Hello!
i.MX6 RM says that setting software reset bit in CR register of GPT
(general purpose timers) should resets all of the registers of GPT to
their default reset values, except for the CLKSRC, EN, ENMOD, STOPEN,
WAITEN, and DBGEN bits in CR. But current implementation does the
opposite for CR register (it clears CLKSRC and friends bits and
preserves the others).
Most importantly this leads to that software reset bit doesn't clears
automatically.
I have a look at git history and found that software reset bit was being
cleared before 462566fc5e3 commit.
I have doubts about the correct fixing of this problem. I don't really
understand the nature of the "/Soft reset doesn't touch some bits; hard
reset clears them/" comment in /imx_gpt_reset/ function, does it mean
that /imx_gpt_reset/ performs a hard reset or soft reset? I see two
possible fixings:
1. If /imx_gpt_reset/ purpose is to do a software reset of device, then
we should fix this function. My patch at the end of email fixes this
function.
2. If /imx_gpt_reset/ purpose is to do a hard reset of device? then
there should be another function to software reset of device. If so I
can create a new patch.
---
From e12f689a2f41d18a29714771d83e343ca5195b61 Mon Sep 17 00:00:00 2001
From: Kurban Mallachiev <mallach...@ispras.ru>
Date: Fri, 17 Feb 2017 20:30:49 +0300
Subject: [PATCH] i.MX timers: fix software reset
Software reset function clears CR bits that should not clear and
preserves bits that should clear.
Signed-off-by: Kurban Mallachiev <mallach...@ispras.ru>
---
hw/timer/imx_gpt.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/hw/timer/imx_gpt.c b/hw/timer/imx_gpt.c
index 010ccbf207..9777160f49 100644
--- a/hw/timer/imx_gpt.c
+++ b/hw/timer/imx_gpt.c
@@ -306,8 +306,8 @@ static void imx_gpt_reset(DeviceState *dev)
/*
* Soft reset doesn't touch some bits; hard reset clears them
*/
- s->cr &= ~(GPT_CR_EN|GPT_CR_ENMOD|GPT_CR_STOPEN|GPT_CR_DOZEN|
- GPT_CR_WAITEN|GPT_CR_DBGEN);
+ s->cr &= GPT_CR_EN|GPT_CR_ENMOD|GPT_CR_STOPEN|GPT_CR_DOZEN|
+ GPT_CR_WAITEN|GPT_CR_DBGEN;
s->sr = 0;
s->pr = 0;
s->ir = 0;
--
2.11.1
