Improved comments

arch/arm/src/tiva/tiva_gpio.c

@@ -835,9 +835,17 @@ int tiva_configgpio(uint32_t cfgset)
 
   flags = irqsave();
 
-  /* Enable power and clocking for this GPIO peripheral. */
+  /* Enable power and clocking for this GPIO peripheral.
+   *
+   * - Enable Power (TM4C129 family only):  Applies power (only) to the GPIO
+   *   peripheral.  This is not an essential step since enabling clocking
+   *   will also apply power.  The only significance is that the GPIO state
+   *   will be retained if the GPIO clocking is subsequently disabled.
+   * - Enable Clocking (All families):  Applies both power and clocking to
+   *   the GPIO peripheral, bringing it a fully functional state.
+   */
 
-  tiva_gpio_enablepwr(port); /* State will be retained of clocking disabled */
+  tiva_gpio_enablepwr(port);
   tiva_gpio_enableclk(port);
 
   /* First, set the port to digital input.  This is the safest state in which

arch/arm/src/tiva/tiva_i2c.c

@@ -1520,10 +1520,18 @@ static int tiva_i2c_initialize(struct tiva_i2c_priv_s *priv, uint32_t frequency)
 
   i2cvdbg("I2C%d: refs=%d\n", config->devno, priv->refs);
 
-  /* Enable clocking to the I2C peripheral */
+  /* Enable power and clocking to the I2C peripheral.
+   *
+   * - Enable Power (TM4C129 family only):  Applies power (only) to the I2C
+   *   peripheral.  This is not an essential step since enabling clocking
+   *   will also apply power.  The only significance is that the I2C state
+   *   will be retained if the I2C clocking is subsequently disabled.
+   * - Enable Clocking (All families):  Applies both power and clocking to
+   *   the I2C peripheral, bringing it a fully functional state.
+   */
 
 #ifdef TIVA_SYSCON_RCGCI2C
-  tiva_i2c_enablepwr(config->devno); /* State will be retained if clocking stopped */
+  tiva_i2c_enablepwr(config->devno);
   tiva_i2c_enableclk(config->devno);
 
   i2cvdbg("I2C%d: RCGI2C[%08x]=%08x\n",

arch/arm/src/tiva/tiva_lowputc.c

@@ -255,10 +255,17 @@ void up_lowsetup(void)
   /* Enable the selected UARTs and configure GPIO pins needed by the
    * the selected UARTs.  NOTE: The serial driver later depends on
    * this pin configuration -- whether or not a serial console is selected.
+   *
+   * - Enable Power (TM4C129 family only):  Applies power (only) to the UART
+   *   peripheral.  This is not an essential step since enabling clocking
+   *   will also apply power.  The only significance is that the UART state
+   *   will be retained if the UART clocking is subsequently disabled.
+   * - Enable Clocking (All families):  Applies both power and clocking to
+   *   the UART peripheral, bringing it a fully functional state.
    */
 
 #ifdef CONFIG_TIVA_UART0
-  tiva_uart0_enablepwr(); /* State will be retained if clocking disabled */
+  tiva_uart0_enablepwr();
   tiva_uart0_enableclk();
 
   tiva_configgpio(GPIO_UART0_RX);
@@ -266,7 +273,7 @@ void up_lowsetup(void)
 #endif
 
 #ifdef CONFIG_TIVA_UART1
-  tiva_uart1_enablepwr(); /* State will be retained if clocking disabled */
+  tiva_uart1_enablepwr();
   tiva_uart1_enableclk();
 
   tiva_configgpio(GPIO_UART1_RX);
@@ -274,7 +281,7 @@ void up_lowsetup(void)
 #endif
 
 #ifdef CONFIG_TIVA_UART2
-  tiva_uart2_enablepwr(); /* State will be retained if clocking disabled */
+  tiva_uart2_enablepwr();
   tiva_uart2_enableclk();
 
   tiva_configgpio(GPIO_UART2_RX);
@@ -282,7 +289,7 @@ void up_lowsetup(void)
 #endif
 
 #ifdef CONFIG_TIVA_UART3
-  tiva_uart3_enablepwr(); /* State will be retained if clocking disabled */
+  tiva_uart3_enablepwr();
   tiva_uart3_enableclk();
 
   tiva_configgpio(GPIO_UART3_RX);
@@ -290,7 +297,7 @@ void up_lowsetup(void)
 #endif
 
 #ifdef CONFIG_TIVA_UART4
-  tiva_uart4_enablepwr(); /* State will be retained if clocking disabled */
+  tiva_uart4_enablepwr();
   tiva_uart4_enableclk();
 
   tiva_configgpio(GPIO_UART4_RX);
@@ -298,7 +305,7 @@ void up_lowsetup(void)
 #endif
 
 #ifdef CONFIG_TIVA_UART5
-  tiva_uart5_enablepwr(); /* State will be retained if clocking disabled */
+  tiva_uart5_enablepwr();
   tiva_uart5_enableclk();
 
   tiva_configgpio(GPIO_UART5_RX);
@@ -306,7 +313,7 @@ void up_lowsetup(void)
 #endif
 
 #ifdef CONFIG_TIVA_UART6
-  tiva_uart6_enablepwr(); /* State will be retained if clocking disabled */
+  tiva_uart6_enablepwr();
   tiva_uart6_enableclk();
 
   tiva_configgpio(GPIO_UART6_RX);
@@ -314,7 +321,7 @@ void up_lowsetup(void)
 #endif
 
 #ifdef CONFIG_TIVA_UART7
-  tiva_uart7_enablepwr(); /* State will be retained if clocking disabled */
+  tiva_uart7_enablepwr();
   tiva_uart7_enableclk();
 
   tiva_configgpio(GPIO_UART7_RX);

arch/arm/src/tiva/tiva_ssi.c

@@ -1475,9 +1475,18 @@ FAR struct spi_dev_s *up_spiinitialize(int port)
 
       priv = &g_ssidev[SSI0_NDX];
 
-      /* Enable power and clocking to the SSI0 peripheral */
+      /* Enable power and clocking to the SSI0 peripheral.
+       *
+       * - Enable Power (TM4C129 family only):  Applies power (only) to the
+       *   SSI0 peripheral.  This is not an essential step since enabling
+       *   clocking will also apply power.  The only significance is that
+       *   the SSI0 state will be retained if the SSI0 clocking is
+       *   subsequently disabled.
+       * - Enable Clocking (All families):  Applies both power and clocking
+       *   to the SSI0 peripheral, bringing it a fully functional state.
+       */
 
-      tiva_ssi0_enablepwr(); /* State will be ratained if clocking disabled */
+      tiva_ssi0_enablepwr();
       tiva_ssi0_enableclk();
 
       /* Configure SSI0 GPIOs (NOTE that SS is not initialized here, the
@@ -1497,9 +1506,19 @@ FAR struct spi_dev_s *up_spiinitialize(int port)
 
       priv = &g_ssidev[SSI1_NDX];
 
-      /* Enable power and clocking to the SSI1 peripheral */
+      /* Enable power and clocking to the SSI1 peripheral.
+       *
+       * - Enable Power (TM4C129 family only):  Applies power (only) to the
+       *   SSI1 peripheral.  This is not an essential step since enabling
+       *   clocking will also apply power.  The only significance is that
+       *   the SSI1 state will be retained if the SSI1 clocking is
+       *   subsequently disabled.
+       * - Enable Clocking (All families):  Applies both power and clocking
+       *   to the SSI1 peripheral, bringing it a fully functional state.
+       */
 
-      tiva_ssi1_enablepwr(); /* State will be ratained if clocking disabled */
+
+      tiva_ssi1_enablepwr();
       tiva_ssi1_enableclk();
 
       /* Configure SSI1 GPIOs */