x86: ich6_gpio: Add use-lvl-write-cache for I/O access mode

Add a device-tree property use-lvl-write-cache that will cause
writes to lvl to be cached instead of read from lvl before each
write. This is required on some platforms that have the register
implemented as dual read/write (such as Baytrail).

Prior to this fix the blue USB port on the Minnowboard Max was
unusable since USB_HOST_EN0 was set high then immediately set
low when USB_HOST_EN1 was written.

This also resolves the 'gpio clear | set' command warning like:
  "Warning: value of pin is still 0"

Signed-off-by: George McCollister <george.mccollister@gmail.com>
<rebased on latest origin/master, fixed all baytrail boards>
Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Stefan Roese <sr@denx.de>
Reviewed-by: Simon Glass <sjg@chromium.org>

arch/x86/dts/bayleybay.dts

@@ -189,6 +189,7 @@
 				u-boot,dm-pre-reloc;
 				reg = <0 0x20>;
 				bank-name = "A";
+				use-lvl-write-cache;
 			};
 
 			gpiob {
@@ -196,6 +197,7 @@
 				u-boot,dm-pre-reloc;
 				reg = <0x20 0x20>;
 				bank-name = "B";
+				use-lvl-write-cache;
 			};
 
 			gpioc {
@@ -203,6 +205,7 @@
 				u-boot,dm-pre-reloc;
 				reg = <0x40 0x20>;
 				bank-name = "C";
+				use-lvl-write-cache;
 			};
 
 			gpiod {
@@ -210,6 +213,7 @@
 				u-boot,dm-pre-reloc;
 				reg = <0x60 0x20>;
 				bank-name = "D";
+				use-lvl-write-cache;
 			};
 
 			gpioe {
@@ -217,6 +221,7 @@
 				u-boot,dm-pre-reloc;
 				reg = <0x80 0x20>;
 				bank-name = "E";
+				use-lvl-write-cache;
 			};
 
 			gpiof {
@@ -224,6 +229,7 @@
 				u-boot,dm-pre-reloc;
 				reg = <0xA0 0x20>;
 				bank-name = "F";
+				use-lvl-write-cache;
 			};
 		};
 	};

arch/x86/dts/baytrail_som-db5800-som-6867.dts

@@ -212,6 +212,7 @@
 				u-boot,dm-pre-reloc;
 				reg = <0 0x20>;
 				bank-name = "A";
+				use-lvl-write-cache;
 			};
 
 			gpiob {
@@ -219,6 +220,7 @@
 				u-boot,dm-pre-reloc;
 				reg = <0x20 0x20>;
 				bank-name = "B";
+				use-lvl-write-cache;
 			};
 
 			gpioc {
@@ -226,6 +228,7 @@
 				u-boot,dm-pre-reloc;
 				reg = <0x40 0x20>;
 				bank-name = "C";
+				use-lvl-write-cache;
 			};
 
 			gpiod {
@@ -233,6 +236,7 @@
 				u-boot,dm-pre-reloc;
 				reg = <0x60 0x20>;
 				bank-name = "D";
+				use-lvl-write-cache;
 			};
 
 			gpioe {
@@ -240,6 +244,7 @@
 				u-boot,dm-pre-reloc;
 				reg = <0x80 0x20>;
 				bank-name = "E";
+				use-lvl-write-cache;
 			};
 
 			gpiof {
@@ -247,6 +252,7 @@
 				u-boot,dm-pre-reloc;
 				reg = <0xA0 0x20>;
 				bank-name = "F";
+				use-lvl-write-cache;
 			};
 		};
 	};

arch/x86/dts/conga-qeval20-qa3-e3845.dts

@@ -199,6 +199,7 @@
 				u-boot,dm-pre-reloc;
 				reg = <0 0x20>;
 				bank-name = "A";
+				use-lvl-write-cache;
 			};
 
 			gpiob {
@@ -206,6 +207,7 @@
 				u-boot,dm-pre-reloc;
 				reg = <0x20 0x20>;
 				bank-name = "B";
+				use-lvl-write-cache;
 			};
 
 			gpioc {
@@ -213,6 +215,7 @@
 				u-boot,dm-pre-reloc;
 				reg = <0x40 0x20>;
 				bank-name = "C";
+				use-lvl-write-cache;
 			};
 
 			gpiod {
@@ -220,6 +223,7 @@
 				u-boot,dm-pre-reloc;
 				reg = <0x60 0x20>;
 				bank-name = "D";
+				use-lvl-write-cache;
 			};
 
 			gpioe {
@@ -227,6 +231,7 @@
 				u-boot,dm-pre-reloc;
 				reg = <0x80 0x20>;
 				bank-name = "E";
+				use-lvl-write-cache;
 			};
 
 			gpiof {
@@ -234,6 +239,7 @@
 				u-boot,dm-pre-reloc;
 				reg = <0xA0 0x20>;
 				bank-name = "F";
+				use-lvl-write-cache;
 			};
 		};
 	};

arch/x86/dts/dfi-bt700.dtsi

@@ -201,6 +201,7 @@
 				u-boot,dm-pre-reloc;
 				reg = <0 0x20>;
 				bank-name = "A";
+				use-lvl-write-cache;
 			};
 
 			gpiob {
@@ -208,6 +209,7 @@
 				u-boot,dm-pre-reloc;
 				reg = <0x20 0x20>;
 				bank-name = "B";
+				use-lvl-write-cache;
 			};
 
 			gpioc {
@@ -215,6 +217,7 @@
 				u-boot,dm-pre-reloc;
 				reg = <0x40 0x20>;
 				bank-name = "C";
+				use-lvl-write-cache;
 			};
 
 			gpiod {
@@ -222,6 +225,7 @@
 				u-boot,dm-pre-reloc;
 				reg = <0x60 0x20>;
 				bank-name = "D";
+				use-lvl-write-cache;
 			};
 
 			gpioe {
@@ -229,6 +233,7 @@
 				u-boot,dm-pre-reloc;
 				reg = <0x80 0x20>;
 				bank-name = "E";
+				use-lvl-write-cache;
 			};
 
 			gpiof {
@@ -236,6 +241,7 @@
 				u-boot,dm-pre-reloc;
 				reg = <0xA0 0x20>;
 				bank-name = "F";
+				use-lvl-write-cache;
 			};
 		};
 	};

arch/x86/dts/minnowmax.dts

@@ -218,6 +218,7 @@
 				u-boot,dm-pre-reloc;
 				reg = <0 0x20>;
 				bank-name = "A";
+				use-lvl-write-cache;
 			};
 
 			gpiob {
@@ -225,6 +226,7 @@
 				u-boot,dm-pre-reloc;
 				reg = <0x20 0x20>;
 				bank-name = "B";
+				use-lvl-write-cache;
 			};
 
 			gpioc {
@@ -232,6 +234,7 @@
 				u-boot,dm-pre-reloc;
 				reg = <0x40 0x20>;
 				bank-name = "C";
+				use-lvl-write-cache;
 			};
 
 			gpiod {
@@ -239,6 +242,7 @@
 				u-boot,dm-pre-reloc;
 				reg = <0x60 0x20>;
 				bank-name = "D";
+				use-lvl-write-cache;
 			};
 
 			gpioe {
@@ -246,6 +250,7 @@
 				u-boot,dm-pre-reloc;
 				reg = <0x80 0x20>;
 				bank-name = "E";
+				use-lvl-write-cache;
 			};
 
 			gpiof {
@@ -253,6 +258,7 @@
 				u-boot,dm-pre-reloc;
 				reg = <0xA0 0x20>;
 				bank-name = "F";
+				use-lvl-write-cache;
 			};
 		};
 	};

drivers/gpio/intel_ich6_gpio.c

@@ -46,22 +46,31 @@ struct ich6_bank_priv {
 	uint16_t use_sel;
 	uint16_t io_sel;
 	uint16_t lvl;
+	u32 lvl_write_cache;
+	bool use_lvl_write_cache;
 };
 
 #define GPIO_USESEL_OFFSET(x)	(x)
 #define GPIO_IOSEL_OFFSET(x)	(x + 4)
 #define GPIO_LVL_OFFSET(x)	(x + 8)
 
-static int _ich6_gpio_set_value(uint16_t base, unsigned offset, int value)
+static int _ich6_gpio_set_value(struct ich6_bank_priv *bank, unsigned offset,
+				int value)
 {
 	u32 val;
 
-	val = inl(base);
+	if (bank->use_lvl_write_cache)
+		val = bank->lvl_write_cache;
+	else
+		val = inl(bank->lvl);
+
 	if (value)
 		val |= (1UL << offset);
 	else
 		val &= ~(1UL << offset);
-	outl(val, base);
+	outl(val, bank->lvl);
+	if (bank->use_lvl_write_cache)
+		bank->lvl_write_cache = val;
 
 	return 0;
 }
@@ -112,6 +121,7 @@ static int ich6_gpio_probe(struct udevice *dev)
 	struct ich6_bank_platdata *plat = dev_get_platdata(dev);
 	struct gpio_dev_priv *uc_priv = dev_get_uclass_priv(dev);
 	struct ich6_bank_priv *bank = dev_get_priv(dev);
+	const void *prop;
 
 	uc_priv->gpio_count = GPIO_PER_BANK;
 	uc_priv->bank_name = plat->bank_name;
@@ -119,6 +129,14 @@ static int ich6_gpio_probe(struct udevice *dev)
 	bank->io_sel = plat->base_addr + 4;
 	bank->lvl = plat->base_addr + 8;
 
+	prop = fdt_getprop(gd->fdt_blob, dev->of_offset,
+			   "use-lvl-write-cache", NULL);
+	if (prop)
+		bank->use_lvl_write_cache = true;
+	else
+		bank->use_lvl_write_cache = false;
+	bank->lvl_write_cache = 0;
+
 	return 0;
 }
 
@@ -160,7 +178,7 @@ static int ich6_gpio_direction_output(struct udevice *dev, unsigned offset,
 	if (ret)
 		return ret;
 
-	return _ich6_gpio_set_value(bank->lvl, offset, value);
+	return _ich6_gpio_set_value(bank, offset, value);
 }
 
 static int ich6_gpio_get_value(struct udevice *dev, unsigned offset)
@@ -170,6 +188,8 @@ static int ich6_gpio_get_value(struct udevice *dev, unsigned offset)
 	int r;
 
 	tmplong = inl(bank->lvl);
+	if (bank->use_lvl_write_cache)
+		tmplong |= bank->lvl_write_cache;
 	r = (tmplong & (1UL << offset)) ? 1 : 0;
 	return r;
 }
@@ -178,7 +198,7 @@ static int ich6_gpio_set_value(struct udevice *dev, unsigned offset,
 			       int value)
 {
 	struct ich6_bank_priv *bank = dev_get_priv(dev);
-	return _ich6_gpio_set_value(bank->lvl, offset, value);
+	return _ich6_gpio_set_value(bank, offset, value);
 }
 
 static int ich6_gpio_get_function(struct udevice *dev, unsigned offset)