Re: [PATCH v4 2/2] mmc: sdhci-of-dwcmshc: Add HPE GSC eMMC support

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

On 16/03/2026 17:01, nick.hawkins@hpe.com wrote:
> From: Nick Hawkins <nick.hawkins@hpe.com>
> 
> Add support for the eMMC controller integrated in the HPE GSC (ARM64
> Cortex-A53) BMC SoC under the new 'hpe,gsc-dwcmshc' compatible
> string.
> 
> The HPE GSC eMMC controller is based on the DesignWare Cores MSHC IP
> but requires several platform-specific adjustments:
> 
> Clock mux (dwcmshc_hpe_set_clock):
>   The GSC SoC wires SDHCI_CLOCK_CONTROL.freq_sel directly to a clock
>   mux rather than a divider.  Forcing freq_sel = 1 when the requested
>   clock is 200 MHz (HS200) selects the correct high-speed clock source.
>   Using the generic sdhci_set_clock() would otherwise leave the mux on
>   the wrong source after tuning.
> 
> Auto-tuning / vendor config (dwcmshc_hpe_vendor_specific):
>   Disables the command-conflict check (DWCMSHC_HOST_CTRL3 BIT(0)) and
>   programs the ATCTRL register using existing AT_CTRL_* macros:
>     AT_CTRL_AT_EN           auto-tuning circuit enable
>     AT_CTRL_SWIN_TH_EN      sampling window threshold enable
>     AT_CTRL_TUNE_CLK_STOP_EN tune-clock-stop enable
>     PRE_CHANGE_DLY  = 3     pre-change delay
>     POST_CHANGE_DLY = 3     post-change delay
>     SWIN_TH_VAL    = 2      sampling window threshold
>   This combination is required for reliable HS200 signal integrity on
>   the GSC PCB trace topology.
> 
> eMMC mode (dwcmshc_hpe_set_emmc):
>   Helper that sets DWCMSHC_CARD_IS_EMMC unconditionally.  Called from
>   both the reset and UHS-signaling paths.
> 
> Reset (dwcmshc_hpe_reset):
>   Calls dwcmshc_reset(), re-applies the vendor config above via
>   dwcmshc_hpe_vendor_specific(), and then calls dwcmshc_hpe_set_emmc().
>   The GSC controller clears the CARD_IS_EMMC bit on every reset;
>   leaving it clear causes card-detect mis-identification on an
>   eMMC-only slot.
> 
> UHS signaling (dwcmshc_hpe_set_uhs_signaling):
>   Wraps dwcmshc_set_uhs_signaling() and calls dwcmshc_hpe_set_emmc()
>   to ensure CARD_IS_EMMC is set for all timing modes, not just HS400.
> 
> Init (dwcmshc_hpe_gsc_init):
>   Obtains the SoC register block and MSHCCS offset via the
>   'hpe,gxp-sysreg' syscon phandle argument and sets SCGSyncDis
>   (BIT(18)) to allow the HS200 RX delay lines to settle while the
>   card clock is stopped during auto-tuning.  Enables SDHCI v4 mode.
> 
> Quirks:
>   SDHCI_QUIRK_CAP_CLOCK_BASE_BROKEN:  base clock not advertised in
>     capabilities; must be obtained from the DTS 'clocks' property.
>   SDHCI_QUIRK2_PRESET_VALUE_BROKEN:  preset-value registers are not
>     populated in the GSC ROM.
> 
> All HPE-specific code is isolated to the new hpe_gsc_init / hpe_ops /
> hpe_gsc_pdata symbols.  No existing platform (Rockchip, T-Head, sg2042,
> etc.) is affected.
> 
> Signed-off-by: Nick Hawkins <nick.hawkins@hpe.com>

If you re-spin, there is 1 cosmetic comment below.  Otherwise:

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

> ---
>  drivers/mmc/host/sdhci-of-dwcmshc.c | 147 ++++++++++++++++++++++++++++
>  1 file changed, 147 insertions(+)
> 
> diff --git a/drivers/mmc/host/sdhci-of-dwcmshc.c b/drivers/mmc/host/sdhci-of-dwcmshc.c
> index 2b75a36c096b..f4c5c1aa0ebe 100644
> --- a/drivers/mmc/host/sdhci-of-dwcmshc.c
> +++ b/drivers/mmc/host/sdhci-of-dwcmshc.c
> @@ -40,7 +40,10 @@
>  #define DWCMSHC_AREA1_MASK		GENMASK(11, 0)
>  /* Offset inside the  vendor area 1 */
>  #define DWCMSHC_HOST_CTRL3		0x8
> +#define DWCMSHC_HOST_CTRL3_CMD_CONFLICT	BIT(0)
>  #define DWCMSHC_EMMC_CONTROL		0x2c
> +/* HPE GSC SoC MSHCCS register */
> +#define HPE_GSC_MSHCCS_SCGSYNCDIS	BIT(18)
>  #define DWCMSHC_CARD_IS_EMMC		BIT(0)
>  #define DWCMSHC_ENHANCED_STROBE		BIT(8)
>  #define DWCMSHC_EMMC_ATCTRL		0x40
> @@ -1245,6 +1248,127 @@ static int sg2042_init(struct device *dev, struct sdhci_host *host,
>  					     ARRAY_SIZE(clk_ids), clk_ids);
>  }
>  
> +/*
> + * HPE GSC-specific vendor configuration: disable command conflict check
> + * and program Auto-Tuning Control register.
> + */
> +static void dwcmshc_hpe_vendor_specific(struct sdhci_host *host)
> +{
> +	struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
> +	struct dwcmshc_priv *dwc_priv = sdhci_pltfm_priv(pltfm_host);
> +	u32 atctrl;
> +	u8 extra;
> +
> +	extra = sdhci_readb(host, dwc_priv->vendor_specific_area1 + DWCMSHC_HOST_CTRL3);
> +	extra &= ~DWCMSHC_HOST_CTRL3_CMD_CONFLICT;
> +	sdhci_writeb(host, extra, dwc_priv->vendor_specific_area1 + DWCMSHC_HOST_CTRL3);
> +
> +	atctrl = AT_CTRL_AT_EN | AT_CTRL_SWIN_TH_EN | AT_CTRL_TUNE_CLK_STOP_EN |
> +		FIELD_PREP(AT_CTRL_PRE_CHANGE_DLY_MASK, 3) |
> +		FIELD_PREP(AT_CTRL_POST_CHANGE_DLY_MASK, AT_CTRL_POST_CHANGE_DLY) |
> +		FIELD_PREP(AT_CTRL_SWIN_TH_VAL_MASK, 2);
> +	sdhci_writel(host, atctrl, dwc_priv->vendor_specific_area1 + DWCMSHC_EMMC_ATCTRL);
> +}
> +
> +static void dwcmshc_hpe_set_emmc(struct sdhci_host *host)
> +{
> +	struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
> +	struct dwcmshc_priv *dwc_priv = sdhci_pltfm_priv(pltfm_host);
> +	u16 ctrl;
> +
> +	ctrl = sdhci_readw(host, dwc_priv->vendor_specific_area1 + DWCMSHC_EMMC_CONTROL);
> +	ctrl |= DWCMSHC_CARD_IS_EMMC;
> +	sdhci_writew(host, ctrl, dwc_priv->vendor_specific_area1 + DWCMSHC_EMMC_CONTROL);
> +}
> +
> +static void dwcmshc_hpe_reset(struct sdhci_host *host, u8 mask)
> +{
> +	dwcmshc_reset(host, mask);
> +	dwcmshc_hpe_vendor_specific(host);
> +	dwcmshc_hpe_set_emmc(host);
> +}
> +
> +static void dwcmshc_hpe_set_uhs_signaling(struct sdhci_host *host,
> +					   unsigned int timing)

Unnecessary line wrap

> +{
> +	dwcmshc_set_uhs_signaling(host, timing);
> +	dwcmshc_hpe_set_emmc(host);
> +}
> +
> +/*
> + * HPE GSC eMMC controller clock setup.
> + *
> + * The GSC SoC wires the freq_sel field of SDHCI_CLOCK_CONTROL directly to a
> + * clock mux rather than a divider. Force freq_sel = 1 when running at
> + * 200 MHz (HS200) so the mux selects the correct clock source.
> + */
> +static void dwcmshc_hpe_set_clock(struct sdhci_host *host, unsigned int clock)
> +{
> +	u16 clk;
> +
> +	host->mmc->actual_clock = 0;
> +
> +	sdhci_writew(host, 0, SDHCI_CLOCK_CONTROL);
> +
> +	if (clock == 0)
> +		return;
> +
> +	clk = sdhci_calc_clk(host, clock, &host->mmc->actual_clock);
> +
> +	if (host->mmc->actual_clock == 200000000)
> +		clk |= (1 << SDHCI_DIVIDER_SHIFT);
> +
> +	sdhci_enable_clk(host, clk);
> +}
> +
> +/*
> + * HPE GSC eMMC controller init.
> + *
> + * The GSC SoC requires configuring MSHCCS.  Bit 18 (SCGSyncDis) disables clock
> + * synchronisation for phase-select values going to the HS200 RX delay lines,
> + * allowing the card clock to be stopped while the delay selection settles and
> + * the phase shift is applied.  This must be used together with the ATCTRL
> + * settings programmed in dwcmshc_hpe_vendor_specific():
> + *   AT_CTRL_R.TUNE_CLK_STOP_EN  = 0x1
> + *   AT_CTRL_R.POST_CHANGE_DLY   = 0x3
> + *   AT_CTRL_R.PRE_CHANGE_DLY    = 0x3
> + *
> + * The DTS node provides a syscon phandle ('hpe,gxp-sysreg') with the
> + * MSHCCS register offset as an argument.
> + */
> +static int dwcmshc_hpe_gsc_init(struct device *dev, struct sdhci_host *host,
> +				struct dwcmshc_priv *dwc_priv)
> +{
> +	unsigned int reg_offset;
> +	struct regmap *soc_ctrl;
> +	int ret;
> +
> +	/* Disable cmd conflict check and configure auto-tuning */
> +	dwcmshc_hpe_vendor_specific(host);
> +
> +	/* Look up the GXP sysreg syscon and MSHCCS offset */
> +	soc_ctrl = syscon_regmap_lookup_by_phandle_args(dev->of_node,
> +							"hpe,gxp-sysreg",
> +							1, &reg_offset);
> +	if (IS_ERR(soc_ctrl)) {
> +		dev_err(dev, "failed to get hpe,gxp-sysreg syscon\n");
> +		return PTR_ERR(soc_ctrl);
> +	}
> +
> +	/* Set SCGSyncDis (bit 18) to disable sync on HS200 RX delay lines */
> +	ret = regmap_update_bits(soc_ctrl, reg_offset,
> +				 HPE_GSC_MSHCCS_SCGSYNCDIS,
> +				 HPE_GSC_MSHCCS_SCGSYNCDIS);
> +	if (ret) {
> +		dev_err(dev, "failed to set SCGSyncDis in MSHCCS\n");
> +		return ret;
> +	}
> +
> +	sdhci_enable_v4_mode(host);
> +
> +	return 0;
> +}
> +
>  static void sdhci_eic7700_set_clock(struct sdhci_host *host, unsigned int clock)
>  {
>  	struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
> @@ -1834,6 +1958,25 @@ static const struct dwcmshc_pltfm_data sdhci_dwcmshc_eic7700_pdata = {
>  	.init = eic7700_init,
>  };
>  
> +static const struct sdhci_ops sdhci_dwcmshc_hpe_ops = {
> +	.set_clock		= dwcmshc_hpe_set_clock,
> +	.set_bus_width		= sdhci_set_bus_width,
> +	.set_uhs_signaling	= dwcmshc_hpe_set_uhs_signaling,
> +	.get_max_clock		= dwcmshc_get_max_clock,
> +	.reset			= dwcmshc_hpe_reset,
> +	.adma_write_desc	= dwcmshc_adma_write_desc,
> +	.irq			= dwcmshc_cqe_irq_handler,
> +};
> +
> +static const struct dwcmshc_pltfm_data sdhci_dwcmshc_hpe_gsc_pdata = {
> +	.pdata = {
> +		.ops = &sdhci_dwcmshc_hpe_ops,
> +		.quirks = SDHCI_QUIRK_CAP_CLOCK_BASE_BROKEN,
> +		.quirks2 = SDHCI_QUIRK2_PRESET_VALUE_BROKEN,
> +	},
> +	.init = dwcmshc_hpe_gsc_init,
> +};
> +
>  static const struct cqhci_host_ops dwcmshc_cqhci_ops = {
>  	.enable		= dwcmshc_sdhci_cqe_enable,
>  	.disable	= sdhci_cqe_disable,
> @@ -1942,6 +2085,10 @@ static const struct of_device_id sdhci_dwcmshc_dt_ids[] = {
>  		.compatible = "eswin,eic7700-dwcmshc",
>  		.data = &sdhci_dwcmshc_eic7700_pdata,
>  	},
> +	{
> +		.compatible = "hpe,gsc-dwcmshc",
> +		.data = &sdhci_dwcmshc_hpe_gsc_pdata,
> +	},
>  	{},
>  };
>  MODULE_DEVICE_TABLE(of, sdhci_dwcmshc_dt_ids);