + REG_MMU_WR_LEN);
>>> reg->misc_ctrl = readl_relaxed(base + REG_MMU_MISC_CTRL);
>>> reg->dcm_dis = readl_relaxed(base + REG_MMU_DCM_DIS);
>>> reg->ctrl_reg = readl_relaxed(base + REG_MMU_CTRL_REG);
>>> @@ -761,6 +770,7 @@ static int __maybe_unused mtk_iommu_resume(struct device *dev)
>>> dev_err(data->dev, "Failed to enable clk(%d) in resume\n", ret);
>>> return ret;
>>> }
>>> + writel_relaxed(reg->wr_len, base + REG_MMU_WR_LEN);
>>> writel_relaxed(reg->misc_ctrl, base + REG_MMU_MISC_CTRL);
>>> writel_relaxed(reg->dcm_dis, base + REG_MMU_DCM_DIS);
>>> writel_relaxed(reg->ctrl_reg, base + REG_MMU_CTRL_REG);
>>> diff --git a/drivers/iommu/mtk_iommu.h b/drivers/iommu/mtk_iommu.h
>>> index be6d32ee5bda..ce4f4e8f03aa 100644
>>> --- a/drivers/iommu/mtk_iommu.h
>>> +++ b/drivers/iommu/mtk_iommu.h
>>> @@ -24,6 +24,7 @@
>>> #define RESET_AXI BIT(3)
>>> #define OUT_ORDER_EN BIT(4)
>>> #define HAS_SUB_COMM BIT(5)
>>> +#define WR_THROT_EN BIT(6)
>>>
>>> #define MTK_IOMMU_HAS_FLAG(pdata, _x) \
>>> ((((pdata)->flags) & (_x)) == (_x))
>>> @@ -36,6 +37,7 @@ struct mtk_iommu_suspend_reg {
>>> u32 int_main_control;
>>> u32 ivrp_paddr;
>>> u32 vld_pa_rng;
>>> + u32 wr_len;
>>> };
>>>
>>> enum mtk_iommu_plat {
>>>
>

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