Re: [U-Boot] [PATCH 2/2] gpio: tegra: use named constants

[Stephen Warren]

On 10/03/2015 08:14 AM, Simon Glass wrote:
> Hi Stephen,
> 
> On 2 October 2015 at 00:29, Stephen Warren  wrote:
>> On 10/01/2015 05:00 PM, Simon Glass wrote:
>>>
>>> On Friday, 25 September 2015, Stephen Warren 
>>> wrote:

 From: Stephen Warren 

 In order to make it clear what the parameters to set_config() and
 set_direction() mean, and similarly for the return values from the
 respective get_*(), define named constants for these values.

 Disassembly shows no diff in the generated code, except that the
 order of the code in the branches of tegra_gpio_get_function() gets
 modified without affecting behaviour.
>>
>>
 diff --git a/drivers/gpio/tegra_gpio.c b/drivers/gpio/tegra_gpio.c
>>
>>
 +static const int CONFIG_SFIO = 0;
 +static const int CONFIG_GPIO = 1;
 +static const int DIRECTION_INPUT = 0;
 +static const int DIRECTION_OUTPUT = 1;
>>>
>>>
>>> Why not use an enum?
>>
>>
>> I don't think it gives any benefit does it?
>>
>> Doing so would entail 5 extra lines of overhead for the enum { and } lines.
>> I'd want to define two separate enum blocks since I dislike putting
>> logically unrelated enum values into a single enum definition. Even if I
>> didn't do that, it's still 2 lines of useless overhead to add everything
>> into a single enum.
> 
> It's just odd to use const int instead of enum I think.

What makes it odd?
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Re: [U-Boot] [PATCH 2/2] gpio: tegra: use named constants

[Simon Glass]

Hi Stephen,

On 2 October 2015 at 00:29, Stephen Warren  wrote:
> On 10/01/2015 05:00 PM, Simon Glass wrote:
>>
>> On Friday, 25 September 2015, Stephen Warren 
>> wrote:
>>>
>>> From: Stephen Warren 
>>>
>>> In order to make it clear what the parameters to set_config() and
>>> set_direction() mean, and similarly for the return values from the
>>> respective get_*(), define named constants for these values.
>>>
>>> Disassembly shows no diff in the generated code, except that the
>>> order of the code in the branches of tegra_gpio_get_function() gets
>>> modified without affecting behaviour.
>
>
>>> diff --git a/drivers/gpio/tegra_gpio.c b/drivers/gpio/tegra_gpio.c
>
>
>>> +static const int CONFIG_SFIO = 0;
>>> +static const int CONFIG_GPIO = 1;
>>> +static const int DIRECTION_INPUT = 0;
>>> +static const int DIRECTION_OUTPUT = 1;
>>
>>
>> Why not use an enum?
>
>
> I don't think it gives any benefit does it?
>
> Doing so would entail 5 extra lines of overhead for the enum { and } lines.
> I'd want to define two separate enum blocks since I dislike putting
> logically unrelated enum values into a single enum definition. Even if I
> didn't do that, it's still 2 lines of useless overhead to add everything
> into a single enum.

It's just odd to use const int instead of enum I think. Particularly
as you are using capital letters.

Since it's Tegra code I'll leave it up to you.

Regards,
Simon
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Re: [U-Boot] [PATCH 2/2] gpio: tegra: use named constants

[Stephen Warren]

On 10/01/2015 05:00 PM, Simon Glass wrote:

On Friday, 25 September 2015, Stephen Warren  wrote:

From: Stephen Warren 

In order to make it clear what the parameters to set_config() and
set_direction() mean, and similarly for the return values from the
respective get_*(), define named constants for these values.

Disassembly shows no diff in the generated code, except that the
order of the code in the branches of tegra_gpio_get_function() gets
modified without affecting behaviour.



diff --git a/drivers/gpio/tegra_gpio.c b/drivers/gpio/tegra_gpio.c



+static const int CONFIG_SFIO = 0;
+static const int CONFIG_GPIO = 1;
+static const int DIRECTION_INPUT = 0;
+static const int DIRECTION_OUTPUT = 1;


Why not use an enum?


I don't think it gives any benefit does it?

Doing so would entail 5 extra lines of overhead for the enum { and } 
lines. I'd want to define two separate enum blocks since I dislike 
putting logically unrelated enum values into a single enum definition. 
Even if I didn't do that, it's still 2 lines of useless overhead to add 
everything into a single enum.

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Re: [U-Boot] [PATCH 2/2] gpio: tegra: use named constants

[Simon Glass]

Hi Stephen.

On Friday, 25 September 2015, Stephen Warren  wrote:
>
> From: Stephen Warren 
>
> In order to make it clear what the parameters to set_config() and
> set_direction() mean, and similarly for the return values from the
> respective get_*(), define named constants for these values.
>
> Disassembly shows no diff in the generated code, except that the
> order of the code in the branches of tegra_gpio_get_function() gets
> modified without affecting behaviour.
>
> Suggested-by: Tom Warren 
> Signed-off-by: Stephen Warren 
> ---
>  drivers/gpio/tegra_gpio.c | 33 +++--
>  1 file changed, 19 insertions(+), 14 deletions(-)
>
> diff --git a/drivers/gpio/tegra_gpio.c b/drivers/gpio/tegra_gpio.c
> index f9c06fe88b71..8e880e276f0a 100644
> --- a/drivers/gpio/tegra_gpio.c
> +++ b/drivers/gpio/tegra_gpio.c
> @@ -1,6 +1,6 @@
>  /*
>   * NVIDIA Tegra20 GPIO handling.
> - *  (C) Copyright 2010-2012
> + *  (C) Copyright 2010-2012,2015
>   *  NVIDIA Corporation 
>   *
>   * SPDX-License-Identifier:GPL-2.0+
> @@ -25,6 +25,11 @@
>
>  DECLARE_GLOBAL_DATA_PTR;
>
> +static const int CONFIG_SFIO = 0;
> +static const int CONFIG_GPIO = 1;
> +static const int DIRECTION_INPUT = 0;
> +static const int DIRECTION_OUTPUT = 1;
> +


Why not use an enum?

>
>  struct tegra_gpio_platdata {
> struct gpio_ctlr_bank *bank;
> const char *port_name;  /* Name of port, e.g. "B" */
> @@ -37,7 +42,7 @@ struct tegra_port_info {
> int base_gpio;  /* Port number for this port (0, 1,.., n-1) */
>  };
>
> -/* Return config of pin 'gpio' as GPIO (1) or SFPIO (0) */
> +/* Return config of pin 'gpio' as GPIO (1) or SFIO (0) */
>  static int get_config(unsigned gpio)
>  {
> struct gpio_ctlr *ctlr = (struct gpio_ctlr *)NV_PA_GPIO_BASE;
> @@ -46,15 +51,15 @@ static int get_config(unsigned gpio)
> int type;
>
> u = readl(&bank->gpio_config[GPIO_PORT(gpio)]);
> -   type =  (u >> GPIO_BIT(gpio)) & 1;
> +   type = (u >> GPIO_BIT(gpio)) & 1;
>
> debug("get_config: port = %d, bit = %d is %s\n",
> GPIO_FULLPORT(gpio), GPIO_BIT(gpio), type ? "GPIO" : "SFPIO");
>
> -   return type;
> +   return type ? CONFIG_GPIO : CONFIG_SFIO;
>  }
>
> -/* Config pin 'gpio' as GPIO or SFPIO, based on 'type' */
> +/* Config pin 'gpio' as GPIO or SFIO, based on 'type' */
>  static void set_config(unsigned gpio, int type)
>  {
> struct gpio_ctlr *ctlr = (struct gpio_ctlr *)NV_PA_GPIO_BASE;
> @@ -65,7 +70,7 @@ static void set_config(unsigned gpio, int type)
> GPIO_FULLPORT(gpio), GPIO_BIT(gpio), type ? "GPIO" : "SFPIO");
>
> u = readl(&bank->gpio_config[GPIO_PORT(gpio)]);
> -   if (type)   /* GPIO */
> +   if (type != CONFIG_SFIO)
> u |= 1 << GPIO_BIT(gpio);
> else
> u &= ~(1 << GPIO_BIT(gpio));
> @@ -86,7 +91,7 @@ static int get_direction(unsigned gpio)
> debug("get_direction: port = %d, bit = %d, %s\n",
> GPIO_FULLPORT(gpio), GPIO_BIT(gpio), dir ? "OUT" : "IN");
>
> -   return dir;
> +   return dir ? DIRECTION_OUTPUT : DIRECTION_INPUT;
>  }
>
>  /* Config GPIO pin 'gpio' as input or output (OE) as per 'output' */
> @@ -100,7 +105,7 @@ static void set_direction(unsigned gpio, int output)
> GPIO_FULLPORT(gpio), GPIO_BIT(gpio), output ? "OUT" : "IN");
>
> u = readl(&bank->gpio_dir_out[GPIO_PORT(gpio)]);
> -   if (output)
> +   if (output != DIRECTION_INPUT)
> u |= 1 << GPIO_BIT(gpio);
> else
> u &= ~(1 << GPIO_BIT(gpio));
> @@ -135,7 +140,7 @@ static int tegra_gpio_direction_input(struct udevice 
> *dev, unsigned offset)
> struct tegra_port_info *state = dev_get_priv(dev);
>
> /* Configure GPIO direction as input. */
> -   set_direction(state->base_gpio + offset, 0);
> +   set_direction(state->base_gpio + offset, DIRECTION_INPUT);
>
> /* Enable the pin as a GPIO */
> set_config(state->base_gpio + offset, 1);
> @@ -154,7 +159,7 @@ static int tegra_gpio_direction_output(struct udevice 
> *dev, unsigned offset,
> set_level(gpio, value);
>
> /* Configure GPIO direction as output. */
> -   set_direction(gpio, 1);
> +   set_direction(gpio, DIRECTION_OUTPUT);
>
> /* Enable the pin as a GPIO */
> set_config(state->base_gpio + offset, 1);
> @@ -199,18 +204,18 @@ void gpio_config_table(const struct tegra_gpio_config 
> *config, int len)
> for (i = 0; i < len; i++) {
> switch (config[i].init) {
> case TEGRA_GPIO_INIT_IN:
> -   set_direction(config[i].gpio, 0);
> +   set_direction(config[i].gpio, DIRECTION_INPUT);
> break;
> case TEGRA_GPIO_INIT_OUT0:
> set_level(config[i].gpio, 0);
> -   set_direction(config[i].gpio,

[U-Boot] [PATCH 2/2] gpio: tegra: use named constants

[Stephen Warren]

From: Stephen Warren 

In order to make it clear what the parameters to set_config() and
set_direction() mean, and similarly for the return values from the
respective get_*(), define named constants for these values.

Disassembly shows no diff in the generated code, except that the
order of the code in the branches of tegra_gpio_get_function() gets
modified without affecting behaviour.

Suggested-by: Tom Warren 
Signed-off-by: Stephen Warren 
---
 drivers/gpio/tegra_gpio.c | 33 +++--
 1 file changed, 19 insertions(+), 14 deletions(-)

diff --git a/drivers/gpio/tegra_gpio.c b/drivers/gpio/tegra_gpio.c
index f9c06fe88b71..8e880e276f0a 100644
--- a/drivers/gpio/tegra_gpio.c
+++ b/drivers/gpio/tegra_gpio.c
@@ -1,6 +1,6 @@
 /*
  * NVIDIA Tegra20 GPIO handling.
- *  (C) Copyright 2010-2012
+ *  (C) Copyright 2010-2012,2015
  *  NVIDIA Corporation 
  *
  * SPDX-License-Identifier:GPL-2.0+
@@ -25,6 +25,11 @@
 
 DECLARE_GLOBAL_DATA_PTR;
 
+static const int CONFIG_SFIO = 0;
+static const int CONFIG_GPIO = 1;
+static const int DIRECTION_INPUT = 0;
+static const int DIRECTION_OUTPUT = 1;
+
 struct tegra_gpio_platdata {
struct gpio_ctlr_bank *bank;
const char *port_name;  /* Name of port, e.g. "B" */
@@ -37,7 +42,7 @@ struct tegra_port_info {
int base_gpio;  /* Port number for this port (0, 1,.., n-1) */
 };
 
-/* Return config of pin 'gpio' as GPIO (1) or SFPIO (0) */
+/* Return config of pin 'gpio' as GPIO (1) or SFIO (0) */
 static int get_config(unsigned gpio)
 {
struct gpio_ctlr *ctlr = (struct gpio_ctlr *)NV_PA_GPIO_BASE;
@@ -46,15 +51,15 @@ static int get_config(unsigned gpio)
int type;
 
u = readl(&bank->gpio_config[GPIO_PORT(gpio)]);
-   type =  (u >> GPIO_BIT(gpio)) & 1;
+   type = (u >> GPIO_BIT(gpio)) & 1;
 
debug("get_config: port = %d, bit = %d is %s\n",
GPIO_FULLPORT(gpio), GPIO_BIT(gpio), type ? "GPIO" : "SFPIO");
 
-   return type;
+   return type ? CONFIG_GPIO : CONFIG_SFIO;
 }
 
-/* Config pin 'gpio' as GPIO or SFPIO, based on 'type' */
+/* Config pin 'gpio' as GPIO or SFIO, based on 'type' */
 static void set_config(unsigned gpio, int type)
 {
struct gpio_ctlr *ctlr = (struct gpio_ctlr *)NV_PA_GPIO_BASE;
@@ -65,7 +70,7 @@ static void set_config(unsigned gpio, int type)
GPIO_FULLPORT(gpio), GPIO_BIT(gpio), type ? "GPIO" : "SFPIO");
 
u = readl(&bank->gpio_config[GPIO_PORT(gpio)]);
-   if (type)   /* GPIO */
+   if (type != CONFIG_SFIO)
u |= 1 << GPIO_BIT(gpio);
else
u &= ~(1 << GPIO_BIT(gpio));
@@ -86,7 +91,7 @@ static int get_direction(unsigned gpio)
debug("get_direction: port = %d, bit = %d, %s\n",
GPIO_FULLPORT(gpio), GPIO_BIT(gpio), dir ? "OUT" : "IN");
 
-   return dir;
+   return dir ? DIRECTION_OUTPUT : DIRECTION_INPUT;
 }
 
 /* Config GPIO pin 'gpio' as input or output (OE) as per 'output' */
@@ -100,7 +105,7 @@ static void set_direction(unsigned gpio, int output)
GPIO_FULLPORT(gpio), GPIO_BIT(gpio), output ? "OUT" : "IN");
 
u = readl(&bank->gpio_dir_out[GPIO_PORT(gpio)]);
-   if (output)
+   if (output != DIRECTION_INPUT)
u |= 1 << GPIO_BIT(gpio);
else
u &= ~(1 << GPIO_BIT(gpio));
@@ -135,7 +140,7 @@ static int tegra_gpio_direction_input(struct udevice *dev, 
unsigned offset)
struct tegra_port_info *state = dev_get_priv(dev);
 
/* Configure GPIO direction as input. */
-   set_direction(state->base_gpio + offset, 0);
+   set_direction(state->base_gpio + offset, DIRECTION_INPUT);
 
/* Enable the pin as a GPIO */
set_config(state->base_gpio + offset, 1);
@@ -154,7 +159,7 @@ static int tegra_gpio_direction_output(struct udevice *dev, 
unsigned offset,
set_level(gpio, value);
 
/* Configure GPIO direction as output. */
-   set_direction(gpio, 1);
+   set_direction(gpio, DIRECTION_OUTPUT);
 
/* Enable the pin as a GPIO */
set_config(state->base_gpio + offset, 1);
@@ -199,18 +204,18 @@ void gpio_config_table(const struct tegra_gpio_config 
*config, int len)
for (i = 0; i < len; i++) {
switch (config[i].init) {
case TEGRA_GPIO_INIT_IN:
-   set_direction(config[i].gpio, 0);
+   set_direction(config[i].gpio, DIRECTION_INPUT);
break;
case TEGRA_GPIO_INIT_OUT0:
set_level(config[i].gpio, 0);
-   set_direction(config[i].gpio, 1);
+   set_direction(config[i].gpio, DIRECTION_OUTPUT);
break;
case TEGRA_GPIO_INIT_OUT1:
set_level(config[i].gpio, 1);
-   set_direction(config[i].gpio, 1);
+   set_direction(config[i].