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mailbox: omap: Remove kernel FIFO message queuing

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The kernel FIFO queue has a couple issues. The biggest issue is that
it causes extra latency in a path that can be used in real-time tasks,
such as communication with real-time remote processors.

The whole FIFO idea itself looks to be a leftover from before the
unified mailbox framework. The current mailbox framework expects
mbox_chan_received_data() to be called with data immediately as it
arrives. Remove the FIFO and pass the messages to the mailbox
framework directly as part of a threaded IRQ handler.

Signed-off-by: Andrew Davis <afd@ti.com>
Signed-off-by: Jassi Brar <jassisinghbrar@gmail.com>
This commit is contained in:
Andrew Davis 2024-04-10 08:59:42 -05:00 committed by Jassi Brar
parent 04a07a3441
commit 3f58c1f420
2 changed files with 5 additions and 111 deletions
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9
drivers/mailbox/Kconfig
View file

@ -68,15 +68,6 @@ config OMAP2PLUS_MBOX
OMAP2/3; or IPU, IVA HD and DSP in OMAP4/5. Say Y here if you
want to use OMAP2+ Mailbox framework support.
config OMAP_MBOX_KFIFO_SIZE
int "Mailbox kfifo default buffer size (bytes)"
depends on OMAP2PLUS_MBOX
default 256
help
Specify the default size of mailbox's kfifo buffers (bytes).
This can also be changed at runtime (via the mbox_kfifo_size
module parameter).
config ROCKCHIP_MBOX
bool "Rockchip Soc Integrated Mailbox Support"
depends on ARCH_ROCKCHIP || COMPILE_TEST

107
drivers/mailbox/omap-mailbox.c
View file

@ -65,14 +65,6 @@ struct omap_mbox_fifo {
u32 intr_bit;
};
struct omap_mbox_queue {
spinlock_t lock;
struct kfifo fifo;
struct work_struct work;
struct omap_mbox *mbox;
bool full;
};
struct omap_mbox_match_data {
u32 intr_type;
};
@ -90,7 +82,6 @@ struct omap_mbox_device {
struct omap_mbox {
const char *name;
int irq;
struct omap_mbox_queue *rxq;
struct omap_mbox_device *parent;
struct omap_mbox_fifo tx_fifo;
struct omap_mbox_fifo rx_fifo;
@ -99,10 +90,6 @@ struct omap_mbox {
bool send_no_irq;
};
static unsigned int mbox_kfifo_size = CONFIG_OMAP_MBOX_KFIFO_SIZE;
module_param(mbox_kfifo_size, uint, S_IRUGO);
MODULE_PARM_DESC(mbox_kfifo_size, "Size of omap's mailbox kfifo (bytes)");
static inline
unsigned int mbox_read_reg(struct omap_mbox_device *mdev, size_t ofs)
{
@ -202,30 +189,6 @@ static void omap_mbox_disable_irq(struct omap_mbox *mbox, omap_mbox_irq_t irq)
mbox_write_reg(mbox->parent, bit, irqdisable);
}
/*
* Message receiver(workqueue)
*/
static void mbox_rx_work(struct work_struct *work)
{
struct omap_mbox_queue *mq =
container_of(work, struct omap_mbox_queue, work);
u32 msg;
int len;
while (kfifo_len(&mq->fifo) >= sizeof(msg)) {
len = kfifo_out(&mq->fifo, (unsigned char *)&msg, sizeof(msg));
WARN_ON(len != sizeof(msg));
mbox_chan_received_data(mq->mbox->chan, (void *)(uintptr_t)msg);
spin_lock_irq(&mq->lock);
if (mq->full) {
mq->full = false;
omap_mbox_enable_irq(mq->mbox, IRQ_RX);
}
spin_unlock_irq(&mq->lock);
}
}
/*
* Mailbox interrupt handler
*/
@ -238,27 +201,15 @@ static void __mbox_tx_interrupt(struct omap_mbox *mbox)
static void __mbox_rx_interrupt(struct omap_mbox *mbox)
{
struct omap_mbox_queue *mq = mbox->rxq;
u32 msg;
int len;
while (!mbox_fifo_empty(mbox)) {
if (unlikely(kfifo_avail(&mq->fifo) < sizeof(msg))) {
omap_mbox_disable_irq(mbox, IRQ_RX);
mq->full = true;
goto nomem;
}
msg = mbox_fifo_read(mbox);
len = kfifo_in(&mq->fifo, (unsigned char *)&msg, sizeof(msg));
WARN_ON(len != sizeof(msg));
mbox_chan_received_data(mbox->chan, (void *)(uintptr_t)msg);
}
/* no more messages in the fifo. clear IRQ source. */
/* clear IRQ source. */
ack_mbox_irq(mbox, IRQ_RX);
nomem:
schedule_work(&mbox->rxq->work);
}
static irqreturn_t mbox_interrupt(int irq, void *p)
@ -274,57 +225,15 @@ static irqreturn_t mbox_interrupt(int irq, void *p)
return IRQ_HANDLED;
}
static struct omap_mbox_queue *mbox_queue_alloc(struct omap_mbox *mbox,
void (*work)(struct work_struct *))
{
struct omap_mbox_queue *mq;
unsigned int size;
if (!work)
return NULL;
mq = kzalloc(sizeof(*mq), GFP_KERNEL);
if (!mq)
return NULL;
spin_lock_init(&mq->lock);
/* kfifo size sanity check: alignment and minimal size */
size = ALIGN(mbox_kfifo_size, sizeof(u32));
size = max_t(unsigned int, size, sizeof(u32));
if (kfifo_alloc(&mq->fifo, size, GFP_KERNEL))
goto error;
INIT_WORK(&mq->work, work);
return mq;
error:
kfree(mq);
return NULL;
}
static void mbox_queue_free(struct omap_mbox_queue *q)
{
kfifo_free(&q->fifo);
kfree(q);
}
static int omap_mbox_startup(struct omap_mbox *mbox)
{
int ret = 0;
struct omap_mbox_queue *mq;
mq = mbox_queue_alloc(mbox, mbox_rx_work);
if (!mq)
return -ENOMEM;
mbox->rxq = mq;
mq->mbox = mbox;
ret = request_irq(mbox->irq, mbox_interrupt, IRQF_SHARED,
mbox->name, mbox);
ret = request_threaded_irq(mbox->irq, NULL, mbox_interrupt,
IRQF_ONESHOT, mbox->name, mbox);
if (unlikely(ret)) {
pr_err("failed to register mailbox interrupt:%d\n", ret);
goto fail_request_irq;
return ret;
}
if (mbox->send_no_irq)
@ -333,18 +242,12 @@ static int omap_mbox_startup(struct omap_mbox *mbox)
omap_mbox_enable_irq(mbox, IRQ_RX);
return 0;
fail_request_irq:
mbox_queue_free(mbox->rxq);
return ret;
}
static void omap_mbox_fini(struct omap_mbox *mbox)
{
omap_mbox_disable_irq(mbox, IRQ_RX);
free_irq(mbox->irq, mbox);
flush_work(&mbox->rxq->work);
mbox_queue_free(mbox->rxq);
}
static int omap_mbox_chan_startup(struct mbox_chan *chan)