[RFC] ARM: OMAP: hwmod: wait for sysreset complete after enabling hwmod

[Paul Walmsley]

Hi Tero,

On Mon, 22 Oct 2012, Tero Kristo wrote:

> When waking up from off-mode, some IP blocks are reset automatically by
> hardware. For this reason, software must wait until the reset has
> completed before attempting to access the IP block.
> 
> This patch fixes for example the bug introduced by commit
> 6c31b2150ff96755d24e0ab6d6fea08a7bf5c44c ("mmc: omap_hsmmc: remove access
> to SYSCONFIG register"), in which the MMC IP block is reset during
> off-mode entry, but the code expects the module to be already available
> during the execution of context restore.
> 
> Signed-off-by: Tero Kristo <t-kristo at ti.com>
> Cc: Paul Walmsley <paul at pwsan.com>
> Cc: Benoit Cousson <b-cousson at ti.com>
> Cc: Venkatraman S <svenkatr at ti.com>

What do you think about these modifications?  The code is quite similar to 
what was in the _ocp_softreset() function, so just moved it into a 
function.  Also moved the callsite from the end of _enable_sysc() to the 
beginning, which makes more sense to me, but would like to get your 
opinion.

- Paul

From: Tero Kristo <t-kristo at ti.com>
Date: Mon, 22 Oct 2012 19:15:32 +0300
Subject: [PATCH] [RFC] ARM: OMAP: hwmod: wait for sysreset complete after
 enabling hwmod

When waking up from off-mode, some IP blocks are reset automatically by
hardware. For this reason, software must wait until the reset has
completed before attempting to access the IP block.

This patch fixes for example the bug introduced by commit
6c31b2150ff96755d24e0ab6d6fea08a7bf5c44c ("mmc: omap_hsmmc: remove access
to SYSCONFIG register"), in which the MMC IP block is reset during
off-mode entry, but the code expects the module to be already available
during the execution of context restore.

Signed-off-by: Tero Kristo <t-kristo at ti.com>
Cc: Paul Walmsley <paul at pwsan.com>
Cc: Benoit Cousson <b-cousson at ti.com>
Cc: Venkatraman S <svenkatr at ti.com>
[paul at pwsan.com: moved softreset wait code into separate function; call
 from top of _enable_sysc() rather than the bottom]

---
 arch/arm/mach-omap2/omap_hwmod.c |   56 ++++++++++++++++++++++++++++----------
 1 file changed, 42 insertions(+), 14 deletions(-)

diff --git a/arch/arm/mach-omap2/omap_hwmod.c b/arch/arm/mach-omap2/omap_hwmod.c
index 504e0e0..0356a09 100644
--- a/arch/arm/mach-omap2/omap_hwmod.c
+++ b/arch/arm/mach-omap2/omap_hwmod.c
@@ -423,6 +423,38 @@ static int _set_softreset(struct omap_hwmod *oh, u32 *v)
 }
 
 /**
+ * _wait_softreset_complete - wait for an OCP softreset to complete
+ * @oh: struct omap_hwmod * to wait on
+ *
+ * Wait until the IP block represented by @oh reports that its OCP
+ * softreset is complete.  This can be triggered by software (see
+ * _ocp_softreset()) or by hardware upon returning from off-mode (one
+ * example is HSMMC).  Waits for up to MAX_MODULE_SOFTRESET_WAIT
+ * microseconds.  Returns the number of microseconds waited.
+ */
+static int _wait_softreset_complete(struct omap_hwmod *oh)
+{
+	struct omap_hwmod_class_sysconfig *sysc;
+	u32 softrst_mask;
+	int c = 0;
+
+	sysc = oh->class->sysc;
+
+	if (sysc->sysc_flags & SYSS_HAS_RESET_STATUS)
+		omap_test_timeout((omap_hwmod_read(oh, sysc->syss_offs)
+				   & SYSS_RESETDONE_MASK),
+				  MAX_MODULE_SOFTRESET_WAIT, c);
+	else if (sysc->sysc_flags & SYSC_HAS_RESET_STATUS) {
+		softrst_mask = (0x1 << sysc->sysc_fields->srst_shift);
+		omap_test_timeout(!(omap_hwmod_read(oh, sysc->sysc_offs)
+				    & softrst_mask),
+				  MAX_MODULE_SOFTRESET_WAIT, c);
+	}
+
+	return c;
+}
+
+/**
  * _set_dmadisable: set OCP_SYSCONFIG.DMADISABLE bit in @v
  * @oh: struct omap_hwmod *
  *
@@ -1283,6 +1315,14 @@ static void _enable_sysc(struct omap_hwmod *oh)
 	if (!oh->class->sysc)
 		return;
 
+	/*
+	 * Wait until reset has completed, this is needed as the IP
+	 * block is reset automatically by hardware in some cases
+	 * (off-mode for example), and the drivers require the
+	 * IP to be ready when they access it
+	 */
+	_wait_softreset_complete(oh);
+
 	v = oh->_sysc_cache;
 	sf = oh->class->sysc->sysc_flags;
 
@@ -1805,7 +1845,7 @@ static int _am33xx_disable_module(struct omap_hwmod *oh)
  */
 static int _ocp_softreset(struct omap_hwmod *oh)
 {
-	u32 v, softrst_mask;
+	u32 v;
 	int c = 0;
 	int ret = 0;
 
@@ -1835,19 +1875,7 @@ static int _ocp_softreset(struct omap_hwmod *oh)
 	if (oh->class->sysc->srst_udelay)
 		udelay(oh->class->sysc->srst_udelay);
 
-	if (oh->class->sysc->sysc_flags & SYSS_HAS_RESET_STATUS)
-		omap_test_timeout((omap_hwmod_read(oh,
-						    oh->class->sysc->syss_offs)
-				   & SYSS_RESETDONE_MASK),
-				  MAX_MODULE_SOFTRESET_WAIT, c);
-	else if (oh->class->sysc->sysc_flags & SYSC_HAS_RESET_STATUS) {
-		softrst_mask = (0x1 << oh->class->sysc->sysc_fields->srst_shift);
-		omap_test_timeout(!(omap_hwmod_read(oh,
-						     oh->class->sysc->sysc_offs)
-				   & softrst_mask),
-				  MAX_MODULE_SOFTRESET_WAIT, c);
-	}
-
+	c = _wait_softreset_complete(oh);
 	if (c == MAX_MODULE_SOFTRESET_WAIT)
 		pr_warning("omap_hwmod: %s: softreset failed (waited %d usec)\n",
 			   oh->name, MAX_MODULE_SOFTRESET_WAIT);
-- 
1.7.10.4