linux-kernel - [PATCH] ARC: [plat-hsdk]: Temporary fix to set CPU frequency to 1GHz

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Date:   Thu, 28 Sep 2017 17:33:29 +0300
From:   Eugeniy Paltsev <Eugeniy.Paltsev@...opsys.com>
To:     linux-snps-arc@...ts.infradead.org
Cc:     linux-kernel@...r.kernel.org,
        Vineet Gupta <Vineet.Gupta1@...opsys.com>,
        Alexey Brodkin <Alexey.Brodkin@...opsys.com>,
        Eugeniy Paltsev <Eugeniy.Paltsev@...opsys.com>
Subject: [PATCH] ARC: [plat-hsdk]: Temporary fix to set CPU frequency to 1GHz

Add temporary fix to HSDK platform code to setup CPU frequency
to 1GHz on early boot.
We can remove this fix when smart hsdk pll driver will be
introduced, see discussion:
https://www.mail-archive.com/linux-snps-arc@lists.infradead.org/msg02689.html

Signed-off-by: Eugeniy Paltsev <Eugeniy.Paltsev@...opsys.com>
---
 arch/arc/plat-hsdk/platform.c | 42 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 42 insertions(+)

diff --git a/arch/arc/plat-hsdk/platform.c b/arch/arc/plat-hsdk/platform.c
index a2e7fd1..744e62e 100644
--- a/arch/arc/plat-hsdk/platform.c
+++ b/arch/arc/plat-hsdk/platform.c
@@ -38,6 +38,42 @@ static void __init hsdk_init_per_cpu(unsigned int cpu)
 #define CREG_PAE		(CREG_BASE + 0x180)
 #define CREG_PAE_UPDATE		(CREG_BASE + 0x194)
 
+#define CREG_CORE_IF_CLK_DIV	(CREG_BASE + 0x4B8)
+#define CREG_CORE_IF_CLK_DIV_2	0x1
+#define CGU_BASE		ARC_PERIPHERAL_BASE
+#define CGU_PLL_STATUS		(ARC_PERIPHERAL_BASE + 0x4)
+#define CGU_PLL_CTRL		(ARC_PERIPHERAL_BASE + 0x0)
+#define CGU_PLL_STATUS_LOCK	BIT(0)
+#define CGU_PLL_STATUS_ERR	BIT(1)
+#define CGU_PLL_CTRL_1GHZ	0x3A10
+#define HSDK_PLL_LOCK_TIMEOUT	500
+
+#define HSDK_PLL_LOCKED() \
+	!!(ioread32((void __iomem *) CGU_PLL_STATUS) & CGU_PLL_STATUS_LOCK)
+
+#define HSDK_PLL_ERR() \
+	!!(ioread32((void __iomem *) CGU_PLL_STATUS) & CGU_PLL_STATUS_ERR)
+
+static void __init hsdk_set_cpu_freq_1ghz(void)
+{
+	u32 timeout = HSDK_PLL_LOCK_TIMEOUT;
+
+	/*
+	 * As we set cpu clock which exceeds 500MHz, the divider for the interface
+	 * clock must be programmed to div-by-2.
+	 */
+	iowrite32(CREG_CORE_IF_CLK_DIV_2, (void __iomem *) CREG_CORE_IF_CLK_DIV);
+
+	/* Set cpu clock to 1GHz */
+	iowrite32(CGU_PLL_CTRL_1GHZ, (void __iomem *) CGU_PLL_CTRL);
+
+	while (!HSDK_PLL_LOCKED() && timeout--)
+		cpu_relax();
+
+	if (!HSDK_PLL_LOCKED() || HSDK_PLL_ERR())
+		pr_err("Failed to setup CPU frequency to 1GHz!");
+}
+
 static void __init hsdk_init_early(void)
 {
 	/*
@@ -52,6 +88,12 @@ static void __init hsdk_init_early(void)
 
 	/* Really apply settings made above */
 	writel(1, (void __iomem *) CREG_PAE_UPDATE);
+
+	/*
+	 * Setup CPU frequency to 1GHz.
+	 * TODO: remove it after smart hsdk pll driver will be introduced.
+	 */
+	hsdk_set_cpu_freq_1ghz();
 }
 
 static const char *hsdk_compat[] __initconst = {
-- 
2.9.3