ardupilot/libraries/AP_HAL_ChibiOS/shared_dma.h

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/*
* This file is free software: you can redistribute it and/or modify it
* under the terms of the GNU General Public License as published by the
* Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This file is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
* See the GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License along
* with this program. If not, see <http://www.gnu.org/licenses/>.
*
* Code by Andrew Tridgell and Siddharth Bharat Purohit
*/
#pragma once
#include "AP_HAL_ChibiOS.h"
#define SHARED_DMA_MAX_STREAM_ID (8*2)
// DMA stream ID for stream_id2 when only one is needed
#define SHARED_DMA_NONE 255
class ChibiOS::Shared_DMA
{
public:
FUNCTOR_TYPEDEF(dma_allocate_fn_t, void, Shared_DMA *);
FUNCTOR_TYPEDEF(dma_deallocate_fn_t, void, Shared_DMA *);
// the use of two stream IDs is for support of peripherals that
// need both a RX and TX DMA channel
Shared_DMA(uint8_t stream_id1, uint8_t stream_id2,
dma_allocate_fn_t allocate,
dma_allocate_fn_t deallocate);
// initialise the stream locks
static void init(void);
// blocking lock call
void lock(void);
// non-blocking lock call
bool lock_nonblock(void);
// unlock call. The DMA channel will not be immediately
// deallocated. Instead it will be deallocated if another driver
// needs it
void unlock(void);
// unlock call from an IRQ
void unlock_from_IRQ(void);
// unlock call from a chSysLock zone
void unlock_from_lockzone(void);
//should be called inside the destructor of Shared DMA participants
void unregister(void);
// return true if this DMA channel is being actively contended for
// by multiple drivers
bool has_contention(void) const { return contention; }
// lock all shared DMA channels. Used on reboot
static void lock_all(void);
private:
dma_allocate_fn_t allocate;
dma_allocate_fn_t deallocate;
uint8_t stream_id1;
uint8_t stream_id2;
bool have_lock;
// we set the contention flag if two drivers are fighting over a DMA channel.
// the UART driver uses this to change its max transmit size to reduce latency
bool contention;
// core of lock call, after semaphores gained
void lock_core(void);
static struct dma_lock {
// semaphore to ensure only one peripheral uses a DMA channel at a time
binary_semaphore_t semaphore;
// a de-allocation function that is called to release an existing user
dma_deallocate_fn_t deallocate;
// point to object that holds the allocation, if allocated
Shared_DMA *obj;
} locks[SHARED_DMA_MAX_STREAM_ID];
};