linux-kernel - Re: [PATCH] mmc: sdhci-of-arasan: Ensure CD logic stabilization before power-up

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Message-ID: <cf04326b-4de4-4637-aa3b-fa1c358b9ae4@intel.com>
Date: Thu, 24 Jul 2025 19:20:07 +0300
From: Adrian Hunter <adrian.hunter@...el.com>
To: Sai Krishna Potthuri <sai.krishna.potthuri@....com>, Michal Simek
	<michal.simek@....com>, Ulf Hansson <ulf.hansson@...aro.org>
CC: <linux-mmc@...r.kernel.org>, <linux-arm-kernel@...ts.infradead.org>,
	<linux-kernel@...r.kernel.org>, <git@....com>, <saikrishna12468@...il.com>
Subject: Re: [PATCH] mmc: sdhci-of-arasan: Ensure CD logic stabilization
 before power-up

On 21/07/2025 12:53, Sai Krishna Potthuri wrote:
> During SD suspend/resume without a full card rescan (when using
> non-removable SD cards for rootfs), the SD card initialization may fail
> after resume. This occurs because, after a host controller reset, the
> card detect logic may take time to stabilize due to debounce logic.
> Without waiting for stabilization, the host may attempt powering up the
> card prematurely, leading to command timeouts during resume flow.
> Add sdhci_arasan_set_power_and_bus_voltage() to wait for the card detect
> stable bit before power up the card. Since the stabilization time
> is not fixed, a maximum timeout of one second is used to ensure
> sufficient wait time for the card detect signal to stabilize.
> 
> Signed-off-by: Sai Krishna Potthuri <sai.krishna.potthuri@....com>
> ---
>  drivers/mmc/host/sdhci-of-arasan.c | 24 ++++++++++++++++++++++--
>  1 file changed, 22 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/mmc/host/sdhci-of-arasan.c b/drivers/mmc/host/sdhci-of-arasan.c
> index 42878474e56e..3ce55009ba4a 100644
> --- a/drivers/mmc/host/sdhci-of-arasan.c
> +++ b/drivers/mmc/host/sdhci-of-arasan.c
> @@ -99,6 +99,9 @@
>  #define HIWORD_UPDATE(val, mask, shift) \
>  		((val) << (shift) | (mask) << ((shift) + 16))
>  
> +#define CD_STABLE_TIMEOUT_US		1000000
> +#define CD_STABLE_MAX_SLEEP_US		10
> +
>  /**
>   * struct sdhci_arasan_soc_ctl_field - Field used in sdhci_arasan_soc_ctl_map
>   *
> @@ -514,6 +517,23 @@ static int sdhci_arasan_voltage_switch(struct mmc_host *mmc,
>  	return -EINVAL;
>  }
>  
> +static void sdhci_arasan_set_power_and_bus_voltage(struct sdhci_host *host, unsigned char mode,
> +						   unsigned short vdd)
> +{
> +	u32 reg;
> +
> +	/*
> +	 * Ensure that the card detect logic has stabilized before powering up, this is
> +	 * necessary after a host controller reset.
> +	 */
> +	if (mode == MMC_POWER_UP) {
> +		readl_poll_timeout(host->ioaddr + SDHCI_PRESENT_STATE, reg, reg & SDHCI_CD_STABLE,
> +				   CD_STABLE_MAX_SLEEP_US, CD_STABLE_TIMEOUT_US);
> +	}

Doesn't need {}

Will this work with all Arasan variants?

> +
> +	sdhci_set_power_and_bus_voltage(host, mode, vdd);
> +}
> +
>  static const struct sdhci_ops sdhci_arasan_ops = {
>  	.set_clock = sdhci_arasan_set_clock,
>  	.get_max_clock = sdhci_pltfm_clk_get_max_clock,
> @@ -521,7 +541,7 @@ static const struct sdhci_ops sdhci_arasan_ops = {
>  	.set_bus_width = sdhci_set_bus_width,
>  	.reset = sdhci_arasan_reset,
>  	.set_uhs_signaling = sdhci_set_uhs_signaling,
> -	.set_power = sdhci_set_power_and_bus_voltage,
> +	.set_power = sdhci_arasan_set_power_and_bus_voltage,
>  	.hw_reset = sdhci_arasan_hw_reset,
>  };
>  
> @@ -570,7 +590,7 @@ static const struct sdhci_ops sdhci_arasan_cqe_ops = {
>  	.set_bus_width = sdhci_set_bus_width,
>  	.reset = sdhci_arasan_reset,
>  	.set_uhs_signaling = sdhci_set_uhs_signaling,
> -	.set_power = sdhci_set_power_and_bus_voltage,
> +	.set_power = sdhci_arasan_set_power_and_bus_voltage,
>  	.irq = sdhci_arasan_cqhci_irq,
>  };
>