Subject: Re: [PATCH 02/12] mmc: sdhci-omap: Add card_busy host ops
To: Kishon Vijay Abraham I <kishon@ti.com>,
        Ulf Hansson <ulf.hansson@linaro.org>, Rob Herring <robh+dt@kernel.org>,
        Tony Lindgren <tony@atomide.com>
Cc: Mark Rutland <mark.rutland@arm.com>,
        Russell King <linux@armlinux.org.uk>, linux-mmc@vger.kernel.org,
        devicetree@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-omap@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        nsekhar@ti.com
References: <20171214130941.26666-1-kishon@ti.com>
 <20171214130941.26666-3-kishon@ti.com>
From: Adrian Hunter <adrian.hunter@intel.com>
Organization: Intel Finland Oy, Registered Address: PL 281, 00181 Helsinki,
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Message-ID: <c5c61373-aa0e-f4d1-4463-88e31474b80a@intel.com>
Date: Thu, 21 Dec 2017 10:59:56 +0200
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On 14/12/17 15:09, Kishon Vijay Abraham I wrote:
> card_busy ops is used by mmc core in
>   1) mmc_set_uhs_voltage to verify voltage switch
>   2) __mmc_start_request/mmc_poll_for_busy to check the card busy status
> 
> While only DAT0 can be used to check the card busy status (in '2' above),
> CMD and DAT[0..3] is used to verify voltage switch (in '1' above).
> 
> The voltage switching sequence for AM572x platform is mentioned
> in Figure 25-48. eMMC/SD/SDIO Power Switching Procedure of
> AM572x Sitara Processors Silicon Revision 2.0, 1.1 TRM
> (SPRUHZ6I - October 2014–Revised April 2017 [1]).
> 
> Add card_busy host ops in sdhci_omap that checks for both CMD and
> DAT[0..3]. card_busy here returns true if one of CMD and DAT[0..3] is
> low though during voltage switch sequence all of CMD and DAT[0..3] has
> to be low (however haven't observed a case where some DAT lines are low
> and some are high).

Isn't it better to check DAT0 only since that is all that is defined for 'busy'.

> 
> In the voltage switching sequence, CLKEXTFREE bit in MMCHS_CON
> should also be set after switching to 1.8v which is also taken
> care in the card_busy ops.
> 
> [1] -> http://www.ti.com/lit/ug/spruhz6i/spruhz6i.pdf
> 
> Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
> ---
>  drivers/mmc/host/sdhci-omap.c | 62 +++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 62 insertions(+)
> 
> diff --git a/drivers/mmc/host/sdhci-omap.c b/drivers/mmc/host/sdhci-omap.c
> index 96985786cadf..defe4eac020d 100644
> --- a/drivers/mmc/host/sdhci-omap.c
> +++ b/drivers/mmc/host/sdhci-omap.c
> @@ -31,11 +31,20 @@
>  #define SDHCI_OMAP_CON		0x12c
>  #define CON_DW8			BIT(5)
>  #define CON_DMA_MASTER		BIT(20)
> +#define CON_CLKEXTFREE		BIT(16)
> +#define CON_PADEN		BIT(15)
>  #define CON_INIT		BIT(1)
>  #define CON_OD			BIT(0)
>  
>  #define SDHCI_OMAP_CMD		0x20c
>  
> +#define SDHCI_OMAP_PSTATE	0x0224
> +#define PSTATE_CLEV             BIT(24)
> +#define PSTATE_DLEV_SHIFT	20
> +#define PSTATE_DLEV_DAT(x)	(1 << (PSTATE_DLEV_SHIFT + (x)))
> +#define PSTATE_DLEV		(PSTATE_DLEV_DAT(0) | PSTATE_DLEV_DAT(1) | \
> +					PSTATE_DLEV_DAT(2) | PSTATE_DLEV_DAT(3))
> +
>  #define SDHCI_OMAP_HCTL		0x228
>  #define HCTL_SDBP		BIT(8)
>  #define HCTL_SDVS_SHIFT		9
> @@ -191,6 +200,58 @@ static void sdhci_omap_conf_bus_power(struct sdhci_omap_host *omap_host,
>  	}
>  }
>  
> +static int sdhci_omap_card_busy(struct mmc_host *mmc)
> +{
> +	int i;
> +	u32 reg, ac12;
> +	int ret = true;
> +	struct sdhci_host *host = mmc_priv(mmc);
> +	struct sdhci_pltfm_host *pltfm_host;
> +	struct sdhci_omap_host *omap_host;
> +	u32 ier = host->ier;
> +
> +	pltfm_host = sdhci_priv(host);
> +	omap_host = sdhci_pltfm_priv(pltfm_host);
> +
> +	reg = sdhci_omap_readl(omap_host, SDHCI_OMAP_CON);
> +	ac12 = sdhci_omap_readl(omap_host, SDHCI_OMAP_AC12);
> +	reg &= ~CON_CLKEXTFREE;
> +	if (ac12 & AC12_V1V8_SIGEN)
> +		reg |= CON_CLKEXTFREE;
> +	reg |= CON_PADEN;
> +	sdhci_omap_writel(omap_host, SDHCI_OMAP_CON, reg);
> +
> +	disable_irq(host->irq);
> +	ier |= SDHCI_INT_CARD_INT;
> +	sdhci_writel(host, ier, SDHCI_INT_ENABLE);
> +	sdhci_writel(host, ier, SDHCI_SIGNAL_ENABLE);
> +
> +	for (i = 0; i < 5; i++) {
> +		/*
> +		 * Delay is required for PSTATE to correctly reflect
> +		 * DLEV/CLEV values after PADEM is set.
> +		 */
> +		usleep_range(100, 200);
> +		reg = sdhci_omap_readl(omap_host, SDHCI_OMAP_PSTATE);
> +		if ((reg & PSTATE_CLEV) &&
> +		    ((reg & PSTATE_DLEV) == PSTATE_DLEV)) {
> +			ret = false;
> +			goto ret;

'break' is better than 'goto'

> +		}
> +	}
> +
> +ret:
> +	reg = sdhci_omap_readl(omap_host, SDHCI_OMAP_CON);
> +	reg &= ~(CON_CLKEXTFREE | CON_PADEN);
> +	sdhci_omap_writel(omap_host, SDHCI_OMAP_CON, reg);
> +
> +	sdhci_writel(host, host->ier, SDHCI_INT_ENABLE);
> +	sdhci_writel(host, host->ier, SDHCI_SIGNAL_ENABLE);
> +	enable_irq(host->irq);
> +
> +	return ret;
> +}
> +
>  static int sdhci_omap_start_signal_voltage_switch(struct mmc_host *mmc,
>  						  struct mmc_ios *ios)
>  {
> @@ -562,6 +623,7 @@ static int sdhci_omap_probe(struct platform_device *pdev)
>  	host->mmc_host_ops.start_signal_voltage_switch =
>  					sdhci_omap_start_signal_voltage_switch;
>  	host->mmc_host_ops.set_ios = sdhci_omap_set_ios;
> +	host->mmc_host_ops.card_busy = sdhci_omap_card_busy;
>  
>  	sdhci_read_caps(host);
>  	host->caps |= SDHCI_CAN_DO_ADMA2;
>