FAILED: patch "[PATCH] mmc: sdhci-esdhc-imx: allow 1.8V modes without 100/200MHz" failed to apply to 4.4-stable tree

The patch below does not apply to the 4.4-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From: Stefan Agner <[email protected]>
Date: Wed, 4 Jul 2018 17:07:45 +0200
Subject: [PATCH] mmc: sdhci-esdhc-imx: allow 1.8V modes without 100/200MHz
pinctrl states

If pinctrl nodes for 100/200MHz are missing, the controller should not select any mode which need signal frequencies 100MHz or higher. To prevent such speed modes the driver currently uses the quirk flag SDHCI_QUIRK2_NO_1_8_V. This works nicely for SD cards since 1.8V signaling is required for all faster modes and slower modes use 3.3V signaling only.

However, there are eMMC modes which use 1.8V signaling and run below 100MHz, e.g. DDR52 at 1.8V. With using SDHCI_QUIRK2_NO_1_8_V this mode is prevented. When using a fixed 1.8V regulator as vqmmc-supply the stack has no valid mode to use. In this tenuous situation the kernel continuously prints voltage switching errors:
mmc1: Switching to 3.3V signalling voltage failed

Avoid using SDHCI_QUIRK2_NO_1_8_V and prevent faster modes by altering the SDHCI capability register. With that the stack is able to select 1.8V modes even if no faster pinctrl states are available:

  # cat /sys/kernel/debug/mmc1/ios
  ...
  timing spec:    8 (mmc DDR52)
  signal voltage: 1 (1.80 V)
  ...

to uhs mode")

index d6aef70d34fa..4eb3d29ecde1 100644
@@ -312,6 +312,15 @@ static u32 esdhc_readl_le(struct sdhci_host *host, int reg)
 
 			if (imx_data->socdata->flags & ESDHC_FLAG_HS400)
 				val |= SDHCI_SUPPORT_HS400;
+
+			/*
+			 * Do not advertise faster UHS modes if there are no
+			 * pinctrl states for 100MHz/200MHz.
+			 */
+			if (IS_ERR_OR_NULL(imx_data->pins_100mhz) ||
+			    IS_ERR_OR_NULL(imx_data->pins_200mhz))
+				val &= ~(SDHCI_SUPPORT_SDR50 | SDHCI_SUPPORT_DDR50
+					 | SDHCI_SUPPORT_SDR104 | SDHCI_SUPPORT_HS400);
 		}
 	}
 

@@ -1158,18 +1167,6 @@ sdhci_esdhc_imx_probe_dt(struct platform_device *pdev,
 						ESDHC_PINCTRL_STATE_100MHZ);
 		imx_data->pins_200mhz = pinctrl_lookup_state(imx_data->pinctrl,
 						ESDHC_PINCTRL_STATE_200MHZ);
-		if (IS_ERR(imx_data->pins_100mhz) ||
-				IS_ERR(imx_data->pins_200mhz)) {
-			dev_warn(mmc_dev(host->mmc),
-				"could not get ultra high speed state, work on normal mode\n");
-			/*
-			 * fall back to not supporting uhs by specifying no
-			 * 1.8v quirk
-			 */
-			host->quirks2 |= SDHCI_QUIRK2_NO_1_8_V;
-		}
-	} else {
-		host->quirks2 |= SDHCI_QUIRK2_NO_1_8_V;
 	}
 
 	/* call to generic mmc_of_parse to support additional capabilities */