linux-kernel - Re: [PATCH v4 1/4] firmware: ti_sci: Support transfers without response

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Message-ID: <20241220114118.uwi5bsefxnue46re@lcpd911>
Date: Fri, 20 Dec 2024 17:11:18 +0530
From: Dhruva Gole <d-gole@...com>
To: Markus Schneider-Pargmann <msp@...libre.com>
CC: Nishanth Menon <nm@...com>, Tero Kristo <kristo@...nel.org>,
        Santosh
 Shilimkar <ssantosh@...nel.org>,
        Vignesh Raghavendra <vigneshr@...com>, Rob
 Herring <robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor
 Dooley <conor+dt@...nel.org>, Anand Gadiyar <gadiyar@...com>,
        <linux-arm-kernel@...ts.infradead.org>, <linux-kernel@...r.kernel.org>,
        <devicetree@...r.kernel.org>, Vishal Mahaveer <vishalm@...com>,
        Kevin Hilman
	<khilman@...libre.com>
Subject: Re: [PATCH v4 1/4] firmware: ti_sci: Support transfers without
 response

On Dec 19, 2024 at 21:02:12 +0100, Markus Schneider-Pargmann wrote:
> Check the header flags if an response is expected or not. If it is not
> expected skip the receive part of ti_sci_do_xfer(). This prepares the
> driver for one-way messages as prepare_sleep for Partial-IO.
> 
> Signed-off-by: Markus Schneider-Pargmann <msp@...libre.com>
> ---
>  drivers/firmware/ti_sci.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/drivers/firmware/ti_sci.c b/drivers/firmware/ti_sci.c
> index 806a975fff22ae00ecb88587b2c47ba172120bc2..ec0c54935ac0d667323d98b86ac9d288b73be6aa 100644
> --- a/drivers/firmware/ti_sci.c
> +++ b/drivers/firmware/ti_sci.c
> @@ -398,10 +398,13 @@ static void ti_sci_put_one_xfer(struct ti_sci_xfers_info *minfo,
>  static inline int ti_sci_do_xfer(struct ti_sci_info *info,
>  				 struct ti_sci_xfer *xfer)
>  {
> +	struct ti_sci_msg_hdr *hdr = (struct ti_sci_msg_hdr *)xfer->tx_message.buf;

I think it's best to sort this in order? so it will come below struct
device?

>  	int ret;
>  	int timeout;
>  	struct device *dev = info->dev;
>  	bool done_state = true;
> +	bool response_expected = !!(hdr->flags & (TI_SCI_FLAG_REQ_ACK_ON_PROCESSED |
> +						  TI_SCI_FLAG_REQ_ACK_ON_RECEIVED));
>  
>  	ret = mbox_send_message(info->chan_tx, &xfer->tx_message);
>  	if (ret < 0)
> @@ -409,6 +412,9 @@ static inline int ti_sci_do_xfer(struct ti_sci_info *info,
>  
>  	ret = 0;
>  
> +	if (!response_expected)
> +		goto no_response;
> +

I am not a very big fan of using goto here, it feels like we should be
more clear in our implementation and make the else part below more
specific by using `else if` and checking for more specific SYSTEM_XX
states. Then based on POWEROFF, skip any polling or whatever wait for
response.
Infact, with that we may not even need the response_expected part, but I
am okay keeping both checks in place just for the clarity in design.

>  	if (system_state <= SYSTEM_RUNNING) {
>  		/* And we wait for the response. */
>  		timeout = msecs_to_jiffies(info->desc->max_rx_timeout_ms);
> @@ -429,6 +435,7 @@ static inline int ti_sci_do_xfer(struct ti_sci_info *info,
>  		dev_err(dev, "Mbox timedout in resp(caller: %pS)\n",
>  			(void *)_RET_IP_);
>  

-- 
Best regards,
Dhruva Gole
Texas Instruments Incorporated