Thara,
> -----Original Message-----
> From: Gopinath, Thara
> Sent: Friday, July 02, 2010 3:48 PM
> To: linux-omap@vger.kernel.org
> Cc: khil...@deeprootsystems.com; p...@pwsan.com; Cousson, Benoit; Sripathy,
> Vishwanath; Sawant, Anand; Basak, Partha; Gopinath, Thara
> Subject: [RFC 1/7] OMAP: Introduce a user list for each voltage domain
> instance in
> the voltage driver.
>
> This patch introduces a user list of devices associated with each
> voltage domain instance. The user list is implemented using plist
> structure with priority node populated with the voltage values.
> This patch also adds an API which will take in a device and
> requested voltage as parameters, adds the info to the user list
> and returns back the maximum voltage requested by all the user
> devices. This can be used anytime to get the voltage that the
> voltage domain instance can be transitioned into.
>
> Signed-off-by: Thara Gopinath <th...@ti.com>
> ---
> arch/arm/mach-omap2/voltage.c | 83
> +++++++++++++++++++++++++++++
> arch/arm/plat-omap/include/plat/voltage.h | 2 +
> 2 files changed, 85 insertions(+), 0 deletions(-)
>
> diff --git a/arch/arm/mach-omap2/voltage.c b/arch/arm/mach-omap2/voltage.c
> index 30f1770..a2f30a4 100644
> --- a/arch/arm/mach-omap2/voltage.c
> +++ b/arch/arm/mach-omap2/voltage.c
> @@ -24,6 +24,9 @@
> #include <linux/clk.h>
> #include <linux/err.h>
> #include <linux/debugfs.h>
> +#include <linux/spinlock.h>
> +#include <linux/plist.h>
> +#include <linux/slab.h>
>
> #include <plat/omap-pm.h>
> #include <plat/omap34xx.h>
> @@ -93,6 +96,20 @@ struct vp_reg_val {
> };
>
> /**
> + * omap_vdd_user_list - The per vdd user list
> + *
> + * @dev : The device asking for the vdd to be set at a
> particular
> + * voltage
> + * @node : The list head entry
> + * @volt : The voltage requested by the device <dev>
> + */
> +struct omap_vdd_user_list {
> + struct device *dev;
> + struct plist_node node;
> + u32 volt;
> +};
> +
> +/**
> * omap_vdd_info - Per Voltage Domain info
> *
> * @volt_data : voltage table having the distinct voltages
> supported
> @@ -103,6 +120,9 @@ struct vp_reg_val {
> * vp registers
> * @volt_clk : the clock associated with the vdd.
> * @opp_dev : the 'struct device' associated with this vdd.
> + * @user_lock : the lock to be used by the plist user_list
> + * @user_list : the list head maintaining the various users
> + * of this vdd with the voltage requested by each user.
> * @volt_data_count : Number of distinct voltages supported by this vdd.
> * @nominal_volt : Nominal voltaged for this vdd.
> * cmdval_reg : Voltage controller cmdval register.
> @@ -115,6 +135,8 @@ struct omap_vdd_info{
> struct clk *volt_clk;
> struct device *opp_dev;
> struct omap_volt_domain volt_domain;
> + spinlock_t user_lock;
> + struct plist_head user_list;
> int volt_data_count;
> unsigned long nominal_volt;
> u8 cmdval_reg;
> @@ -361,6 +383,10 @@ static void __init omap3_vdd_data_configure(struct
> omap_vdd_info *vdd)
> struct clk *sys_ck;
> u32 sys_clk_speed, timeout_val, waittime;
>
> + /* Init the plist */
> + spin_lock_init(&vdd->user_lock);
> + plist_head_init(&vdd->user_list, &vdd->user_lock);
> +
> if (!strcmp(vdd->volt_domain.name, "mpu")) {
> if (cpu_is_omap3630()) {
> vdd->vp_reg.vlimitto_vddmin =
> @@ -881,6 +907,63 @@ unsigned long omap_voltageprocessor_get_curr_volt(
> }
>
> /**
> + * omap_voltage_get_final : API to keep track of various requests to
[minor] This name does not match the actual API
> + * scale the VDD and returns the best possible
> + * voltage the VDD can be put to.
> + * @volt_domain: pointer to the voltage domain.
> + * @dev : the device pointer.
> + * @volt : the voltage which is requested by the device.
> + *
> + * This API is to be called before the actual voltage scaling is
> + * done to determine what is the best possible voltage the VDD can
> + * be put to. This API adds the device <dev> in the user list of the
> + * vdd <volt_domain> with <volt> as the requested voltage. The user list
> + * is a plist with the priority element absolute voltage values.
> + * The API then finds the maximum of all the requested voltages for
> + * the VDD and returns it back through <volt> pointer itself.
> + * Returns error value in case of any errors.
> + */
> +int omap_volt_get_final(struct omap_volt_domain *volt_domain,
> + struct device *dev, unsigned long *volt)
> +{
> + struct omap_vdd_info *vdd;
> + struct omap_vdd_user_list *user;
> + struct plist_node *node;
> + int found = 0;
> +
> + if (!volt_domain || IS_ERR(volt_domain)) {
> + pr_warning("%s: VDD specified does not exist!\n", __func__);
> + return -EINVAL;
> + }
> +
> + vdd = container_of(volt_domain, struct omap_vdd_info, volt_domain);
> +
> + plist_for_each_entry(user, &vdd->user_list, node) {
> + if (user->dev == dev) {
> + found = 1;
> + break;
> + }
> + }
> +
> + if (!found) {
> + user = kzalloc(sizeof(struct omap_vdd_user_list), GFP_KERNEL);
> + if (!user) {
> + pr_err("%s: Unable to creat a new user for vdd_%s\n",
> + __func__, volt_domain->name);
> + return -ENOMEM;
> + }
> + user->dev = dev;
> + plist_node_init(&user->node, *volt);
> + plist_add(&user->node, &vdd->user_list);
> + }
> +
> + user->node.prio = *volt;
> + node = plist_first(&vdd->user_list);
> + *volt = node->prio;
> + return 0;
Shouldn't this function be protected using a mutex_lock/semaphore? It's
possible that just after you are done with plist search, some other thread
might get scheduled and try to add the same user.
> +}
> +
> +/**
> * omap_voltageprocessor_enable : API to enable a particular VP
> * @volt_domain: pointer to the VDD whose VP is to be enabled.
> *
> diff --git a/arch/arm/plat-omap/include/plat/voltage.h b/arch/arm/plat-
> omap/include/plat/voltage.h
> index b7ac318..bc1e4d3 100644
> --- a/arch/arm/plat-omap/include/plat/voltage.h
> +++ b/arch/arm/plat-omap/include/plat/voltage.h
> @@ -128,6 +128,8 @@ int omap_get_voltage_table(struct omap_volt_domain
> *volt_domain,
> struct omap_volt_data *omap_get_volt_data(
> struct omap_volt_domain *volt_domain, unsigned long volt);
> unsigned long get_curr_voltage(struct omap_volt_domain *volt_domain);
> +int omap_volt_get_final(struct omap_volt_domain *volt_domain,
> + struct device *dev, unsigned long *volt);
> #ifdef CONFIG_PM
> void omap_voltage_init_vc(struct omap_volt_vc_data *setup_vc);
> #else
> --
> 1.7.0.rc1.33.g07cf0f
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