Commit 3f7a73b5 authored by David Brown's avatar David Brown Committed by Greg Kroah-Hartman

ssbi: Comment the use of udelay()

The ssbi driver uses a busywait loop to read its status register.  Add
a comment explaining the timing of the device itself so that future
developers can better understand this delay, and possibly diagnose any
problems.
Signed-off-by: default avatarDavid Brown <davidb@codeaurora.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 97f00f71
......@@ -87,6 +87,15 @@ static inline void ssbi_writel(struct msm_ssbi *ssbi, u32 val, u32 reg)
writel(val, ssbi->base + reg);
}
/*
* Via private exchange with one of the original authors, the hardware
* should generally finish a transaction in about 5us. The worst
* case, is when using the arbiter and both other CPUs have just
* started trying to use the SSBI bus will result in a time of about
* 20us. It should never take longer than this.
*
* As such, this wait merely spins, with a udelay.
*/
static int ssbi_wait_mask(struct msm_ssbi *ssbi, u32 set_mask, u32 clr_mask)
{
u32 timeout = SSBI_TIMEOUT_US;
......@@ -161,6 +170,10 @@ msm_ssbi_write_bytes(struct msm_ssbi *ssbi, u16 addr, u8 *buf, int len)
return ret;
}
/*
* See ssbi_wait_mask for an explanation of the time and the
* busywait.
*/
static inline int
msm_ssbi_pa_transfer(struct msm_ssbi *ssbi, u32 cmd, u8 *data)
{
......
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