linux-kernel - [PATCH] ARM: OMAP4: clock: Initialize USB DPLL

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Message-ID: <1363873705-3224-1-git-send-email-rogerq@ti.com>
Date:	Thu, 21 Mar 2013 15:48:25 +0200
From:	Roger Quadros <rogerq@...com>
To:	<tony@...mide.com>
CC:	<balbi@...com>, <rnayak@...com>, <t-kristo@...com>,
	<linux-omap@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>,
	<linux-kernel@...r.kernel.org>, Roger Quadros <rogerq@...com>
Subject: [PATCH] ARM: OMAP4: clock: Initialize USB DPLL

If the bootloader doesn't configure USB DPLL (e.g. in u-boot,
disable CONFIG_USB_EHCI_OMAP), then we get all sorts of problems
like
- division by zero errors at boot [1]
- USB DPLL fails to enter locked state
- USB EHCI Host is non functional
- Device can't enter OFF mode

Initializing the USB DPLL fixes all these issues.

[1]

[    0.000000] clock: dpll_usb_ck failed transition to 'locked'
[    0.000000] Division by zero in kernel.
[    0.000000] [<c001b00c>] (unwind_backtrace+0x0/0xf0) from [<c02b2378>] (Ldiv0+0x8/0x10)
[    0.000000] [<c02b2378>] (Ldiv0+0x8/0x10) from [<c041cf3c>] (clk_divider_set_rate+0x10/0x124)
[    0.000000] [<c041cf3c>] (clk_divider_set_rate+0x10/0x124) from [<c041bfc4>] (clk_change_rate+0x3c/0xb4)
[    0.000000] [<c041bfc4>] (clk_change_rate+0x3c/0xb4) from [<c041c028>] (clk_change_rate+0xa0/0xb4)

Signed-off-by: Roger Quadros <rogerq@...com>
---
 arch/arm/mach-omap2/cclock44xx_data.c |   19 +++++++++++++++++++
 1 files changed, 19 insertions(+), 0 deletions(-)

diff --git a/arch/arm/mach-omap2/cclock44xx_data.c b/arch/arm/mach-omap2/cclock44xx_data.c
index bfc46c1..6127bb9 100644
--- a/arch/arm/mach-omap2/cclock44xx_data.c
+++ b/arch/arm/mach-omap2/cclock44xx_data.c
@@ -53,6 +53,12 @@
  */
 #define OMAP4_DPLL_ABE_DEFFREQ				98304000
 
+/*
+ * OMAP4450 TRM Rev X, section "3.6.3.9.5 DPLL_USB Preferred Settings"
+ * states it must be at 960MHz
+ */
+#define OMAP4_DPLL_USB_DEFFREQ				960000000
+
 /* Root clocks */
 
 DEFINE_CLK_FIXED_RATE(extalt_clkin_ck, CLK_IS_ROOT, 59000000, 0x0);
@@ -1729,6 +1735,19 @@ int __init omap4xxx_clk_init(void)
 	omap2_clk_disable_autoidle_all();
 
 	/*
+	 * Lock USB_DPLL to avoid issues with USB host and OFF mode
+	 */
+	rc = clk_set_rate(&dpll_usb_ck, OMAP4_DPLL_USB_DEFFREQ);
+	if (rc) {
+		pr_err("%s: failed to configure DPLL_USB: %d\n", __func__, rc);
+	} else {
+		rc = clk_set_rate(&dpll_usb_m2_ck, OMAP4_DPLL_USB_DEFFREQ/2);
+		if (rc)
+			pr_err("%s: failed to configure DPLL_USB_M2: %d\n",
+								__func__, rc);
+	}
+
+	/*
 	 * On OMAP4460 the ABE DPLL fails to turn on if in idle low-power
 	 * state when turning the ABE clock domain. Workaround this by
 	 * locking the ABE DPLL on boot.
-- 
1.7.4.1

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