ref: 606901dc5da9cb09acb5593c5cf74ce1b52ca6e2
dir: /os/sa1110/l3gpio.c/
/* * L3 emulation using GPIO pins * * from the Linux sa1100-uda1341.c, * Copyright (c) 2000 Nicolas Pitre <[email protected]> * Portions are Copyright (C) 2000 Lernout & Hauspie Speech Products, N.V. * * This program is free software; you can redistribute it and/or * modify it under the terms of the GNU General Public License. * * Modified by Vita Nuova 2001 * */ #include "u.h" #include "../port/lib.h" #include "mem.h" #include "dat.h" #include "fns.h" #include "../port/error.h" #include "io.h" /* * GPIO based L3 bus support. * * This provides control of Philips L3 type devices. * GPIO lines are used for clock, data and mode pins. * * Note: The L3 pins are shared with I2C devices. This should not present * any problems as long as an I2C start sequence is not generated. This is * defined as a 1->0 transition on the data lines when the clock is high. * It is critical this code only allow data transitions when the clock * is low. This is always legal in L3. * * The IIC interface requires the clock and data pin to be LOW when idle. We * must make sure we leave them in this state. * * It appears the read data is generated on the falling edge of the clock * and should be held stable during the clock high time. */ /* * L3 setup and hold times (expressed in us) */ enum { L3DataSetupTime = 1, /* 190 ns */ L3DataHoldTime = 1, /* 30 ns */ L3ModeSetupTime = 1, /* 190 ns */ L3ModeHoldTime = 1, /* 190 ns */ L3ClockHighTime = 1, /* 250 ns (min is 64*fs, 35us @ 44.1 Khz) */ L3ClockLowTime = 1, /* 250 ns (min is 64*fs, 35us @ 44.1 Khz) */ L3HaltTime = 1, /* 190 ns */ }; /* * Grab control of the IIC/L3 shared pins */ static void L3acquirepins(void) { GpioReg *g = GPIOREG; int s; s = splhi(); g->gpsr = (L3Mode | L3Clock | L3Data); g->gpdr |= (L3Mode | L3Clock | L3Data); splx(s); // microdelay(2); } /* * Release control of the IIC/L3 shared pins */ static void L3releasepins(void) { GpioReg *g = GPIOREG; int s; s = splhi(); g->gpdr &= ~(L3Mode | L3Clock | L3Data); splx(s); } /* * Initialize the interface */ void L3init(void) { GpioReg *g = GPIOREG; int s; s = splhi(); g->gafr &= ~(L3Data | L3Clock | L3Mode); splx(s); L3releasepins(); } /* * Send a byte. The mode line is set or pulsed based on the mode sequence * count. The mode line is high on entry and exit. The mod line is pulsed * before the second data byte and before ech byte thereafter. */ static void L3sendbyte(int data, int mode) { int i; GpioReg *g = GPIOREG; switch(mode) { case 0: /* Address mode */ g->gpcr = L3Mode; break; case 1: /* First data byte */ break; default: /* Subsequent bytes */ g->gpcr = L3Mode; microdelay(L3HaltTime); g->gpsr = L3Mode; break; } microdelay(L3ModeSetupTime); for (i = 0; i < 8; i++){ microdelay(2); /* * Send a bit. The clock is high on entry and on exit. Data is sent only * when the clock is low (I2C compatibility). */ g->gpcr = L3Clock; if (data & (1<<i)) g->gpsr = L3Data; else g->gpcr = L3Data; /* Assumes L3DataSetupTime < L3ClockLowTime */ microdelay(L3ClockLowTime); g->gpsr = L3Clock; microdelay(L3ClockHighTime); } if (mode == 0) /* Address mode */ g->gpsr = L3Mode; microdelay(L3ModeHoldTime); } /* * Get a byte. The mode line is set or pulsed based on the mode sequence * count. The mode line is high on entry and exit. The mod line is pulsed * before the second data byte and before each byte thereafter. This * function is never valid with mode == 0 (address cycle) as the address * is always sent on the bus, not read. */ static int L3getbyte(int mode) { int data = 0; int i; GpioReg *g = GPIOREG; switch(mode) { case 0: /* Address mode - never valid */ break; case 1: /* First data byte */ break; default: /* Subsequent bytes */ g->gpcr = L3Mode; microdelay(L3HaltTime); g->gpsr = L3Mode; break; } microdelay(L3ModeSetupTime); for (i = 0; i < 8; i++){ /* * Get a bit. The clock is high on entry and on exit. Data is read after * the clock low time has expired. */ g->gpcr = L3Clock; microdelay(L3ClockLowTime); if(g->gplr & L3Data) data |= 1<<i; g->gpsr = L3Clock; microdelay(L3ClockHighTime); } microdelay(L3ModeHoldTime); return data; } /* * Write data to a device on the L3 bus. The address is passed as well as * the data and length. The length written is returned. The register space * is encoded in the address (low two bits are set and device address is * in the upper 6 bits). */ int L3write(int addr, void *data, int len) { int mode = 0; int bytes = len; uchar *b; L3acquirepins(); L3sendbyte(addr, mode++); for(b = data; --len >= 0;) L3sendbyte(*b++, mode++); L3releasepins(); return bytes; } /* * Read data from a device on the L3 bus. The address is passed as well as * the data and length. The length read is returned. The register space * is encoded in the address (low two bits are set and device address is * in the upper 6 bits). */ int L3read(int addr, void *data, int len) { int mode = 0; int bytes = len; uchar *b; int s; L3acquirepins(); L3sendbyte(addr, mode++); s = splhi(); GPIOREG->gpdr &= ~(L3Data); splx(s); for(b = data; --len >= 0;) *b++ = L3getbyte(mode++); L3releasepins(); return bytes; }