Re: [PATCH v1 2/2] mmc: sdhci-of-dwcmshc: Add support for StarFive JHB100

[Adrian Hunter <adrian.hunter@intel.com>]

On 19/09/2026 12:29, Changhuang Liang wrote:
> Add support for the DWCMSHC controller found on the StarFive JHB100
> SoC.
> 
> The JHB100 CMSHC controller has only 32-bit DMA capability by default.
> The higher DMA address bits [35:32] can be configured through the
> PER1 SYSCON, extending the DMA address range up to 36 bits. Fix these
> bits to 4, which limits the DMA range to [0x40000000 - 0x4ffffffff].

0x40000000 missing a 0 ?

> 
> The cclk_tx clock must be disabled before sdhci_set_clock() to
> eliminate glitches, and re-enabled afterwards. It is enabled during
> probe and disabled in the platform deinit callback, which is invoked
> from dwcmshc_remove().
> 
> Additionally, clear the PHY_DLLDL_CNFG_R register and re-initialize
> the PHY when setting UHS signaling, and force 1.8V fixed I/O when the
> DT specifies a DDR/HS200/HS400 1.8V mode.
> 
> Signed-off-by: Changhuang Liang <changhuang.liang@starfivetech.com>
> ---
>  drivers/mmc/host/sdhci-of-dwcmshc.c | 158 ++++++++++++++++++++++++++++
>  1 file changed, 158 insertions(+)
> 
> diff --git a/drivers/mmc/host/sdhci-of-dwcmshc.c b/drivers/mmc/host/sdhci-of-dwcmshc.c
> index 1baa2379c9c3..021b03c17312 100644
> --- a/drivers/mmc/host/sdhci-of-dwcmshc.c
> +++ b/drivers/mmc/host/sdhci-of-dwcmshc.c
> @@ -48,6 +48,9 @@
>  #define DWCMSHC_ENHANCED_STROBE		BIT(8)
>  #define DWCMSHC_EMMC_ATCTRL		0x40
>  #define DWCMSHC_AT_STAT			0x44
> +/* StarFive JHB100 SoC MSHCCS register */
> +#define DWCMSHC_ARWADDR			GENMASK(3, 0)
> +#define DWCMSHC_ARWADDR_DEFAULT		4
>  /* Tuning and auto-tuning fields in AT_CTRL_R control register */
>  #define AT_CTRL_AT_EN			BIT(0) /* autotuning is enabled */
>  #define AT_CTRL_CI_SEL			BIT(1) /* interval to drive center phase select */
> @@ -294,6 +297,11 @@ struct k230_priv  {
>  	struct regmap *hi_sys_regmap;
>  };
> 
> +struct jhb100_priv {
> +	struct clk *cclk_tx;
> +	bool cclk_tx_on;
> +};
> +
>  #define DWCMSHC_MAX_OTHER_CLKS 3
> 
>  struct dwcmshc_priv {
> @@ -314,6 +322,7 @@ struct dwcmshc_pltfm_data {
>  	const struct sdhci_pltfm_data pdata;
>  	const struct cqhci_host_ops *cqhci_host_ops;
>  	int (*init)(struct device *dev, struct sdhci_host *host, struct dwcmshc_priv *dwc_priv);
> +	void (*deinit)(struct dwcmshc_priv *dwc_priv);
>  	void (*postinit)(struct sdhci_host *host, struct dwcmshc_priv *dwc_priv);
>  };
> 
> @@ -2257,6 +2266,145 @@ static const struct dwcmshc_pltfm_data sdhci_dwcmshc_hpe_gsc_pdata = {
>  	.init = dwcmshc_hpe_gsc_init,
>  };
> 
> +static int sdhci_jhb100_set_dma_mask(struct sdhci_host *host)
> +{
> +	struct mmc_host *mmc = host->mmc;
> +	struct device *dev = mmc_dev(mmc);
> +	int ret;
> +
> +	/*
> +	 * The StarFive JHB100's CMSHC controller only has 32-bit DMA
> +	 * capability by default, but the higher DMA address bits [35:32]
> +	 * can be configured through SYSCON, thus supporting up to 36-bit
> +	 * DMA capability.

Doesn't really explain how a 36-bit DMA mask works if the valid range
is 0x400000000 - 0x4ffffffff

Sashiko questions whether it works:

	https://sashiko.dev/#/patchset/20260919092950.178617-1-changhuang.liang%40starfivetech.com

Perhaps also check its point about leaving cclk_tx on during suspend.

> +	 */
> +	ret = dma_set_mask_and_coherent(dev, DMA_BIT_MASK(36));
> +	if (ret)
> +		dev_err(dev, "Failed to set 36-bit DMA mask.\n");
> +
> +	return ret;
> +}
> +
> +static void sdhci_jhb100_set_clock(struct sdhci_host *host, unsigned int clock)
> +{
> +	struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
> +	struct dwcmshc_priv *dwc_priv = sdhci_pltfm_priv(pltfm_host);
> +	struct jhb100_priv *priv = dwc_priv->priv;
> +
> +	/* the cclk_tx clock is disabled before sdhci_set_clock() to eliminate glitches */
> +	if (priv->cclk_tx_on) {
> +		clk_disable_unprepare(priv->cclk_tx);
> +		priv->cclk_tx_on = false;
> +	}
> +
> +	fsleep(15);

The delay could use a comment explaining why it is needed and
where the value comes from.

> +
> +	sdhci_set_clock(host, clock);
> +
> +	if (clk_prepare_enable(priv->cclk_tx))
> +		dev_err(mmc_dev(host->mmc), "failed to re-enable cclk_tx\n");
> +	else
> +		priv->cclk_tx_on = true;
> +}
> +
> +static void sdhci_jhb100_set_uhs_signaling(struct sdhci_host *host,
> +					   unsigned int timing)
> +{
> +	dwcmshc_set_uhs_signaling(host, timing);
> +	sdhci_writeb(host, 0, PHY_DLLDL_CNFG_R);
> +	th1520_sdhci_set_phy(host);
> +}
> +
> +static const struct sdhci_ops starfive_jhb100_ops = {
> +	.set_dma_mask		= sdhci_jhb100_set_dma_mask,
> +	.set_clock		= sdhci_jhb100_set_clock,
> +	.set_uhs_signaling	= sdhci_jhb100_set_uhs_signaling,
> +	.set_bus_width		= sdhci_set_bus_width,
> +	.reset			= sdhci_reset,

Everywhere else seems to reset via dwcmshc_reset().
Is sdhci_reset() ok here?

> +	.get_max_clock		= dwcmshc_get_max_clock,
> +	.adma_write_desc	= dwcmshc_adma_write_desc,
> +	.irq			= dwcmshc_cqe_irq_handler,
> +	.voltage_switch		= dwcmshc_phy_init,
> +	.platform_execute_tuning = th1520_execute_tuning,
> +};
> +
> +static int dwcmshc_starfive_jhb100_init(struct device *dev, struct sdhci_host *host,
> +					struct dwcmshc_priv *dwc_priv)
> +{
> +	struct reset_control *reset;
> +	struct jhb100_priv *priv;
> +	unsigned int reg_offset;
> +	struct regmap *syscon;
> +	int ret;
> +
> +	priv = devm_kzalloc(dev, sizeof(struct jhb100_priv), GFP_KERNEL);
> +	if (!priv)
> +		return -ENOMEM;
> +
> +	syscon = syscon_regmap_lookup_by_phandle_args(dev->of_node,
> +						      "starfive,jhb100-per1-syscon",
> +						      1, &reg_offset);
> +	if (IS_ERR(syscon))
> +		return PTR_ERR(syscon);
> +
> +	/* configure the higher DMA address bits [35:32] */
> +	ret = regmap_update_bits(syscon, reg_offset, DWCMSHC_ARWADDR,
> +				 DWCMSHC_ARWADDR_DEFAULT);
> +	if (ret)
> +		return ret;
> +
> +	reset = devm_reset_control_get_exclusive_deasserted(mmc_dev(host->mmc), NULL);
> +	if (IS_ERR(reset))
> +		return dev_err_probe(mmc_dev(host->mmc), PTR_ERR(reset),
> +				     "Failed to get&deassert reset control\n");
> +
> +	priv->cclk_tx = devm_clk_get(dev, "cclk_tx");
> +	if (IS_ERR(priv->cclk_tx))
> +		return dev_err_probe(dev, PTR_ERR(priv->cclk_tx),
> +				     "Failed to get cclk_tx clock\n");
> +
> +	ret = clk_prepare_enable(priv->cclk_tx);
> +	if (ret)
> +		return dev_err_probe(dev, ret, "Failed to enable cclk_tx clock\n");
> +
> +	priv->cclk_tx_on = true;
> +
> +	if (device_property_read_bool(mmc_dev(host->mmc), "mmc-ddr-1_8v") ||
> +	    device_property_read_bool(mmc_dev(host->mmc), "mmc-hs200-1_8v") ||
> +	    device_property_read_bool(mmc_dev(host->mmc), "mmc-hs400-1_8v"))
> +		dwc_priv->flags |= FLAG_IO_FIXED_1V8;
> +	else
> +		dwc_priv->flags &= ~FLAG_IO_FIXED_1V8;
> +
> +	dwc_priv->delay_line = 0x10;

Everywhere else delay_line value is a named define.

> +	dwc_priv->priv = priv;
> +
> +	if (dwc_priv->flags & FLAG_IO_FIXED_1V8) {
> +		host->flags &= ~SDHCI_SIGNALING_330;
> +		host->flags |=  SDHCI_SIGNALING_180;
> +	}
> +
> +	return 0;
> +}
> +
> +static void dwcmshc_starfive_jhb100_deinit(struct dwcmshc_priv *dwc_priv)
> +{
> +	struct jhb100_priv *priv = dwc_priv->priv;
> +
> +	if (priv->cclk_tx_on)
> +		clk_disable_unprepare(priv->cclk_tx);
> +}
> +
> +static const struct dwcmshc_pltfm_data sdhci_dwcmshc_jhb100_pdata = {
> +	.pdata = {
> +		.ops = &starfive_jhb100_ops,
> +		.quirks = SDHCI_QUIRK_CAP_CLOCK_BASE_BROKEN,
> +		.quirks2 = SDHCI_QUIRK2_PRESET_VALUE_BROKEN,
> +	},
> +	.init = dwcmshc_starfive_jhb100_init,
> +	.deinit = dwcmshc_starfive_jhb100_deinit,
> +};
> +
>  static const struct cqhci_host_ops dwcmshc_cqhci_ops = {
>  	.enable		= dwcmshc_sdhci_cqe_enable,
>  	.disable	= sdhci_cqe_disable,
> @@ -2377,6 +2525,10 @@ static const struct of_device_id sdhci_dwcmshc_dt_ids[] = {
>  		.compatible = "hpe,gsc-dwcmshc",
>  		.data = &sdhci_dwcmshc_hpe_gsc_pdata,
>  	},
> +	{
> +		.compatible = "starfive,jhb100-dwcmshc",
> +		.data = &sdhci_dwcmshc_jhb100_pdata,
> +	},
>  	{},
>  };
>  MODULE_DEVICE_TABLE(of, sdhci_dwcmshc_dt_ids);
> @@ -2503,6 +2655,8 @@ static int dwcmshc_probe(struct platform_device *pdev)
>  err_rpm:
>  	pm_runtime_disable(dev);
>  	pm_runtime_put_noidle(dev);
> +	if (pltfm_data->deinit)
> +		pltfm_data->deinit(priv);
>  err_bus_clk:
>  	clk_disable_unprepare(priv->bus_clk);
>  err_clk:
> @@ -2527,6 +2681,7 @@ static void dwcmshc_remove(struct platform_device *pdev)
>  	struct sdhci_host *host = platform_get_drvdata(pdev);
>  	struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
>  	struct dwcmshc_priv *priv = sdhci_pltfm_priv(pltfm_host);
> +	const struct dwcmshc_pltfm_data *pltfm_data = priv->dwcmshc_pdata;
> 
>  	pm_runtime_get_sync(&pdev->dev);
>  	pm_runtime_disable(&pdev->dev);
> @@ -2534,6 +2689,9 @@ static void dwcmshc_remove(struct platform_device *pdev)
> 
>  	sdhci_remove_host(host, 0);
> 
> +	if (pltfm_data->deinit)
> +		pltfm_data->deinit(priv);
> +
>  	dwcmshc_disable_card_clk(host);
> 
>  	clk_disable_unprepare(pltfm_host->clk);
> --
> 2.25.1