Re: [PATCH] mmc: arasan: add runtime power management support
From: Ulf Hansson
Date: Tue Nov 23 2021 - 15:10:01 EST
On Sat, 20 Nov 2021 at 12:23, Kyle Copperfield <kmcopper@xxxxxxxxxxxxx> wrote:
>
> Add runtime power management support in Arasan SDHCI driver.
>
> This patch is largely based on the original Arasan PM patch from
> https://lore.kernel.org/linux-mmc/1537283046-13985-1-git-send-email-manish.narani@xxxxxxxxxx/
> that was left abandoned since 2018 for an unknown reason.
>
> Changes made to the original patch include reducing the runtime
> suspend timeout to 50 ms and reusing the runtime PM configuration
> found in sdhci-of-at91 driver.
>
> Power consumption is measurably reduced on the Pinebook Pro and
> PinePhone Pro, on which the patch was tested. More precisely,
> a reduction of about 200 mW was measured on the latter.
>
> Originally-by: Manish Narani <manish.narani@xxxxxxxxxx>
> Reviewed-by: Dragan Simic <dragan.simic@xxxxxxxxx>
> Tested-by: Ondrej Jirman <megous@xxxxxxxxxx>
> Signed-off-by: Kyle Copperfield <kmcopper@xxxxxxxxxxxxx>
> ---
> drivers/mmc/host/sdhci-of-arasan.c | 88 +++++++++++++++++++++++++++++-
> 1 file changed, 86 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/mmc/host/sdhci-of-arasan.c b/drivers/mmc/host/sdhci-of-arasan.c
> index 737e2bfdedc2..63095d91a672 100644
> --- a/drivers/mmc/host/sdhci-of-arasan.c
> +++ b/drivers/mmc/host/sdhci-of-arasan.c
> @@ -19,6 +19,7 @@
> #include <linux/mfd/syscon.h>
> #include <linux/module.h>
> #include <linux/of_device.h>
> +#include <linux/pm_runtime.h>
> #include <linux/phy/phy.h>
> #include <linux/regmap.h>
> #include <linux/of.h>
> @@ -27,6 +28,7 @@
> #include "cqhci.h"
> #include "sdhci-pltfm.h"
>
> +#define SDHCI_ARASAN_AUTOSUSPEND_DELAY 50 /* ms */
> #define SDHCI_ARASAN_VENDOR_REGISTER 0x78
>
> #define SDHCI_ARASAN_ITAPDLY_REGISTER 0xF0F8
> @@ -456,6 +458,70 @@ static const struct sdhci_pltfm_data sdhci_arasan_cqe_pdata = {
> SDHCI_QUIRK2_CLOCK_DIV_ZERO_BROKEN,
> };
>
> +static int __maybe_unused sdhci_arasan_runtime_suspend(struct device *dev)
> +{
> + struct platform_device *pdev = to_platform_device(dev);
> + struct sdhci_host *host = platform_get_drvdata(pdev);
> + struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
> + struct sdhci_arasan_data *sdhci_arasan = sdhci_pltfm_priv(pltfm_host);
> + int ret;
> +
> + if (sdhci_arasan->has_cqe) {
> + ret = cqhci_suspend(host->mmc);
> + if (ret)
> + return ret;
> + }
> +
> + ret = sdhci_runtime_suspend_host(host);
> + if (ret)
> + return ret;
> +
> + if (host->tuning_mode != SDHCI_TUNING_MODE_3)
> + mmc_retune_needed(host->mmc);
> +
> + clk_disable(pltfm_host->clk);
> + clk_disable(sdhci_arasan->clk_ahb);
These should be clk_disable_unprepare() - and the corresponding
clk_enable() below, needs to be converted to clk_prepare_enable().
Moreover, I am wondering about why the phy is to be turned off with
phy_power_off() during system suspend, but not during runtime suspend?
When is it safe to turn off the phy?
> +
> + return 0;
> +}
> +
> +static int __maybe_unused sdhci_arasan_runtime_resume(struct device *dev)
> +{
> + struct platform_device *pdev = to_platform_device(dev);
> + struct sdhci_host *host = platform_get_drvdata(pdev);
> + struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
> + struct sdhci_arasan_data *sdhci_arasan = sdhci_pltfm_priv(pltfm_host);
> + int ret;
> +
> + ret = clk_enable(sdhci_arasan->clk_ahb);
> + if (ret) {
> + dev_err(dev, "Cannot enable AHB clock: %d\n", ret);
> + return ret;
> + }
> +
> + ret = clk_enable(pltfm_host->clk);
> + if (ret) {
> + dev_err(dev, "Cannot enable SD clock: %d\n", ret);
> + goto err_clk_ahb;
> + }
> +
> + ret = sdhci_runtime_resume_host(host, 0);
> + if (ret)
> + goto err_clk_disable;
> +
> + if (sdhci_arasan->has_cqe)
> + return cqhci_resume(host->mmc);
> +
> + return 0;
> +
> +err_clk_disable:
> + clk_disable(pltfm_host->clk);
> +err_clk_ahb:
> + clk_disable(sdhci_arasan->clk_ahb);
> +
> + return ret;
> +}
> +
> #ifdef CONFIG_PM_SLEEP
> /**
> * sdhci_arasan_suspend - Suspend method for the driver
> @@ -552,8 +618,10 @@ static int sdhci_arasan_resume(struct device *dev)
> }
> #endif /* ! CONFIG_PM_SLEEP */
>
> -static SIMPLE_DEV_PM_OPS(sdhci_arasan_dev_pm_ops, sdhci_arasan_suspend,
> - sdhci_arasan_resume);
> +static const struct dev_pm_ops sdhci_arasan_dev_pm_ops = {
> + SET_SYSTEM_SLEEP_PM_OPS(sdhci_arasan_suspend, sdhci_arasan_resume)
In sdhci_arasan_suspend() we assume that the clocks, etc are turned
on. This may not be the case anymore, as
sdhci_arasan_runtime_suspend() may already have done that.
There are a couple of options to deal with that, like using
pm_runtime_force_suspend|resume(). But then don't forget that you may
need to manage system wakeups, if that is supported.
> + SET_RUNTIME_PM_OPS(sdhci_arasan_runtime_suspend,
> + sdhci_arasan_runtime_resume, NULL) };
>
> /**
> * sdhci_arasan_sdcardclk_recalc_rate - Return the card clock rate
> @@ -1681,13 +1749,25 @@ static int sdhci_arasan_probe(struct platform_device *pdev)
> host->mmc->caps2 |= MMC_CAP2_CQE_DCMD;
> }
>
> + pm_runtime_get_noresume(&pdev->dev);
> + pm_runtime_set_active(&pdev->dev);
> + pm_runtime_enable(&pdev->dev);
> + pm_runtime_set_autosuspend_delay(&pdev->dev, SDHCI_ARASAN_AUTOSUSPEND_DELAY);
> + pm_runtime_use_autosuspend(&pdev->dev);
> +
> ret = sdhci_arasan_add_host(sdhci_arasan);
> if (ret)
> goto err_add_host;
>
> + pm_runtime_put_autosuspend(&pdev->dev);
> +
> return 0;
>
> err_add_host:
> + pm_runtime_disable(&pdev->dev);
> + pm_runtime_set_suspended(&pdev->dev);
> + pm_runtime_put_noidle(&pdev->dev);
> +
> if (!IS_ERR(sdhci_arasan->phy))
> phy_exit(sdhci_arasan->phy);
> unreg_clk:
> @@ -1715,6 +1795,10 @@ static int sdhci_arasan_remove(struct platform_device *pdev)
> phy_exit(sdhci_arasan->phy);
> }
>
> + pm_runtime_get_sync(&pdev->dev);
> + pm_runtime_disable(&pdev->dev);
> + pm_runtime_put_noidle(&pdev->dev);
> +
> sdhci_arasan_unregister_sdclk(&pdev->dev);
>
> ret = sdhci_pltfm_unregister(pdev);
Kind regards
Uffe