linux-kernel - Re: [PATCH 13/40] mmc: tegra: Poll for calibration completion

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Message-ID: <20180809124616.GV21639@ulmo>
Date:   Thu, 9 Aug 2018 14:46:16 +0200
From:   Thierry Reding <thierry.reding@...il.com>
To:     Aapo Vienamo <avienamo@...dia.com>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Mikko Perttunen <mperttunen@...dia.com>,
        Stefan Agner <stefan@...er.ch>, devicetree@...r.kernel.org,
        linux-tegra@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mmc@...r.kernel.org
Subject: Re: [PATCH 13/40] mmc: tegra: Poll for calibration completion

On Wed, Aug 01, 2018 at 07:32:03PM +0300, Aapo Vienamo wrote:
> Implement polling with 10 ms timeout for automatic pad drive strength
> calibration.
> 
> Signed-off-by: Aapo Vienamo <avienamo@...dia.com>
> ---
>  drivers/mmc/host/sdhci-tegra.c | 21 ++++++++++++++++-----
>  1 file changed, 16 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/mmc/host/sdhci-tegra.c b/drivers/mmc/host/sdhci-tegra.c
> index 7d98455..c8ff267 100644
> --- a/drivers/mmc/host/sdhci-tegra.c
> +++ b/drivers/mmc/host/sdhci-tegra.c
> @@ -16,6 +16,7 @@
>  #include <linux/err.h>
>  #include <linux/module.h>
>  #include <linux/init.h>
> +#include <linux/iopoll.h>
>  #include <linux/platform_device.h>
>  #include <linux/clk.h>
>  #include <linux/io.h>
> @@ -50,6 +51,9 @@
>  #define SDHCI_AUTO_CAL_START			BIT(31)
>  #define SDHCI_AUTO_CAL_ENABLE			BIT(29)
>  
> +#define SDHCI_TEGRA_AUTO_CAL_STATUS		0x1ec
> +#define SDHCI_TEGRA_AUTO_CAL_ACTIVE		BIT(31)
> +
>  #define NVQUIRK_FORCE_SDHCI_SPEC_200	BIT(0)
>  #define NVQUIRK_ENABLE_BLOCK_GAP_DET	BIT(1)
>  #define NVQUIRK_ENABLE_SDHCI_SPEC_300	BIT(2)
> @@ -228,13 +232,20 @@ static void tegra_sdhci_reset(struct sdhci_host *host, u8 mask)
>  
>  static void tegra_sdhci_pad_autocalib(struct sdhci_host *host)
>  {
> -	u32 val;
> +	u32 reg;
> +	int ret;
> +
> +	reg = sdhci_readl(host, SDHCI_TEGRA_AUTO_CAL_CONFIG);
> +	reg |= SDHCI_AUTO_CAL_ENABLE | SDHCI_AUTO_CAL_START;
> +	sdhci_writel(host, reg, SDHCI_TEGRA_AUTO_CAL_CONFIG);
>  

I know this is preexisting, but I want to make sure we cover this so we
don't run into this down the road: do these bits automatically clear on
calibration completion? Can we run these multiple times and get
everything properly calibrated?

Thierry

> -	mdelay(1);
> +	/* 10 ms timeout */
> +	ret = readl_poll_timeout(host->ioaddr + SDHCI_TEGRA_AUTO_CAL_STATUS,
> +				 reg, !(reg & SDHCI_TEGRA_AUTO_CAL_ACTIVE),
> +				 1, 10000);
>  
> -	val = sdhci_readl(host, SDHCI_TEGRA_AUTO_CAL_CONFIG);
> -	val |= SDHCI_AUTO_CAL_ENABLE | SDHCI_AUTO_CAL_START;
> -	sdhci_writel(host,val, SDHCI_TEGRA_AUTO_CAL_CONFIG);
> +	if (ret)
> +		dev_err(mmc_dev(host->mmc), "Pad autocal timed out\n");
>  }
>  
>  static void tegra_sdhci_set_clock(struct sdhci_host *host, unsigned int clock)
> -- 
> 2.7.4
> 

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