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tinySA/os/hal/ports/STM32/LLD/USBv1/usb_lld.c

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/*
ChibiOS/RT - Copyright (C) 2006-2013 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 STM32/USBv1/usb_lld.c
* @brief STM32 USB subsystem low level driver source.
*
* @addtogroup USB
* @{
*/
#include <string.h>
#include "hal.h"
#if HAL_USE_USB || defined(__DOXYGEN__)
/*===========================================================================*/
/* Driver local definitions. */
/*===========================================================================*/
#define BTABLE_ADDR 0x0000
/*===========================================================================*/
/* Driver exported variables. */
/*===========================================================================*/
/** @brief USB1 driver identifier.*/
#if STM32_USB_USE_USB1 || defined(__DOXYGEN__)
USBDriver USBD1;
#endif
/*===========================================================================*/
/* Driver local variables and types. */
/*===========================================================================*/
/**
* @brief EP0 state.
* @note It is an union because IN and OUT endpoints are never used at the
* same time for EP0.
*/
static union {
/**
* @brief IN EP0 state.
*/
USBInEndpointState in;
/**
* @brief OUT EP0 state.
*/
USBOutEndpointState out;
} ep0_state;
/**
* @brief Buffer for the EP0 setup packets.
*/
static uint8_t ep0setup_buffer[8];
/**
* @brief EP0 initialization structure.
*/
static const USBEndpointConfig ep0config = {
USB_EP_MODE_TYPE_CTRL,
_usb_ep0setup,
_usb_ep0in,
_usb_ep0out,
0x40,
0x40,
&ep0_state.in,
&ep0_state.out,
1,
ep0setup_buffer
};
/*===========================================================================*/
/* Driver local functions. */
/*===========================================================================*/
/**
* @brief Resets the packet memory allocator.
*
* @param[in] usbp pointer to the @p USBDriver object
*/
static void usb_pm_reset(USBDriver *usbp) {
/* The first 64 bytes are reserved for the descriptors table. The effective
available RAM for endpoint buffers is just 448 bytes.*/
usbp->pmnext = 64;
}
/**
* @brief Resets the packet memory allocator.
*
* @param[in] usbp pointer to the @p USBDriver object
* @param[in] size size of the packet buffer to allocate
*/
static uint32_t usb_pm_alloc(USBDriver *usbp, size_t size) {
uint32_t next;
next = usbp->pmnext;
usbp->pmnext += size;
osalDbgAssert(usbp->pmnext <= USB_PMA_SIZE, "PMA overflow");
return next;
}
/**
* @brief Reads from a dedicated packet buffer.
*
* @param[in] udp pointer to a @p stm32_usb_descriptor_t
* @param[out] buf buffer where to copy the packet data
* @param[in] n maximum number of bytes to copy. This value must
* not exceed the maximum packet size for this endpoint.
*
* @notapi
*/
static void usb_packet_read_to_buffer(stm32_usb_descriptor_t *udp,
uint8_t *buf, size_t n) {
uint32_t *pmap= USB_ADDR2PTR(udp->RXADDR0);
n = (n + 1) / 2;
while (n > 0) {
/* Note, this line relies on the Cortex-M3/M4 ability to perform
unaligned word accesses.*/
*(uint16_t *)buf = (uint16_t)*pmap++;
buf += 2;
n--;
}
}
/**
* @brief Reads from a dedicated packet buffer.
*
* @param[in] udp pointer to a @p stm32_usb_descriptor_t
* @param[in] iqp pointer to an @p input_queue_t object
* @param[in] n maximum number of bytes to copy. This value must
* not exceed the maximum packet size for this endpoint.
*
* @notapi
*/
static void usb_packet_read_to_queue(stm32_usb_descriptor_t *udp,
input_queue_t *iqp, size_t n) {
size_t nhw;
uint32_t *pmap= USB_ADDR2PTR(udp->RXADDR0);
nhw = n / 2;
while (nhw > 0) {
uint32_t w;
w = *pmap++;
*iqp->q_wrptr++ = (uint8_t)w;
if (iqp->q_wrptr >= iqp->q_top)
iqp->q_wrptr = iqp->q_buffer;
*iqp->q_wrptr++ = (uint8_t)(w >> 8);
if (iqp->q_wrptr >= iqp->q_top)
iqp->q_wrptr = iqp->q_buffer;
nhw--;
}
/* Last byte for odd numbers.*/
if ((n & 1) != 0) {
*iqp->q_wrptr++ = (uint8_t)*pmap;
if (iqp->q_wrptr >= iqp->q_top)
iqp->q_wrptr = iqp->q_buffer;
}
/* Updating queue.*/
osalSysLockFromISR();
iqp->q_counter += n;
osalThreadDequeueAllI(&iqp->q_waiting, Q_OK);
osalSysUnlockFromISR();
}
/**
* @brief Writes to a dedicated packet buffer.
*
* @param[in] udp pointer to a @p stm32_usb_descriptor_t
* @param[in] buf buffer where to fetch the packet data
* @param[in] n maximum number of bytes to copy. This value must
* not exceed the maximum packet size for this endpoint.
*
* @notapi
*/
static void usb_packet_write_from_buffer(stm32_usb_descriptor_t *udp,
const uint8_t *buf,
size_t n) {
uint32_t *pmap = USB_ADDR2PTR(udp->TXADDR0);
udp->TXCOUNT0 = (uint16_t)n;
n = (n + 1) / 2;
while (n > 0) {
/* Note, this line relies on the Cortex-M3/M4 ability to perform
unaligned word accesses.*/
*pmap++ = *(uint16_t *)buf;
buf += 2;
n--;
}
}
/**
* @brief Writes to a dedicated packet buffer.
*
* @param[in] udp pointer to a @p stm32_usb_descriptor_t
* @param[in] buf buffer where to fetch the packet data
* @param[in] n maximum number of bytes to copy. This value must
* not exceed the maximum packet size for this endpoint.
*
* @notapi
*/
static void usb_packet_write_from_queue(stm32_usb_descriptor_t *udp,
output_queue_t *oqp, size_t n) {
size_t nhw;
syssts_t sts;
uint32_t *pmap = USB_ADDR2PTR(udp->TXADDR0);
udp->TXCOUNT0 = (uint16_t)n;
nhw = n / 2;
while (nhw > 0) {
uint32_t w;
w = (uint32_t)*oqp->q_rdptr++;
if (oqp->q_rdptr >= oqp->q_top)
oqp->q_rdptr = oqp->q_buffer;
w |= (uint32_t)*oqp->q_rdptr++ << 8;
if (oqp->q_rdptr >= oqp->q_top)
oqp->q_rdptr = oqp->q_buffer;
*pmap++ = w;
nhw--;
}
/* Last byte for odd numbers.*/
if ((n & 1) != 0) {
*pmap = (uint32_t)*oqp->q_rdptr++;
if (oqp->q_rdptr >= oqp->q_top)
oqp->q_rdptr = oqp->q_buffer;
}
/* Updating queue.*/
sts = osalSysGetStatusAndLockX();
oqp->q_counter += n;
osalThreadDequeueAllI(&oqp->q_waiting, Q_OK);
osalSysRestoreStatusX(sts);
}
/*===========================================================================*/
/* Driver interrupt handlers. */
/*===========================================================================*/
#if STM32_USB_USE_USB1 || defined(__DOXYGEN__)
#if !defined(STM32_USB1_HP_HANDLER)
#error "STM32_USB1_HP_HANDLER not defined"
#endif
/**
* @brief USB high priority interrupt handler.
*
* @isr
*/
CH_IRQ_HANDLER(STM32_USB1_HP_HANDLER) {
CH_IRQ_PROLOGUE();
CH_IRQ_EPILOGUE();
}
#if !defined(STM32_USB1_LP_HANDLER)
#error "STM32_USB1_LP_HANDLER not defined"
#endif
/**
* @brief USB low priority interrupt handler.
*
* @isr
*/
CH_IRQ_HANDLER(STM32_USB1_LP_HANDLER) {
uint32_t istr;
USBDriver *usbp = &USBD1;
CH_IRQ_PROLOGUE();
istr = STM32_USB->ISTR;
/* USB bus reset condition handling.*/
if (istr & ISTR_RESET) {
_usb_reset(usbp);
_usb_isr_invoke_event_cb(usbp, USB_EVENT_RESET);
STM32_USB->ISTR = ~ISTR_RESET;
}
/* USB bus SUSPEND condition handling.*/
if (istr & ISTR_SUSP) {
STM32_USB->CNTR |= CNTR_FSUSP;
_usb_isr_invoke_event_cb(usbp, USB_EVENT_SUSPEND);
#if STM32_USB_LOW_POWER_ON_SUSPEND
STM32_USB->CNTR |= CNTR_LP_MODE;
#endif
STM32_USB->ISTR = ~ISTR_SUSP;
}
/* USB bus WAKEUP condition handling.*/
if (istr & ISTR_WKUP) {
uint32_t fnr = STM32_USB->FNR;
if (!(fnr & FNR_RXDP)) {
STM32_USB->CNTR &= ~CNTR_FSUSP;
_usb_isr_invoke_event_cb(usbp, USB_EVENT_WAKEUP);
}
#if STM32_USB_LOW_POWER_ON_SUSPEND
else {
/* Just noise, going back in SUSPEND mode, reference manual 22.4.5,
table 169.*/
STM32_USB->CNTR |= CNTR_LP_MODE;
}
#endif
STM32_USB->ISTR = ~ISTR_WKUP;
}
/* SOF handling.*/
if (istr & ISTR_SOF) {
_usb_isr_invoke_sof_cb(usbp);
STM32_USB->ISTR = ~ISTR_SOF;
}
/* Endpoint events handling.*/
while (istr & ISTR_CTR) {
size_t n;
uint32_t ep;
uint32_t epr = STM32_USB->EPR[ep = istr & ISTR_EP_ID_MASK];
const USBEndpointConfig *epcp = usbp->epc[ep];
if (epr & EPR_CTR_TX) {
size_t transmitted;
/* IN endpoint, transmission.*/
EPR_CLEAR_CTR_TX(ep);
transmitted = (size_t)USB_GET_DESCRIPTOR(ep)->TXCOUNT0;
epcp->in_state->txcnt += transmitted;
n = epcp->in_state->txsize - epcp->in_state->txcnt;
if (n > 0) {
/* Transfer not completed, there are more packets to send.*/
if (n > epcp->in_maxsize)
n = epcp->in_maxsize;
if (epcp->in_state->txqueued)
usb_packet_write_from_queue(USB_GET_DESCRIPTOR(ep),
epcp->in_state->mode.queue.txqueue,
n);
else {
epcp->in_state->mode.linear.txbuf += transmitted;
usb_packet_write_from_buffer(USB_GET_DESCRIPTOR(ep),
epcp->in_state->mode.linear.txbuf,
n);
}
osalSysLockFromISR();
usb_lld_start_in(usbp, ep);
osalSysUnlockFromISR();
}
else {
/* Transfer completed, invokes the callback.*/
_usb_isr_invoke_in_cb(usbp, ep);
}
}
if (epr & EPR_CTR_RX) {
EPR_CLEAR_CTR_RX(ep);
/* OUT endpoint, receive.*/
if (epr & EPR_SETUP) {
/* Setup packets handling, setup packets are handled using a
specific callback.*/
_usb_isr_invoke_setup_cb(usbp, ep);
}
else {
stm32_usb_descriptor_t *udp = USB_GET_DESCRIPTOR(ep);
n = (size_t)udp->RXCOUNT0 & RXCOUNT_COUNT_MASK;
/* Reads the packet into the defined buffer.*/
if (epcp->out_state->rxqueued)
usb_packet_read_to_queue(udp,
epcp->out_state->mode.queue.rxqueue,
n);
else {
usb_packet_read_to_buffer(udp,
epcp->out_state->mode.linear.rxbuf,
n);
epcp->out_state->mode.linear.rxbuf += n;
}
/* Transaction data updated.*/
epcp->out_state->rxcnt += n;
epcp->out_state->rxsize -= n;
epcp->out_state->rxpkts -= 1;
/* The transaction is completed if the specified number of packets
has been received or the current packet is a short packet.*/
if ((n < epcp->out_maxsize) || (epcp->out_state->rxpkts == 0)) {
/* Transfer complete, invokes the callback.*/
_usb_isr_invoke_out_cb(usbp, ep);
}
else {
/* Transfer not complete, there are more packets to receive.*/
EPR_SET_STAT_RX(ep, EPR_STAT_RX_VALID);
}
}
}
istr = STM32_USB->ISTR;
}
CH_IRQ_EPILOGUE();
}
#endif
/*===========================================================================*/
/* Driver exported functions. */
/*===========================================================================*/
/**
* @brief Low level USB driver initialization.
*
* @notapi
*/
void usb_lld_init(void) {
/* Driver initialization.*/
usbObjectInit(&USBD1);
}
/**
* @brief Configures and activates the USB peripheral.
*
* @param[in] usbp pointer to the @p USBDriver object
*
* @notapi
*/
void usb_lld_start(USBDriver *usbp) {
if (usbp->state == USB_STOP) {
/* Clock activation.*/
#if STM32_USB_USE_USB1
if (&USBD1 == usbp) {
/* USB clock enabled.*/
rccEnableUSB(FALSE);
/* Powers up the transceiver while holding the USB in reset state.*/
STM32_USB->CNTR = CNTR_FRES;
/* Enabling the USB IRQ vectors, this also gives enough time to allow
the transceiver power up (1uS).*/
nvicEnableVector(STM32_USB1_HP_NUMBER, STM32_USB_USB1_HP_IRQ_PRIORITY);
nvicEnableVector(STM32_USB1_LP_NUMBER, STM32_USB_USB1_LP_IRQ_PRIORITY);
/* Releases the USB reset.*/
STM32_USB->CNTR = 0;
}
#endif
/* Reset procedure enforced on driver start.*/
_usb_reset(usbp);
}
/* Configuration.*/
}
/**
* @brief Deactivates the USB peripheral.
*
* @param[in] usbp pointer to the @p USBDriver object
*
* @notapi
*/
void usb_lld_stop(USBDriver *usbp) {
/* If in ready state then disables the USB clock.*/
if (usbp->state == USB_STOP) {
#if STM32_USB_USE_USB1
if (&USBD1 == usbp) {
nvicDisableVector(STM32_USB1_HP_NUMBER);
nvicDisableVector(STM32_USB1_LP_NUMBER);
STM32_USB->CNTR = CNTR_PDWN | CNTR_FRES;
rccDisableUSB(FALSE);
}
#endif
}
}
/**
* @brief USB low level reset routine.
*
* @param[in] usbp pointer to the @p USBDriver object
*
* @notapi
*/
void usb_lld_reset(USBDriver *usbp) {
uint32_t cntr;
/* Post reset initialization.*/
STM32_USB->BTABLE = 0;
STM32_USB->ISTR = 0;
STM32_USB->DADDR = DADDR_EF;
cntr = /*CNTR_ESOFM | */ CNTR_RESETM | CNTR_SUSPM |
CNTR_WKUPM | /*CNTR_ERRM | CNTR_PMAOVRM |*/ CNTR_CTRM;
/* The SOF interrupt is only enabled if a callback is defined for
this service because it is an high rate source.*/
if (usbp->config->sof_cb != NULL)
cntr |= CNTR_SOFM;
STM32_USB->CNTR = cntr;
/* Resets the packet memory allocator.*/
usb_pm_reset(usbp);
/* EP0 initialization.*/
usbp->epc[0] = &ep0config;
usb_lld_init_endpoint(usbp, 0);
}
/**
* @brief Sets the USB address.
*
* @param[in] usbp pointer to the @p USBDriver object
*
* @notapi
*/
void usb_lld_set_address(USBDriver *usbp) {
STM32_USB->DADDR = (uint32_t)(usbp->address) | DADDR_EF;
}
/**
* @brief Enables an endpoint.
*
* @param[in] usbp pointer to the @p USBDriver object
* @param[in] ep endpoint number
*
* @notapi
*/
void usb_lld_init_endpoint(USBDriver *usbp, usbep_t ep) {
uint16_t nblocks, epr;
stm32_usb_descriptor_t *dp;
const USBEndpointConfig *epcp = usbp->epc[ep];
/* Setting the endpoint type.*/
switch (epcp->ep_mode & USB_EP_MODE_TYPE) {
case USB_EP_MODE_TYPE_ISOC:
epr = EPR_EP_TYPE_ISO;
break;
case USB_EP_MODE_TYPE_BULK:
epr = EPR_EP_TYPE_BULK;
break;
case USB_EP_MODE_TYPE_INTR:
epr = EPR_EP_TYPE_INTERRUPT;
break;
default:
epr = EPR_EP_TYPE_CONTROL;
}
/* IN endpoint initially in NAK mode.*/
if (epcp->in_cb != NULL)
epr |= EPR_STAT_TX_NAK;
/* OUT endpoint initially in NAK mode.*/
if (epcp->out_cb != NULL)
epr |= EPR_STAT_RX_NAK;
/* EPxR register setup.*/
EPR_SET(ep, epr | ep);
EPR_TOGGLE(ep, epr);
/* Endpoint size and address initialization.*/
if (epcp->out_maxsize > 62)
nblocks = (((((epcp->out_maxsize - 1) | 0x1f) + 1) / 32) << 10) |
0x8000;
else
nblocks = ((((epcp->out_maxsize - 1) | 1) + 1) / 2) << 10;
dp = USB_GET_DESCRIPTOR(ep);
dp->TXCOUNT0 = 0;
dp->RXCOUNT0 = nblocks;
dp->TXADDR0 = usb_pm_alloc(usbp, epcp->in_maxsize);
dp->RXADDR0 = usb_pm_alloc(usbp, epcp->out_maxsize);
}
/**
* @brief Disables all the active endpoints except the endpoint zero.
*
* @param[in] usbp pointer to the @p USBDriver object
*
* @notapi
*/
void usb_lld_disable_endpoints(USBDriver *usbp) {
unsigned i;
/* Resets the packet memory allocator.*/
usb_pm_reset(usbp);
/* Disabling all endpoints.*/
for (i = 1; i <= USB_ENDOPOINTS_NUMBER; i++) {
EPR_TOGGLE(i, 0);
EPR_SET(i, 0);
}
}
/**
* @brief Returns the status of an OUT endpoint.
*
* @param[in] usbp pointer to the @p USBDriver object
* @param[in] ep endpoint number
* @return The endpoint status.
* @retval EP_STATUS_DISABLED The endpoint is not active.
* @retval EP_STATUS_STALLED The endpoint is stalled.
* @retval EP_STATUS_ACTIVE The endpoint is active.
*
* @notapi
*/
usbepstatus_t usb_lld_get_status_out(USBDriver *usbp, usbep_t ep) {
(void)usbp;
switch (STM32_USB->EPR[ep] & EPR_STAT_RX_MASK) {
case EPR_STAT_RX_DIS:
return EP_STATUS_DISABLED;
case EPR_STAT_RX_STALL:
return EP_STATUS_STALLED;
default:
return EP_STATUS_ACTIVE;
}
}
/**
* @brief Returns the status of an IN endpoint.
*
* @param[in] usbp pointer to the @p USBDriver object
* @param[in] ep endpoint number
* @return The endpoint status.
* @retval EP_STATUS_DISABLED The endpoint is not active.
* @retval EP_STATUS_STALLED The endpoint is stalled.
* @retval EP_STATUS_ACTIVE The endpoint is active.
*
* @notapi
*/
usbepstatus_t usb_lld_get_status_in(USBDriver *usbp, usbep_t ep) {
(void)usbp;
switch (STM32_USB->EPR[ep] & EPR_STAT_TX_MASK) {
case EPR_STAT_TX_DIS:
return EP_STATUS_DISABLED;
case EPR_STAT_TX_STALL:
return EP_STATUS_STALLED;
default:
return EP_STATUS_ACTIVE;
}
}
/**
* @brief Reads a setup packet from the dedicated packet buffer.
* @details This function must be invoked in the context of the @p setup_cb
* callback in order to read the received setup packet.
* @pre In order to use this function the endpoint must have been
* initialized as a control endpoint.
* @post The endpoint is ready to accept another packet.
*
* @param[in] usbp pointer to the @p USBDriver object
* @param[in] ep endpoint number
* @param[out] buf buffer where to copy the packet data
*
* @notapi
*/
void usb_lld_read_setup(USBDriver *usbp, usbep_t ep, uint8_t *buf) {
uint32_t *pmap;
stm32_usb_descriptor_t *udp;
uint32_t n;
(void)usbp;
udp = USB_GET_DESCRIPTOR(ep);
pmap = USB_ADDR2PTR(udp->RXADDR0);
for (n = 0; n < 4; n++) {
*(uint16_t *)buf = (uint16_t)*pmap++;
buf += 2;
}
}
/**
* @brief Prepares for a receive operation.
*
* @param[in] usbp pointer to the @p USBDriver object
* @param[in] ep endpoint number
*
* @notapi
*/
void usb_lld_prepare_receive(USBDriver *usbp, usbep_t ep) {
USBOutEndpointState *osp = usbp->epc[ep]->out_state;
/* Transfer initialization.*/
if (osp->rxsize == 0) /* Special case for zero sized packets.*/
osp->rxpkts = 1;
else
osp->rxpkts = (uint16_t)((osp->rxsize + usbp->epc[ep]->out_maxsize - 1) /
usbp->epc[ep]->out_maxsize);
}
/**
* @brief Prepares for a transmit operation.
*
* @param[in] usbp pointer to the @p USBDriver object
* @param[in] ep endpoint number
*
* @notapi
*/
void usb_lld_prepare_transmit(USBDriver *usbp, usbep_t ep) {
size_t n;
USBInEndpointState *isp = usbp->epc[ep]->in_state;
/* Transfer initialization.*/
n = isp->txsize;
if (n > (size_t)usbp->epc[ep]->in_maxsize)
n = (size_t)usbp->epc[ep]->in_maxsize;
if (isp->txqueued)
usb_packet_write_from_queue(USB_GET_DESCRIPTOR(ep),
isp->mode.queue.txqueue, n);
else
usb_packet_write_from_buffer(USB_GET_DESCRIPTOR(ep),
isp->mode.linear.txbuf, n);
}
/**
* @brief Starts a receive operation on an OUT endpoint.
*
* @param[in] usbp pointer to the @p USBDriver object
* @param[in] ep endpoint number
*
* @notapi
*/
void usb_lld_start_out(USBDriver *usbp, usbep_t ep) {
(void)usbp;
EPR_SET_STAT_RX(ep, EPR_STAT_RX_VALID);
}
/**
* @brief Starts a transmit operation on an IN endpoint.
*
* @param[in] usbp pointer to the @p USBDriver object
* @param[in] ep endpoint number
*
* @notapi
*/
void usb_lld_start_in(USBDriver *usbp, usbep_t ep) {
(void)usbp;
EPR_SET_STAT_TX(ep, EPR_STAT_TX_VALID);
}
/**
* @brief Brings an OUT endpoint in the stalled state.
*
* @param[in] usbp pointer to the @p USBDriver object
* @param[in] ep endpoint number
*
* @notapi
*/
void usb_lld_stall_out(USBDriver *usbp, usbep_t ep) {
(void)usbp;
EPR_SET_STAT_RX(ep, EPR_STAT_RX_STALL);
}
/**
* @brief Brings an IN endpoint in the stalled state.
*
* @param[in] usbp pointer to the @p USBDriver object
* @param[in] ep endpoint number
*
* @notapi
*/
void usb_lld_stall_in(USBDriver *usbp, usbep_t ep) {
(void)usbp;
EPR_SET_STAT_TX(ep, EPR_STAT_TX_STALL);
}
/**
* @brief Brings an OUT endpoint in the active state.
*
* @param[in] usbp pointer to the @p USBDriver object
* @param[in] ep endpoint number
*
* @notapi
*/
void usb_lld_clear_out(USBDriver *usbp, usbep_t ep) {
(void)usbp;
/* Makes sure to not put to NAK an endpoint that is already
transferring.*/
if ((STM32_USB->EPR[ep] & EPR_STAT_RX_MASK) != EPR_STAT_RX_VALID)
EPR_SET_STAT_TX(ep, EPR_STAT_RX_NAK);
}
/**
* @brief Brings an IN endpoint in the active state.
*
* @param[in] usbp pointer to the @p USBDriver object
* @param[in] ep endpoint number
*
* @notapi
*/
void usb_lld_clear_in(USBDriver *usbp, usbep_t ep) {
(void)usbp;
/* Makes sure to not put to NAK an endpoint that is already
transferring.*/
if ((STM32_USB->EPR[ep] & EPR_STAT_TX_MASK) != EPR_STAT_TX_VALID)
EPR_SET_STAT_TX(ep, EPR_STAT_TX_NAK);
}
#endif /* HAL_USE_USB */
/** @} */
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