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Message-ID: <aSSQ0wPU5I3Fss9s@lizhi-Precision-Tower-5810>
Date: Mon, 24 Nov 2025 12:07:31 -0500
From: Frank Li <Frank.li@....com>
To: Carlos Song <carlos.song@....com>
Cc: aisheng.dong@....com, andi.shyti@...nel.org, shawnguo@...nel.org,
s.hauer@...gutronix.de, kernel@...gutronix.de, festevam@...il.com,
linux-i2c@...r.kernel.org, imx@...ts.linux.dev,
linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] i2c: imx-lpi2c: Add runtime PM support for IRQ and clock
management on i.MX8QXP/8QM
On Mon, Nov 24, 2025 at 02:17:43PM +0800, Carlos Song wrote:
> On i.MX8QXP/8QM SoCs, both the lvds/mipi and lvds/mipi-lpi2c power domains
> must enter low-power mode during runtime suspend to achieve deep power
> savings.
>
> LPI2C resides in the lvds-lpi2c/mipi-lpi2c power domain, while its IRQ is
> routed through an irqsteer located in the lvds/mipi power domain. The LPI2C
> clock source comes from an LPCG within the lvds-lpi2c domain.
>
> For example, the hierarchy for lvds0 and lvds0-lpi2c0 domains is:
> ┌───────────────────────┐
> │ pm-domain : lvds0 │
> │ │
> │ ┌──────────────┐ │
> │ │ irqsteer │ │
> │ └───────▲──────┘ │
> │ │irq │
> │ │ │
> └────────────┼──────────┘
> ┌────────────┼──────────┐
> │ ┌───┼───┐ │
> │ │lpi2c0 │ │
> │ └───┬───┘clk │
> │ ┌────────┼───────┐ │
> │ │ LPCG │ │
> │ └────────────────┘ │
> │pm-domain:lvds0-lpi2c0 │
> └───────────────────────┘
>
> To allow these domains to power down in system runtime suspend:
>
> - All irqsteer clients must release IRQs.
> - All LPCG clients must disable and unprepare clocks.
>
> Thus, LPI2C must:
>
> - Free its IRQ during runtime suspend and re-request it on resume.
> - Disable and unprepare all clocks during runtime suspend and prepare
> and rne ble them on resume.
>
> This enables the lvds/mipi domains to enter deep low-power mode,
> significantly reducing power consumption compared to active mode.
>
> Signed-off-by: Carlos Song <carlos.song@....com>
> ---
...
>
> diff --git a/drivers/i2c/busses/i2c-imx-lpi2c.c b/drivers/i2c/busses/i2c-imx-lpi2c.c
> index 39088567db59..87e34746fad3 100644
> --- a/drivers/i2c/busses/i2c-imx-lpi2c.c
> +++ b/drivers/i2c/busses/i2c-imx-lpi2c.c
> @@ -132,6 +132,7 @@
> #define CHUNK_DATA 256
>
> #define I2C_PM_TIMEOUT 10 /* ms */
> +#define I2C_PM_LONG_TIMEOUT 1000 /* Avoid dead lock caused by big clock prepare lock */
Add unit, I2C_PM_LONG_TIMEOUT_MS,
You'd better add more detail about why need longer PM TIMEOUT in comments.
> #define I2C_DMA_THRESHOLD 8 /* bytes */
>
> enum lpi2c_imx_mode {
> @@ -149,6 +150,11 @@ enum lpi2c_imx_pincfg {
> FOUR_PIN_PP,
> };
>
> +struct imx_lpi2c_hwdata {
> + bool need_request_free_irq; /* Needed by irqsteer */
> + bool need_prepare_unprepare_clk; /* Needed by LPCG */
> +};
> +
> struct lpi2c_imx_dma {
> bool using_pio_mode;
> u8 rx_cmd_buf_len;
> @@ -187,6 +193,21 @@ struct lpi2c_imx_struct {
> bool can_use_dma;
> struct lpi2c_imx_dma *dma;
> struct i2c_client *target;
> + int irqsteer_irq;
irq should be enough
> + const struct imx_lpi2c_hwdata *hwdata;
> +};
> +
> +static const struct imx_lpi2c_hwdata imx7ulp_lpi2c_hwdata = {
> +};
> +
> +static const struct imx_lpi2c_hwdata imx8qxp_lpi2c_hwdata = {
> + .need_request_free_irq = true,
> + .need_prepare_unprepare_clk = true,
> +};
> +
> +static const struct imx_lpi2c_hwdata imx8qm_lpi2c_hwdata = {
> + .need_request_free_irq = true,
> + .need_prepare_unprepare_clk = true,
> };
>
> #define lpi2c_imx_read_msr_poll_timeout(atomic, val, cond) \
> @@ -1423,7 +1444,9 @@ static const struct i2c_algorithm lpi2c_imx_algo = {
> };
>
> static const struct of_device_id lpi2c_imx_of_match[] = {
> - { .compatible = "fsl,imx7ulp-lpi2c" },
> + { .compatible = "fsl,imx7ulp-lpi2c", .data = &imx7ulp_lpi2c_hwdata,},
> + { .compatible = "fsl,imx8qxp-lpi2c", .data = &imx8qxp_lpi2c_hwdata,},
> + { .compatible = "fsl,imx8qm-lpi2c", .data = &imx8qm_lpi2c_hwdata,},
> { }
> };
> MODULE_DEVICE_TABLE(of, lpi2c_imx_of_match);
> @@ -1440,6 +1463,10 @@ static int lpi2c_imx_probe(struct platform_device *pdev)
> if (!lpi2c_imx)
> return -ENOMEM;
>
> + lpi2c_imx->hwdata = of_device_get_match_data(&pdev->dev);
> + if (!lpi2c_imx->hwdata)
> + return -ENODEV;
> +
> lpi2c_imx->base = devm_platform_get_and_ioremap_resource(pdev, 0, &res);
> if (IS_ERR(lpi2c_imx->base))
> return PTR_ERR(lpi2c_imx->base);
> @@ -1448,6 +1475,9 @@ static int lpi2c_imx_probe(struct platform_device *pdev)
> if (irq < 0)
> return irq;
>
> + if (lpi2c_imx->hwdata->need_request_free_irq)
> + lpi2c_imx->irqsteer_irq = irq;
> +
Needn't check this flags here, just uncondtional save irq number/
lpi2c_imx->irq = irq;
> lpi2c_imx->adapter.owner = THIS_MODULE;
> lpi2c_imx->adapter.algo = &lpi2c_imx_algo;
> lpi2c_imx->adapter.dev.parent = &pdev->dev;
> @@ -1492,7 +1522,11 @@ static int lpi2c_imx_probe(struct platform_device *pdev)
> return dev_err_probe(&pdev->dev, -EINVAL,
> "can't get I2C peripheral clock rate\n");
>
> - pm_runtime_set_autosuspend_delay(&pdev->dev, I2C_PM_TIMEOUT);
> + if (lpi2c_imx->hwdata->need_prepare_unprepare_clk)
> + pm_runtime_set_autosuspend_delay(&pdev->dev, I2C_PM_LONG_TIMEOUT);
> + else
> + pm_runtime_set_autosuspend_delay(&pdev->dev, I2C_PM_TIMEOUT);
> +
> pm_runtime_use_autosuspend(&pdev->dev);
> pm_runtime_get_noresume(&pdev->dev);
> pm_runtime_set_active(&pdev->dev);
> @@ -1544,31 +1578,78 @@ static void lpi2c_imx_remove(struct platform_device *pdev)
> pm_runtime_dont_use_autosuspend(&pdev->dev);
> }
>
> -static int __maybe_unused lpi2c_runtime_suspend(struct device *dev)
> +static int __maybe_unused _lpi2c_runtime_suspend(struct lpi2c_imx_struct *lpi2c_imx,
> + bool need_request_free_irq,
> + bool need_prepare_unprepare_clk)
> {
> - struct lpi2c_imx_struct *lpi2c_imx = dev_get_drvdata(dev);
> + if (need_request_free_irq)
> + devm_free_irq(lpi2c_imx->adapter.dev.parent, lpi2c_imx->irqsteer_irq, lpi2c_imx);
>
> - clk_bulk_disable(lpi2c_imx->num_clks, lpi2c_imx->clks);
> - pinctrl_pm_select_sleep_state(dev);
> + if (need_prepare_unprepare_clk)
> + clk_bulk_disable_unprepare(lpi2c_imx->num_clks, lpi2c_imx->clks);
> + else
> + clk_bulk_disable(lpi2c_imx->num_clks, lpi2c_imx->clks);
> + pinctrl_pm_select_sleep_state(lpi2c_imx->adapter.dev.parent);
>
> return 0;
> }
>
> -static int __maybe_unused lpi2c_runtime_resume(struct device *dev)
> +static int __maybe_unused _lpi2c_runtime_resume(struct lpi2c_imx_struct *lpi2c_imx,
> + bool need_request_free_irq,
> + bool need_prepare_unprepare_clk)
> {
look like both helper() have not big beneafit. you can direct put code
in original lpi2c_runtime_suspend() and lpi2c_runtime_resume().
Frank
> - struct lpi2c_imx_struct *lpi2c_imx = dev_get_drvdata(dev);
> int ret;
>
> - pinctrl_pm_select_default_state(dev);
> - ret = clk_bulk_enable(lpi2c_imx->num_clks, lpi2c_imx->clks);
> - if (ret) {
> - dev_err(dev, "failed to enable I2C clock, ret=%d\n", ret);
> - return ret;
> + pinctrl_pm_select_default_state(lpi2c_imx->adapter.dev.parent);
> + if (need_prepare_unprepare_clk) {
> + ret = clk_bulk_prepare_enable(lpi2c_imx->num_clks, lpi2c_imx->clks);
> + if (ret) {
> + dev_err(lpi2c_imx->adapter.dev.parent, "failed to enable clock %d\n", ret);
> + return ret;
> + }
> + } else {
> + ret = clk_bulk_enable(lpi2c_imx->num_clks, lpi2c_imx->clks);
> + if (ret) {
> + dev_err(lpi2c_imx->adapter.dev.parent, "failed to enable clock %d\n", ret);
> + return ret;
> + }
> + }
> +
> + if (need_request_free_irq) {
> + ret = devm_request_irq(lpi2c_imx->adapter.dev.parent, lpi2c_imx->irqsteer_irq,
> + lpi2c_imx_isr, IRQF_NO_SUSPEND,
> + dev_name(lpi2c_imx->adapter.dev.parent),
> + lpi2c_imx);
> + if (ret) {
> + dev_err(lpi2c_imx->adapter.dev.parent, "can't claim irq %d\n",
> + lpi2c_imx->irqsteer_irq);
> + return ret;
> + }
> }
>
> return 0;
> }
>
> +static int __maybe_unused lpi2c_runtime_resume(struct device *dev)
> +{
> + struct lpi2c_imx_struct *lpi2c_imx = dev_get_drvdata(dev);
> + bool need_request_free_irq = lpi2c_imx->hwdata->need_request_free_irq;
> + bool need_prepare_unprepare_clk = lpi2c_imx->hwdata->need_prepare_unprepare_clk;
> +
> + return _lpi2c_runtime_resume(lpi2c_imx, need_request_free_irq,
> + need_prepare_unprepare_clk);
> +}
> +
> +static int __maybe_unused lpi2c_runtime_suspend(struct device *dev)
> +{
> + struct lpi2c_imx_struct *lpi2c_imx = dev_get_drvdata(dev);
> + bool need_request_free_irq = lpi2c_imx->hwdata->need_request_free_irq;
> + bool need_prepare_unprepare_clk = lpi2c_imx->hwdata->need_prepare_unprepare_clk;
> +
> + return _lpi2c_runtime_suspend(lpi2c_imx, need_request_free_irq,
> + need_prepare_unprepare_clk);
> +}
> +
> static int __maybe_unused lpi2c_suspend_noirq(struct device *dev)
> {
> return pm_runtime_force_suspend(dev);
> --
> 2.34.1
>
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