[PATCH v3 2/2] mmc: sdhci-of-dwcmshc: Add HPE GSC eMMC support

[nick . hawkins]

From: Nick Hawkins <nick.hawkins@xxxxxxx>

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.

Reset (dwcmshc_hpe_reset):
  Calls sdhci_reset(), re-applies the vendor config above, and then
  sets DWCMSHC_CARD_IS_EMMC unconditionally.  The GSC controller
  clears this 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 unconditionally sets
  CARD_IS_EMMC for all timing modes, not just HS400.

Init (dwcmshc_hpe_gsc_init):
  Obtains the SoC register block via the 'hpe,gxp-sysreg' syscon
  phandle and sets SCGSyncDis (BIT(18)) in MSHCCS (offset 0x110)
  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@xxxxxxx>
---
 drivers/mmc/host/sdhci-of-dwcmshc.c | 149 ++++++++++++++++++++++++++++
 1 file changed, 149 insertions(+)

diff --git a/drivers/mmc/host/sdhci-of-dwcmshc.c b/drivers/mmc/host/sdhci-of-dwcmshc.c
index 2b75a36c096b..46662071cc61 100644
--- a/drivers/mmc/host/sdhci-of-dwcmshc.c
+++ b/drivers/mmc/host/sdhci-of-dwcmshc.c
@@ -1245,6 +1245,132 @@ 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 &= ~BIT(0);
+	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_reset(struct sdhci_host *host, u8 mask)
+{
+	struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
+	struct dwcmshc_priv *dwc_priv = sdhci_pltfm_priv(pltfm_host);
+	u16 ctrl;
+
+	dwcmshc_reset(host, mask);
+
+	dwcmshc_hpe_vendor_specific(host);
+
+	/* HPE GSC eMMC always needs CARD_IS_EMMC set after reset */
+	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_set_uhs_signaling(struct sdhci_host *host,
+					  unsigned int timing)
+{
+	struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
+	struct dwcmshc_priv *priv = sdhci_pltfm_priv(pltfm_host);
+	u16 ctrl;
+
+	dwcmshc_set_uhs_signaling(host, timing);
+
+	/* HPE GSC: always set CARD_IS_EMMC for all timing modes */
+	ctrl = sdhci_readw(host, priv->vendor_specific_area1 + DWCMSHC_EMMC_CONTROL);
+	ctrl |= DWCMSHC_CARD_IS_EMMC;
+	sdhci_writew(host, ctrl, priv->vendor_specific_area1 + DWCMSHC_EMMC_CONTROL);
+}
+
+/*
+ * 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') to access
+ * this register at offset 0x110 within the SoC control block.
+ */
+#define HPE_GSC_MSHCCS_OFFSET		0x110
+#define HPE_GSC_MSHCCS_SCGSYNCDIS	BIT(18)
+
+static int dwcmshc_hpe_gsc_init(struct device *dev, struct sdhci_host *host,
+				struct dwcmshc_priv *dwc_priv)
+{
+	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 for MSHCCS access */
+	soc_ctrl = syscon_regmap_lookup_by_phandle(dev->of_node, "hpe,gxp-sysreg");
+	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, HPE_GSC_MSHCCS_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 +1960,25 @@ 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 +2087,10 @@ 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);
-- 
2.34.1