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X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 30 Sep 2025 17:58:22.9495 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 729d12ae-feb4-4a1a-bb4e-08de004af298 X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=3dd8961f-e488-4e60-8e11-a82d994e183d;Ip=[165.204.84.17];Helo=[satlexmb08.amd.com] X-MS-Exchange-CrossTenant-AuthSource: CO1PEPF000042A7.namprd03.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: SA1PR12MB8888 On 9/30/25 12:33 PM, Jassi Brar wrote: > On Tue, Sep 30, 2025 at 11:52 AM Tanmay Shah wrote: >> >> Hi Jassi, >> >> Please find my comments below. >> >> On 9/30/25 9:11 AM, Jassi Brar wrote: >>> On Thu, Sep 25, 2025 at 1:51 PM Tanmay Shah wrote: >>>> >>>> Sometimes clients need to know if mailbox queue is full or not before >>>> posting new message via mailbox. If mailbox queue is full clients can >>>> choose not to post new message. This doesn't mean current queue length >>>> should be increased, but clients may want to wait till previous Tx is >>>> done. This API can help avoid false positive warning from mailbox >>>> framework "Try increasing MBOX_TX_QUEUE_LEN". >>>> >>>> Signed-off-by: Tanmay Shah >>>> --- >>>> drivers/mailbox/mailbox.c | 24 ++++++++++++++++++++++++ >>>> drivers/remoteproc/xlnx_r5_remoteproc.c | 4 ++++ >>>> include/linux/mailbox_client.h | 1 + >>>> 3 files changed, 29 insertions(+) >>>> >>>> diff --git a/drivers/mailbox/mailbox.c b/drivers/mailbox/mailbox.c >>>> index 5cd8ae222073..7afdb2c9006d 100644 >>>> --- a/drivers/mailbox/mailbox.c >>>> +++ b/drivers/mailbox/mailbox.c >>>> @@ -217,6 +217,30 @@ bool mbox_client_peek_data(struct mbox_chan *chan) >>>> } >>>> EXPORT_SYMBOL_GPL(mbox_client_peek_data); >>>> >>>> +/** >>>> + * mbox_queue_full - check if mailbox queue is full or not >>>> + * @chan: Mailbox channel assigned to this client. >>>> + * >>>> + * Clients can choose not to send new msg if mbox queue is full. >>>> + * >>>> + * Return: true if queue is full else false. < 0 for error >>>> + */ >>>> +int mbox_queue_full(struct mbox_chan *chan) >>>> +{ >>>> + unsigned long flags; >>>> + int res; >>>> + >>>> + if (!chan) >>>> + return -EINVAL; >>>> + >>>> + spin_lock_irqsave(&chan->lock, flags); >>>> + res = (chan->msg_count == (MBOX_TX_QUEUE_LEN - 1)); >>>> >>> 1) If we really need this, it should be >>> res = (chan->msg_count == MBOX_TX_QUEUE_LEN); >>> >> >> Ack here. >> >>> 2) I am thinking instead, introduce a >>> struct mbox_client.msg_slots_ro; >>> Which is a read-only field for the client, denoting how many message >>> slots are currently available. >>> The mailbox api will always adjust it when msg_count changes... >>> chan->cl->msg_slots_ro = MBOX_TX_QUEUE_LEN - chan->msg_count; >>> >> >> It's not possible to make msg_slots_ro true Read-Only. Nothing prevents >> clients to write to that variable as far as I know. >> > Correct, nothing prevents a client from changing 'msg_slots_ro', just > like nothing > prevents it from setting tx_done or rx_callback to 0xdeadbabe. > The '_ro' suffix is to tell the client developer to not mess with it. > I am slightly more inclined towards this approach because it avoids > adding another > convenience api and is more immediately available without needing a spinlock. To avoid spinlock, msg_slots_ro should be atomic right? > Then in the remoteproc driver, before using mbox_send_message, I can simply check (chan->cl->msg_slots_ro == 0) then don't use mbox_send_message. > -jassi