[RFC PATCH 1/5] thermal: MT8173: Replace mutex with spinlock

Pi-Cheng Chen
2016-01-22T08:40:25Z

Currently switching between the block of banked registers of Mediatek
thermal controller is synchronized by a mutex. Replace it with spinlock
since switching between register banks might happen in interrupt
context in SVS driver which will be introduced later.

Signed-off-by: Pi-Cheng Chen <pi-cheng.chen@linaro.org>
---
drivers/thermal/mtk_thermal.c | 35 ++++++++++++-----------------------
1 file changed, 12 insertions(+), 23 deletions(-)

diff --git a/drivers/thermal/mtk_thermal.c b/drivers/thermal/mtk_thermal.c
index 3c233b8..f20e784 100644
--- a/drivers/thermal/mtk_thermal.c
+++ b/drivers/thermal/mtk_thermal.c
@@ -135,7 +135,7 @@ struct mtk_thermal {

struct mtk_thermal_bank banks[MT8173_NUM_ZONES];

- struct mutex lock;
+ spinlock_t lock;

/* Calibration values */
s32 adc_ge;
@@ -222,19 +222,17 @@ static int raw_to_mcelsius(struct mtk_thermal *mt, int sensno, s32 raw)
}

/**
- * mtk_thermal_get_bank - get bank
+ * mtk_thermal_switch_bank - switch to bank
* @bank: The bank
*
* The bank registers are banked, we have to select a bank in the
* PTPCORESEL register to access it.
*/
-static void mtk_thermal_get_bank(struct mtk_thermal_bank *bank)
+static void mtk_thermal_switch_bank(struct mtk_thermal_bank *bank)
{
struct mtk_thermal *mt = bank->mt;
u32 val;

- mutex_lock(&mt->lock);
-
val = readl(mt->thermal_base + PTPCORESEL);
val &= ~0xf;
val |= bank->id;
@@ -242,19 +240,6 @@ static void mtk_thermal_get_bank(struct mtk_thermal_bank *bank)
}

/**
- * mtk_thermal_put_bank - release bank
- * @bank: The bank
- *
- * release a bank previously taken with mtk_thermal_get_bank,
- */
-static void mtk_thermal_put_bank(struct mtk_thermal_bank *bank)
-{
- struct mtk_thermal *mt = bank->mt;
-
- mutex_unlock(&mt->lock);
-}
-
-/**
* mtk_thermal_bank_temperature - get the temperature of a bank
* @bank: The bank
*
@@ -297,13 +282,15 @@ static int mtk_read_temp(void *data, int *temperature)

for (i = 0; i < MT8173_NUM_ZONES; i++) {
struct mtk_thermal_bank *bank = &mt->banks[i];
+ unsigned long flags;
int t;

- mtk_thermal_get_bank(bank);
+ spin_lock_irqsave(&mt->lock, flags);
+ mtk_thermal_switch_bank(bank);

t = mtk_thermal_bank_temperature(bank);

- mtk_thermal_put_bank(bank);
+ spin_unlock_irqrestore(&mt->lock, flags);

if (t > tempmax)
tempmax = t;
@@ -323,12 +310,14 @@ static void mtk_thermal_init_bank(struct mtk_thermal *mt, int num,
{
struct mtk_thermal_bank *bank = &mt->banks[num];
const struct mtk_thermal_bank_cfg *cfg = &bank_data[num];
+ unsigned long flags;
int i;

bank->id = num;
bank->mt = mt;

- mtk_thermal_get_bank(bank);
+ spin_lock_irqsave(&mt->lock, flags);
+ mtk_thermal_switch_bank(bank);

/* bus clock 66M counting unit is 12 * 15.15ns * 256 = 46.540us */
writel(TEMP_MONCTL1_PERIOD_UNIT(12), mt->thermal_base + TEMP_MONCTL1);
@@ -416,7 +405,7 @@ static void mtk_thermal_init_bank(struct mtk_thermal *mt, int num,
writel(TEMP_ADCWRITECTRL_ADC_PNP_WRITE | TEMP_ADCWRITECTRL_ADC_MUX_WRITE,
mt->thermal_base + TEMP_ADCWRITECTRL);

- mtk_thermal_put_bank(bank);
+ spin_unlock_irqrestore(&mt->lock, flags);
}

static u64 of_get_phys_base(struct device_node *np)
@@ -513,7 +502,7 @@ static int mtk_thermal_probe(struct platform_device *pdev)
if (ret)
return ret;

- mutex_init(&mt->lock);
+ spin_lock_init(&mt->lock);

mt->dev = &pdev->dev;

--
1.9.1