mmc: use downstream DT property to modify CQE and/or SD CQ behaviour

Implement a tristate-style option for "supports-cqe". If the property is
absent or zero, disable CQ completely. For 1, enable CQ unconditionally
for eMMC cards, and known-good SD cards. For 2, enable for eMMC cards,
and all SD cards that are not known-bad.

The sdhci-brcmstb driver needs to know about the tristate as its probe
sequence would otherwise override a disable in mmc_of_parse().

Signed-off-by: Jonathan Bell <jonathan@raspberrypi.com>

Author: P33M

drivers/mmc/core/host.c

@@ -272,7 +272,7 @@ EXPORT_SYMBOL(mmc_of_parse_clk_phase);
 int mmc_of_parse(struct mmc_host *host)
 {
 	struct device *dev = host->parent;
-	u32 bus_width, drv_type, cd_debounce_delay_ms;
+	u32 bus_width, drv_type, cd_debounce_delay_ms, cq_allow;
 	int ret;
 
 	if (!dev || !dev_fwnode(dev))
@@ -407,6 +407,15 @@ int mmc_of_parse(struct mmc_host *host)
 		host->caps2 &= ~(MMC_CAP2_HS400_1_8V | MMC_CAP2_HS400_1_2V |
 				 MMC_CAP2_HS400_ES);
 
+	cq_allow = 0;
+	/*
+	 * Downstream property - if a u32 and 2 instead of a bool,
+	 * trust most A2 SD cards claiming CQ support.
+	 */
+	device_property_read_u32(dev, "supports-cqe", &cq_allow);
+	if (cq_allow == 2)
+		host->caps2 |= MMC_CAP2_SD_CQE_PERMISSIVE;
+
 	/* Must be after "non-removable" check */
 	if (device_property_read_u32(dev, "fixed-emmc-driver-type", &drv_type) == 0) {
 		if (host->caps & MMC_CAP_NONREMOVABLE)

drivers/mmc/core/sd.c

@@ -1501,8 +1501,8 @@ static int mmc_sd_init_card(struct mmc_host *host, u32 ocr,
 			goto free_card;
 	}
 
-	/* Disallow command queueing on unvetted cards */
-	if (!mmc_card_working_sd_cq(card))
+	/* Disallow command queueing on unvetted cards unless overridden */
+	if (!(host->caps2 & MMC_CAP2_SD_CQE_PERMISSIVE) && !mmc_card_working_sd_cq(card))
 		card->ext_csd.cmdq_support = false;
 
 	/* Enable command queueing if supported */

drivers/mmc/host/sdhci-brcmstb.c

@@ -571,7 +571,7 @@ static int sdhci_brcmstb_probe(struct platform_device *pdev)
 	struct sdhci_pltfm_host *pltfm_host;
 	const struct of_device_id *match;
 	struct sdhci_brcmstb_priv *priv;
-	u32 actual_clock_mhz;
+	u32 actual_clock_mhz, cqe;
 	struct sdhci_host *host;
 	struct resource *iomem;
 	bool no_pinctrl = false;
@@ -600,7 +600,9 @@ static int sdhci_brcmstb_probe(struct platform_device *pdev)
 	pltfm_host->clk = clk;
 
 	priv = sdhci_pltfm_priv(pltfm_host);
-	if (device_property_read_bool(&pdev->dev, "supports-cqe")) {
+	cqe = 0;
+	device_property_read_u32(&pdev->dev, "supports-cqe", &cqe);
+	if (cqe > 0) {
 		priv->flags |= BRCMSTB_PRIV_FLAGS_HAS_CQE;
 		match_priv->ops->irq = sdhci_brcmstb_cqhci_irq;
 	}

include/linux/mmc/host.h

@@ -404,6 +404,7 @@ struct mmc_host {
 #define MMC_CAP2_CRYPTO		0
 #endif
 #define MMC_CAP2_ALT_GPT_TEGRA	(1 << 28)	/* Host with eMMC that has GPT entry at a non-standard location */
+#define MMC_CAP2_SD_CQE_PERMISSIVE	(1 << 31)	/* Ignore allow-list for CQ capable SD card detection */
 
 	int			fixed_drv_type;	/* fixed driver type for non-removable media */