zcy
/
tinySA
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity
tinySA/os/hal/ports/STM32/LLD/DMAv1/stm32_dma.c

649 lines
20 KiB
C
Raw Blame History

/*
ChibiOS - Copyright (C) 2006..2015 Giovanni Di Sirio
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/
/**
* @file STM32F3xx/stm32_dma.c
* @brief DMA helper driver code.
*
* @addtogroup STM32F3xx_DMA
* @details DMA sharing helper driver. In the STM32 the DMA streams are a
* shared resource, this driver allows to allocate and free DMA
* streams at runtime in order to allow all the other device
* drivers to coordinate the access to the resource.
* @note The DMA ISR handlers are all declared into this module because
* sharing, the various device drivers can associate a callback to
* ISRs when allocating streams.
* @{
*/
#include "hal.h"
/* The following macro is only defined if some driver requiring DMA services
has been enabled.*/
#if defined(STM32_DMA_REQUIRED) || defined(__DOXYGEN__)
/*===========================================================================*/
/* Driver local definitions. */
/*===========================================================================*/
/**
* @brief Mask of the DMA1 streams in @p dma_streams_mask.
*/
#define STM32_DMA1_STREAMS_MASK ((1U << STM32_DMA1_NUM_CHANNELS) - 1U)
/**
* @brief Mask of the DMA2 streams in @p dma_streams_mask.
*/
#define STM32_DMA2_STREAMS_MASK (((1U << STM32_DMA2_NUM_CHANNELS) - \
1U) << STM32_DMA1_NUM_CHANNELS)
/**
* @brief Post-reset value of the stream CCR register.
*/
#define STM32_DMA_CCR_RESET_VALUE 0x00000000U
/*
* Handling devices with shared DMA IRQ handlers.
*/
#if defined(STM32_DMA1_CH23_NUMBER)
#define STM32_DMA1_CH2_NUMBER STM32_DMA1_CH23_NUMBER
#define STM32_DMA1_CH3_NUMBER STM32_DMA1_CH23_NUMBER
#endif
#if defined(STM32_DMA1_CH4567_NUMBER)
#define STM32_DMA1_CH4_NUMBER STM32_DMA1_CH4567_NUMBER
#define STM32_DMA1_CH5_NUMBER STM32_DMA1_CH4567_NUMBER
#define STM32_DMA1_CH6_NUMBER STM32_DMA1_CH4567_NUMBER
#define STM32_DMA1_CH7_NUMBER STM32_DMA1_CH4567_NUMBER
#endif
#if defined(STM32_DMA2_CH45_NUMBER)
#define STM32_DMA2_CH4_NUMBER STM32_DMA2_CH45_NUMBER
#define STM32_DMA2_CH5_NUMBER STM32_DMA2_CH45_NUMBER
#endif
#if STM32_DMA_SUPPORTS_CSELR == TRUE
#define ADDR_DMA1_CSELR &DMA1_CSELR->CSELR
#define ADDR_DMA2_CSELR &DMA2_CSELR->CSELR
#else
#define ADDR_DMA1_CSELR NULL
#define ADDR_DMA2_CSELR NULL
#endif
/*
* ISR collision masks.
*/
#define DMA1_CH1_CMASK 0x00000001U
#if !defined(STM32_DMA1_CH23_NUMBER)
#define DMA1_CH2_CMASK 0x00000002U
#define DMA1_CH3_CMASK 0x00000004U
#else
#define DMA1_CH2_CMASK 0x00000006U
#define DMA1_CH3_CMASK 0x00000006U
#endif
#if !defined(STM32_DMA1_CH4567_NUMBER)
#define DMA1_CH4_CMASK 0x00000008U
#define DMA1_CH5_CMASK 0x00000010U
#define DMA1_CH6_CMASK 0x00000020U
#define DMA1_CH7_CMASK 0x00000040U
#else
#define DMA1_CH4_CMASK 0x00000078U
#define DMA1_CH5_CMASK 0x00000078U
#define DMA1_CH6_CMASK 0x00000078U
#define DMA1_CH7_CMASK 0x00000078U
#endif
#define DMA2_CH1_CMASK 0x00000080U
#define DMA2_CH2_CMASK 0x00000100U
#define DMA2_CH3_CMASK 0x00000200U
#if !defined(STM32_DMA2_CH45_NUMBER)
#define DMA2_CH4_CMASK 0x00000400U
#define DMA2_CH5_CMASK 0x00000800U
#else
#define DMA2_CH4_CMASK 0x00000C00U
#define DMA2_CH5_CMASK 0x00000C00U
#endif
/*===========================================================================*/
/* Driver exported variables. */
/*===========================================================================*/
/**
* @brief DMA streams descriptors.
* @details This table keeps the association between an unique stream
* identifier and the involved physical registers.
* @note Don't use this array directly, use the appropriate wrapper macros
* instead: @p STM32_DMA1_STREAM1, @p STM32_DMA1_STREAM2 etc.
*/
const stm32_dma_stream_t _stm32_dma_streams[STM32_DMA_STREAMS] = {
{DMA1_Channel1, DMA1_CH1_CMASK, &DMA1->IFCR, ADDR_DMA1_CSELR, 0, 0, STM32_DMA1_CH1_NUMBER},
{DMA1_Channel2, DMA1_CH2_CMASK, &DMA1->IFCR, ADDR_DMA1_CSELR, 4, 1, STM32_DMA1_CH2_NUMBER},
{DMA1_Channel3, DMA1_CH3_CMASK, &DMA1->IFCR, ADDR_DMA1_CSELR, 8, 2, STM32_DMA1_CH3_NUMBER},
{DMA1_Channel4, DMA1_CH4_CMASK, &DMA1->IFCR, ADDR_DMA1_CSELR, 12, 3, STM32_DMA1_CH4_NUMBER},
{DMA1_Channel5, DMA1_CH5_CMASK, &DMA1->IFCR, ADDR_DMA1_CSELR, 16, 4, STM32_DMA1_CH5_NUMBER},
#if STM32_DMA1_NUM_CHANNELS > 5
{DMA1_Channel6, DMA1_CH6_CMASK, &DMA1->IFCR, ADDR_DMA1_CSELR, 20, 5, STM32_DMA1_CH6_NUMBER},
#endif
#if STM32_DMA1_NUM_CHANNELS > 6
{DMA1_Channel7, DMA1_CH7_CMASK, &DMA1->IFCR, ADDR_DMA1_CSELR, 24, 6, STM32_DMA1_CH7_NUMBER},
#endif
#if STM32_DMA2_NUM_CHANNELS > 0
{DMA2_Channel1, DMA2_CH1_CMASK, &DMA2->IFCR, ADDR_DMA2_CSELR, 0, 8, STM32_DMA2_CH1_NUMBER},
{DMA2_Channel2, DMA2_CH2_CMASK, &DMA2->IFCR, ADDR_DMA2_CSELR, 4, 9, STM32_DMA2_CH2_NUMBER},
{DMA2_Channel3, DMA2_CH3_CMASK, &DMA2->IFCR, ADDR_DMA2_CSELR, 8, 10, STM32_DMA2_CH3_NUMBER},
{DMA2_Channel4, DMA2_CH4_CMASK, &DMA2->IFCR, ADDR_DMA2_CSELR, 12, 11, STM32_DMA2_CH4_NUMBER},
{DMA2_Channel5, DMA2_CH5_CMASK, &DMA2->IFCR, ADDR_DMA2_CSELR, 16, 13, STM32_DMA2_CH5_NUMBER},
#endif
};
/*===========================================================================*/
/* Driver local variables and types. */
/*===========================================================================*/
/**
* @brief DMA ISR redirector type.
*/
typedef struct {
stm32_dmaisr_t dma_func; /**< @brief DMA callback function. */
void *dma_param; /**< @brief DMA callback parameter. */
} dma_isr_redir_t;
/**
* @brief Mask of the allocated streams.
*/
static uint32_t dma_streams_mask;
/**
* @brief DMA IRQ redirectors.
*/
static dma_isr_redir_t dma_isr_redir[STM32_DMA_STREAMS];
/*===========================================================================*/
/* Driver local functions. */
/*===========================================================================*/
/*===========================================================================*/
/* Driver interrupt handlers. */
/*===========================================================================*/
/**
* @brief DMA1 stream 1 shared interrupt handler.
*
* @isr
*/
OSAL_IRQ_HANDLER(STM32_DMA1_CH1_HANDLER) {
uint32_t flags;
OSAL_IRQ_PROLOGUE();
flags = (DMA1->ISR >> 0) & STM32_DMA_ISR_MASK;
DMA1->IFCR = flags << 0;
if (dma_isr_redir[0].dma_func)
dma_isr_redir[0].dma_func(dma_isr_redir[0].dma_param, flags);
OSAL_IRQ_EPILOGUE();
}
/* Channels 2 and 3 are shared on some devices.*/
#if defined(STM32_DMA1_CH23_HANDLER)
/**
* @brief DMA1 streams 2 and 3 shared interrupt handler.
*
* @isr
*/
OSAL_IRQ_HANDLER(STM32_DMA1_CH23_HANDLER) {
uint32_t flags;
OSAL_IRQ_PROLOGUE();
/* Check on channel 2.*/
flags = (DMA1->ISR >> 4) & STM32_DMA_ISR_MASK;
if (flags & STM32_DMA_ISR_MASK) {
DMA1->IFCR = flags << 4;
if (dma_isr_redir[1].dma_func)
dma_isr_redir[1].dma_func(dma_isr_redir[1].dma_param, flags);
}
/* Check on channel 3.*/
flags = (DMA1->ISR >> 8) & STM32_DMA_ISR_MASK;
if (flags & STM32_DMA_ISR_MASK) {
DMA1->IFCR = flags << 8;
if (dma_isr_redir[2].dma_func)
dma_isr_redir[2].dma_func(dma_isr_redir[2].dma_param, flags);
}
OSAL_IRQ_EPILOGUE();
}
#else /*!defined(STM32_DMA1_CH23_HANDLER) */
/**
* @brief DMA1 stream 2 shared interrupt handler.
*
* @isr
*/
OSAL_IRQ_HANDLER(STM32_DMA1_CH2_HANDLER) {
uint32_t flags;
OSAL_IRQ_PROLOGUE();
flags = (DMA1->ISR >> 4) & STM32_DMA_ISR_MASK;
DMA1->IFCR = flags << 4;
if (dma_isr_redir[1].dma_func)
dma_isr_redir[1].dma_func(dma_isr_redir[1].dma_param, flags);
OSAL_IRQ_EPILOGUE();
}
/**
* @brief DMA1 stream 3 shared interrupt handler.
*
* @isr
*/
OSAL_IRQ_HANDLER(STM32_DMA1_CH3_HANDLER) {
uint32_t flags;
OSAL_IRQ_PROLOGUE();
flags = (DMA1->ISR >> 8) & STM32_DMA_ISR_MASK;
DMA1->IFCR = flags << 8;
if (dma_isr_redir[2].dma_func)
dma_isr_redir[2].dma_func(dma_isr_redir[2].dma_param, flags);
OSAL_IRQ_EPILOGUE();
}
#endif /*!defined(STM32_DMA1_CH23_HANDLER) */
/* Channels 4, 5, 6 and 7 are shared on some devices.*/
#if defined(STM32_DMA1_CH4567_HANDLER)
/**
* @brief DMA1 streams 4 and 5 shared interrupt handler.
*
* @isr
*/
OSAL_IRQ_HANDLER(STM32_DMA1_CH4567_HANDLER) {
uint32_t flags;
OSAL_IRQ_PROLOGUE();
/* Check on channel 4.*/
flags = (DMA1->ISR >> 12) & STM32_DMA_ISR_MASK;
if (flags & STM32_DMA_ISR_MASK) {
DMA1->IFCR = flags << 12;
if (dma_isr_redir[3].dma_func)
dma_isr_redir[3].dma_func(dma_isr_redir[3].dma_param, flags);
}
/* Check on channel 5.*/
flags = (DMA1->ISR >> 16) & STM32_DMA_ISR_MASK;
if (flags & STM32_DMA_ISR_MASK) {
DMA1->IFCR = flags << 16;
if (dma_isr_redir[4].dma_func)
dma_isr_redir[4].dma_func(dma_isr_redir[4].dma_param, flags);
}
#if STM32_DMA1_NUM_CHANNELS > 5
/* Check on channel 6.*/
flags = (DMA1->ISR >> 20) & STM32_DMA_ISR_MASK;
if (flags & STM32_DMA_ISR_MASK) {
DMA1->IFCR = flags << 20;
if (dma_isr_redir[5].dma_func)
dma_isr_redir[5].dma_func(dma_isr_redir[5].dma_param, flags);
}
#endif
#if STM32_DMA1_NUM_CHANNELS > 6
/* Check on channel 7.*/
flags = (DMA1->ISR >> 24) & STM32_DMA_ISR_MASK;
if (flags & STM32_DMA_ISR_MASK) {
DMA1->IFCR = flags << 24;
if (dma_isr_redir[6].dma_func)
dma_isr_redir[6].dma_func(dma_isr_redir[6].dma_param, flags);
}
#endif
OSAL_IRQ_EPILOGUE();
}
#else /* !defined(STM32_DMA1_CH4567_HANDLER) */
/**
* @brief DMA1 stream 4 shared interrupt handler.
*
* @isr
*/
OSAL_IRQ_HANDLER(STM32_DMA1_CH4_HANDLER) {
uint32_t flags;
OSAL_IRQ_PROLOGUE();
flags = (DMA1->ISR >> 12) & STM32_DMA_ISR_MASK;
DMA1->IFCR = flags << 12;
if (dma_isr_redir[3].dma_func)
dma_isr_redir[3].dma_func(dma_isr_redir[3].dma_param, flags);
OSAL_IRQ_EPILOGUE();
}
/**
* @brief DMA1 stream 5 shared interrupt handler.
*
* @isr
*/
OSAL_IRQ_HANDLER(STM32_DMA1_CH5_HANDLER) {
uint32_t flags;
OSAL_IRQ_PROLOGUE();
flags = (DMA1->ISR >> 16) & STM32_DMA_ISR_MASK;
DMA1->IFCR = flags << 16;
if (dma_isr_redir[4].dma_func)
dma_isr_redir[4].dma_func(dma_isr_redir[4].dma_param, flags);
OSAL_IRQ_EPILOGUE();
}
#if (STM32_DMA1_NUM_CHANNELS > 5) || defined(__DOXYGEN__)
/**
* @brief DMA1 stream 6 shared interrupt handler.
*
* @isr
*/
OSAL_IRQ_HANDLER(STM32_DMA1_CH6_HANDLER) {
uint32_t flags;
OSAL_IRQ_PROLOGUE();
flags = (DMA1->ISR >> 20) & STM32_DMA_ISR_MASK;
DMA1->IFCR = flags << 20;
if (dma_isr_redir[5].dma_func)
dma_isr_redir[5].dma_func(dma_isr_redir[5].dma_param, flags);
OSAL_IRQ_EPILOGUE();
}
#endif /* STM32_DMA1_NUM_CHANNELS > 5 */
#if (STM32_DMA1_NUM_CHANNELS > 6) || defined(__DOXYGEN__)
/**
* @brief DMA1 stream 7 shared interrupt handler.
*
* @isr
*/
OSAL_IRQ_HANDLER(STM32_DMA1_CH7_HANDLER) {
uint32_t flags;
OSAL_IRQ_PROLOGUE();
flags = (DMA1->ISR >> 24) & STM32_DMA_ISR_MASK;
DMA1->IFCR = flags << 24;
if (dma_isr_redir[6].dma_func)
dma_isr_redir[6].dma_func(dma_isr_redir[6].dma_param, flags);
OSAL_IRQ_EPILOGUE();
}
#endif /* STM32_DMA1_NUM_CHANNELS > 6 */
#endif /* !defined(STM32_DMA1_CH4567_HANDLER) */
#if (STM32_DMA2_NUM_CHANNELS > 0) || defined(__DOXYGEN__)
/**
* @brief DMA2 stream 1 shared interrupt handler.
*
* @isr
*/
OSAL_IRQ_HANDLER(STM32_DMA2_CH1_HANDLER) {
uint32_t flags;
OSAL_IRQ_PROLOGUE();
flags = (DMA2->ISR >> 0) & STM32_DMA_ISR_MASK;
DMA2->IFCR = flags << 0;
if (dma_isr_redir[7].dma_func)
dma_isr_redir[7].dma_func(dma_isr_redir[7].dma_param, flags);
OSAL_IRQ_EPILOGUE();
}
/**
* @brief DMA2 stream 2 shared interrupt handler.
*
* @isr
*/
OSAL_IRQ_HANDLER(STM32_DMA2_CH2_HANDLER) {
uint32_t flags;
OSAL_IRQ_PROLOGUE();
flags = (DMA2->ISR >> 4) & STM32_DMA_ISR_MASK;
DMA2->IFCR = flags << 4;
if (dma_isr_redir[8].dma_func)
dma_isr_redir[8].dma_func(dma_isr_redir[8].dma_param, flags);
OSAL_IRQ_EPILOGUE();
}
/**
* @brief DMA2 stream 3 shared interrupt handler.
*
* @isr
*/
OSAL_IRQ_HANDLER(STM32_DMA2_CH3_HANDLER) {
uint32_t flags;
OSAL_IRQ_PROLOGUE();
flags = (DMA2->ISR >> 8) & STM32_DMA_ISR_MASK;
DMA2->IFCR = flags << 8;
if (dma_isr_redir[9].dma_func)
dma_isr_redir[9].dma_func(dma_isr_redir[9].dma_param, flags);
OSAL_IRQ_EPILOGUE();
}
/* Channels 4 and 5 are shared on some devices.*/
#if defined(STM32_DMA2_CH45_HANDLER)
/**
* @brief DMA2 streams 4 and 5 shared interrupt handler.
*
* @isr
*/
OSAL_IRQ_HANDLER(STM32_DMA2_CH4_HANDLER) {
uint32_t flags;
OSAL_IRQ_PROLOGUE();
flags = (DMA2->ISR >> 12) & STM32_DMA_ISR_MASK;
DMA2->IFCR = flags << 12;
if (dma_isr_redir[10].dma_func)
dma_isr_redir[10].dma_func(dma_isr_redir[10].dma_param, flags);
flags = (DMA2->ISR >> 16) & STM32_DMA_ISR_MASK;
DMA2->IFCR = flags << 16;
if (dma_isr_redir[11].dma_func)
dma_isr_redir[11].dma_func(dma_isr_redir[11].dma_param, flags);
OSAL_IRQ_EPILOGUE();
}
#else /* !defined(STM32_DMA2_CH45_HANDLER) */
/**
* @brief DMA2 stream 4 shared interrupt handler.
*
* @isr
*/
OSAL_IRQ_HANDLER(STM32_DMA2_CH4_HANDLER) {
uint32_t flags;
OSAL_IRQ_PROLOGUE();
flags = (DMA2->ISR >> 12) & STM32_DMA_ISR_MASK;
DMA2->IFCR = flags << 12;
if (dma_isr_redir[10].dma_func)
dma_isr_redir[10].dma_func(dma_isr_redir[10].dma_param, flags);
OSAL_IRQ_EPILOGUE();
}
/**
* @brief DMA2 stream 5 shared interrupt handler.
*
* @isr
*/
OSAL_IRQ_HANDLER(STM32_DMA2_CH5_HANDLER) {
uint32_t flags;
OSAL_IRQ_PROLOGUE();
flags = (DMA2->ISR >> 16) & STM32_DMA_ISR_MASK;
DMA2->IFCR = flags << 16;
if (dma_isr_redir[11].dma_func)
dma_isr_redir[11].dma_func(dma_isr_redir[11].dma_param, flags);
OSAL_IRQ_EPILOGUE();
}
#endif /* defined(STM32_DMA2_CH45_HANDLER) */
#endif /* STM32_DMA2_NUM_CHANNELS > 0 */
/*===========================================================================*/
/* Driver exported functions. */
/*===========================================================================*/
/**
* @brief STM32 DMA helper initialization.
*
* @init
*/
void dmaInit(void) {
int i;
dma_streams_mask = 0U;
for (i = 0; i < STM32_DMA_STREAMS; i++) {
_stm32_dma_streams[i].channel->CCR = 0U;
dma_isr_redir[i].dma_func = NULL;
}
DMA1->IFCR = 0xFFFFFFFFU;
#if STM32_DMA2_NUM_CHANNELS > 0
DMA2->IFCR = 0xFFFFFFFFU;
#endif
}
/**
* @brief Allocates a DMA stream.
* @details The stream is allocated and, if required, the DMA clock enabled.
* The function also enables the IRQ vector associated to the stream
* and initializes its priority.
* @pre The stream must not be already in use or an error is returned.
* @post The stream is allocated and the default ISR handler redirected
* to the specified function.
* @post The stream ISR vector is enabled and its priority configured.
* @post The stream must be freed using @p dmaStreamRelease() before it can
* be reused with another peripheral.
* @post The stream is in its post-reset state.
* @note This function can be invoked in both ISR or thread context.
*
* @param[in] dmastp pointer to a stm32_dma_stream_t structure
* @param[in] priority IRQ priority mask for the DMA stream
* @param[in] func handling function pointer, can be @p NULL
* @param[in] param a parameter to be passed to the handling function
* @return The operation status.
* @retval false no error, stream taken.
* @retval true error, stream already taken.
*
* @special
*/
bool dmaStreamAllocate(const stm32_dma_stream_t *dmastp,
uint32_t priority,
stm32_dmaisr_t func,
void *param) {
osalDbgCheck(dmastp != NULL);
/* Checks if the stream is already taken.*/
if ((dma_streams_mask & (1U << dmastp->selfindex)) != 0U)
return true;
/* Installs the DMA handler.*/
dma_isr_redir[dmastp->selfindex].dma_func = func;
dma_isr_redir[dmastp->selfindex].dma_param = param;
/* Enabling DMA clocks required by the current streams set.*/
if ((dma_streams_mask & STM32_DMA1_STREAMS_MASK) == 0U) {
rccEnableDMA1(false);
}
#if STM32_DMA2_NUM_CHANNELS > 0
if ((dma_streams_mask & STM32_DMA2_STREAMS_MASK) == 0U) {
rccEnableDMA2(false);
}
#endif
/* Putting the stream in a safe state.*/
dmaStreamDisable(dmastp);
dmastp->channel->CCR = STM32_DMA_CCR_RESET_VALUE;
/* Enables the associated IRQ vector if not alread enabled and if a
callback is defined.*/
if (((dma_streams_mask & dmastp->cmask) == 0U) &&
(func != NULL)) {
nvicEnableVector(dmastp->vector, priority);
}
/* Marks the stream as allocated.*/
dma_streams_mask |= (1U << dmastp->selfindex);
return false;
}
/**
* @brief Releases a DMA stream.
* @details The stream is freed and, if required, the DMA clock disabled.
* Trying to release a unallocated stream is an illegal operation
* and is trapped if assertions are enabled.
* @pre The stream must have been allocated using @p dmaStreamAllocate().
* @post The stream is again available.
* @note This function can be invoked in both ISR or thread context.
*
* @param[in] dmastp pointer to a stm32_dma_stream_t structure
*
* @special
*/
void dmaStreamRelease(const stm32_dma_stream_t *dmastp) {
osalDbgCheck(dmastp != NULL);
/* Check if the streams is not taken.*/
osalDbgAssert((dma_streams_mask & (1 << dmastp->selfindex)) != 0U,
"not allocated");
/* Marks the stream as not allocated.*/
dma_streams_mask &= ~(1U << dmastp->selfindex);
/* Disables the associated IRQ vector if it is no more in use.*/
if ((dma_streams_mask & dmastp->cmask) == 0U) {
nvicDisableVector(dmastp->vector);
}
/* Removes the DMA handler.*/
dma_isr_redir[dmastp->selfindex].dma_func = NULL;
dma_isr_redir[dmastp->selfindex].dma_param = NULL;
/* Shutting down clocks that are no more required, if any.*/
if ((dma_streams_mask & STM32_DMA1_STREAMS_MASK) == 0U) {
rccDisableDMA1(false);
}
#if STM32_DMA2_NUM_CHANNELS > 0
if ((dma_streams_mask & STM32_DMA2_STREAMS_MASK) == 0U) {
rccDisableDMA2(false);
}
#endif
}
#endif /* STM32_DMA_REQUIRED */
/** @} */
Reference in New Issue View Git Blame Copy Permalink