linux-kernel - Re: [PATCH] mmc: dw_mmc: rockchip: Keep controller working for card detect

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Message-ID: <4920950.GXAFRqVoOG@diego>
Date: Sat, 14 Sep 2024 13:52:32 +0200
From: Heiko Stübner <heiko@...ech.de>
To: Kever Yang <kever.yang@...k-chips.com>
Cc: linux-rockchip@...ts.infradead.org,
 Kever Yang <kever.yang@...k-chips.com>,
 Jaehoon Chung <jh80.chung@...sung.com>, Ulf Hansson <ulf.hansson@...aro.org>,
 linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
 linux-mmc@...r.kernel.org
Subject:
 Re: [PATCH] mmc: dw_mmc: rockchip: Keep controller working for card detect

Am Donnerstag, 12. September 2024, 09:26:14 CEST schrieb Kever Yang:
> In order to make the SD card hotplug working we need the card detect
> function logic inside the controller always working. The runtime PM will
> gate the clock and the power domain, which stops controller working when
> no data transfer happen.
> 
> So lets skip enable runtime PM when the card needs to detected by the
> controller and the card is removable.
> 
> Signed-off-by: Kever Yang <kever.yang@...k-chips.com>

So for the change itself this looks good, i.e. it fixes an issue for baords relying
on the on-chip-card-detect.


But for boards doing that, the controller will be running _all the time_
even if there is never any card inserted.

So relying on the on-soc card-detect will effectively increase the power-
consumption of the board - even it it'll never use any sd-card?

> ---
> 
>  drivers/mmc/host/dw_mmc-rockchip.c | 23 +++++++++++++++++------
>  1 file changed, 17 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/mmc/host/dw_mmc-rockchip.c b/drivers/mmc/host/dw_mmc-rockchip.c
> index b07190ba4b7a..df91205f9cd3 100644
> --- a/drivers/mmc/host/dw_mmc-rockchip.c
> +++ b/drivers/mmc/host/dw_mmc-rockchip.c
> @@ -345,28 +345,39 @@ static int dw_mci_rockchip_probe(struct platform_device *pdev)
>  	const struct dw_mci_drv_data *drv_data;
>  	const struct of_device_id *match;
>  	int ret;
> +	bool use_rpm = true;
>  
>  	if (!pdev->dev.of_node)
>  		return -ENODEV;
>  
> +	if (!device_property_read_bool(&pdev->dev, "non-removable") &&

It would be nice to add a comment here about the fact that this will
disable power-management for the controller.

Also shouldn't non-removable already work, making the case above not
necessary?


Thanks
Heiko

> +	     !device_property_read_bool(&pdev->dev, "cd-gpios"))
> +		use_rpm = false;
> +
>  	match = of_match_node(dw_mci_rockchip_match, pdev->dev.of_node);
>  	drv_data = match->data;
>  
>  	pm_runtime_get_noresume(&pdev->dev);
>  	pm_runtime_set_active(&pdev->dev);
> -	pm_runtime_enable(&pdev->dev);
> -	pm_runtime_set_autosuspend_delay(&pdev->dev, 50);
> -	pm_runtime_use_autosuspend(&pdev->dev);
> +
> +	if (use_rpm) {
> +		pm_runtime_enable(&pdev->dev);
> +		pm_runtime_set_autosuspend_delay(&pdev->dev, 50);
> +		pm_runtime_use_autosuspend(&pdev->dev);
> +	}
>  
>  	ret = dw_mci_pltfm_register(pdev, drv_data);
>  	if (ret) {
> -		pm_runtime_disable(&pdev->dev);
> -		pm_runtime_set_suspended(&pdev->dev);
> +		if (use_rpm) {
> +			pm_runtime_disable(&pdev->dev);
> +			pm_runtime_set_suspended(&pdev->dev);
> +		}
>  		pm_runtime_put_noidle(&pdev->dev);
>  		return ret;
>  	}
>  
> -	pm_runtime_put_autosuspend(&pdev->dev);
> +	if (use_rpm)
> +		pm_runtime_put_autosuspend(&pdev->dev);
>  
>  	return 0;
>  }
>