[U-Boot] [PATCH v3 3/9] tegra: Enhance clock support to handle 16-bit clock divisors
Simon Glass
sjg at chromium.org
Sat Feb 4 02:13:54 CET 2012
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 at chromium.org>
---
Changes in v3:
- Add new patch to support 16-bit clock divisors required by I2C
arch/arm/cpu/armv7/tegra2/clock.c | 63 ++++++++++++++++++----------
arch/arm/include/asm/arch-tegra2/clk_rst.h | 10 ++++-
2 files changed, 49 insertions(+), 24 deletions(-)
diff --git a/arch/arm/cpu/armv7/tegra2/clock.c b/arch/arm/cpu/armv7/tegra2/clock.c
index 11d2346..e58cb3b 100644
--- a/arch/arm/cpu/armv7/tegra2/clock.c
+++ b/arch/arm/cpu/armv7/tegra2/clock.c
@@ -67,6 +67,7 @@ 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,
@@ -98,6 +99,7 @@ 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) },
};
@@ -211,8 +213,8 @@ 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),
@@ -246,7 +248,7 @@ 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 */
@@ -256,7 +258,7 @@ 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 */
@@ -518,14 +520,16 @@ 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);
@@ -533,7 +537,7 @@ 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;
@@ -571,6 +575,7 @@ 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
@@ -578,8 +583,8 @@ 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;
@@ -588,7 +593,8 @@ 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;
@@ -614,10 +620,11 @@ 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;
@@ -631,11 +638,18 @@ 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)
@@ -661,24 +675,22 @@ 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) {
@@ -696,14 +708,21 @@ 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,
+ ÷r_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),
diff --git a/arch/arm/include/asm/arch-tegra2/clk_rst.h b/arch/arm/include/asm/arch-tegra2/clk_rst.h
index 0b6e004..415e420 100644
--- a/arch/arm/include/asm/arch-tegra2/clk_rst.h
+++ b/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)
--
1.7.7.3
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