From 7cfe249475fdd82ad3c2767a9b906cc775dab868 Mon Sep 17 00:00:00 2001 From: Russell King Date: Thu, 15 Jul 2010 10:47:14 +0100 Subject: ARM: AMBA: Add pclk support to AMBA bus infrastructure Some platforms gate the pclk (APB - the bus - clock) to the peripherals for power saving, along with the functional clock. When devices are accessed without pclk enabled, the kernel will oops. This gives them two options: 1. Leave all clocks on all the time. 2. Attempt to gate pclk along with the functional clock. (With some hardware, pclk and the functional clock are gated by a single bit in a register.) (1) has the disadvantage that it causes increased power usage, which is bad news for battery operated devices. (2) can lead to kernel oops if registers are accessed without the functional clock being enabled. So, introduce the apb_pclk signal in such a way existing drivers don't need to be updated. Essentially, this means we guarantee that: 1. pclk will be enabled whenever the driver is bound to a device - from probe() to remove() time. 2. pclk will also be enabled when reading the primecell IDs from the device. In order to allow drivers to be incrementally updated to achieve greater power savings, we provide two additional calls to allow drivers to manage the pclk - amba_pclk_enable()/amba_pclk_disable(). Signed-off-by: Russell King --- include/linux/amba/bus.h | 11 +++++++++++ 1 file changed, 11 insertions(+) (limited to 'include') diff --git a/include/linux/amba/bus.h b/include/linux/amba/bus.h index 8b103860783..b0c17401243 100644 --- a/include/linux/amba/bus.h +++ b/include/linux/amba/bus.h @@ -14,14 +14,19 @@ #ifndef ASMARM_AMBA_H #define ASMARM_AMBA_H +#include #include +#include #include #define AMBA_NR_IRQS 2 +struct clk; + struct amba_device { struct device dev; struct resource res; + struct clk *pclk; u64 dma_mask; unsigned int periphid; unsigned int irq[AMBA_NR_IRQS]; @@ -59,6 +64,12 @@ struct amba_device *amba_find_device(const char *, struct device *, unsigned int int amba_request_regions(struct amba_device *, const char *); void amba_release_regions(struct amba_device *); +#define amba_pclk_enable(d) \ + (IS_ERR((d)->pclk) ? 0 : clk_enable((d)->pclk)) + +#define amba_pclk_disable(d) \ + do { if (!IS_ERR((d)->pclk)) clk_disable((d)->pclk); } while (0) + #define amba_config(d) (((d)->periphid >> 24) & 0xff) #define amba_rev(d) (((d)->periphid >> 20) & 0x0f) #define amba_manf(d) (((d)->periphid >> 12) & 0xff) -- cgit v1.2.3-70-g09d2