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Date:   Thu, 21 Dec 2017 11:09:00 +0200
From:   Adrian Hunter <adrian.hunter@...el.com>
To:     Kishon Vijay Abraham I <kishon@...com>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Tony Lindgren <tony@...mide.com>
Cc:     Mark Rutland <mark.rutland@....com>,
        Russell King <linux@...linux.org.uk>,
        linux-mmc@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-omap@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, nsekhar@...com
Subject: Re: [PATCH 04/12] mmc: sdhci-omap: Add tuning support

On 14/12/17 15:09, Kishon Vijay Abraham I wrote:
> MMC tuning procedure is required to support SD card
> UHS1-SDR104 mode and EMMC HS200 mode.
> 
> SDR104/HS200 DLL Tuning Procedure for AM572x platform is mentioned
> in Figure 25-51. SDR104/HS200 DLL Tuning Procedure of
> AM572x Sitara Processors Silicon Revision 2.0, 1.1 TRM
> (SPRUHZ6I - October 2014–Revised April 2017 [1]).
> 
> The tuning function sdhci_omap_execute_tuning() will only be
> called by the MMC/SD core if the corresponding speed modes
> are supported by the OMAP silicon which is set in the mmc
> host "caps" field.
> 
> [1] -> http://www.ti.com/lit/ug/spruhz6i/spruhz6i.pdf
> 
> Signed-off-by: Kishon Vijay Abraham I <kishon@...com>

Apart from 1 minor comment below:

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

> ---
>  drivers/mmc/host/sdhci-omap.c | 130 ++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 130 insertions(+)
> 
> diff --git a/drivers/mmc/host/sdhci-omap.c b/drivers/mmc/host/sdhci-omap.c
> index 8f7239e2edc2..df8a0a472996 100644
> --- a/drivers/mmc/host/sdhci-omap.c
> +++ b/drivers/mmc/host/sdhci-omap.c
> @@ -37,6 +37,13 @@
>  #define CON_INIT		BIT(1)
>  #define CON_OD			BIT(0)
>  
> +#define SDHCI_OMAP_DLL		0x0134
> +#define DLL_SWT			BIT(20)
> +#define DLL_FORCE_SR_C_SHIFT	13
> +#define DLL_FORCE_SR_C_MASK	(0x7f << DLL_FORCE_SR_C_SHIFT)
> +#define DLL_FORCE_VALUE		BIT(12)
> +#define DLL_CALIB		BIT(1)
> +
>  #define SDHCI_OMAP_CMD		0x20c
>  
>  #define SDHCI_OMAP_PSTATE	0x0224
> @@ -66,12 +73,16 @@
>  
>  #define SDHCI_OMAP_AC12		0x23c
>  #define AC12_V1V8_SIGEN		BIT(19)
> +#define AC12_SCLK_SEL		BIT(23)
>  
>  #define SDHCI_OMAP_CAPA		0x240
>  #define CAPA_VS33		BIT(24)
>  #define CAPA_VS30		BIT(25)
>  #define CAPA_VS18		BIT(26)
>  
> +#define SDHCI_OMAP_CAPA2	0x0244
> +#define CAPA2_TSDR50		BIT(13)
> +
>  #define SDHCI_OMAP_TIMEOUT	1		/* 1 msec */
>  
>  #define SYSCTL_CLKD_MAX		0x3FF
> @@ -80,6 +91,8 @@
>  #define IOV_3V0			3000000		/* 300000 uV */
>  #define IOV_3V3			3300000		/* 330000 uV */
>  
> +#define MAX_PHASE_DELAY		0x7C
> +
>  struct sdhci_omap_data {
>  	u32 offset;
>  };
> @@ -204,6 +217,120 @@ static void sdhci_omap_conf_bus_power(struct sdhci_omap_host *omap_host,
>  	}
>  }
>  
> +static inline void sdhci_omap_set_dll(struct sdhci_omap_host *omap_host,
> +				      int count)
> +{
> +	int i;
> +	u32 reg;
> +
> +	reg = sdhci_omap_readl(omap_host, SDHCI_OMAP_DLL);
> +	reg |= DLL_FORCE_VALUE;
> +	reg &= ~DLL_FORCE_SR_C_MASK;
> +	reg |= (count << DLL_FORCE_SR_C_SHIFT);
> +	sdhci_omap_writel(omap_host, SDHCI_OMAP_DLL, reg);
> +
> +	reg |= DLL_CALIB;
> +	sdhci_omap_writel(omap_host, SDHCI_OMAP_DLL, reg);
> +	for (i = 0; i < 1000; i++) {
> +		reg = sdhci_omap_readl(omap_host, SDHCI_OMAP_DLL);
> +		if (reg & DLL_CALIB)
> +			break;
> +	}
> +	reg &= ~DLL_CALIB;
> +	sdhci_omap_writel(omap_host, SDHCI_OMAP_DLL, reg);
> +}
> +
> +static void sdhci_omap_disable_tuning(struct sdhci_omap_host *omap_host)
> +{
> +	u32 reg;
> +
> +	reg = sdhci_omap_readl(omap_host, SDHCI_OMAP_AC12);
> +	reg &= ~AC12_SCLK_SEL;
> +	sdhci_omap_writel(omap_host, SDHCI_OMAP_AC12, reg);
> +
> +	reg = sdhci_omap_readl(omap_host, SDHCI_OMAP_DLL);
> +	reg &= ~(DLL_FORCE_VALUE | DLL_SWT);
> +	sdhci_omap_writel(omap_host, SDHCI_OMAP_DLL, reg);
> +}
> +
> +static int sdhci_omap_execute_tuning(struct mmc_host *mmc, u32 opcode)
> +{
> +	u32 reg;
> +	int ret = 0;
> +	u8 cur_match, prev_match = 0;
> +	u32 phase_delay = 0;
> +	u32 start_window = 0, max_window = 0;
> +	u32 length = 0, max_len = 0;
> +	struct mmc_ios *ios = &mmc->ios;
> +	struct sdhci_host *host = mmc_priv(mmc);
> +	struct sdhci_pltfm_host *pltfm_host;
> +	struct sdhci_omap_host *omap_host;
> +	struct device *dev;
> +
> +	pltfm_host = sdhci_priv(host);
> +	omap_host = sdhci_pltfm_priv(pltfm_host);
> +	dev = omap_host->dev;

These initializations can be combined with the declarations.  Also try to
arrange local variable declaration lines in descending order of length e.g.

	struct sdhci_host *host = mmc_priv(mmc);
	struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
	struct sdhci_omap_host *omap_host = sdhci_pltfm_priv(pltfm_host);
	struct device *dev = omap_host->dev;
	struct mmc_ios *ios = &mmc->ios;
	u32 start_window = 0, max_window = 0;
	u8 cur_match, prev_match = 0;
	u32 length = 0, max_len = 0;
	u32 phase_delay = 0;
	int ret = 0;
	u32 reg;

> +
> +	/* clock tuning is not needed for upto 52MHz */
> +	if (ios->clock <= 52000000)
> +		return 0;
> +
> +	reg = sdhci_omap_readl(omap_host, SDHCI_OMAP_CAPA2);
> +	if (ios->timing == MMC_TIMING_UHS_SDR50 && !(reg & CAPA2_TSDR50))
> +		return 0;
> +
> +	reg = sdhci_omap_readl(omap_host, SDHCI_OMAP_DLL);
> +	reg |= DLL_SWT;
> +	sdhci_omap_writel(omap_host, SDHCI_OMAP_DLL, reg);
> +
> +	while (phase_delay <= MAX_PHASE_DELAY) {
> +		sdhci_omap_set_dll(omap_host, phase_delay);
> +
> +		cur_match = !mmc_send_tuning(mmc, opcode, NULL);
> +		if (cur_match) {
> +			if (prev_match) {
> +				length++;
> +			} else {
> +				start_window = phase_delay;
> +				length = 1;
> +			}
> +		}
> +
> +		if (length > max_len) {
> +			max_window = start_window;
> +			max_len = length;
> +		}
> +
> +		prev_match = cur_match;
> +		phase_delay += 4;
> +	}
> +
> +	if (!max_len) {
> +		dev_err(dev, "Unable to find match\n");
> +		ret = -EIO;
> +		goto tuning_error;
> +	}
> +
> +	reg = sdhci_omap_readl(omap_host, SDHCI_OMAP_AC12);
> +	if (!(reg & AC12_SCLK_SEL)) {
> +		ret = -EIO;
> +		goto tuning_error;
> +	}
> +
> +	phase_delay = max_window + 4 * (max_len >> 1);
> +	sdhci_omap_set_dll(omap_host, phase_delay);
> +
> +	goto ret;
> +
> +tuning_error:
> +	dev_err(dev, "Tuning failed\n");
> +	sdhci_omap_disable_tuning(omap_host);
> +
> +ret:
> +	sdhci_reset(host, SDHCI_RESET_CMD | SDHCI_RESET_DATA);
> +	return ret;
> +}
> +
>  static int sdhci_omap_card_busy(struct mmc_host *mmc)
>  {
>  	int i;
> @@ -312,6 +439,8 @@ static int sdhci_omap_start_signal_voltage_switch(struct mmc_host *mmc,
>  static void sdhci_omap_set_power_mode(struct sdhci_omap_host *omap_host,
>  				      u8 power_mode)
>  {
> +	if (omap_host->bus_mode == MMC_POWER_OFF)
> +		sdhci_omap_disable_tuning(omap_host);
>  	omap_host->power_mode = power_mode;
>  }
>  
> @@ -648,6 +777,7 @@ static int sdhci_omap_probe(struct platform_device *pdev)
>  					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;
> +	host->mmc_host_ops.execute_tuning = sdhci_omap_execute_tuning;
>  
>  	sdhci_read_caps(host);
>  	host->caps |= SDHCI_CAN_DO_ADMA2;
> 

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