OMAP3: PM: Ensure MUSB is accessible before we attempt to reset it

PATCH In review Jon Hunter 3 participants 8 messages Aug 13, 2009 – Aug 18, 2009

Subsystems (4)

Arm (32-bit) Arm sub-architectures OMAP2+ support OMAP USB support

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Jon Hunter

author

2009-08-13 20:47 UTC #0 lore raw

PATCH v2 1/1 OMAP3: PM: Ensure MUSB is accessible before we attempt to reset it

From: Jon Hunter <[email protected]>

This is version 2 of this patch. I have incorporated the changes recommended by Kevin Hilman.

Depending on the OMAP3 boot mode the MUSB peripheral may or may not be accessible when the kernel starts.

The OMAP3 can boot from several devices including USB. The sequence of the devices the OMAP will attempt to boot from is configured via the sys_boot pins on the device. If USB is one of the devices the OMAP boot ROM attempts to boot from on power-on, then the interface clock to the MUSB peripheral will be enabled by the boot ROM and the MUSB peripheral will be accessible when the kernel boots. However, if USB is not one of the devices OMAP attempts to boot from, then the interface clock is not enabled and the MUSB peripheral will not be accessible on start-up.

If the MUSB peripheral is not accessible when the kernel boots, then the kernel will crash when attempting to access the OTG_SYSCONFIG in the function musb_platform_init(). The actual cause of the crash is the write to the OTG_SYSCONFIG register in the function usb_musb_pm_init() to reset the MUSB peripheral which occurs prior to calling musb_platform_init(). The function usb_musb_pm_init() does not check to see if the interface clock for the MUSB peripheral is enabled before writing to MUSB register. This write access does not generate a data-abort at this point, but because this write does not complete all future accesses to the MUSB controller will generate data-aborts regardless of whether the interface clock has been enabled at a later stage. The only way I have found to recover from this is resetting the device. My understanding is that the interconnect works in this way to prevent a bad access locking up the system.

This patch ensures the interface clock for the MUSB in the function usb_musb_pm_init() is enabled. This patch also ensures that the interface clock is disabled after the reset is complete. My reasoning for always disabling the clock rather than maintaing its state is:

1). If the MUSB peripheral is not being used then the interface clock should be disabled.
2). The musb_set_clock() function uses a static variable called "clk_on" to determine if the MUSB interface clock is on or off. On boot-up clk_on will be 0 and so this function assumes that the clock is off by default which may not be the case in the current code.

I have also added a while-loop to wait for the reset of the MUSB module to complete before this function exits and the interface clock it disabled.

Signed-off-by Jon Hunter <[email protected]>

---
 arch/arm/mach-omap2/usb-musb.c |   34 +++++++++++++++++++++++++++++++---
 1 files changed, 31 insertions(+), 3 deletions(-)

arch/arm/mach-omap2/usb-musb.c +31 -3

index 3efa19c..247f653 100644
@@ -35,10 +35,20 @@
 
 #define OTG_SYSCONFIG	   0x404
 #define OTG_SYSC_SOFTRESET BIT(1)
+#define OTG_SYSSTATUS     0x408
+#define OTG_SYSS_RESETDONE BIT(0)
+
+static struct platform_device dummy_pdev = {
+	.dev = {
+		.bus = &platform_bus_type,
+	},
+};
 
 static void __init usb_musb_pm_init(void)
 {
 	void __iomem *otg_base;
+	struct clk *otg_clk;
+	struct device *dev = &dummy_pdev.dev;
 
 	if (!cpu_is_omap34xx())
 		return;

@@ -47,9 +57,27 @@ static void __init usb_musb_pm_init(void)
 	if (WARN_ON(!otg_base))
 		return;
 
-	/* Reset OTG controller.  After reset, it will be in
-	 * force-idle, force-standby mode. */
-	__raw_writel(OTG_SYSC_SOFTRESET, otg_base + OTG_SYSCONFIG);
+	dev_set_name(dev, "musb_hdrc");
+	otg_clk = clk_get(dev, "ick");
+
+	if (otg_clk && clk_enable(otg_clk)) {
+		printk(KERN_WARNING
+			"%s: Unable to enable clocks for MUSB, "
+			"cannot reset.\n",  __func__);
+	} else {
+		/* Reset OTG controller. After reset, it will be in
+		 * force-idle, force-standby mode. */
+		__raw_writel(OTG_SYSC_SOFTRESET, otg_base + OTG_SYSCONFIG);
+
+		while (!(OTG_SYSS_RESETDONE &
+					__raw_readl(otg_base + OTG_SYSSTATUS)))
+			cpu_relax();
+	}
+
+	if (otg_clk) {
+		clk_disable(otg_clk);
+		clk_put(otg_clk);
+	}
 
 	iounmap(otg_base);
 }

Signature · 1 line

1.6.0.4

Kevin Hilman

2009-08-13 22:20 UTC #1 lore raw

Quoted 41 lines · Jon Hunter

This is version 2 of this patch. I have incorporated the changes recommended by Kevin Hilman.
Depending on the OMAP3 boot mode the MUSB peripheral may or may not be accessible when the kernel starts.
The OMAP3 can boot from several devices including USB. The sequence of the devices the OMAP will attempt to boot from is configured via the sys_boot pins on the device. If USB is one of the devices the OMAP boot ROM attempts to boot from on power-on, then the interface clock to the MUSB peripheral will be enabled by the boot ROM and the MUSB peripheral will be accessible when the kernel boots. However, if USB is not one of the devices OMAP attempts to boot from, then the interface clock is not enabled and the MUSB peripheral will not be accessible on start-up.
If the MUSB peripheral is not accessible when the kernel boots, then the kernel will crash when attempting to access the OTG_SYSCONFIG in the function musb_platform_init(). The actual cause of the crash is the write to the OTG_SYSCONFIG register in the function usb_musb_pm_init() to reset the MUSB peripheral which occurs prior to calling musb_platform_init(). The function usb_musb_pm_init() does not check to see if the interface clock for the MUSB peripheral is enabled before writing to MUSB register. This write access does not generate a data-abort at this point, but because this write does not complete all future accesses to the MUSB controller will generate data-aborts regardless of whether the interface clock has been enabled at a later stage. The only way I have found to recover from this is resetting the device. My understanding is that the interconnect works in this way to prevent a bad access locking up the system.
This patch ensures the interface clock for the MUSB in the function usb_musb_pm_init() is enabled. This patch also ensures that the interface clock is disabled after the reset is complete. My reasoning for always disabling the clock rather than maintaing its state is:
1). If the MUSB peripheral is not being used then the interface clock should be disabled.
2). The musb_set_clock() function uses a static variable called "clk_on" to determine if the MUSB interface clock is on or off. On boot-up clk_on will be 0 and so this function assumes that the clock is off by default which may not be the case in the current code.

Quoted 5 lines

I have also added a while-loop to wait for the reset of the MUSB module to complete before this function exits and the interface clock it disabled.
Signed-off-by Jon Hunter <[email protected]>
---

Jon, you're raising the bar and spoiling us with such descriptive changelogs. If everyone was as thorough as you, the world would be a merrier place. :)

Thanks, pushing to PM branch and pm-2.6.29.

Kevin

Quoted 66 lines

 arch/arm/mach-omap2/usb-musb.c |   34 +++++++++++++++++++++++++++++++---
 1 files changed, 31 insertions(+), 3 deletions(-)

arch/arm/mach-omap2/usb-musb.c +31 -3

index 3efa19c..247f653 100644
@@ -35,10 +35,20 @@
 
 #define OTG_SYSCONFIG	   0x404
 #define OTG_SYSC_SOFTRESET BIT(1)
+#define OTG_SYSSTATUS     0x408
+#define OTG_SYSS_RESETDONE BIT(0)
+
+static struct platform_device dummy_pdev = {
+	.dev = {
+		.bus = &platform_bus_type,
+	},
+};
 
 static void __init usb_musb_pm_init(void)
 {
 	void __iomem *otg_base;
+	struct clk *otg_clk;
+	struct device *dev = &dummy_pdev.dev;
 
 	if (!cpu_is_omap34xx())
 		return;

@@ -47,9 +57,27 @@ static void __init usb_musb_pm_init(void)
 	if (WARN_ON(!otg_base))
 		return;
 
-	/* Reset OTG controller.  After reset, it will be in
-	 * force-idle, force-standby mode. */
-	__raw_writel(OTG_SYSC_SOFTRESET, otg_base + OTG_SYSCONFIG);
+	dev_set_name(dev, "musb_hdrc");
+	otg_clk = clk_get(dev, "ick");
+
+	if (otg_clk && clk_enable(otg_clk)) {
+		printk(KERN_WARNING
+			"%s: Unable to enable clocks for MUSB, "
+			"cannot reset.\n",  __func__);
+	} else {
+		/* Reset OTG controller. After reset, it will be in
+		 * force-idle, force-standby mode. */
+		__raw_writel(OTG_SYSC_SOFTRESET, otg_base + OTG_SYSCONFIG);
+
+		while (!(OTG_SYSS_RESETDONE &
+					__raw_readl(otg_base + OTG_SYSSTATUS)))
+			cpu_relax();
+	}
+
+	if (otg_clk) {
+		clk_disable(otg_clk);
+		clk_put(otg_clk);
+	}
 
 	iounmap(otg_base);
 }

Signature · 6 lines

1.6.0.4

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Kevin Hilman

2009-08-13 22:52 UTC #2 lore raw

Quoted 5 lines · Kevin Hilman

Quoted 3 lines · Jon Hunter
This is version 2 of this patch. I have incorporated the changes recommended by Kevin Hilman.

[...]

Quoted 3 lines

Thanks, pushing to PM branch and pm-2.6.29.

Just FYI in case you cant find this patch in the PM branch. While rebasing the PM branch, I grouped this patch along with hwmod and the MMC reset removal so you wont set it on the tip of the PM branch.

Kevin

Jon Hunter

author

2009-08-14 17:25 UTC #3 lore raw

In reply to Kevin Hilman

Quoted 7 lines · Kevin Hilman

Jon, you're raising the bar and spoiling us with such descriptive changelogs. If everyone was as thorough as you, the world would be a merrier place. :)
Thanks, pushing to PM branch and pm-2.6.29.
Kevin

No problem. You are welcome. Just an FYI, but for 2.6.29, I was doing some testing this morning and I found that I needed to make the following change to the patch to make it work for 2.6.29. You are probably aware already as this makes the patch similar to your original patch for mmc-reset.

- dev_set_name(dev, "musb_hdrc");
- otg_clk = clk_get(dev, "ick");
+ otg_clk = clk_get(dev, "hsotgusb_ick");

Cheers
Jon

Kevin Hilman

2009-08-14 18:11 UTC #4 lore raw

Quoted 15 lines · Jon Hunter

Quoted 7 lines · Kevin Hilman
Jon, you're raising the bar and spoiling us with such descriptive changelogs. If everyone was as thorough as you, the world would be a merrier place. :)
Thanks, pushing to PM branch and pm-2.6.29.
Kevin
No problem. You are welcome. Just an FYI, but for 2.6.29, I was doing some testing this morning and I found that I needed to make the following change to the patch to make it work for 2.6.29. You are probably aware already as this makes the patch similar to your original patch for mmc-reset.

Review

Quoted 3 lines

(quoted diff) +1 -2

-	dev_set_name(dev, "musb_hdrc");
-	otg_clk = clk_get(dev, "ick");
+	otg_clk = clk_get(dev, "hsotgusb_ick");

Ah yes, I thought of that when I first saw the patch but forgot to do that on pm-2.6.29.

Thanks, pushing to pm-2.6.29.

Kevin

Tony Lindgren

maintainer

2009-08-17 08:14 UTC #5 lore raw

Quoted 17 lines · Kevin Hilman

Quoted 15 lines · Jon Hunter
Quoted 7 lines · Kevin Hilman
Jon, you're raising the bar and spoiling us with such descriptive changelogs. If everyone was as thorough as you, the world would be a merrier place. :)
Thanks, pushing to PM branch and pm-2.6.29.
Kevin
No problem. You are welcome. Just an FYI, but for 2.6.29, I was doing some testing this morning and I found that I needed to make the following change to the patch to make it work for 2.6.29. You are probably aware already as this makes the patch similar to your original patch for mmc-reset.

Quoted 8 lines

Review
Quoted 3 lines
(quoted diff) +1 -2
-	dev_set_name(dev, "musb_hdrc");
-	otg_clk = clk_get(dev, "ick");
+	otg_clk = clk_get(dev, "hsotgusb_ick");
Ah yes, I thought of that when I first saw the patch but forgot to do that on pm-2.6.29.
Thanks, pushing to pm-2.6.29.

Where's the dependency with this patch to the PM branch? If there is a dependency, can it be removed for mainline?

To me it looks like we should send a patch against the mainline tree via linux-usb list.

Regards,

Tony

Quoted 6 lines

Kevin
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Kevin Hilman

2009-08-18 09:04 UTC #6 lore raw

Quoted 25 lines · Tony Lindgren

Quoted 24 lines · Kevin Hilman
Quoted 15 lines · Jon Hunter
Quoted 7 lines · Kevin Hilman
Jon, you're raising the bar and spoiling us with such descriptive changelogs. If everyone was as thorough as you, the world would be a merrier place. :)
Thanks, pushing to PM branch and pm-2.6.29.
Kevin
No problem. You are welcome. Just an FYI, but for 2.6.29, I was doing some testing this morning and I found that I needed to make the following change to the patch to make it work for 2.6.29. You are probably aware already as this makes the patch similar to your original patch for mmc-reset.
Review
Quoted 3 lines
(quoted diff) +1 -2
-	dev_set_name(dev, "musb_hdrc");
-	otg_clk = clk_get(dev, "ick");
+	otg_clk = clk_get(dev, "hsotgusb_ick");
Ah yes, I thought of that when I first saw the patch but forgot to do that on pm-2.6.29.

Quoted 7 lines

Quoted 1 line
Thanks, pushing to pm-2.6.29.
Where's the dependency with this patch to the PM branch? If there is a dependency, can it be removed for mainline?
To me it looks like we should send a patch against the mainline tree via linux-usb list.

No, this is a temporary patch until OTG support is added to omap_hwmod.

Kevin

Kevin Hilman

2009-08-18 09:07 UTC #7 lore raw

In reply to Tony Lindgren

Quoted 25 lines · Tony Lindgren

Quoted 24 lines · Kevin Hilman
Quoted 15 lines · Jon Hunter
Quoted 7 lines · Kevin Hilman
Jon, you're raising the bar and spoiling us with such descriptive changelogs. If everyone was as thorough as you, the world would be a merrier place. :)
Thanks, pushing to PM branch and pm-2.6.29.
Kevin
No problem. You are welcome. Just an FYI, but for 2.6.29, I was doing some testing this morning and I found that I needed to make the following change to the patch to make it work for 2.6.29. You are probably aware already as this makes the patch similar to your original patch for mmc-reset.
Review
Quoted 3 lines
(quoted diff) +1 -2
-	dev_set_name(dev, "musb_hdrc");
-	otg_clk = clk_get(dev, "ick");
+	otg_clk = clk_get(dev, "hsotgusb_ick");
Ah yes, I thought of that when I first saw the patch but forgot to do that on pm-2.6.29.

Quoted 7 lines

Quoted 1 line
Thanks, pushing to pm-2.6.29.
Where's the dependency with this patch to the PM branch? If there is a dependency, can it be removed for mainline?
To me it looks like we should send a patch against the mainline tree via linux-usb list.

No, this is a temporary patch until OTG support is added to omap_hwmod.

Kevin