linux-kernel - Re: [PATCH] mmc: sdhci-xenon: fix 1.8v regulator stabilization

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Date:   Tue, 15 Dec 2020 10:03:55 +0200
From:   Adrian Hunter <adrian.hunter@...el.com>
To:     Marcin Wojtas <mw@...ihalf.com>, linux-kernel@...r.kernel.org,
        linux-mmc@...r.kernel.org
Cc:     ulf.hansson@...aro.org, huziji@...vell.com, jaz@...ihalf.com,
        tn@...ihalf.com, kostap@...vell.com,
        Alex Leibovich <alexl@...vell.com>, stable@...r.kernel.org
Subject: Re: [PATCH] mmc: sdhci-xenon: fix 1.8v regulator stabilization

On 11/12/20 4:16 pm, Marcin Wojtas wrote:
> From: Alex Leibovich <alexl@...vell.com>
> 
> Automatic Clock Gating is a feature used for the power
> consumption optimisation. It turned out that
> during early init phase it may prevent the stable voltage
> switch to 1.8V - due to that on some platfroms an endless

platfroms -> platforms

> printout in dmesg can be observed:
> "mmc1: 1.8V regulator output did not became stable"
> Fix the problem by disabling the ACG at very beginning
> of the sdhci_init and let that be enabled later.
> 
> Fixes: 3a3748dba881 ("mmc: sdhci-xenon: Add Marvell Xenon SDHC core functionality")
> Signed-off-by: Alex Leibovich <alexl@...vell.com>
> Signed-off-by: Marcin Wojtas <mw@...ihalf.com>
> Cc: stable@...r.kernel.org

Acked-by: Adrian Hunter <adrian.hunter@...el.com>

> ---
>  drivers/mmc/host/sdhci-xenon.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/mmc/host/sdhci-xenon.c b/drivers/mmc/host/sdhci-xenon.c
> index c67611fdaa8a..4b05f6fdefb4 100644
> --- a/drivers/mmc/host/sdhci-xenon.c
> +++ b/drivers/mmc/host/sdhci-xenon.c
> @@ -168,7 +168,12 @@ static void xenon_reset_exit(struct sdhci_host *host,
>  	/* Disable tuning request and auto-retuning again */
>  	xenon_retune_setup(host);
>  
> -	xenon_set_acg(host, true);
> +	/*
> +	 * The ACG should be turned off at the early init time, in order
> +	 * to solve a possile issues with the 1.8V regulator stabilization.

a possile -> possible

> +	 * The feature is enabled in later stage.
> +	 */
> +	xenon_set_acg(host, false);
>  
>  	xenon_set_sdclk_off_idle(host, sdhc_id, false);
>  
>