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watchdog: stm32: add dynamic prescaler support 

This patch allows to define the max prescaler by compatible.
To set a large range of timeout, the prescaler should be set
dynamically (from the timeout request) to improve the resolution
in order to have a timeout close to the expected value.

Signed-off-by: Ludovic Barre <ludovic.barre@st.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>
This commit is contained in:
Ludovic Barre 2019-05-03 15:48:26 +02:00 committed by Wim Van Sebroeck
parent 345f162510
commit e9974166a5
1 changed files with 47 additions and 37 deletions
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84
drivers/watchdog/stm32_iwdg.c
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@ -34,36 +34,44 @@
#define KR_KEY_EWA 0x5555 /* write access enable */
#define KR_KEY_DWA 0x0000 /* write access disable */
/* IWDG_PR register bit values */
#define PR_4 0x00 /* prescaler set to 4 */
#define PR_8 0x01 /* prescaler set to 8 */
#define PR_16 0x02 /* prescaler set to 16 */
#define PR_32 0x03 /* prescaler set to 32 */
#define PR_64 0x04 /* prescaler set to 64 */
#define PR_128 0x05 /* prescaler set to 128 */
#define PR_256 0x06 /* prescaler set to 256 */
/* IWDG_PR register */
#define PR_SHIFT 2
#define PR_MIN BIT(PR_SHIFT)
/* IWDG_RLR register values */
#define RLR_MIN 0x07C /* min value supported by reload register */
#define RLR_MAX 0xFFF /* max value supported by reload register */
#define RLR_MIN 0x2 /* min value recommended */
#define RLR_MAX GENMASK(11, 0) /* max value of reload register */
/* IWDG_SR register bit mask */
#define FLAG_PVU BIT(0) /* Watchdog prescaler value update */
#define FLAG_RVU BIT(1) /* Watchdog counter reload value update */
#define SR_PVU BIT(0) /* Watchdog prescaler value update */
#define SR_RVU BIT(1) /* Watchdog counter reload value update */
/* set timeout to 100000 us */
#define TIMEOUT_US 100000
#define SLEEP_US 1000
#define HAS_PCLK true
struct stm32_iwdg_data {
bool has_pclk;
u32 max_prescaler;
};
static const struct stm32_iwdg_data stm32_iwdg_data = {
.has_pclk = false,
.max_prescaler = 256,
};
static const struct stm32_iwdg_data stm32mp1_iwdg_data = {
.has_pclk = true,
.max_prescaler = 1024,
};
struct stm32_iwdg {
struct watchdog_device wdd;
const struct stm32_iwdg_data *data;
void __iomem *regs;
struct clk *clk_lsi;
struct clk *clk_pclk;
unsigned int rate;
bool has_pclk;
};
static inline u32 reg_read(void __iomem *base, u32 reg)
@ -79,31 +87,35 @@ static inline void reg_write(void __iomem *base, u32 reg, u32 val)
static int stm32_iwdg_start(struct watchdog_device *wdd)
{
struct stm32_iwdg *wdt = watchdog_get_drvdata(wdd);
u32 val = FLAG_PVU | FLAG_RVU;
u32 reload;
u32 tout, presc, iwdg_rlr, iwdg_pr, iwdg_sr;
int ret;
dev_dbg(wdd->parent, "%s\n", __func__);
/* prescaler fixed to 256 */
reload = clamp_t(unsigned int, ((wdd->timeout * wdt->rate) / 256) - 1,
RLR_MIN, RLR_MAX);
tout = clamp_t(unsigned int, wdd->timeout,
wdd->min_timeout, wdd->max_hw_heartbeat_ms / 1000);
presc = DIV_ROUND_UP(tout * wdt->rate, RLR_MAX + 1);
/* The prescaler is align on power of 2 and start at 2 ^ PR_SHIFT. */
presc = roundup_pow_of_two(presc);
iwdg_pr = presc <= 1 << PR_SHIFT ? 0 : ilog2(presc) - PR_SHIFT;
iwdg_rlr = ((tout * wdt->rate) / presc) - 1;
/* enable write access */
reg_write(wdt->regs, IWDG_KR, KR_KEY_EWA);
/* set prescaler & reload registers */
reg_write(wdt->regs, IWDG_PR, PR_256); /* prescaler fix to 256 */
reg_write(wdt->regs, IWDG_RLR, reload);
reg_write(wdt->regs, IWDG_PR, iwdg_pr);
reg_write(wdt->regs, IWDG_RLR, iwdg_rlr);
reg_write(wdt->regs, IWDG_KR, KR_KEY_ENABLE);
/* wait for the registers to be updated (max 100ms) */
ret = readl_relaxed_poll_timeout(wdt->regs + IWDG_SR, val,
!(val & (FLAG_PVU | FLAG_RVU)),
ret = readl_relaxed_poll_timeout(wdt->regs + IWDG_SR, iwdg_sr,
!(iwdg_sr & (SR_PVU | SR_RVU)),
SLEEP_US, TIMEOUT_US);
if (ret) {
dev_err(wdd->parent,
"Fail to set prescaler or reload registers\n");
dev_err(wdd->parent, "Fail to set prescaler, reload regs\n");
return ret;
}
@ -156,7 +168,7 @@ static int stm32_iwdg_clk_init(struct platform_device *pdev,
}
/* optional peripheral clock */
if (wdt->has_pclk) {
if (wdt->data->has_pclk) {
wdt->clk_pclk = devm_clk_get(dev, "pclk");
if (IS_ERR(wdt->clk_pclk)) {
dev_err(dev, "Unable to get pclk clock\n");
@ -205,8 +217,8 @@ static const struct watchdog_ops stm32_iwdg_ops = {
};
static const struct of_device_id stm32_iwdg_of_match[] = {
{ .compatible = "st,stm32-iwdg", .data = (void *)!HAS_PCLK },
{ .compatible = "st,stm32mp1-iwdg", .data = (void *)HAS_PCLK },
{ .compatible = "st,stm32-iwdg", .data = &stm32_iwdg_data },
{ .compatible = "st,stm32mp1-iwdg", .data = &stm32mp1_iwdg_data },
{ /* end node */ }
};
MODULE_DEVICE_TABLE(of, stm32_iwdg_of_match);
@ -215,19 +227,16 @@ static int stm32_iwdg_probe(struct platform_device *pdev)
{
struct device *dev = &pdev->dev;
struct watchdog_device *wdd;
const struct of_device_id *match;
struct stm32_iwdg *wdt;
int ret;
match = of_match_device(stm32_iwdg_of_match, dev);
if (!match)
return -ENODEV;
wdt = devm_kzalloc(dev, sizeof(*wdt), GFP_KERNEL);
if (!wdt)
return -ENOMEM;
wdt->has_pclk = match->data;
wdt->data = of_device_get_match_data(&pdev->dev);
if (!wdt->data)
return -ENODEV;
/* This is the timer base. */
wdt->regs = devm_platform_ioremap_resource(pdev, 0);
@ -242,11 +251,12 @@ static int stm32_iwdg_probe(struct platform_device *pdev)
/* Initialize struct watchdog_device. */
wdd = &wdt->wdd;
wdd->parent = dev;
wdd->info = &stm32_iwdg_info;
wdd->ops = &stm32_iwdg_ops;
wdd->min_timeout = ((RLR_MIN + 1) * 256) / wdt->rate;
wdd->max_hw_heartbeat_ms = ((RLR_MAX + 1) * 256 * 1000) / wdt->rate;
wdd->parent = dev;
wdd->min_timeout = DIV_ROUND_UP((RLR_MIN + 1) * PR_MIN, wdt->rate);
wdd->max_hw_heartbeat_ms = ((RLR_MAX + 1) * wdt->data->max_prescaler *
1000) / wdt->rate;
watchdog_set_drvdata(wdd, wdt);
watchdog_set_nowayout(wdd, WATCHDOG_NOWAYOUT);