Re: [PATCHv2 3/8] devfreq: exynos4: Add ppmu's clock control and code clean about regulator control

From: Tomasz Figa
Date: Fri Mar 14 2014 - 13:42:41 EST

Hi Chanwoo,

On 13.03.2014 09:17, Chanwoo Choi wrote:
There are not the clock controller of ppmudmc0/1. This patch control the clock
of ppmudmc0/1 which is used for monitoring memory bus utilization.

Also, this patch code clean about regulator control and free resource
when calling exit/remove function.

For example,
busfreq@106A0000 {
compatible = "samsung,exynos4x12-busfreq";

/* Clock for PPMUDMC0/1 */
clocks = <&clock CLK_PPMUDMC0>, <&clock CLK_PPMUDMC1>;
clock-names = "ppmudmc0", "ppmudmc1";

/* Regulator for MIF/INT block */
vdd_mif-supply = <&buck1_reg>;
vdd_int-supply = <&buck3_reg>;
};

Signed-off-by: Chanwoo Choi <cw00.choi@xxxxxxxxxxx>
---
drivers/devfreq/exynos/exynos4_bus.c | 114 ++++++++++++++++++++++++++++++-----
1 file changed, 100 insertions(+), 14 deletions(-)

diff --git a/drivers/devfreq/exynos/exynos4_bus.c b/drivers/devfreq/exynos/exynos4_bus.c
index 1a0effa..a2a3a47 100644
--- a/drivers/devfreq/exynos/exynos4_bus.c
+++ b/drivers/devfreq/exynos/exynos4_bus.c
@@ -62,6 +62,11 @@ enum exynos_ppmu_idx {
PPMU_END,
};

+static const char *exynos_ppmu_clk_name[] = {
+ [PPMU_DMC0] = "ppmudmc0",
+ [PPMU_DMC1] = "ppmudmc1",
+};
+
#define EX4210_LV_MAX LV_2
#define EX4x12_LV_MAX LV_4
#define EX4210_LV_NUM (LV_2 + 1)
@@ -86,6 +91,7 @@ struct busfreq_data {
struct regulator *vdd_mif; /* Exynos4412/4212 only */
struct busfreq_opp_info curr_oppinfo;
struct exynos_ppmu ppmu[PPMU_END];
+ struct clk *clk_ppmu[PPMU_END];

struct notifier_block pm_notifier;
struct mutex lock;
@@ -722,8 +728,26 @@ static int exynos4_bus_get_dev_status(struct device *dev,
static void exynos4_bus_exit(struct device *dev)
{
struct busfreq_data *data = dev_get_drvdata(dev);
+ int i;
+
+ /*
+ * Un-map memory map and disable regulator/clocks
+ * to prevent power leakage.
+ */
+ regulator_disable(data->vdd_int);
+ if (data->type == TYPE_BUSF_EXYNOS4x12)
+ regulator_disable(data->vdd_mif);
+
+ for (i = 0; i < PPMU_END; i++) {
+ if (data->clk_ppmu[i])

This check is invalid. Clock pointers must be checked for validity using the IS_ERR() macro, because NULL is a valid clock pointer value indicating a dummy clock.

+ clk_disable_unprepare(data->clk_ppmu[i]);
+ }

- devfreq_unregister_opp_notifier(dev, data->devfreq);
+ for (i = 0; i < PPMU_END; i++) {
+ if (data->ppmu[i].hw_base)

Can this even happen? Is there a PPMU without registers?

+ iounmap(data->ppmu[i].hw_base);
+
+ }
}

static struct devfreq_dev_profile exynos4_devfreq_profile = {
@@ -987,6 +1011,7 @@ static int exynos4_busfreq_parse_dt(struct busfreq_data *data)
{
struct device *dev = data->dev;
struct device_node *np = dev->of_node;
+ const char **clk_name = exynos_ppmu_clk_name;
int i, ret;

if (!np) {
@@ -1005,8 +1030,70 @@ static int exynos4_busfreq_parse_dt(struct busfreq_data *data)
}
}

+ /*
+ * Get PPMU's clocks to control them. But, if PPMU's clocks
+ * is default 'pass' state, this driver don't need control
+ * PPMU's clock.
+ */
+ for (i = 0; i < PPMU_END; i++) {
+ data->clk_ppmu[i] = devm_clk_get(dev, clk_name[i]);
+ if (IS_ERR_OR_NULL(data->clk_ppmu[i])) {

Again, this check is invalid. Only IS_ERR() is the correct way to check whether returned clock pointer is valid.

+ dev_warn(dev, "Cannot get %s clock\n", clk_name[i]);
+ data->clk_ppmu[i] = NULL;

This assignment is wrong. To allow further checking whether the clock was found the value returned from devm_clk_get() must be retained and then IS_ERR() used in further code.

However, I believe it should be an error if a clock is not provided. The driver must make sure that PPMU clocks are ungated before trying to access them, otherwise the system might hang.

+ }
+
+ ret = clk_prepare_enable(data->clk_ppmu[i]);

The code above allows the clock to be skipped, but this line doesn't check whether it is valid. Still, I think the clock should be always required.

+ if (ret < 0) {
+ dev_warn(dev, "Cannot enable %s clock\n", clk_name[i]);
+ data->clk_ppmu[i] = NULL;
+ goto err_clocks;
+ }
+ }
+
+ /* Get regulator to control voltage of int block */
+ data->vdd_int = devm_regulator_get(dev, "vdd_int");
+ if (IS_ERR(data->vdd_int)) {
+ dev_err(dev, "Failed to get the regulator of vdd_int\n");
+ ret = PTR_ERR(data->vdd_int);
+ goto err_clocks;
+ }
+ ret = regulator_enable(data->vdd_int);
+ if (ret < 0) {
+ dev_err(dev, "Failed to enable regulator of vdd_int\n");
+ goto err_clocks;
+ }
+
+ switch (data->type) {
+ case TYPE_BUSF_EXYNOS4210:
+ break;
+ case TYPE_BUSF_EXYNOS4x12:
+ /* Get regulator to control voltage of mif blk if Exynos4x12 */
+ data->vdd_mif = devm_regulator_get(dev, "vdd_mif");
+ if (IS_ERR(data->vdd_mif)) {
+ dev_err(dev, "Failed to get the regulator vdd_mif\n");
+ ret = PTR_ERR(data->vdd_mif);
+ goto err_regulator;
+ }
+ ret = regulator_enable(data->vdd_mif);
+ if (ret < 0) {
+ dev_err(dev, "Failed to enable regulator of vdd_mif\n");
+ goto err_regulator;
+ }
+ break;
+ default:
+ dev_err(dev, "Unknown device type : %d\n", data->type);
+ return -EINVAL;
+ };
+
return 0;

+err_regulator:
+ regulator_disable(data->vdd_int);
+err_clocks:
+ for (i = 0; i < PPMU_END; i++) {
+ if (data->clk_ppmu[i])

Invalid check.

Best regards,
Tomasz
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