297 lines
9.3 KiB
C
297 lines
9.3 KiB
C
/*
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* Copyright (C) 2013-2015 Apple Inc. All rights reserved.
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*
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* This document is the property of Apple Inc.
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* It is considered confidential and proprietary.
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*
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* This document may not be reproduced or transmitted in any form,
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* in whole or in part, without the express written permission of
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* Apple Inc.
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*/
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#include <debug.h>
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#include <cbuffer.h>
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#include <drivers/power.h>
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#include <platform.h>
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#include <platform/dockchannel_config.h>
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#include <platform/int.h>
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#include <platform/soc/hwclocks.h>
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#include <sys.h>
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#include <sys/task.h>
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#include <platform/timer.h>
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#include "dockchannel_regs.h"
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extern int DebugUartReady;
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#define DOCKCHANNEL_UART_RX_LEN (16)
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// Allow a 30ms stall of wall clock time before DockFIFO starts dropping characters
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#define DOCKCHANNEL_WR_MAX_STALL_US (60*1000)
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static CBUFFER dockchannel_uart_rx_cbuf;
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static struct task_event dockchannel_uart_rx_event;
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static uint64_t prev_dockchannel_drained_time; // Last time we've seen the DockFIFO drained by an external agent
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static uint64_t prev_dockchannel_spaces; // Previous w_stat level of the DockFIFO.
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static uint32_t dockchannel_capacity;
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#define INSTRUMENT_DOCKCHANNEL_DRAIN_COUNTER 1
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#if INSTRUMENT_DOCKCHANNEL_DRAIN_COUNTER
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#define DOCKCHANNEL_STAT_INCR(x) ((x)++)
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static unsigned int dockchannel_stat_active_stall_loops;
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static unsigned int dockchannel_stat_dropped_characters;
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#else
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#define DOCKCHANNEL_STAT_INCR(x)
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#endif
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//=======================
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// Local funtions
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//=======================
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// <rdar://problem/20473403> M8: Remove drain timer logic in DockChannel driver after verifying on silicon
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static int dockchannel_drain_on_stall()
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{
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// Called when DockFIFO runs out of spaces.
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// Check if the DockFIFO reader has stalled. If so, empty the DockFIFO ourselves.
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// Return number of bytes drained.
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if (timer_ticks_to_usecs(timer_get_ticks() - prev_dockchannel_drained_time) >= DOCKCHANNEL_WR_MAX_STALL_US) {
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// It's been more than DOCKFIFO_WR_MAX_STALL_US and nobody read from the FIFO
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// Drop a character.
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DOCKCHANNEL_STAT_INCR(dockchannel_stat_dropped_characters);
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(void)rDOCKCHANNELS_DOCK_RDATA1(DOCKCHANNEL_UART);
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prev_dockchannel_spaces++;
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return 1;
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}
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return 0;
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}
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static int32_t dockchannel_uart_write_byte(uint8_t byte)
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{
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/**
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* DockFIFO Draining algorithm:
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*
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* We want DockFIFO UART to try hard to preserve characters as long as someone is
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* listening to the DockFIFO. But we also want DockFIFO to drop characters rapidly
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* when the FIFO is full and nobody is listening.
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*
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* So, when the DockFIFO is full, we will hang and poll for a max of DOCKFIFO_WR_MAX_STALL_US
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* If this time expires, we will begin instantly dropping the oldest character when we notice
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* the DockFIFO to be full (e.g. nobody is listening to DockFIFO).
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*
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* But, the moment we see someone start emptying the DockFIFO, the timer resets.
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* This will achieve a good balance between making sure we don't drop chars when the host is listening,
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* and making sure UART write overhead is low when nobody is attached to it.
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*
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**/
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// Atomically check for free space in write fifo and enqueue a byte.
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enter_critical_section();
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for (;;) {
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uint32_t spaces = rDOCKCHANNELS_DEV_WSTAT(DOCKCHANNEL_UART) & 0x1ff;
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if (spaces >= dockchannel_capacity || spaces > prev_dockchannel_spaces) {
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// More spaces showed up. That can only mean someone read the FIFO.
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// Note that if the DockFIFO is empty we cannot tell if someone is listening,
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// we can only give them the benefit of the doubt.
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prev_dockchannel_drained_time = timer_get_ticks();
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}
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prev_dockchannel_spaces = spaces;
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if (spaces > 0 || dockchannel_drain_on_stall()) {
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// We either had spaces, or just kicked out a stale byte on a stalled DockFIFO.
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break;
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}
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exit_critical_section();
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// If we reached here, the DockFIFO is still full, probably due to heavy UART
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// traffic with an active reader.
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DOCKCHANNEL_STAT_INCR(dockchannel_stat_active_stall_loops);
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enter_critical_section();
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}
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rDOCKCHANNELS_DEV_WDATA1(DOCKCHANNEL_UART) = byte;
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prev_dockchannel_spaces--; // After writing a byte we have one fewer space than previously expected.
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exit_critical_section();
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return 0;
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}
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static int32_t dockchannel_uart_write(const uint8_t *data, size_t count, bool wait)
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{
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RELEASE_ASSERT(data != NULL);
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int32_t ret = 0;
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for (size_t i = 0; ret == 0 && i < count; ++i) {
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ret = dockchannel_uart_write_byte(data[i]);
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}
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return ret;
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}
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static int32_t dockchannel_uart_read(uint8_t *data, size_t count, bool wait)
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{
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int32_t bytes_read = 0;
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RELEASE_ASSERT(data != NULL);
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retry_read:
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if (wait && (!cb_readable_size(&dockchannel_uart_rx_cbuf)))
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event_wait(&dockchannel_uart_rx_event);
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/* disable rx interrupt */
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rDOCKCHANNELS_AGENT_AP_INTR_CTRL &= ~(1<<1);
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mask_int(INT_DOCKCHANNELS_AP);
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bytes_read += cb_read_unsafe(&dockchannel_uart_rx_cbuf, data + bytes_read, count - bytes_read);
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/* enable rx interrupt */
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rDOCKCHANNELS_AGENT_AP_INTR_CTRL |= (1<<1);
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unmask_int(INT_DOCKCHANNELS_AP);
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if (((size_t)bytes_read < count) && wait)
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goto retry_read;
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return bytes_read;
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}
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static int dockchannel_uart_reader_task(void *arg)
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{
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for(;;) {
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char c;
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int32_t len;
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len = dockchannel_uart_read((uint8_t *)&c, 1, true);
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if ((len > 0) && ((DebugUartReady & kPowerNVRAMiBootDebugIAPSerial) != 0))
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debug_pushchar(c);
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}
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return 0;
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}
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static void dockchannel_uart_interrupt(void *arg)
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{
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uint32_t intr_status = rDOCKCHANNELS_AGENT_AP_INTR_STATUS;
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// Clear status to deassert interrupt
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rDOCKCHANNELS_AGENT_AP_INTR_STATUS = (1<<1);
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// Disable interrupts and mask so that we dont get interrupted while processing
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// this data
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rDOCKCHANNELS_AGENT_AP_INTR_CTRL &= ~(1<<1);
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mask_int(INT_DOCKCHANNELS_AP);
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// Read watermark interrupt
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if ((intr_status >> 1) & 1) { // Rx
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while (((rDOCKCHANNELS_DEV_RSTAT(DOCKCHANNEL_UART) & 0x1ff) != 0) && cb_free_space(&dockchannel_uart_rx_cbuf))
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cb_putc_unsafe(&dockchannel_uart_rx_cbuf, (rDOCKCHANNELS_DEV_RDATA1(DOCKCHANNEL_UART) >> 8) & 0xff);
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/* signal reader */
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event_signal(&dockchannel_uart_rx_event);
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} else {
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// Spurious interrupt since we only enable the dock channel 0 read watermark interrupt
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// Unmask interrupts and continue
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rDOCKCHANNELS_AGENT_AP_INTR_CTRL |= (1<<1);
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unmask_int(INT_DOCKCHANNELS_AP);
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}
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}
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//=======================
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// Global funtions
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//=======================
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int32_t dockchannel_uart_init()
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{
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// Setup clock
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clock_gate(CLK_AOP, true);
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// reset fifos
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rDOCKCHANNELS_DEV_FIFO_CTRL(DOCKCHANNEL_UART) = 1;
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rDOCKCHANNELS_DOCK_FIFO_CTRL(DOCKCHANNEL_UART) = 1;
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// Empty the DockChannel by draining it until OCCUPANCY is 0, then measure its capacity
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while (rDOCKCHANNELS_DOCK_RDATA3(DOCKCHANNEL_UART) & 0x7F);
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dockchannel_capacity = rDOCKCHANNELS_DEV_WSTAT(DOCKCHANNEL_UART) & 0xffff;
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// Setup drain timer
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// Each tick is an AOP clock cycle and we want the period to be 30 ms
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// which is ~ twice the kanzi sampling time
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uint32_t period = clock_get_frequency(CLK_AOP) * (0.003);
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if (period == 0)
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dprintf(DEBUG_CRITICAL, "Disabling DockChannel Drain Timer. This can lead to loss of data. \n");
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rDOCKCHANNELS_DOCK_DRAIN_CFG(DOCKCHANNEL_UART) = period;
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dprintf(DEBUG_SPEW, "%s: Drain timer period %d \n", __FUNCTION__, period);
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cb_create(&dockchannel_uart_rx_cbuf, DOCKCHANNEL_UART_RX_LEN);
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event_init(&dockchannel_uart_rx_event, EVENT_FLAG_AUTO_UNSIGNAL, false);
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// Using watermark for the purpose of signalling not empty fifo
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rDOCKCHANNELS_DEV_CONFIG_RD_WATERMARK(DOCKCHANNEL_UART) = 1;
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rDOCKCHANNELS_AGENT_AP_INTR_CTRL = (1<<1);
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// AP has a shared interrupt for all channels. We only enable the relevant interrupts (read watermark)
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// for dock channel in iBoot. If there are multiple dockchannel clients we will need an interrupt filter
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// type function.
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install_int_handler(INT_DOCKCHANNELS_AP, &dockchannel_uart_interrupt, (void *)NULL);
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unmask_int(INT_DOCKCHANNELS_AP);
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task_start(task_create("dockchannel_uart reader", dockchannel_uart_reader_task, NULL, 0x200));
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dprintf(DEBUG_SPEW, "%s\n", __FUNCTION__);
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return 0;
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}
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int32_t dockchannel_uart_putc(char c)
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{
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return dockchannel_uart_write((uint8_t *)&c, 1, true);
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}
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int32_t dockchannel_uart_getc(bool wait) /* returns -1 if no data available */
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{
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char c;
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int32_t len;
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len = dockchannel_uart_read((uint8_t *)&c, 1, wait);
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if (len == 0)
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return -1;
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return c;
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}
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void dockchannel_enable_clock_gating(uint32_t channel)
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{
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rDOCKCHANNELS_GLOBAL(DOCK_CHANNELS_DOCKCHANNELS_GLOBAL_DC_CFG_OFFSET) |= (1 << (4 * (channel + 1)));
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}
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void dockchannel_enable_top_clock_gating()
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{
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rDOCKCHANNELS_GLOBAL(DOCK_CHANNELS_DOCKCHANNELS_GLOBAL_DC_CFG_OFFSET) |= 1;
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}
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void dockchannel_access_enable(uint32_t enable_flags)
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{
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uint32_t curr_value = rDOCKCHANNELS_GLOBAL(DOCK_CHANNELS_DOCKCHANNELS_GLOBAL_DOCK_ACCESS_OFFSET);
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dprintf(DEBUG_SPEW, "%s: dockchannel_access_reg:0x%08x, requested:0x%08x\n", __FUNCTION__, curr_value, enable_flags);
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// XXX Easy WA but bug (18708180) should have been fixed. Decide whether to keep or not.
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if (curr_value)
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panic("dockchannel_access_enable already nonzero (0x%08x), this can cause a hang due to <rdar://problem/18708180>", curr_value);
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rDOCKCHANNELS_GLOBAL(DOCK_CHANNELS_DOCKCHANNELS_GLOBAL_DOCK_ACCESS_OFFSET) = enable_flags;
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dprintf(DEBUG_SPEW, "%s: finished, dockchannel_access_reg:0x%08x \n", __FUNCTION__, rDOCKCHANNELS_GLOBAL(DOCK_CHANNELS_DOCKCHANNELS_GLOBAL_DOCK_ACCESS_OFFSET));
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}
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