Subject: Re: [PATCH 2/3] mmc: sdhci-of-at91: rework clocks management to support SAM9x60 device

From: <[email-masked]>
Date: Fri, 20 Sep 2019 09:34:50 +0000

On 12.09.2019 23:09, Ludovic Desroches wrote:

> 
> In the SAM9x60 SoC, there are only two clocks instead of three for the
> SDHCI device. The base clk is no longer provided, it is generated
> internally from the mult clk.
> 
> The values of the base clk and mul in the capabilities registers may not
> reflect the reality as the mult clk is a programmable clock which can take
> several rates. As we can't trust those values, take them from the clock
> tree and update the capabilities according to.
> 
> As we can have the same pitfall, in some cases, with the SAMA5D2 Soc,
> stop relying on capabilities too.
> 
> Signed-off-by: Ludovic Desroches <[email-masked]>
> ---
>   drivers/mmc/host/sdhci-of-at91.c | 104 +++++++++++++++++--------------
>   1 file changed, 57 insertions(+), 47 deletions(-)
> 
> diff --git a/drivers/mmc/host/sdhci-of-at91.c b/drivers/mmc/host/sdhci-of-at91.c
> index e7d1920729fb..a9c126f14d85 100644
> --- a/drivers/mmc/host/sdhci-of-at91.c
> +++ b/drivers/mmc/host/sdhci-of-at91.c
> @@ -30,7 +30,14 @@
>   
>   #define SDHCI_AT91_PRESET_COMMON_CONF	0x400 /* drv type B, programmable clock mode */
>   
> +struct sdhci_at91_soc_data {
> +	const struct sdhci_pltfm_data *pdata;
> +	bool baseclk_is_generated_internally;
> +	unsigned int divider_for_baseclk;
> +};
> +
>   struct sdhci_at91_priv {
> +	const struct sdhci_at91_soc_data *soc_data;
>   	struct clk *hclock;
>   	struct clk *gck;
>   	struct clk *mainck;
> @@ -130,12 +137,24 @@ static const struct sdhci_ops sdhci_at91_sama5d2_ops = {
>   	.set_power		= sdhci_at91_set_power,
>   };
>   
> -static const struct sdhci_pltfm_data soc_data_sama5d2 = {
> +static const struct sdhci_pltfm_data sdhci_sama5d2_pdata = {
>   	.ops = &sdhci_at91_sama5d2_ops,
>   };
>   
> +static const struct sdhci_at91_soc_data soc_data_sama5d2 = {
> +	.pdata = &sdhci_sama5d2_pdata,
> +	.baseclk_is_generated_internally = false,
> +};
> +
> +static const struct sdhci_at91_soc_data soc_data_sam9x60 = {
> +	.pdata = &sdhci_sama5d2_pdata,
> +	.baseclk_is_generated_internally = true,
> +	.divider_for_baseclk = 2,
> +};
> +
>   static const struct of_device_id sdhci_at91_dt_match[] = {
>   	{ .compatible = "atmel,sama5d2-sdhci", .data = &soc_data_sama5d2 },
> +	{ .compatible = "microchip,sam9x60-sdhci", .data = &soc_data_sam9x60 },
>   	{}
>   };
>   MODULE_DEVICE_TABLE(of, sdhci_at91_dt_match);
> @@ -145,50 +164,36 @@ static int sdhci_at91_set_clks_presets(struct device *dev)
>   	struct sdhci_host *host = dev_get_drvdata(dev);
>   	struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
>   	struct sdhci_at91_priv *priv = sdhci_pltfm_priv(pltfm_host);
> -	int ret;
>   	unsigned int			caps0, caps1;
>   	unsigned int			clk_base, clk_mul;
> -	unsigned int			gck_rate, real_gck_rate;
> +	unsigned int			gck_rate, clk_base_rate;
>   	unsigned int			preset_div;
>   
> -	/*
> -	 * The mult clock is provided by as a generated clock by the PMC
> -	 * controller. In order to set the rate of gck, we have to get the
> -	 * base clock rate and the clock mult from capabilities.
> -	 */
>   	clk_prepare_enable(priv->hclock);
>   	caps0 = readl(host->ioaddr + SDHCI_CAPABILITIES);
>   	caps1 = readl(host->ioaddr + SDHCI_CAPABILITIES_1);
> -	clk_base = (caps0 & SDHCI_CLOCK_V3_BASE_MASK) >> SDHCI_CLOCK_BASE_SHIFT;
> -	clk_mul = (caps1 & SDHCI_CLOCK_MUL_MASK) >> SDHCI_CLOCK_MUL_SHIFT;
> -	gck_rate = clk_base * 1000000 * (clk_mul + 1);
> -	ret = clk_set_rate(priv->gck, gck_rate);
> -	if (ret < 0) {
> -		dev_err(dev, "failed to set gck");
> -		clk_disable_unprepare(priv->hclock);
> -		return ret;
> -	}
> -	/*
> -	 * We need to check if we have the requested rate for gck because in
> -	 * some cases this rate could be not supported. If it happens, the rate
> -	 * is the closest one gck can provide. We have to update the value
> -	 * of clk mul.
> -	 */
> -	real_gck_rate = clk_get_rate(priv->gck);
> -	if (real_gck_rate != gck_rate) {
> -		clk_mul = real_gck_rate / (clk_base * 1000000) - 1;
> -		caps1 &= (~SDHCI_CLOCK_MUL_MASK);
> -		caps1 |= ((clk_mul << SDHCI_CLOCK_MUL_SHIFT) &
> -			  SDHCI_CLOCK_MUL_MASK);
> -		/* Set capabilities in r/w mode. */
> -		writel(SDMMC_CACR_KEY | SDMMC_CACR_CAPWREN,
> -		       host->ioaddr + SDMMC_CACR);
> -		writel(caps1, host->ioaddr + SDHCI_CAPABILITIES_1);
> -		/* Set capabilities in ro mode. */
> -		writel(0, host->ioaddr + SDMMC_CACR);
> -		dev_info(dev, "update clk mul to %u as gck rate is %u Hz\n",
> -			 clk_mul, real_gck_rate);
> -	}
> +
> +	gck_rate = clk_get_rate(priv->gck);
> +	if (priv->soc_data->baseclk_is_generated_internally)
> +		clk_base_rate = gck_rate / priv->soc_data->divider_for_baseclk;
> +	else
> +		clk_base_rate = clk_get_rate(priv->mainck);
> +
> +	clk_base = clk_base_rate / 1000000;
> +	clk_mul = gck_rate / clk_base_rate - 1;
> +
> +	caps0 &= (~SDHCI_CLOCK_V3_BASE_MASK);
> +	caps0 |= ((clk_base << SDHCI_CLOCK_BASE_SHIFT) & SDHCI_CLOCK_V3_BASE_MASK);
> +	caps1 &= (~SDHCI_CLOCK_MUL_MASK);
> +	caps1 |= ((clk_mul << SDHCI_CLOCK_MUL_SHIFT) & SDHCI_CLOCK_MUL_MASK);
> +	/* Set capabilities in r/w mode. */
> +	writel(SDMMC_CACR_KEY | SDMMC_CACR_CAPWREN, host->ioaddr + SDMMC_CACR);

Hi Ludovic,

I have a feeling that here you may wish to also write the caps0 to the 
SDHC_CAPABILITIES:
writel(caps0, host->ioaddr + SDHCI_CAPABILITIES);

You are computing the caps0 but not writing them to register.

Eugen

> +	writel(caps1, host->ioaddr + SDHCI_CAPABILITIES_1);
> +	/* Set capabilities in ro mode. */
> +	writel(0, host->ioaddr + SDMMC_CACR);
> +
> +	dev_info(dev, "update clk mul to %u as gck rate is %u Hz and clk base is %u Hz\n",
> +		 clk_mul, gck_rate, clk_base_rate);
>   
>   	/*
>   	 * We have to set preset values because it depends on the clk_mul
> @@ -196,19 +201,19 @@ static int sdhci_at91_set_clks_presets(struct device *dev)
>   	 * maximum sd clock value is 120 MHz instead of 208 MHz. For that
>   	 * reason, we need to use presets to support SDR104.
>   	 */
> -	preset_div = DIV_ROUND_UP(real_gck_rate, 24000000) - 1;
> +	preset_div = DIV_ROUND_UP(gck_rate, 24000000) - 1;
>   	writew(SDHCI_AT91_PRESET_COMMON_CONF | preset_div,
>   	       host->ioaddr + SDHCI_PRESET_FOR_SDR12);
> -	preset_div = DIV_ROUND_UP(real_gck_rate, 50000000) - 1;
> +	preset_div = DIV_ROUND_UP(gck_rate, 50000000) - 1;
>   	writew(SDHCI_AT91_PRESET_COMMON_CONF | preset_div,
>   	       host->ioaddr + SDHCI_PRESET_FOR_SDR25);
> -	preset_div = DIV_ROUND_UP(real_gck_rate, 100000000) - 1;
> +	preset_div = DIV_ROUND_UP(gck_rate, 100000000) - 1;
>   	writew(SDHCI_AT91_PRESET_COMMON_CONF | preset_div,
>   	       host->ioaddr + SDHCI_PRESET_FOR_SDR50);
> -	preset_div = DIV_ROUND_UP(real_gck_rate, 120000000) - 1;
> +	preset_div = DIV_ROUND_UP(gck_rate, 120000000) - 1;
>   	writew(SDHCI_AT91_PRESET_COMMON_CONF | preset_div,
>   	       host->ioaddr + SDHCI_PRESET_FOR_SDR104);
> -	preset_div = DIV_ROUND_UP(real_gck_rate, 50000000) - 1;
> +	preset_div = DIV_ROUND_UP(gck_rate, 50000000) - 1;
>   	writew(SDHCI_AT91_PRESET_COMMON_CONF | preset_div,
>   	       host->ioaddr + SDHCI_PRESET_FOR_DDR50);
>   
> @@ -303,7 +308,7 @@ static const struct dev_pm_ops sdhci_at91_dev_pm_ops = {
>   static int sdhci_at91_probe(struct platform_device *pdev)
>   {
>   	const struct of_device_id	*match;
> -	const struct sdhci_pltfm_data	*soc_data;
> +	const struct sdhci_at91_soc_data	*soc_data;
>   	struct sdhci_host		*host;
>   	struct sdhci_pltfm_host		*pltfm_host;
>   	struct sdhci_at91_priv		*priv;
> @@ -314,17 +319,22 @@ static int sdhci_at91_probe(struct platform_device *pdev)
>   		return -EINVAL;
>   	soc_data = match->data;
>   
> -	host = sdhci_pltfm_init(pdev, soc_data, sizeof(*priv));
> +	host = sdhci_pltfm_init(pdev, soc_data->pdata, sizeof(*priv));
>   	if (IS_ERR(host))
>   		return PTR_ERR(host);
>   
>   	pltfm_host = sdhci_priv(host);
>   	priv = sdhci_pltfm_priv(pltfm_host);
> +	priv->soc_data = soc_data;
>   
>   	priv->mainck = devm_clk_get(&pdev->dev, "baseclk");
>   	if (IS_ERR(priv->mainck)) {
> -		dev_err(&pdev->dev, "failed to get baseclk\n");
> -		return PTR_ERR(priv->mainck);
> +		if (soc_data->baseclk_is_generated_internally) {
> +			priv->mainck = NULL;
> +		} else {
> +			dev_err(&pdev->dev, "failed to get baseclk\n");
> +			return PTR_ERR(priv->mainck);
> +		}
>   	}
>   
>   	priv->hclock = devm_clk_get(&pdev->dev, "hclock");
> 
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