Re: [PATCH v8 07/28] mailbox: Allow direct registration to a channel

From: Alex Elder
Date: Mon Jan 09 2023 - 16:36:18 EST

On 12/19/22 4:58 PM, Elliot Berman wrote:
Support virtual mailbox controllers and clients which are not platform
devices or come from the devicetree by allowing them to match client to
channel via some other mechanism.

The new function behaves very much like mbox_request_channel()
did before.

The new function differs from omap_mbox_request_channel() in that
it can change the if chan->txdone_method is TXDONE_BY_POLL, it
is changed to TXDONE_BY_ACK if the client's knows_txdone field is
set. Is this OK? Why?

It also assumes chan->mbox->ops->startup us non-null (though that
isn't really a problem).


Signed-off-by: Elliot Berman <quic_eberman@xxxxxxxxxxx>
---
drivers/mailbox/mailbox.c | 96 ++++++++++++++++++++++++----------
drivers/mailbox/omap-mailbox.c | 18 ++-----
drivers/mailbox/pcc.c | 18 ++-----
include/linux/mailbox_client.h | 1 +
4 files changed, 76 insertions(+), 57 deletions(-)

diff --git a/drivers/mailbox/mailbox.c b/drivers/mailbox/mailbox.c
index 4229b9b5da98..adf36c05fa43 100644
--- a/drivers/mailbox/mailbox.c
+++ b/drivers/mailbox/mailbox.c
@@ -317,6 +317,71 @@ int mbox_flush(struct mbox_chan *chan, unsigned long timeout)
}
EXPORT_SYMBOL_GPL(mbox_flush);
+static int __mbox_bind_client(struct mbox_chan *chan, struct mbox_client *cl)

There should be an unbind_client() call. At a minimum, you are
calling try_module_get(), and the matching module_put() call
would belong there. And even though one might just call
module_put() elsewhere for this, it would be cleaner to have
a function that similarly encapsulates the shutdown call
as well.

-Alex

+{
+ struct device *dev = cl->dev;
+ unsigned long flags;
+ int ret;
+
+ if (chan->cl || !try_module_get(chan->mbox->dev->driver->owner)) {
+ dev_dbg(dev, "%s: mailbox not free\n", __func__);
+ return -EBUSY;
+ }
+
+ spin_lock_irqsave(&chan->lock, flags);
+ chan->msg_free = 0;
+ chan->msg_count = 0;
+ chan->active_req = NULL;
+ chan->cl = cl;
+ init_completion(&chan->tx_complete);
+
+ if (chan->txdone_method == TXDONE_BY_POLL && cl->knows_txdone)
+ chan->txdone_method = TXDONE_BY_ACK;
+
+ spin_unlock_irqrestore(&chan->lock, flags);
+
+ if (chan->mbox->ops->startup) {
+ ret = chan->mbox->ops->startup(chan);
+
+ if (ret) {
+ dev_err(dev, "Unable to startup the chan (%d)\n", ret);
+ mbox_free_channel(chan);
+ return ret;
+ }
+ }
+
+ return 0;
+}
+
+/**
+ * mbox_bind_client - Request a mailbox channel.
+ * @chan: The mailbox channel to bind the client to.
+ * @cl: Identity of the client requesting the channel.
+ *
+ * The Client specifies its requirements and capabilities while asking for
+ * a mailbox channel. It can't be called from atomic context.
+ * The channel is exclusively allocated and can't be used by another
+ * client before the owner calls mbox_free_channel.
+ * After assignment, any packet received on this channel will be
+ * handed over to the client via the 'rx_callback'.
+ * The framework holds reference to the client, so the mbox_client
+ * structure shouldn't be modified until the mbox_free_channel returns.
+ *
+ * Return: 0 if the channel was assigned to the client successfully.
+ * <0 for request failure.
+ */
+int mbox_bind_client(struct mbox_chan *chan, struct mbox_client *cl)
+{
+ int ret;
+
+ mutex_lock(&con_mutex);
+ ret = __mbox_bind_client(chan, cl);
+ mutex_unlock(&con_mutex);
+
+ return ret;
+}
+EXPORT_SYMBOL_GPL(mbox_bind_client);
+
/**
* mbox_request_channel - Request a mailbox channel.
* @cl: Identity of the client requesting the channel.
@@ -340,7 +405,6 @@ struct mbox_chan *mbox_request_channel(struct mbox_client *cl, int index)
struct mbox_controller *mbox;
struct of_phandle_args spec;
struct mbox_chan *chan;
- unsigned long flags;
int ret;
if (!dev || !dev->of_node) {
@@ -372,33 +436,9 @@ struct mbox_chan *mbox_request_channel(struct mbox_client *cl, int index)
return chan;
}
- if (chan->cl || !try_module_get(mbox->dev->driver->owner)) {
- dev_dbg(dev, "%s: mailbox not free\n", __func__);
- mutex_unlock(&con_mutex);
- return ERR_PTR(-EBUSY);
- }
-
- spin_lock_irqsave(&chan->lock, flags);
- chan->msg_free = 0;
- chan->msg_count = 0;
- chan->active_req = NULL;
- chan->cl = cl;
- init_completion(&chan->tx_complete);
-
- if (chan->txdone_method == TXDONE_BY_POLL && cl->knows_txdone)
- chan->txdone_method = TXDONE_BY_ACK;
-
- spin_unlock_irqrestore(&chan->lock, flags);
-
- if (chan->mbox->ops->startup) {
- ret = chan->mbox->ops->startup(chan);
-
- if (ret) {
- dev_err(dev, "Unable to startup the chan (%d)\n", ret);
- mbox_free_channel(chan);
- chan = ERR_PTR(ret);
- }
- }
+ ret = __mbox_bind_client(chan, cl);
+ if (ret)
+ chan = ERR_PTR(ret);
mutex_unlock(&con_mutex);
return chan;
diff --git a/drivers/mailbox/omap-mailbox.c b/drivers/mailbox/omap-mailbox.c
index 098c82d87137..711a56ec8592 100644
--- a/drivers/mailbox/omap-mailbox.c
+++ b/drivers/mailbox/omap-mailbox.c
@@ -441,21 +441,9 @@ struct mbox_chan *omap_mbox_request_channel(struct mbox_client *cl,
if (!mbox || !mbox->chan)
return ERR_PTR(-ENOENT);
- chan = mbox->chan;
- spin_lock_irqsave(&chan->lock, flags);
- chan->msg_free = 0;
- chan->msg_count = 0;
- chan->active_req = NULL;
- chan->cl = cl;
- init_completion(&chan->tx_complete);
- spin_unlock_irqrestore(&chan->lock, flags);
-
- ret = chan->mbox->ops->startup(chan);
- if (ret) {
- pr_err("Unable to startup the chan (%d)\n", ret);
- mbox_free_channel(chan);
- chan = ERR_PTR(ret);
- }
+ ret = mbox_bind_client(mbox->chan, cl);
+ if (ret)
+ return ERR_PTR(ret);
return chan;
}
diff --git a/drivers/mailbox/pcc.c b/drivers/mailbox/pcc.c
index 3c2bc0ca454c..f655be083369 100644
--- a/drivers/mailbox/pcc.c
+++ b/drivers/mailbox/pcc.c
@@ -283,7 +283,7 @@ pcc_mbox_request_channel(struct mbox_client *cl, int subspace_id)
struct pcc_chan_info *pchan;
struct mbox_chan *chan;
struct device *dev;
- unsigned long flags;
+ int rc;
if (subspace_id < 0 || subspace_id >= pcc_chan_count)
return ERR_PTR(-ENOENT);
@@ -296,21 +296,11 @@ pcc_mbox_request_channel(struct mbox_client *cl, int subspace_id)
}
dev = chan->mbox->dev;
- spin_lock_irqsave(&chan->lock, flags);
- chan->msg_free = 0;
- chan->msg_count = 0;
- chan->active_req = NULL;
- chan->cl = cl;
- init_completion(&chan->tx_complete);
-
- if (chan->txdone_method == TXDONE_BY_POLL && cl->knows_txdone)
- chan->txdone_method = TXDONE_BY_ACK;
-
- spin_unlock_irqrestore(&chan->lock, flags);
+ rc = mbox_bind_client(chan, cl);
+ if (rc)
+ return ERR_PTR(rc);
if (pchan->plat_irq > 0) {
- int rc;
-
rc = devm_request_irq(dev, pchan->plat_irq, pcc_mbox_irq, 0,
MBOX_IRQ_NAME, chan);
if (unlikely(rc)) {
diff --git a/include/linux/mailbox_client.h b/include/linux/mailbox_client.h
index 65229a45590f..734694912ef7 100644
--- a/include/linux/mailbox_client.h
+++ b/include/linux/mailbox_client.h
@@ -37,6 +37,7 @@ struct mbox_client {
void (*tx_done)(struct mbox_client *cl, void *mssg, int r);
};
+int mbox_bind_client(struct mbox_chan *chan, struct mbox_client *cl);
struct mbox_chan *mbox_request_channel_byname(struct mbox_client *cl,
const char *name);
struct mbox_chan *mbox_request_channel(struct mbox_client *cl, int index);