linux-kernel - Re: [PATCH V1 2/3] rpmsg: glink: Add support to handle signals command

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Message-ID: <CAE-0n52Wn6_70-3Y6a+Yk5zkoA_hiA5w51rTeCVX-DN37Gc=ig@mail.gmail.com>
Date:   Thu, 30 Sep 2021 09:33:21 -0700
From:   Stephen Boyd <swboyd@...omium.org>
To:     Deepak Kumar Singh <deesin@...eaurora.org>,
        bjorn.andersson@...aro.org, clew@...eaurora.org,
        mathieu.poirier@...aro.org
Cc:     linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        linux-remoteproc@...r.kernel.org, Andy Gross <agross@...nel.org>,
        Ohad Ben-Cohen <ohad@...ery.com>
Subject: Re: [PATCH V1 2/3] rpmsg: glink: Add support to handle signals command

Quoting Deepak Kumar Singh (2021-09-30 08:32:03)
> diff --git a/drivers/rpmsg/qcom_glink_native.c b/drivers/rpmsg/qcom_glink_native.c
> index 05533c7..384fcd2 100644
> --- a/drivers/rpmsg/qcom_glink_native.c
> +++ b/drivers/rpmsg/qcom_glink_native.c
> @@ -976,6 +984,68 @@ static int qcom_glink_rx_open_ack(struct qcom_glink *glink, unsigned int lcid)
>         return 0;
>  }
>
> +/**
> + * qcom_glink_set_flow_control() - convert a signal cmd to wire format and
> + *                                transmit
> + * @ept:       Rpmsg endpoint for channel.
> + * @enable:    True/False - enable or disable flow control
> + *
> + * Return: 0 on success or standard Linux error code.
> + */
> +static int qcom_glink_set_flow_control(struct rpmsg_endpoint *ept, bool enable)
> +{
> +       struct glink_channel *channel = to_glink_channel(ept);
> +       struct qcom_glink *glink = channel->glink;
> +       struct glink_msg msg;
> +       u32 sigs = 0;

Drop assignment.

> +
> +       /**
> +        * convert signals from TIOCM to NATIVE
> +        * sigs = TIOCM_DTR|TIOCM_RTS
> +        */
> +       if (enable)
> +               sigs |= (NATIVE_DTR_SIG | NATIVE_CTS_SIG);

sigs = NATIVE_DTR_SIG | NATIVE_CTS_SIG;

> +       else
> +               sigs |= (~(NATIVE_DTR_SIG | NATIVE_CTS_SIG));

sigs = ~(NATIVE_DTR_SIG | NATIVE_CTS_SIG);

> +
> +       msg.cmd = cpu_to_le16(RPM_CMD_SIGNALS);
> +       msg.param1 = cpu_to_le16(channel->lcid);
> +       msg.param2 = cpu_to_le32(sigs);
> +
> +       return qcom_glink_tx(glink, &msg, sizeof(msg), NULL, 0, true);
> +}
> +
> +static int qcom_glink_handle_signals(struct qcom_glink *glink,
> +                                    unsigned int rcid, unsigned int sigs)
> +{
> +       struct glink_channel *channel;
> +       unsigned long flags;
> +
> +       spin_lock_irqsave(&glink->idr_lock, flags);

irqsave can be skipped because this is only called from an irq handler.

> +       channel = idr_find(&glink->rcids, rcid);
> +       spin_unlock_irqrestore(&glink->idr_lock, flags);
> +       if (!channel) {
> +               dev_err(glink->dev, "signal for non-existing channel\n");
> +               return -EINVAL;
> +       }
> +
> +       /* convert signals from NATIVE to TIOCM */
> +       if (sigs & NATIVE_DTR_SIG)
> +               sigs |= TIOCM_DSR;
> +       if (sigs & NATIVE_CTS_SIG)
> +               sigs |= TIOCM_CTS;
> +       if (sigs & NATIVE_CD_SIG)
> +               sigs |= TIOCM_CD;
> +       if (sigs & NATIVE_RI_SIG)
> +               sigs |= TIOCM_RI;
> +       sigs &= 0x0fff;

Is this to only keep TIOCM_* bits? Maybe make this an ORed together mask
of those bits so we know what 0xfff means.

> +
> +       if (channel->ept.sig_cb)
> +               channel->ept.sig_cb(channel->ept.rpdev, channel->ept.priv, sigs);
> +
> +       return 0;
> +}
> +
>  static irqreturn_t qcom_glink_native_intr(int irq, void *data)
>  {
>         struct qcom_glink *glink = data;
> @@ -1037,6 +1107,10 @@ static irqreturn_t qcom_glink_native_intr(int irq, void *data)
>                         qcom_glink_handle_intent_req_ack(glink, param1, param2);
>                         qcom_glink_rx_advance(glink, ALIGN(sizeof(msg), 8));
>                         break;
> +               case RPM_CMD_SIGNALS:
> +                       qcom_glink_handle_signals(glink, param1, param2);

Should the return value be handled and if there isn't a channel then
treat it as a spurious irq?

> +                       qcom_glink_rx_advance(glink, ALIGN(sizeof(msg), 8));
> +                       break;
>                 default:
>                         dev_err(glink->dev, "unhandled rx cmd: %d\n", cmd);
>                         ret = -EINVAL;