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stm32: ethernet: clarify DMA descriptors buffer requirements

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This commit is contained in:
Paul Fertser 2018-01-03 13:25:16 +03:00 committed by Karl Palsson
parent 1de1886384
commit 965d28ecbe
1 changed files with 14 additions and 9 deletions
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23
lib/ethernet/mac_stm32fxx7.c
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@ -56,23 +56,28 @@ void eth_set_mac(uint8_t *mac)
}
/*---------------------------------------------------------------------------*/
/** @brief Initialize descriptors
/** @brief Initialize buffers and descriptors.
*
* @param[in] buf uint8_t* Buffer for the descriptors
* @param[in] nTx uint32_t Count of Transmit Descriptors
* @param[in] nRx uint32_t Count of Receive Descriptors
* @param[in] cTx uint32_t Bytes in each Transmit Descriptor
* @param[in] cRx uint32_t Bytes in each Receive Descriptor
* @param[in] isext bool true, if extended descriptors should be used
* @param[in] buf uint8_t* Memory area for the descriptors and data buffers
* @param[in] nTx uint32_t Count of transmit descriptors (equal to count of buffers)
* @param[in] nRx uint32_t Count of receive descriptors (equal to count of buffers)
* @param[in] cTx uint32_t Bytes in each transmit buffer, must be a
* multiple of 4
* @param[in] cRx uint32_t Bytes in each receive buffer, must be a
* multiple of 4
* @param[in] isext bool true if extended descriptors should be used
*
* Note, the space passed via buf pointer must be large enough to
* hold all the buffers and one descriptor per buffer.
*/
void eth_desc_init(uint8_t *buf, uint32_t nTx, uint32_t nRx, uint32_t cTx,
uint32_t cRx, bool isext)
{
memset(buf, 0, nTx * cTx + nRx * cRx);
uint32_t bd = (uint32_t)buf;
uint32_t sz = isext ? ETH_DES_EXT_SIZE : ETH_DES_STD_SIZE;
memset(buf, 0, nTx * (cTx + sz) + nRx * (cRx + sz));
/* enable / disable extended frames */
if (isext) {
ETH_DMABMR |= ETH_DMABMR_EDFE;