ARM: OMAP4: VC: setup I2C parameters based on board data

VC code now provides a table of pre-calculated I2C setup parameters,
which will be used based on the capacitance value calculated for the I2C
trace on the PCB. A default trace length of 6.3cm is used unless board
defines its own value during init. The parameters set will be the I2C
internal pull setup and the I2C timing parameters for high speed use
mode. Full speed mode is not supported as of now.

Signed-off-by: Tero Kristo <t-kristo@ti.com>
Signed-off-by: Kevin Hilman <khilman@ti.com>

arch/arm/mach-omap2/omap_twl.c

@@ -183,6 +183,7 @@ static struct omap_voltdm_pmic omap4_mpu_pmic = {
 	.volt_reg_addr		= OMAP4_VDD_MPU_SR_VOLT_REG,
 	.cmd_reg_addr		= OMAP4_VDD_MPU_SR_CMD_REG,
 	.i2c_high_speed		= true,
+	.i2c_pad_load		= 3,
 	.vsel_to_uv		= twl6030_vsel_to_uv,
 	.uv_to_vsel		= twl6030_uv_to_vsel,
 };
@@ -200,6 +201,7 @@ static struct omap_voltdm_pmic omap4_iva_pmic = {
 	.volt_reg_addr		= OMAP4_VDD_IVA_SR_VOLT_REG,
 	.cmd_reg_addr		= OMAP4_VDD_IVA_SR_CMD_REG,
 	.i2c_high_speed		= true,
+	.i2c_pad_load		= 3,
 	.vsel_to_uv		= twl6030_vsel_to_uv,
 	.uv_to_vsel		= twl6030_uv_to_vsel,
 };
@@ -216,6 +218,7 @@ static struct omap_voltdm_pmic omap4_core_pmic = {
 	.i2c_slave_addr		= OMAP4_SRI2C_SLAVE_ADDR,
 	.volt_reg_addr		= OMAP4_VDD_CORE_SR_VOLT_REG,
 	.cmd_reg_addr		= OMAP4_VDD_CORE_SR_CMD_REG,
+	.i2c_pad_load		= 3,
 	.vsel_to_uv		= twl6030_vsel_to_uv,
 	.uv_to_vsel		= twl6030_uv_to_vsel,
 };

arch/arm/mach-omap2/pm.h

@@ -132,9 +132,11 @@ static inline int omap4_twl_init(void)
 #ifdef CONFIG_PM
 extern void omap_pm_setup_oscillator(u32 tstart, u32 tshut);
 extern void omap_pm_get_oscillator(u32 *tstart, u32 *tshut);
+extern void omap_pm_setup_sr_i2c_pcb_length(u32 mm);
 #else
 static inline void omap_pm_setup_oscillator(u32 tstart, u32 tshut) { }
 static inline void omap_pm_get_oscillator(u32 *tstart, u32 *tshut) { }
+static inline void omap_pm_setup_sr_i2c_pcb_length(u32 mm) { }
 #endif
 
 #endif

arch/arm/mach-omap2/vc.c

@@ -24,6 +24,7 @@
 #include "prm44xx.h"
 #include "pm.h"
 #include "scrm44xx.h"
+#include "control.h"
 
 /**
  * struct omap_vc_channel_cfg - describe the cfg_channel bitfield
@@ -69,6 +70,9 @@ static struct omap_vc_channel_cfg vc_mutant_channel_cfg = {
 };
 
 static struct omap_vc_channel_cfg *vc_cfg_bits;
+
+/* Default I2C trace length on pcb, 6.3cm. Used for capacitance calculations. */
+static u32 sr_i2c_pcb_length = 63;
 #define CFG_CHANNEL_MASK 0x1f
 
 /**
@@ -464,22 +468,135 @@ static void omap4_set_timings(struct voltagedomain *voltdm, bool off_mode)
 /* OMAP4 specific voltage init functions */
 static void __init omap4_vc_init_channel(struct voltagedomain *voltdm)
 {
-	static bool is_initialized;
-	u32 vc_val;
-
 	omap4_set_timings(voltdm, true);
 	omap4_set_timings(voltdm, false);
-
-	if (is_initialized)
-		return;
-
-	/* XXX These are magic numbers and do not belong! */
-	vc_val = (0x60 << OMAP4430_SCLL_SHIFT | 0x26 << OMAP4430_SCLH_SHIFT);
-	voltdm->write(vc_val, OMAP4_PRM_VC_CFG_I2C_CLK_OFFSET);
-
-	is_initialized = true;
 }
 
+struct i2c_init_data {
+	u8 loadbits;
+	u8 load;
+	u8 hsscll_38_4;
+	u8 hsscll_26;
+	u8 hsscll_19_2;
+	u8 hsscll_16_8;
+	u8 hsscll_12;
+};
+
+static const __initdata struct i2c_init_data omap4_i2c_timing_data[] = {
+	{
+		.load = 50,
+		.loadbits = 0x3,
+		.hsscll_38_4 = 13,
+		.hsscll_26 = 11,
+		.hsscll_19_2 = 9,
+		.hsscll_16_8 = 9,
+		.hsscll_12 = 8,
+	},
+	{
+		.load = 25,
+		.loadbits = 0x2,
+		.hsscll_38_4 = 13,
+		.hsscll_26 = 11,
+		.hsscll_19_2 = 9,
+		.hsscll_16_8 = 9,
+		.hsscll_12 = 8,
+	},
+	{
+		.load = 12,
+		.loadbits = 0x1,
+		.hsscll_38_4 = 11,
+		.hsscll_26 = 10,
+		.hsscll_19_2 = 9,
+		.hsscll_16_8 = 9,
+		.hsscll_12 = 8,
+	},
+	{
+		.load = 0,
+		.loadbits = 0x0,
+		.hsscll_38_4 = 12,
+		.hsscll_26 = 10,
+		.hsscll_19_2 = 9,
+		.hsscll_16_8 = 8,
+		.hsscll_12 = 8,
+	},
+};
+
+/**
+ * omap4_vc_i2c_timing_init - sets up board I2C timing parameters
+ * @voltdm: voltagedomain pointer to get data from
+ *
+ * Use PMIC + board supplied settings for calculating the total I2C
+ * channel capacitance and set the timing parameters based on this.
+ * Pre-calculated values are provided in data tables, as it is not
+ * too straightforward to calculate these runtime.
+ */
+static void __init omap4_vc_i2c_timing_init(struct voltagedomain *voltdm)
+{
+	u32 capacitance;
+	u32 val;
+	u16 hsscll;
+	const struct i2c_init_data *i2c_data;
+
+	if (!voltdm->pmic->i2c_high_speed) {
+		pr_warn("%s: only high speed supported!\n", __func__);
+		return;
+	}
+
+	/* PCB trace capacitance, 0.125pF / mm => mm / 8 */
+	capacitance = DIV_ROUND_UP(sr_i2c_pcb_length, 8);
+
+	/* OMAP pad capacitance */
+	capacitance += 4;
+
+	/* PMIC pad capacitance */
+	capacitance += voltdm->pmic->i2c_pad_load;
+
+	/* Search for capacitance match in the table */
+	i2c_data = omap4_i2c_timing_data;
+
+	while (i2c_data->load > capacitance)
+		i2c_data++;
+
+	/* Select proper values based on sysclk frequency */
+	switch (voltdm->sys_clk.rate) {
+	case 38400000:
+		hsscll = i2c_data->hsscll_38_4;
+		break;
+	case 26000000:
+		hsscll = i2c_data->hsscll_26;
+		break;
+	case 19200000:
+		hsscll = i2c_data->hsscll_19_2;
+		break;
+	case 16800000:
+		hsscll = i2c_data->hsscll_16_8;
+		break;
+	case 12000000:
+		hsscll = i2c_data->hsscll_12;
+		break;
+	default:
+		pr_warn("%s: unsupported sysclk rate: %d!\n", __func__,
+			voltdm->sys_clk.rate);
+		return;
+	}
+
+	/* Loadbits define pull setup for the I2C channels */
+	val = i2c_data->loadbits << 25 | i2c_data->loadbits << 29;
+
+	/* Write to SYSCTRL_PADCONF_WKUP_CTRL_I2C_2 to setup I2C pull */
+	__raw_writel(val, OMAP2_L4_IO_ADDRESS(OMAP4_CTRL_MODULE_PAD_WKUP +
+				OMAP4_CTRL_MODULE_PAD_WKUP_CONTROL_I2C_2));
+
+	/* HSSCLH can always be zero */
+	val = hsscll << OMAP4430_HSSCLL_SHIFT;
+	val |= (0x28 << OMAP4430_SCLL_SHIFT | 0x2c << OMAP4430_SCLH_SHIFT);
+
+	/* Write setup times to I2C config register */
+	voltdm->write(val, OMAP4_PRM_VC_CFG_I2C_CLK_OFFSET);
+}
+
+
+
 /**
  * omap_vc_i2c_init - initialize I2C interface to PMIC
  * @voltdm: voltage domain containing VC data
@@ -519,6 +636,9 @@ static void __init omap_vc_i2c_init(struct voltagedomain *voltdm)
 			    mcode << __ffs(vc->common->i2c_mcode_mask),
 			    vc->common->i2c_cfg_reg);
 
+	if (cpu_is_omap44xx())
+		omap4_vc_i2c_timing_init(voltdm);
+
 	initialized = true;
 }
 
@@ -546,6 +666,19 @@ static u8 omap_vc_calc_vsel(struct voltagedomain *voltdm, u32 uvolt)
 	return voltdm->pmic->uv_to_vsel(uvolt);
 }
 
+/**
+ * omap_pm_setup_sr_i2c_pcb_length - set length of SR I2C traces on PCB
+ * @mm: length of the PCB trace in millimetres
+ *
+ * Sets the PCB trace length for the I2C channel. By default uses 63mm.
+ * This is needed for properly calculating the capacitance value for
+ * the PCB trace, and for setting the SR I2C channel timing parameters.
+ */
+void __init omap_pm_setup_sr_i2c_pcb_length(u32 mm)
+{
+	sr_i2c_pcb_length = mm;
+}
+
 void __init omap_vc_init_channel(struct voltagedomain *voltdm)
 {
 	struct omap_vc_channel *vc = voltdm->vc;

arch/arm/mach-omap2/voltage.h

@@ -139,6 +139,7 @@ struct omap_voltdm_pmic {
 	u32 vddmax;
 	u8 vp_timeout_us;
 	bool i2c_high_speed;
+	u32 i2c_pad_load;
 	u8 i2c_mcode;
 	unsigned long (*vsel_to_uv) (const u8 vsel);
 	u8 (*uv_to_vsel) (unsigned long uV);