> -----Original Message-----
> From: linux-omap-ow...@vger.kernel.org
> [mailto:linux-omap-ow...@vger.kernel.org] On Behalf Of Grant Erickson
> Sent: Monday, November 15, 2010 12:59 AM
> To: linux-omap@vger.kernel.org
> Cc: Tony Lindgren
> Subject: [PATCH] Add OMAP Support for Generic PWM Devices
> using Dual-mode Timers
>
> This patch adds support to request and use one or more of the OMAP
> dual-mode timers as a generic PWM device compatible with other generic
> PWM drivers such as the PWM backlight or PWM beeper driver.
>
> Boards can register such devices using platform data such as
> in the following
> example:
>
> static struct omap2_pwm_platform_config pwm_config = {
> .timer_id = 10, // GPT10_PWM_EVT
> .polarity = 1 // Active-high
> };
>
> static struct platform_device pwm_device = {
> .name = "omap-pwm",
> .id = 0,
> .dev = {
> .platform_data = &pwm_config
> }
> };
>
> Signed-off-by: Grant Erickson <maratho...@gmail.com>
[snip]...[snip]
[sp] Few additional comments that should be considered while submitting
next patch revision.
> +/* Preprocessor Definitions */
> +
> +#undef OMAP_PWM_DEBUG
> +
> +#if defined(OMAP_PWM_DEBUG)
> +#define DBG(args...) \
> + do { \
> + pr_info(args); \
> + } while (0)
> +#define DEV_DBG(dev, args...) \
> + do { \
> + dev_info(dev, args); \
> + } while (0)
> +#else
> +#define DBG(args...) \
> + do { } while (0)
> +#define DEV_DBG(dev, args...) \
> + do { } while (0)
> +#endif /* defined(OMAP_PWM_DEBUG) */
[sp] pr_info(), dev_info() are already macros - conditional to DEBUG.
We should use them instead of defining another layer.
> +
> +#define DM_TIMER_LOAD_MIN 0xFFFFFFFE
> +
> +/* Type Definitions */
> +
> +/**
> + * struct pwm_device - opaque internal PWM device instance state
> + * @head: list head for all PWMs managed by this driver.
> + * @pdev: corresponding platform device associated with this
> device instance.
> + * @dm_timer: corresponding dual-mode timer associated with
> this device
> + * instance.
> + * @config: platform-specific configuration data.
> + * @label: description label.
> + * @use_count: use count.
> + * @pwm_id: generic PWM ID requested for this device instance.
> + *
> + * As far as clients of the PWM driver are concerned, PWM devices are
> + * opaque abstract objects. Consequently, this structure is used for
> + * tracking internal device instance state but is otherwise just a
> + * instance reference externally.
> + */
> +
> +struct pwm_device {
> + struct list_head head;
> + struct platform_device *pdev;
> + struct omap_dm_timer *dm_timer;
> + struct omap2_pwm_platform_config config;
> + const char
> *label;
> + unsigned int use_count;
> + unsigned int pwm_id;
> +};
[sp] This block has mix of tabs and white spaces. We should be consistent.
There are similar instances below as well...
You may also want to line up the field names - they start at different
columns.
> +
> +/* Function Prototypes */
> +
> +static int __devinit omap_pwm_probe(struct platform_device *pdev);
> +static int __devexit omap_pwm_remove(struct platform_device *pdev);
> +
> +/* Global Variables */
> +
> +static struct platform_driver omap_pwm_driver = {
> + .driver = {
> + .name = "omap-pwm",
> + .owner = THIS_MODULE,
> + },
> + .probe = omap_pwm_probe,
> + .remove = __devexit_p(omap_pwm_remove)
> +};
> +
> +/* List and associated lock for managing generic PWM devices bound to
> + * this driver.
> + */
> +
[sp] White space not needed. Similar instances below as well.
> +static DEFINE_MUTEX(pwm_lock);
> +static LIST_HEAD(pwm_list);
> +
[snip]...[snip]
> +/**
> + * pwm_config - configures the generic PWM device to the
> specified parameters.
> + * @pwm: A pointer to the PWM device to configure.
> + * @duty_ns: The duty period of the PWM, in nanoseconds.
> + * @period_ns: The overall period of the PWM, in nanoseconds.
> + *
> + * Returns 0 if the generic PWM device was successfully configured;
> + * otherwise, < 0 on error.
> + */
> +int pwm_config(struct pwm_device *pwm, int duty_ns, int period_ns)
> +{
> + int status = 0;
> + const bool enable = true;
> + const bool autoreload = true;
> + const bool toggle = true;
> + const int trigger = OMAP_TIMER_TRIGGER_OVERFLOW_AND_COMPARE;
[sp] Based on code abobe, I believe that OMAP...COMPARE is macro;
shouldn't we use it as is - where trigger is used in code below?
> + int load_value, match_value;
> + unsigned long clk_rate;
> +
> + DEV_DBG(&pwm->pdev->dev,
> + "duty cycle: %d, period %d\n",
> + duty_ns, period_ns);
> +
> + clk_rate = clk_get_rate(omap_dm_timer_get_fclk(pwm->dm_timer));
> +
> + /* Calculate the appropriate load and match values based on the
> + * specified period and duty cycle. The load value determines the
> + * cycle time and the match value determines the duty cycle.
> + */
> +
> + load_value = pwm_calc_value(clk_rate, period_ns);
> + match_value = pwm_calc_value(clk_rate, period_ns - duty_ns);
> +
> + /* We MUST enable yet stop the associated dual-mode timer before
> + * attempting to write its registers.
> + */
> +
> + omap_dm_timer_enable(pwm->dm_timer);
> + omap_dm_timer_stop(pwm->dm_timer);
> +
> + omap_dm_timer_set_load(pwm->dm_timer, autoreload, load_value);
> + omap_dm_timer_set_match(pwm->dm_timer, enable, match_value);
> +
> + DEV_DBG(&pwm->pdev->dev,
> + "load value: %#08x (%d), "
> + "match value: %#08x (%d)\n",
> + load_value, load_value,
> + match_value, match_value);
> +
> + omap_dm_timer_set_pwm(pwm->dm_timer,
> + !pwm->config.polarity,
> + toggle,
> + trigger);
> +
> + /* Set the counter to generate an overflow event immediately. */
> +
> + omap_dm_timer_write_counter(pwm->dm_timer, DM_TIMER_LOAD_MIN);
[sp] I am assuming that call to this function would be followed by
another call to pwm_enable().
omap_dm_timer_write_counter() is being called in pwm_enable()
with exactly same arguments. Is is necessary duplication?
If no, call here should be removed.
> +
> + /* Now that we're done configuring the dual-mode timer, disable it
> + * again. We'll enable and start it later, when requested.
> + */
> +
> + omap_dm_timer_disable(pwm->dm_timer);
> +
> + return status;
> +}
> +EXPORT_SYMBOL(pwm_config);
> +
> +/**
> + * pwm_enable - enable the generic PWM device.
> + * @pwm: A pointer to the generic PWM device to enable.
> + *
> + * Returns 0 if the generic PWM device was successfully enabled;
> + * otherwise, < 0 on error.
> + */
> +int pwm_enable(struct pwm_device *pwm)
> +{
> + int status = 0;
[sp] This variable isn't assigned/modified below. Not required.
function can simply return 0.
> +
> + /* Enable the counter--always--before attempting to write its
> + * registers and then set the timer to its minimum load value to
> + * ensure we get an overflow event right away once we start it.
> + */
> +
> + omap_dm_timer_enable(pwm->dm_timer);
> + omap_dm_timer_write_counter(pwm->dm_timer, DM_TIMER_LOAD_MIN);
> + omap_dm_timer_start(pwm->dm_timer);
> +
> + return status;
> +}
> +EXPORT_SYMBOL(pwm_enable);
> +
> +/**
> + * pwm_disable - disable the generic PWM device.
> + * @pwm: A pointer to the generic PWM device to disable.
> + */
> +void pwm_disable(struct pwm_device *pwm)
> +{
> + omap_dm_timer_enable(pwm->dm_timer);
> + omap_dm_timer_stop(pwm->dm_timer);
> + omap_dm_timer_disable(pwm->dm_timer);
> +}
> +EXPORT_SYMBOL(pwm_disable);
> +
> +/**
> + * omap_pwm_probe - check for the PWM and bind it to the driver.
> + * @pdev: A pointer to the platform device node associated with the
> + * PWM instance to be probed for driver binding.
> + *
> + * Returns 0 if the PWM instance was successfully bound to
> the driver;
> + * otherwise, < 0 on error.
> + */
> +static int __devinit omap_pwm_probe(struct platform_device *pdev)
> +{
> + struct pwm_device *pwm = NULL;
> + struct omap2_pwm_platform_config *pdata = NULL;
> + int status = 0;
> +
> + pdata = ((struct omap2_pwm_platform_config
> *)(pdev->dev.platform_data));
> +
> + BUG_ON(pdata == NULL);
> +
> + if (pdata == NULL) {
> + dev_err(&pdev->dev, "Could not find required
> platform data.\n");
> + status = -ENOENT;
> + goto done;
[sp] We can simply return status from here. goto and label can be avoided.
> + }
> +
> + /* Allocate memory for the driver-private PWM data and state */
> +
> + pwm = kzalloc(sizeof(struct pwm_device), GFP_KERNEL);
> +
> + if (pwm == NULL) {
> + dev_err(&pdev->dev, "Could not allocate memory.\n");
> + status = -ENOMEM;
> + goto done;
[sp] We can simply return status from here. goto and label can be avoided.
> + }
> +
> + /* Request the OMAP dual-mode timer that will be bound to and
> + * associated with this generic PWM.
> + */
> +
> + pwm->dm_timer = omap_dm_timer_request_specific(pdata->timer_id);
> +
> + if (pwm->dm_timer == NULL) {
> + status = -ENOENT;
> + goto err_free;
> + }
> +
> + /* Configure the source for the dual-mode timer backing this
> + * generic PWM device. The clock source will ultimately
> determine
> + * how small or large the PWM frequency can be.
> + *
> + * At some point, it's probably worth revisiting moving this to
> + * the configure method and choosing either the slow- or
> + * system-clock source as appropriate for the desired
> PWM period.
> + */
> +
> + omap_dm_timer_set_source(pwm->dm_timer, OMAP_TIMER_SRC_SYS_CLK);
> +
> + /* Cache away other miscellaneous driver-private data and state
> + * information and add the driver-private data to the platform
> + * device.
> + */
> +
> + pwm->pdev = pdev;
> + pwm->pwm_id = pdev->id;
> + pwm->config = *pdata;
> +
> + platform_set_drvdata(pdev, pwm);
> +
> + /* Finally, push the added generic PWM device to the end of the
> + * list of available generic PWM devices.
> + */
> +
> + mutex_lock(&pwm_lock);
> + list_add_tail(&pwm->head, &pwm_list);
> + mutex_unlock(&pwm_lock);
> +
> + status = 0;
> + goto done;
> +
> + err_free:
> + kfree(pwm);
> +
> + done:
> + return status;
> +}
> +
> +/**
> + * omap_pwm_remove - unbind the specified PWM platform
> device from the driver.
> + * @pdev: A pointer to the platform device node associated with the
> + * PWM instance to be unbound/removed.
> + *
> + * Returns 0 if the PWM was successfully removed as a
> platform device;
> + * otherwise, < 0 on error.
> + */
> +static int __devexit omap_pwm_remove(struct platform_device *pdev)
> +{
> + struct pwm_device *pwm = NULL;
> + int status = 0;
> +
> + /* Attempt to get the driver-private data from the
> platform device
> + * node.
> + */
> +
> + pwm = platform_get_drvdata(pdev);
> +
> + if (pwm == NULL) {
> + status = -ENODEV;
> + goto done;
[sp] We can simply return status from here. goto and label can be avoided.
> + }
> +
> + /* Remove the generic PWM device from the list of available
> + * generic PWM devices.
> + */
> +
> + mutex_lock(&pwm_lock);
> + list_del(&pwm->head);
> + mutex_unlock(&pwm_lock);
> +
> + /* Unbind the OMAP dual-mode timer associated with the
> generic PWM
> + * device.
> + */
> +
> + omap_dm_timer_free(pwm->dm_timer);
> +
> + /* Finally, release the memory associated with the
> driver-private
> + * data and state.
> + */
> +
> + kfree(pwm);
> +
> + done:
> + return status;
> +}
[snip]...[snip]
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