Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752845AbbLaSJZ (ORCPT ); Thu, 31 Dec 2015 13:09:25 -0500 Received: from smtp40.i.mail.ru ([94.100.177.100]:56378 "EHLO smtp40.i.mail.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752454AbbLaSJV (ORCPT ); Thu, 31 Dec 2015 13:09:21 -0500 From: Roman Volkov To: arm@kernel.org Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Arnd Bergmann , Alexey Charkov , Roman Volkov , Tony Prisk , Daniel Lezcano , Thomas Gleixner Subject: [PATCH v2 RESEND 3/3] clocksource/vt8500: Add register R/W functions Date: Thu, 31 Dec 2015 21:02:07 +0300 Message-Id: <1451584927-4051-4-git-send-email-v1ron@mail.ru> X-Mailer: git-send-email 2.6.4 In-Reply-To: <1451584927-4051-1-git-send-email-v1ron@mail.ru> References: <1451584927-4051-1-git-send-email-v1ron@mail.ru> X-Mras: Ok Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5855 Lines: 178 From: Roman Volkov vt8500 timer requires special synchronization for accessing some of its registers. Define special read and write functions to handle this process transparently. Use relaxed read/write, according to the following: http://permalink.gmane.org/gmane.linux.ports.arm.kernel/117658: "For accesses to the same device we don't actually need any barriers on ARM as this is guaranteed by the architecture." To perform a read from the Timer Count register, user must write a one to the Timer Control register and wait for completion flag by polling the Timer Read Count Active bit. To perform a write to the Count or Match registers, user must poll the write completion flag for the corresponding register to ensure that the previous write completed and then write the actual value. Signed-off-by: Roman Volkov --- drivers/clocksource/vt8500_timer.c | 88 ++++++++++++++++++++++++++++---------- 1 file changed, 66 insertions(+), 22 deletions(-) diff --git a/drivers/clocksource/vt8500_timer.c b/drivers/clocksource/vt8500_timer.c index eb08d96..fd88a5b 100644 --- a/drivers/clocksource/vt8500_timer.c +++ b/drivers/clocksource/vt8500_timer.c @@ -38,32 +38,75 @@ #define VT8500_TIMER_OFFSET 0x0100 #define VT8500_TIMER_HZ 3000000 -#define TIMER_MATCH_VAL 0x0000 +#define TIMER_MATCH0_VAL 0x0000 +#define TIMER_MATCH1_VAL 0x0004 +#define TIMER_MATCH2_VAL 0x0008 +#define TIMER_MATCH3_VAL 0x000c #define TIMER_COUNT_VAL 0x0010 #define TIMER_STATUS_VAL 0x0014 #define TIMER_IER_VAL 0x001c /* interrupt enable */ #define TIMER_CTRL_VAL 0x0020 #define TIMER_AS_VAL 0x0024 /* access status */ -#define TIMER_COUNT_R_ACTIVE (1 << 5) /* not ready for read */ -#define TIMER_COUNT_W_ACTIVE (1 << 4) /* not ready for write */ -#define TIMER_MATCH_W_ACTIVE (1 << 0) /* not ready for write */ +/* R/W status flags */ +#define TIMER_COUNT_R_ACTIVE (1 << 5) +#define TIMER_COUNT_W_ACTIVE (1 << 4) +#define TIMER_MATCH3_W_ACTIVE (1 << 3) +#define TIMER_MATCH2_W_ACTIVE (1 << 2) +#define TIMER_MATCH1_W_ACTIVE (1 << 1) +#define TIMER_MATCH0_W_ACTIVE (1 << 0) #define MIN_OSCR_DELTA 16 +#define vt8500_timer_sync(bit) { while (readl_relaxed \ + (regbase + TIMER_AS_VAL) & bit) \ + cpu_relax(); } + static void __iomem *regbase; -static cycle_t vt8500_timer_read(struct clocksource *cs) +static void vt8500_timer_write(u32 value, unsigned long reg) { - writel(3, regbase + TIMER_CTRL_VAL); - while (readl(regbase + TIMER_AS_VAL) & TIMER_COUNT_R_ACTIVE) - cpu_relax(); - return readl(regbase + TIMER_COUNT_VAL); + switch (reg) { + case TIMER_COUNT_VAL: + vt8500_timer_sync(TIMER_COUNT_W_ACTIVE); + break; + case TIMER_MATCH0_VAL: + vt8500_timer_sync(TIMER_MATCH0_W_ACTIVE); + break; + case TIMER_MATCH1_VAL: + vt8500_timer_sync(TIMER_MATCH1_W_ACTIVE); + break; + case TIMER_MATCH2_VAL: + vt8500_timer_sync(TIMER_MATCH2_W_ACTIVE); + break; + case TIMER_MATCH3_VAL: + vt8500_timer_sync(TIMER_MATCH3_W_ACTIVE); + break; + } + + writel_relaxed(value, regbase + reg); +} + +static u32 vt8500_timer_read(unsigned long reg) +{ + if (reg == TIMER_COUNT_VAL) { + vt8500_timer_write(3, TIMER_CTRL_VAL); + vt8500_timer_sync(TIMER_COUNT_R_ACTIVE); + + return readl_relaxed(regbase + TIMER_COUNT_VAL); + } + + return readl_relaxed(regbase + reg); +} + +static cycle_t vt8500_oscr0_read(struct clocksource *cs) +{ + return vt8500_timer_read(TIMER_COUNT_VAL); } static struct clocksource clocksource = { .name = "vt8500_timer", .rating = 200, - .read = vt8500_timer_read, + .read = vt8500_oscr0_read, .mask = CLOCKSOURCE_MASK(32), .flags = CLOCK_SOURCE_IS_CONTINUOUS, }; @@ -71,23 +114,24 @@ static struct clocksource clocksource = { static int vt8500_timer_set_next_event(unsigned long cycles, struct clock_event_device *evt) { - cycle_t alarm = clocksource.read(&clocksource) + cycles; - while (readl(regbase + TIMER_AS_VAL) & TIMER_MATCH_W_ACTIVE) - cpu_relax(); - writel((unsigned long)alarm, regbase + TIMER_MATCH_VAL); + unsigned long alarm = vt8500_timer_read(TIMER_COUNT_VAL) + cycles; - if ((signed)(alarm - clocksource.read(&clocksource)) <= MIN_OSCR_DELTA) + vt8500_timer_write(alarm, TIMER_MATCH0_VAL); + if ((signed)(alarm - vt8500_timer_read( + TIMER_COUNT_VAL)) <= MIN_OSCR_DELTA) { return -ETIME; + } - writel(1, regbase + TIMER_IER_VAL); + vt8500_timer_write(1, TIMER_IER_VAL); return 0; } static int vt8500_shutdown(struct clock_event_device *evt) { - writel(readl(regbase + TIMER_CTRL_VAL) | 1, regbase + TIMER_CTRL_VAL); - writel(0, regbase + TIMER_IER_VAL); + vt8500_timer_write(vt8500_timer_read(TIMER_CTRL_VAL) | 1, + TIMER_CTRL_VAL); + vt8500_timer_write(0, TIMER_IER_VAL); return 0; } @@ -103,7 +147,7 @@ static struct clock_event_device clockevent = { static irqreturn_t vt8500_timer_interrupt(int irq, void *dev_id) { struct clock_event_device *evt = dev_id; - writel(0xf, regbase + TIMER_STATUS_VAL); + vt8500_timer_write(0xf, TIMER_STATUS_VAL); evt->event_handler(evt); return IRQ_HANDLED; @@ -133,9 +177,9 @@ static void __init vt8500_timer_init(struct device_node *np) return; } - writel(1, regbase + TIMER_CTRL_VAL); - writel(0xf, regbase + TIMER_STATUS_VAL); - writel(~0, regbase + TIMER_MATCH_VAL); + vt8500_timer_write(1, TIMER_CTRL_VAL); + vt8500_timer_write(0xf, TIMER_STATUS_VAL); + vt8500_timer_write(~0, TIMER_MATCH0_VAL); if (clocksource_register_hz(&clocksource, VT8500_TIMER_HZ)) pr_err("%s: vt8500_timer_init: clocksource_register failed for %s\n", -- 2.6.2 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/