linux-kernel - Re: [PATCH 1/4] remoteproc: k3-r5: Fix IPC-only mode detection

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Date: Fri, 28 Jun 2024 13:53:30 -0600
From: Mathieu Poirier <mathieu.poirier@...aro.org>
Cc: Bjorn Andersson <andersson@...nel.org>,
	Philipp Zabel <p.zabel@...gutronix.de>, Suman Anna <s-anna@...com>,
	Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
	Alexandre Belloni <alexandre.belloni@...tlin.com>,
	Udit Kumar <u-kumar1@...com>,
	Thomas Richard <thomas.richard@...tlin.com>,
	Gregory CLEMENT <gregory.clement@...tlin.com>,
	Hari Nagalla <hnagalla@...com>,
	Théo Lebrun <theo.lebrun@...tlin.com>,
	linux-remoteproc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/4] remoteproc: k3-r5: Fix IPC-only mode detection

Good day,

On Fri, Jun 21, 2024 at 05:00:55PM +0200, Richard Genoud wrote:
> ret variable was used to test reset status, get from
> reset_control_status() call. But this variable was overwritten by
> ti_sci_proc_get_status() a few lines bellow.
> And as ti_sci_proc_get_status() returns 0 or a negative value (in this
> latter case, followed by a return), the expression !ret was always true,
> 
> Clearly, this was not what was intended:
> In the comment above it's said that "requires both local and module
> resets to be deasserted"; if reset_control_status() returns 0 it means
> that the reset line is deasserted.
> So, it's pretty clear that the return value of reset_control_status()
> was intended to be used instead of ti_sci_proc_get_status() return
> value.
> 
> This could lead in an incorrect IPC-only mode detection if reset line is
> asserted (so reset_control_status() return > 0) and c_state != 0 and
> halted == 0.
> In this case, the old code would have detected an IPC-only mode instead
> of a mismatched mode.
> 

Your assessment seems to be correct.  That said I'd like to have an RB or a TB
from someone in the TI delegation - guys please have a look.

Thanks,
Mathieu

> Fixes: 1168af40b1ad ("remoteproc: k3-r5: Add support for IPC-only mode for all R5Fs")
> Signed-off-by: Richard Genoud <richard.genoud@...tlin.com>
> ---
>  drivers/remoteproc/ti_k3_r5_remoteproc.c | 13 +++++++------
>  1 file changed, 7 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/remoteproc/ti_k3_r5_remoteproc.c b/drivers/remoteproc/ti_k3_r5_remoteproc.c
> index 50e486bcfa10..39a47540c590 100644
> --- a/drivers/remoteproc/ti_k3_r5_remoteproc.c
> +++ b/drivers/remoteproc/ti_k3_r5_remoteproc.c
> @@ -1144,6 +1144,7 @@ static int k3_r5_rproc_configure_mode(struct k3_r5_rproc *kproc)
>  	u32 atcm_enable, btcm_enable, loczrama;
>  	struct k3_r5_core *core0;
>  	enum cluster_mode mode = cluster->mode;
> +	int reset_ctrl_status;
>  	int ret;
>  
>  	core0 = list_first_entry(&cluster->cores, struct k3_r5_core, elem);
> @@ -1160,11 +1161,11 @@ static int k3_r5_rproc_configure_mode(struct k3_r5_rproc *kproc)
>  			 r_state, c_state);
>  	}
>  
> -	ret = reset_control_status(core->reset);
> -	if (ret < 0) {
> +	reset_ctrl_status = reset_control_status(core->reset);
> +	if (reset_ctrl_status < 0) {
>  		dev_err(cdev, "failed to get initial local reset status, ret = %d\n",
> -			ret);
> -		return ret;
> +			reset_ctrl_status);
> +		return reset_ctrl_status;
>  	}
>  
>  	/*
> @@ -1199,7 +1200,7 @@ static int k3_r5_rproc_configure_mode(struct k3_r5_rproc *kproc)
>  	 * irrelevant if module reset is asserted (POR value has local reset
>  	 * deasserted), and is deemed as remoteproc mode
>  	 */
> -	if (c_state && !ret && !halted) {
> +	if (c_state && !reset_ctrl_status && !halted) {
>  		dev_info(cdev, "configured R5F for IPC-only mode\n");
>  		kproc->rproc->state = RPROC_DETACHED;
>  		ret = 1;
> @@ -1217,7 +1218,7 @@ static int k3_r5_rproc_configure_mode(struct k3_r5_rproc *kproc)
>  		ret = 0;
>  	} else {
>  		dev_err(cdev, "mismatched mode: local_reset = %s, module_reset = %s, core_state = %s\n",
> -			!ret ? "deasserted" : "asserted",
> +			!reset_ctrl_status ? "deasserted" : "asserted",
>  			c_state ? "deasserted" : "asserted",
>  			halted ? "halted" : "unhalted");
>  		ret = -EINVAL;