tegra: Enhance clock support to handle 16-bit clock divisors

I2C ports have a 16-bit clock divisor. Add code to handle this special
case so that I2C speeds below 150KHz are supported.

Signed-off-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Tom Warren <twarren@nvidia.com>

arch/arm/cpu/armv7/tegra2/clock.c

@@ -68,6 +68,7 @@ enum clock_type_id {
 	CLOCK_TYPE_MCPT,
 	CLOCK_TYPE_PCM,
 	CLOCK_TYPE_PCMT,
+	CLOCK_TYPE_PCMT16,	/* CLOCK_TYPE_PCMT with 16-bit divider */
 	CLOCK_TYPE_PCXTS,
 	CLOCK_TYPE_PDCT,
 
@@ -99,6 +100,7 @@ static enum clock_id clock_source[CLOCK_TYPE_COUNT][CLOCK_MAX_MUX] = {
 	{ CLK(MEMORY),	CLK(CGENERAL),	CLK(PERIPH),	CLK(OSC)	},
 	{ CLK(PERIPH),	CLK(CGENERAL),	CLK(MEMORY),	CLK(NONE)	},
 	{ CLK(PERIPH),	CLK(CGENERAL),	CLK(MEMORY),	CLK(OSC)	},
+	{ CLK(PERIPH),	CLK(CGENERAL),	CLK(MEMORY),	CLK(OSC)	},
 	{ CLK(PERIPH),	CLK(CGENERAL),	CLK(XCPU),	CLK(OSC)	},
 	{ CLK(PERIPH),	CLK(DISPLAY),	CLK(CGENERAL),	CLK(OSC)	},
 };
@@ -212,8 +214,8 @@ static enum clock_type_id clock_periph_type[PERIPHC_COUNT] = {
 
 	/* 0x08 */
 	TYPE(PERIPHC_XIO,	CLOCK_TYPE_PCMT),
-	TYPE(PERIPHC_I2C1,	CLOCK_TYPE_PCMT),
-	TYPE(PERIPHC_DVC_I2C,	CLOCK_TYPE_PCMT),
+	TYPE(PERIPHC_I2C1,	CLOCK_TYPE_PCMT16),
+	TYPE(PERIPHC_DVC_I2C,	CLOCK_TYPE_PCMT16),
 	TYPE(PERIPHC_TWC,	CLOCK_TYPE_PCMT),
 	TYPE(PERIPHC_NONE,	CLOCK_TYPE_NONE),
 	TYPE(PERIPHC_SPI1,	CLOCK_TYPE_PCMT),
@@ -247,7 +249,7 @@ static enum clock_type_id clock_periph_type[PERIPHC_COUNT] = {
 	TYPE(PERIPHC_HDMI,	CLOCK_TYPE_PDCT),
 	TYPE(PERIPHC_NONE,	CLOCK_TYPE_NONE),
 	TYPE(PERIPHC_TVDAC,	CLOCK_TYPE_PDCT),
-	TYPE(PERIPHC_I2C2,	CLOCK_TYPE_PCMT),
+	TYPE(PERIPHC_I2C2,	CLOCK_TYPE_PCMT16),
 	TYPE(PERIPHC_EMC,	CLOCK_TYPE_MCPT),
 
 	/* 0x28 */
@@ -257,7 +259,7 @@ static enum clock_type_id clock_periph_type[PERIPHC_COUNT] = {
 	TYPE(PERIPHC_NONE,	CLOCK_TYPE_NONE),
 	TYPE(PERIPHC_NONE,	CLOCK_TYPE_NONE),
 	TYPE(PERIPHC_SPI4,	CLOCK_TYPE_PCMT),
-	TYPE(PERIPHC_I2C3,	CLOCK_TYPE_PCMT),
+	TYPE(PERIPHC_I2C3,	CLOCK_TYPE_PCMT16),
 	TYPE(PERIPHC_SDMMC3,	CLOCK_TYPE_PCMT),
 
 	/* 0x30 */
@@ -519,14 +521,16 @@ void clock_ll_set_source(enum periph_id periph_id, unsigned source)
  * Given the parent's rate and the required rate for the children, this works
  * out the peripheral clock divider to use, in 7.1 binary format.
  *
+ * @param divider_bits	number of divider bits (8 or 16)
  * @param parent_rate	clock rate of parent clock in Hz
  * @param rate		required clock rate for this clock
  * @return divider which should be used
  */
-static int clk_div7_1_get_divider(unsigned long parent_rate,
-				  unsigned long rate)
+static int clk_get_divider(unsigned divider_bits, unsigned long parent_rate,
+			   unsigned long rate)
 {
 	u64 divider = parent_rate * 2;
+	unsigned max_divider = 1 << divider_bits;
 
 	divider += rate - 1;
 	do_div(divider, rate);
@@ -534,7 +538,7 @@ static int clk_div7_1_get_divider(unsigned long parent_rate,
 	if ((s64)divider - 2 < 0)
 		return 0;
 
-	if ((s64)divider - 2 > 255)
+	if ((s64)divider - 2 >= max_divider)
 		return -1;
 
 	return divider - 2;
@@ -572,6 +576,7 @@ unsigned long clock_get_periph_rate(enum periph_id periph_id,
  * required child clock rate. This function assumes that a second-stage
  * divisor is available which can divide by powers of 2 from 1 to 256.
  *
+ * @param divider_bits	number of divider bits (8 or 16)
  * @param parent_rate	clock rate of parent clock in Hz
  * @param rate		required clock rate for this clock
  * @param extra_div	value for the second-stage divisor (not set if this
@@ -579,8 +584,8 @@ unsigned long clock_get_periph_rate(enum periph_id periph_id,
  * @return divider which should be used, or -1 if nothing is valid
  *
  */
-static int find_best_divider(unsigned long parent_rate, unsigned long rate,
-		int *extra_div)
+static int find_best_divider(unsigned divider_bits, unsigned long parent_rate,
+			     unsigned long rate, int *extra_div)
 {
 	int shift;
 	int best_divider = -1;
@@ -589,7 +594,8 @@ static int find_best_divider(unsigned long parent_rate, unsigned long rate,
 	/* try dividers from 1 to 256 and find closest match */
 	for (shift = 0; shift <= 8 && best_error > 0; shift++) {
 		unsigned divided_parent = parent_rate >> shift;
-		int divider = clk_div7_1_get_divider(divided_parent, rate);
+		int divider = clk_get_divider(divider_bits, divided_parent,
+					      rate);
 		unsigned effective_rate = get_rate_from_divider(divided_parent,
 						       divider);
 		int error = rate - effective_rate;
@@ -615,10 +621,11 @@ static int find_best_divider(unsigned long parent_rate, unsigned long rate,
  * @param periph_id	peripheral to start
  * @param source	PLL id of required parent clock
  * @param mux_bits	Set to number of bits in mux register: 2 or 4
+ * @param divider_bits	Set to number of divider bits (8 or 16)
  * @return mux value (0-4, or -1 if not found)
  */
 static int get_periph_clock_source(enum periph_id periph_id,
-		enum clock_id parent, int *mux_bits)
+		enum clock_id parent, int *mux_bits, int *divider_bits)
 {
 	enum clock_type_id type;
 	enum periphc_internal_id internal_id;
@@ -632,11 +639,18 @@ static int get_periph_clock_source(enum periph_id periph_id,
 	type = clock_periph_type[internal_id];
 	assert(clock_type_id_isvalid(type));
 
-	/* Special case here for the clock with a 4-bit source mux */
+	/*
+	 * Special cases here for the clock with a 4-bit source mux and I2C
+	 * with its 16-bit divisor
+	 */
 	if (type == CLOCK_TYPE_PCXTS)
 		*mux_bits = 4;
 	else
 		*mux_bits = 2;
+	if (type == CLOCK_TYPE_PCMT16)
+		*divider_bits = 16;
+	else
+		*divider_bits = 8;
 
 	for (mux = 0; mux < CLOCK_MAX_MUX; mux++)
 		if (clock_source[type][mux] == parent)
@@ -662,24 +676,22 @@ static int get_periph_clock_source(enum periph_id periph_id,
  * Adjust peripheral PLL to use the given divider and source.
  *
  * @param periph_id	peripheral to adjust
- * @param parent	Required parent clock (for source mux)
- * @param divider	Required divider in 7.1 format
+ * @param source	Source number (0-3 or 0-7)
+ * @param mux_bits	Number of mux bits (2 or 4)
+ * @param divider	Required divider in 7.1 or 15.1 format
  * @return 0 if ok, -1 on error (requesting a parent clock which is not valid
  *		for this peripheral)
  */
-static int adjust_periph_pll(enum periph_id periph_id,
-		enum clock_id parent, unsigned divider)
+static int adjust_periph_pll(enum periph_id periph_id, int source,
+			     int mux_bits, unsigned divider)
 {
 	u32 *reg = get_periph_source_reg(periph_id);
-	unsigned source;
-	int mux_bits;
 
 	clrsetbits_le32(reg, OUT_CLK_DIVISOR_MASK,
 			divider << OUT_CLK_DIVISOR_SHIFT);
 	udelay(1);
 
 	/* work out the source clock and set it */
-	source = get_periph_clock_source(periph_id, parent, &mux_bits);
 	if (source < 0)
 		return -1;
 	if (mux_bits == 4) {
@@ -697,14 +709,21 @@ unsigned clock_adjust_periph_pll_div(enum periph_id periph_id,
 		enum clock_id parent, unsigned rate, int *extra_div)
 {
 	unsigned effective_rate;
+	int mux_bits, divider_bits, source;
 	int divider;
 
+	/* work out the source clock and set it */
+	source = get_periph_clock_source(periph_id, parent, &mux_bits,
+					 &divider_bits);
+
 	if (extra_div)
-		divider = find_best_divider(pll_rate[parent], rate, extra_div);
+		divider = find_best_divider(divider_bits, pll_rate[parent],
+					    rate, extra_div);
 	else
-		divider = clk_div7_1_get_divider(pll_rate[parent], rate);
+		divider = clk_get_divider(divider_bits, pll_rate[parent],
+					  rate);
 	assert(divider >= 0);
-	if (adjust_periph_pll(periph_id, parent, divider))
+	if (adjust_periph_pll(periph_id, source, mux_bits, divider))
 		return -1U;
 	debug("periph %d, rate=%d, reg=%p = %x\n", periph_id, rate,
 		get_periph_source_reg(periph_id),

arch/arm/include/asm/arch-tegra2/clk_rst.h

@@ -125,9 +125,15 @@ struct clk_rst_ctlr {
 #define OSC_FREQ_SHIFT		30
 #define OSC_FREQ_MASK		(3U << OSC_FREQ_SHIFT)
 
-/* CLK_RST_CONTROLLER_CLK_SOURCE_x_OUT_0 */
+/*
+ * CLK_RST_CONTROLLER_CLK_SOURCE_x_OUT_0 - the mask here is normally 8 bits
+ * but can be 16. We could use knowledge we have to restrict the mask in
+ * the 8-bit cases (the divider_bits value returned by
+ * get_periph_clock_source()) but it does not seem worth it since the code
+ * already checks the ranges of values it is writing, in clk_get_divider().
+ */
 #define OUT_CLK_DIVISOR_SHIFT	0
-#define OUT_CLK_DIVISOR_MASK	(255 << OUT_CLK_DIVISOR_SHIFT)
+#define OUT_CLK_DIVISOR_MASK	(0xffff << OUT_CLK_DIVISOR_SHIFT)
 
 #define OUT_CLK_SOURCE_SHIFT	30
 #define OUT_CLK_SOURCE_MASK	(3U << OUT_CLK_SOURCE_SHIFT)