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Message-ID: <21b097d0-91ed-5cdc-83b0-4594dffaab6a@codeaurora.org> Date: Wed, 6 Dec 2017 11:54:27 -0800 From: Stephen Boyd <sboyd@...eaurora.org> To: Bjorn Andersson <bjorn.andersson@...aro.org>, Jitendra Sharma <shajit@...eaurora.org> Cc: Ohad Ben-Cohen <ohad@...ery.com>, linux-remoteproc@...r.kernel.org, linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org Subject: Re: [PATCH] rpmsg: qcom_smd: Access APCS through mailbox framework On 12/06/2017 11:02 AM, Bjorn Andersson wrote: > On Wed 06 Dec 04:08 PST 2017, Jitendra Sharma wrote: > >> Hi Bjorn, >> > Hi Jitendra, > >> On 11/16/2017 12:38 PM, Bjorn Andersson wrote: > [..] >>> @@ -365,7 +371,12 @@ static void qcom_smd_signal_channel(struct qcom_smd_channel *channel) >>> { >>> struct qcom_smd_edge *edge = channel->edge; >>> - regmap_write(edge->ipc_regmap, edge->ipc_offset, BIT(edge->ipc_bit)); >>> + if (edge->mbox_chan) { >>> + mbox_send_message(edge->mbox_chan, NULL); >> mbox_send_message could fail. So return value should be checked > qcom_apcs_ipc_send_data() can't fail, so the case when > mbox_send_message() would fail is if more than MBOX_TX_QUEUE_LEN (20) > callers that has managed to put their data in the queue but not yet > execute msg_submit(). > > As each bit in the APCS IPC register is modelled as it's own mailbox > channel this error case would mean that as mbox_send_message() returns > with an error there will soon be 20 callers entering > qcom_apcs_ipc_send_data() and trigger this very bit. > > > When this happens mbox_send_message() will print an error in the log, so > there's no point in having the caller also print an error. > > When it comes to dealing with a failing call to mbox_send_message() we > have already posted the message in the FIFO, so we have no way to abort > the transmission, as such the only way to deal with this is to either > retry or ignore the problem; and the mailbox queue will ensure that we > retry 20 times. > Maybe you should wrap this up into a comment in the code? Then we don't have to dig this out of the mail list archives to figure out why we aren't checking for an error. -- Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project
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