Re: [PATCH V4 2/4] rpmsg: glink: Add support to handle signals command

[Mathieu Poirier <mathieu.poirier@linaro.org>]

On Wed, May 13, 2020 at 10:41:09AM +0530, Arun Kumar Neelakantam wrote:
> Remote peripherals send signal notifications over glink with commandID 15.
> 
> Add support to send and receive the signal command and convert the signals
> from NATIVE to TIOCM while receiving and vice versa while sending.
> 
> Signed-off-by: Chris Lew <clew@codeaurora.org>
> Signed-off-by: Arun Kumar Neelakantam <aneela@codeaurora.org>
> ---
>  drivers/rpmsg/qcom_glink_native.c | 126 ++++++++++++++++++++++++++++++++++++++
>  1 file changed, 126 insertions(+)
> 
> diff --git a/drivers/rpmsg/qcom_glink_native.c b/drivers/rpmsg/qcom_glink_native.c
> index fc8ef66..68e039a 100644
> --- a/drivers/rpmsg/qcom_glink_native.c
> +++ b/drivers/rpmsg/qcom_glink_native.c
> @@ -1,5 +1,6 @@
>  // SPDX-License-Identifier: GPL-2.0
>  /*
> + * Copyright (c) 2018, The Linux Foundation.

Again, not sure what this is for.

>   * Copyright (c) 2016-2017, Linaro Ltd
>   */
>  
> @@ -17,6 +18,7 @@
>  #include <linux/rpmsg.h>
>  #include <linux/sizes.h>
>  #include <linux/slab.h>
> +#include <linux/termios.h>
>  #include <linux/workqueue.h>
>  #include <linux/mailbox_client.h>
>  
> @@ -150,6 +152,8 @@ enum {
>   * @intent_req_lock: Synchronises multiple intent requests
>   * @intent_req_result: Result of intent request
>   * @intent_req_comp: Completion for intent_req signalling
> + * @lsigs:	local side signals
> + * @rsigs:	remote side signals
>   */
>  struct glink_channel {
>  	struct rpmsg_endpoint ept;
> @@ -181,6 +185,10 @@ struct glink_channel {
>  	struct mutex intent_req_lock;
>  	bool intent_req_result;
>  	struct completion intent_req_comp;
> +
> +	unsigned int lsigs;
> +	unsigned int rsigs;
> +
>  };
>  
>  #define to_glink_channel(_ept) container_of(_ept, struct glink_channel, ept)
> @@ -201,9 +209,15 @@ static const struct rpmsg_endpoint_ops glink_endpoint_ops;
>  #define RPM_CMD_TX_DATA_CONT		12
>  #define RPM_CMD_READ_NOTIF		13
>  #define RPM_CMD_RX_DONE_W_REUSE		14
> +#define RPM_CMD_SIGNALS			15
>  
>  #define GLINK_FEATURE_INTENTLESS	BIT(1)
>  
> +#define NATIVE_DTR_SIG	BIT(31)
> +#define NATIVE_CTS_SIG	BIT(30)
> +#define NATIVE_CD_SIG	BIT(29)
> +#define NATIVE_RI_SIG	BIT(28)

Please align theres with the BIT(1) of _INTENTLESS.

> +
>  static void qcom_glink_rx_done_work(struct work_struct *work);
>  
>  static struct glink_channel *qcom_glink_alloc_channel(struct qcom_glink *glink,
> @@ -975,6 +989,76 @@ static int qcom_glink_rx_open_ack(struct qcom_glink *glink, unsigned int lcid)
>  	return 0;
>  }
>  
> +/**
> + * qcom_glink_send_signals() - convert a signal  cmd to wire format and transmit

s/signal  cmd/signal cmd

> + * @glink:	The transport to transmit on.
> + * @channel:	The glink channel
> + * @sigs:	The signals to encode.
> + *
> + * Return: 0 on success or standard Linux error code.
> + */
> +static int qcom_glink_send_signals(struct qcom_glink *glink,
> +				   struct glink_channel *channel,
> +				   u32 sigs)
> +{
> +	struct glink_msg msg;
> +
> +	/* convert signals from TIOCM to NATIVE */
> +	sigs &= 0x0fff;
> +	if (sigs & TIOCM_DTR)
> +		sigs |= NATIVE_DTR_SIG;
> +	if (sigs & TIOCM_RTS)
> +		sigs |= NATIVE_CTS_SIG;
> +	if (sigs & TIOCM_CD)
> +		sigs |= NATIVE_CD_SIG;
> +	if (sigs & TIOCM_RI)
> +		sigs |= NATIVE_RI_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 signals)
> +{
> +	struct glink_channel *channel;
> +	unsigned long flags;
> +	u32 old;
> +
> +	spin_lock_irqsave(&glink->idr_lock, flags);
> +	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;
> +	}
> +
> +	old = channel->rsigs;
> +
> +	/* convert signals from NATIVE to TIOCM */
> +	if (signals & NATIVE_DTR_SIG)
> +		signals |= TIOCM_DSR;

In qcom_glink_send_signals(), TIOCM_DTR (and not TIOCM_DSR) converts to
NATIVE_DTR_SIG.  

> +	if (signals & NATIVE_CTS_SIG)
> +		signals |= TIOCM_CTS;

Similarly, NATIVE_CTS_SIG converts to TIOCM_RTS.  I would have expected to have
a match between what gets sent and what comes back up.  If this is intentional
please at some comments to justify your choices.

> +	if (signals & NATIVE_CD_SIG)
> +		signals |= TIOCM_CD;
> +	if (signals & NATIVE_RI_SIG)
> +		signals |= TIOCM_RI;
> +	signals &= 0x0fff;
> +
> +	channel->rsigs = signals;
> +
> +	if (channel->ept.sig_cb) {
> +		channel->ept.sig_cb(channel->ept.rpdev, channel->ept.priv,
> +				    old, channel->rsigs);

What is the relevance of old and channel->rsigs?  They are certainly not used in
patch 4.

> +	}
> +
> +	return 0;
> +}
> +
>  static irqreturn_t qcom_glink_native_intr(int irq, void *data)
>  {
>  	struct qcom_glink *glink = data;
> @@ -1036,6 +1120,10 @@ 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);
> +			qcom_glink_rx_advance(glink, ALIGN(sizeof(msg), 8));
> +			break;
>  		default:
>  			dev_err(glink->dev, "unhandled rx cmd: %d\n", cmd);
>  			ret = -EINVAL;
> @@ -1340,6 +1428,42 @@ static int qcom_glink_trysend(struct rpmsg_endpoint *ept, void *data, int len)
>  	return __qcom_glink_send(channel, data, len, false);
>  }
>  
> +static int qcom_glink_get_sigs(struct rpmsg_endpoint *ept)
> +{
> +	struct glink_channel *channel = to_glink_channel(ept);
> +
> +	return channel->rsigs;
> +}
> +
> +static int qcom_glink_set_sigs(struct rpmsg_endpoint *ept, u32 set, u32 clear)
> +{
> +	struct glink_channel *channel = to_glink_channel(ept);
> +	struct qcom_glink *glink = channel->glink;
> +	u32 sigs = channel->lsigs;
> +
> +	if (set & TIOCM_DTR)
> +		sigs |= TIOCM_DTR;
> +	if (set & TIOCM_RTS)
> +		sigs |= TIOCM_RTS;
> +	if (set & TIOCM_CD)
> +		sigs |= TIOCM_CD;
> +	if (set & TIOCM_RI)
> +		sigs |= TIOCM_RI;
> +
> +	if (clear & TIOCM_DTR)
> +		sigs &= ~TIOCM_DTR;
> +	if (clear & TIOCM_RTS)
> +		sigs &= ~TIOCM_RTS;
> +	if (clear & TIOCM_CD)
> +		sigs &= ~TIOCM_CD;
> +	if (clear & TIOCM_RI)
> +		sigs &= ~TIOCM_RI;
> +
> +	channel->lsigs = sigs;
> +
> +	return qcom_glink_send_signals(glink, channel, sigs);
> +}
> +
>  /*
>   * Finds the device_node for the glink child interested in this channel.
>   */
> @@ -1373,6 +1497,8 @@ static const struct rpmsg_endpoint_ops glink_endpoint_ops = {
>  	.destroy_ept = qcom_glink_destroy_ept,
>  	.send = qcom_glink_send,
>  	.trysend = qcom_glink_trysend,
> +	.get_signals = qcom_glink_get_sigs,
> +	.set_signals = qcom_glink_set_sigs,
>  };
>  
>  static void qcom_glink_rpdev_release(struct device *dev)
> -- 
> 2.7.4