soc/intel/common/uart: Refactor uart_common_init

1. Create a new function uart_lpss_init which takes the UART LPSS
controller out of reset and initializes and enables clock.

2. Instead of passing in m/n clock divider values as parameters to
uart_common_init, introduce Kconfig variables so that uart_lpss_init
can use the values directly without having to query the SoC.

BUG=b:64030366
TEST=Verified that UART still works on APL and KBL boards.

Change-Id: I74d01b0037d8c38fe6480c38ff2283d76097282a
Signed-off-by: Furquan Shaikh <furquan@chromium.org>
Reviewed-on: https://review.coreboot.org/20884
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>

src/soc/intel/apollolake/Kconfig

@@ -351,4 +351,14 @@ config APL_SKIP_SET_POWER_LIMITS
 	  Limits (RAPL) algorithm for a constant power management.
 	  Set this config option to skip the RAPL configuration.
 
+# M and N divisor values for clock frequency configuration.
+# These values get us a 1.836 MHz clock (ideally we want 1.843 MHz)
+config SOC_INTEL_COMMON_LPSS_UART_CLK_M_VAL
+	hex
+	default 0x25a
+
+config SOC_INTEL_COMMON_LPSS_UART_CLK_N_VAL
+	hex
+	default 0x7fff
+
 endif

src/soc/intel/apollolake/include/soc/uart.h

@@ -18,13 +18,6 @@
 #ifndef _SOC_APOLLOLAKE_UART_H_
 #define _SOC_APOLLOLAKE_UART_H_
 
-/*
-* M and N divisor values for clock frequency configuration.
-* These values get us a 1.836 MHz clock (ideally we want 1.843 MHz)
-*/
-#define CLK_M_VAL	0x025a
-#define CLK_N_VAL	0x7fff
-
 /* Initialize the console UART including the pads for the configured UART. */
 void pch_uart_init(void);
 

src/soc/intel/apollolake/uart_early.c

@@ -69,6 +69,6 @@ void pch_uart_init(void)
 	gpio_configure_pads(&uart_gpios[pad_index * 2], 2);
 
 	/* Program UART2 BAR0, command, reset and clock register */
-	uart_common_init(uart, base, CLK_M_VAL, CLK_N_VAL);
+	uart_common_init(uart, base);
 
 }

src/soc/intel/common/block/include/intelblocks/uart.h

@@ -19,8 +19,12 @@
 #include <arch/io.h>
 #include <device/device.h>
 
-void uart_common_init(device_t dev, uintptr_t baseaddr,
-		uint32_t clk_m_val, uint32_t clk_n_val);
+/*
+ * Common routine to initialize UART controller PCI config space, take it out of
+ * reset and configure M/N dividers.
+ */
+void uart_common_init(device_t dev, uintptr_t baseaddr);
+
 
 void pch_uart_read_resources(struct device *dev);
 

src/soc/intel/common/block/uart/Kconfig

@@ -3,3 +3,15 @@ config SOC_INTEL_COMMON_BLOCK_UART
 	select SOC_INTEL_COMMON_BLOCK_LPSS
 	help
 	  Intel Processor common UART support
+
+config SOC_INTEL_COMMON_BLOCK_UART_LPSS_CLK_M_VAL
+	depends on SOC_INTEL_COMMON_BLOCK_UART
+	hex
+	help
+	  Clock m-divisor value for m/n divider
+
+config SOC_INTEL_COMMON_BLOCK_UART_LPSS_CLK_N_VAL
+	depends on SOC_INTEL_COMMON_BLOCK_UART
+	hex
+	help
+	  Clock m-divisor value for m/n divider

src/soc/intel/common/block/uart/uart.c

@@ -19,8 +19,17 @@
 #include <intelblocks/lpss.h>
 #include <intelblocks/uart.h>
 
-void uart_common_init(device_t dev, uintptr_t baseaddr, uint32_t clk_m_val,
-		uint32_t clk_n_val)
+static void uart_lpss_init(uintptr_t baseaddr)
+{
+	/* Take UART out of reset */
+	lpss_reset_release(baseaddr);
+
+	/* Set M and N divisor inputs and enable clock */
+	lpss_clk_update(baseaddr, CONFIG_SOC_INTEL_COMMON_LPSS_UART_CLK_M_VAL,
+			CONFIG_SOC_INTEL_COMMON_LPSS_UART_CLK_N_VAL);
+}
+
+void uart_common_init(device_t dev, uintptr_t baseaddr)
 {
 	/* Set UART base address */
 	pci_write_config32(dev, PCI_BASE_ADDRESS_0, baseaddr);
@@ -29,11 +38,8 @@ void uart_common_init(device_t dev, uintptr_t baseaddr, uint32_t clk_m_val,
 	pci_write_config32(dev, PCI_COMMAND,
 			PCI_COMMAND_MEMORY | PCI_COMMAND_MASTER);
 
-	/* Take UART out of reset */
-	lpss_reset_release(baseaddr);
+	uart_lpss_init(baseaddr);
 
-	/* Set M and N divisor inputs and enable clock */
-	lpss_clk_update(baseaddr, clk_m_val, clk_n_val);
 }
 
 #if ENV_RAMSTAGE

src/soc/intel/skylake/Kconfig

@@ -317,4 +317,13 @@ config CPU_BCLK_MHZ
 	int
 	default 100
 
+# Clock divider parameters for 115200 baud rate
+config SOC_INTEL_COMMON_LPSS_UART_CLK_M_VAL
+	hex
+	default 0x30
+
+config SOC_INTEL_COMMON_LPSS_UART_CLK_N_VAL
+	hex
+	default 0xc35
+
 endif

src/soc/intel/skylake/bootblock/uart.c

@@ -31,10 +31,6 @@
 #define PCR_SIO_PCH_LEGACY_UART1	(1 << 1)
 #define PCR_SIO_PCH_LEGACY_UART2	(1 << 2)
 
-/* Clock divider parameters for 115200 baud rate */
-#define CLK_M_VAL	0x30
-#define CLK_N_VAL	0xc35
-
 /* UART2 pad configuration. Support RXD and TXD for now. */
 static const struct pad_config uart2_pads[] = {
 /* UART2_RXD */		PAD_CFG_NF(GPP_C20, NONE, DEEP, NF1),
@@ -45,7 +41,7 @@ void pch_uart_init(void)
 {
 	uintptr_t base = uart_platform_base(CONFIG_UART_FOR_CONSOLE);
 
-	uart_common_init(PCH_DEV_UART2, base, CLK_M_VAL, CLK_N_VAL);
+	uart_common_init(PCH_DEV_UART2, base);
 
 	/* Put UART2 in byte access mode for 16550 compatibility */
 	if (!IS_ENABLED(CONFIG_DRIVERS_UART_8250MEM_32))