davinci: add support for aemif timing configuration

This patch adds support to configure the AEMIF interface
with supplied timing values.

Since this capability is useful both from NOR and NAND
flashes, it is provided as a new interface and in a file
of its own.

AEMIF timing configuration is required in cases:

1) Where the AEMIF clock rate can change at runtime (a side
   affect of cpu frequency change).

2) Where U-Boot does not support NAND/NOR but supports other
   media like SPI Flash or MMC/SD and thus does not care about
   setting up the AEMIF timing for kernel to use.

3) Where U-Boot just hasn't configured the timing values and
   cannot be upgraded because the box is already in the field.

Since there is now a header file for AEMIF interface, the
common (non-NAND specific) defines for AEMIF registers have
been moved from nand.h into the newly created aemif.h

Signed-off-by: Sekhar Nori <nsekhar@ti.com>
Acked-by: Kevin Hilman <khilman@deeprootsystems.com>
Signed-off-by: Kevin Hilman <khilman@deeprootsystems.com>

1 files changed, 133 insertions, 0 deletions

diff --git a/arch/arm/mach-davinci/aemif.c b/arch/arm/mach-davinci/aemif.c
new file mode 100644
index 00000000000..9c3f500fc12
--- /dev/null
+++ b/arch/arm/mach-davinci/aemif.c
@@ -0,0 +1,133 @@
+/*
+ * AEMIF support for DaVinci SoCs
+ *
+ * Copyright (C) 2010 Texas Instruments Incorporated. http://www.ti.com/
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/kernel.h>
+#include <linux/io.h>
+#include <linux/err.h>
+#include <linux/clk.h>
+#include <linux/module.h>
+#include <linux/time.h>
+
+#include <mach/aemif.h>
+
+/* Timing value configuration */
+
+#define TA(x)		((x) << 2)
+#define RHOLD(x)	((x) << 4)
+#define RSTROBE(x)	((x) << 7)
+#define RSETUP(x)	((x) << 13)
+#define WHOLD(x)	((x) << 17)
+#define WSTROBE(x)	((x) << 20)
+#define WSETUP(x)	((x) << 26)
+
+#define TA_MAX		0x3
+#define RHOLD_MAX	0x7
+#define RSTROBE_MAX	0x3f
+#define RSETUP_MAX	0xf
+#define WHOLD_MAX	0x7
+#define WSTROBE_MAX	0x3f
+#define WSETUP_MAX	0xf
+
+#define TIMING_MASK	(TA(TA_MAX) | \
+				RHOLD(RHOLD_MAX) | \
+				RSTROBE(RSTROBE_MAX) |	\
+				RSETUP(RSETUP_MAX) | \
+				WHOLD(WHOLD_MAX) | \
+				WSTROBE(WSTROBE_MAX) | \
+				WSETUP(WSETUP_MAX))
+
+/*
+ * aemif_calc_rate - calculate timing data.
+ * @wanted: The cycle time needed in nanoseconds.
+ * @clk: The input clock rate in kHz.
+ * @max: The maximum divider value that can be programmed.
+ *
+ * On success, returns the calculated timing value minus 1 for easy
+ * programming into AEMIF timing registers, else negative errno.
+ */
+static int aemif_calc_rate(int wanted, unsigned long clk, int max)
+{
+	int result;
+
+	result = DIV_ROUND_UP((wanted * clk), NSEC_PER_MSEC) - 1;
+
+	pr_debug("%s: result %d from %ld, %d\n", __func__, result, clk, wanted);
+
+	/* It is generally OK to have a more relaxed timing than requested... */
+	if (result < 0)
+		result = 0;
+
+	/* ... But configuring tighter timings is not an option. */
+	else if (result > max)
+		result = -EINVAL;
+
+	return result;
+}
+
+/**
+ * davinci_aemif_setup_timing - setup timing values for a given AEMIF interface
+ * @t: timing values to be progammed
+ * @base: The virtual base address of the AEMIF interface
+ * @cs: chip-select to program the timing values for
+ *
+ * This function programs the given timing values (in real clock) into the
+ * AEMIF registers taking the AEMIF clock into account.
+ *
+ * This function does not use any locking while programming the AEMIF
+ * because it is expected that there is only one user of a given
+ * chip-select.
+ *
+ * Returns 0 on success, else negative errno.
+ */
+int davinci_aemif_setup_timing(struct davinci_aemif_timing *t,
+					void __iomem *base, unsigned cs)
+{
+	unsigned set, val;
+	unsigned ta, rhold, rstrobe, rsetup, whold, wstrobe, wsetup;
+	unsigned offset = A1CR_OFFSET + cs * 4;
+	struct clk *aemif_clk;
+	unsigned long clkrate;
+
+	if (!t)
+		return 0;	/* Nothing to do */
+
+	aemif_clk = clk_get(NULL, "aemif");
+	if (IS_ERR(aemif_clk))
+		return PTR_ERR(aemif_clk);
+
+	clkrate = clk_get_rate(aemif_clk);
+
+	clkrate /= 1000;	/* turn clock into kHz for ease of use */
+
+	ta	= aemif_calc_rate(t->ta, clkrate, TA_MAX);
+	rhold	= aemif_calc_rate(t->rhold, clkrate, RHOLD_MAX);
+	rstrobe	= aemif_calc_rate(t->rstrobe, clkrate, RSTROBE_MAX);
+	rsetup	= aemif_calc_rate(t->rsetup, clkrate, RSETUP_MAX);
+	whold	= aemif_calc_rate(t->whold, clkrate, WHOLD_MAX);
+	wstrobe	= aemif_calc_rate(t->wstrobe, clkrate, WSTROBE_MAX);
+	wsetup	= aemif_calc_rate(t->wsetup, clkrate, WSETUP_MAX);
+
+	if (ta < 0 || rhold < 0 || rstrobe < 0 || rsetup < 0 ||
+			whold < 0 || wstrobe < 0 || wsetup < 0) {
+		pr_err("%s: cannot get suitable timings\n", __func__);
+		return -EINVAL;
+	}
+
+	set = TA(ta) | RHOLD(rhold) | RSTROBE(rstrobe) | RSETUP(rsetup) |
+		WHOLD(whold) | WSTROBE(wstrobe) | WSETUP(wsetup);
+
+	val = __raw_readl(base + offset);
+	val &= ~TIMING_MASK;
+	val |= set;
+	__raw_writel(val, base + offset);
+
+	return 0;
+}
+EXPORT_SYMBOL(davinci_aemif_setup_timing);