linux-kernel - Re: [PATCH v2 5/6] memory: mtk-smi: Add sleep ctrl function

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Date:   Wed, 12 Jan 2022 11:27:59 +0100
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...onical.com>
To:     Yong Wu <yong.wu@...iatek.com>, Rob Herring <robh+dt@...nel.org>,
        Matthias Brugger <matthias.bgg@...il.com>
Cc:     Krzysztof Kozlowski <krzk@...nel.org>,
        Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
        Robin Murphy <robin.murphy@....com>,
        Tomasz Figa <tfiga@...omium.org>,
        linux-mediatek@...ts.infradead.org, srv_heupstream@...iatek.com,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        iommu@...ts.linux-foundation.org, youlin.pei@...iatek.com,
        anan.sun@...iatek.com, lc.kan@...iatek.com, yi.kuo@...iatek.com,
        anthony.huang@...iatek.com,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>
Subject: Re: [PATCH v2 5/6] memory: mtk-smi: Add sleep ctrl function

On 11/01/2022 07:39, Yong Wu wrote:
> Sleep control means that when the larb goes to sleep, we should wait a bit
> until all the current commands are finished. Thus, when the larb runtime
> suspends, we need to enable this function to wait until all the existed
> commands are finished. When the larb resumes, just disable this function.
> This function only improves the safety of bus. Add a new flag for this
> function. Prepare for mt8186.
> 
> Signed-off-by: Anan Sun <anan.sun@...iatek.com>
> Signed-off-by: Yong Wu <yong.wu@...iatek.com>
> ---
>  drivers/memory/mtk-smi.c | 35 ++++++++++++++++++++++++++++++++++-
>  1 file changed, 34 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/memory/mtk-smi.c b/drivers/memory/mtk-smi.c
> index e7b1a22b12ea..d8552f4caba4 100644
> --- a/drivers/memory/mtk-smi.c
> +++ b/drivers/memory/mtk-smi.c
> @@ -8,6 +8,7 @@
>  #include <linux/device.h>
>  #include <linux/err.h>
>  #include <linux/io.h>
> +#include <linux/iopoll.h>
>  #include <linux/module.h>
>  #include <linux/of.h>
>  #include <linux/of_platform.h>
> @@ -32,6 +33,10 @@
>  #define SMI_DUMMY			0x444
>  
>  /* SMI LARB */
> +#define SMI_LARB_SLP_CON                0xc
> +#define SLP_PROT_EN                     BIT(0)
> +#define SLP_PROT_RDY                    BIT(16)
> +
>  #define SMI_LARB_CMD_THRT_CON		0x24
>  #define SMI_LARB_THRT_RD_NU_LMT_MSK	GENMASK(7, 4)
>  #define SMI_LARB_THRT_RD_NU_LMT		(5 << 4)
> @@ -81,6 +86,7 @@
>  
>  #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_CAPS(flags, _x)		(!!((flags) & (_x)))
>  
>  struct mtk_smi_reg_pair {
> @@ -371,6 +377,26 @@ static const struct of_device_id mtk_smi_larb_of_ids[] = {
>  	{}
>  };
>  
> +static int mtk_smi_larb_sleep_ctrl_enable(struct mtk_smi_larb *larb)
> +{
> +	int ret;
> +	u32 tmp;
> +
> +	writel_relaxed(SLP_PROT_EN, larb->base + SMI_LARB_SLP_CON);
> +	ret = readl_poll_timeout_atomic(larb->base + SMI_LARB_SLP_CON,
> +					tmp, !!(tmp & SLP_PROT_RDY), 10, 1000);
> +	if (ret) {
> +		/* TODO: Reset this larb if it fails here. */
> +		dev_warn(larb->smi.dev, "sleep ctrl is not ready(0x%x).\n", tmp);
> +	}
> +	return ret;
> +}
> +
> +static void mtk_smi_larb_sleep_ctrl_disable(struct mtk_smi_larb *larb)
> +{
> +	writel_relaxed(0, larb->base + SMI_LARB_SLP_CON);
> +}
> +
>  static int mtk_smi_device_link_common(struct device *dev, struct device **com_dev)
>  {
>  	struct platform_device *smi_com_pdev;
> @@ -483,6 +509,9 @@ static int __maybe_unused mtk_smi_larb_resume(struct device *dev)
>  	if (ret)
>  		return ret;
>  
> +	if (MTK_SMI_CAPS(larb->larb_gen->flags_general, MTK_SMI_FLAG_SLEEP_CTL))
> +		mtk_smi_larb_sleep_ctrl_disable(larb);
> +
>  	/* Configure the basic setting for this larb */
>  	larb_gen->config_port(dev);
>  
> @@ -492,9 +521,13 @@ static int __maybe_unused mtk_smi_larb_resume(struct device *dev)
>  static int __maybe_unused mtk_smi_larb_suspend(struct device *dev)
>  {
>  	struct mtk_smi_larb *larb = dev_get_drvdata(dev);
> +	int ret = 0;
> +
> +	if (MTK_SMI_CAPS(larb->larb_gen->flags_general, MTK_SMI_FLAG_SLEEP_CTL))
> +		ret = mtk_smi_larb_sleep_ctrl_enable(larb);
>  
>  	clk_bulk_disable_unprepare(larb->smi.clk_num, larb->smi.clks);
> -	return 0;
> +	return ret;

I am wondering whether disabling clocks in error case is a proper step.
On suspend error, the PM core won't run any further callbacks on this
device. This means, it won't be resumed and your clocks stay disabled. I
think you should return early and leave the device in active state in
case of error.


Best regards,
Krzysztof