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Date:   Tue, 6 Jun 2023 19:42:31 +0200
From:   Greg KH <gregkh@linuxfoundation.org>
To:     Ekansh Gupta <quic_ekangupt@quicinc.com>
Cc:     srinivas.kandagatla@linaro.org, linux-arm-msm@vger.kernel.org,
        ekangupt@qti.qualcomm.com, linux-kernel@vger.kernel.org,
        bkumar@qti.qualcomm.com, fastrpc.upstream@qti.qualcomm.com
Subject: Re: [PATCH v1] misc: fastrpc: Collect driver-remote processor
 transaction logs
Message-ID: <2023060608-junction-conclude-f607@gregkh>
References: <1686070555-11154-1-git-send-email-quic_ekangupt@quicinc.com>
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On Tue, Jun 06, 2023 at 10:25:55PM +0530, Ekansh Gupta wrote:
> Add changes to collect driver-remote processor rpmsg transaction
> logs. These logs will carry payload information for the rpmsg message
> instance. These logs are channel specific and are collected in
> channel context structure.
> 
> These rpmsg transaction logs can help in improving debugability as
> all requests from processes are getting captured in channel context
> structure.
> 
> Signed-off-by: Ekansh Gupta <quic_ekangupt@quicinc.com>
> ---
>  drivers/misc/fastrpc.c | 88 ++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 88 insertions(+)
> 
> diff --git a/drivers/misc/fastrpc.c b/drivers/misc/fastrpc.c
> index 30d4d04..6447cee 100644
> --- a/drivers/misc/fastrpc.c
> +++ b/drivers/misc/fastrpc.c
> @@ -104,6 +104,9 @@
>  
>  #define miscdev_to_fdevice(d) container_of(d, struct fastrpc_device, miscdev)
>  
> +/* Length of glink transaction history to store */
> +#define GLINK_MSG_HISTORY_LEN	(128)
> +
>  static const char *domains[FASTRPC_DEV_MAX] = { "adsp", "mdsp",
>  						"sdsp", "cdsp"};
>  struct fastrpc_phy_page {
> @@ -181,6 +184,28 @@ struct fastrpc_invoke_rsp {
>  	int retval;		/* invoke return value */
>  };
>  
> +struct fastrpc_tx_msg {
> +	struct fastrpc_msg msg;	/* Msg sent to remote subsystem */
> +	int rpmsg_send_err;	/* rpmsg error */
> +	s64 ns;			/* Timestamp (in ns) of msg */
> +};
> +
> +struct fastrpc_rx_msg {
> +	struct fastrpc_invoke_rsp rsp;	/* Response from remote subsystem */
> +	s64 ns;		/* Timestamp (in ns) of response */
> +};
> +
> +struct fastrpc_rpmsg_log {
> +	u32 tx_index;	/* Current index of 'tx_msgs' array */
> +	u32 rx_index;	/* Current index of 'rx_msgs' array */
> +	/* Rolling history of messages sent to remote subsystem */
> +	struct fastrpc_tx_msg tx_msgs[GLINK_MSG_HISTORY_LEN];
> +	/* Rolling history of responses from remote subsystem */
> +	struct fastrpc_rx_msg rx_msgs[GLINK_MSG_HISTORY_LEN];
> +	spinlock_t tx_lock;
> +	spinlock_t rx_lock;

Why roll your own ring-buffer logic instead of using one of the many
offerings that the kernel already provides for you?

thanks,

greg k-h