Re: [PATCH 1/2] soc: qcom: rpmh-rsc: Update CMD_MSGID_LEN to 4 bytes for read request

[Bjorn Andersson <andersson@kernel.org>]

On Thu, Sep 10, 2026 at 02:23:01PM +0530, Maulik Shah wrote:
> Newer SoC like hawi with RSC version v4.5 support 4 byte message read
> request instead of default 8 byte on older SoCs. The write request
> continues to be 8 bytes.
> 
> Update the read request message accordingly on RSC v4.5 and higher.
> 
> Signed-off-by: Maulik Shah <maulik.shah@oss.qualcomm.com>
> ---
>  drivers/soc/qcom/rpmh-rsc.c | 13 ++++++++++---
>  1 file changed, 10 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/soc/qcom/rpmh-rsc.c b/drivers/soc/qcom/rpmh-rsc.c
> index c4542318eac4..f84a399fa5dc 100644
> --- a/drivers/soc/qcom/rpmh-rsc.c
> +++ b/drivers/soc/qcom/rpmh-rsc.c
> @@ -86,6 +86,7 @@ enum {
>  #define TCS_AMC_MODE_TRIGGER		BIT(24)
>  
>  /* TCS CMD register bit mask */
> +#define CMD_MSGID_LEN_READ_v4_5		4
>  #define CMD_MSGID_LEN			8
>  #define CMD_MSGID_RESP_REQ		BIT(8)
>  #define CMD_MSGID_WRITE			BIT(16)
> @@ -499,15 +500,21 @@ static void __tcs_buffer_write(struct rsc_drv *drv, int tcs_id, int cmd_id,
>  			       const struct tcs_request *msg)
>  {
>  	u32 msgid;
> -	u32 cmd_msgid = CMD_MSGID_LEN;
> +	u32 cmd_msgid = 0;
>  	u32 cmd_enable = 0;
>  	struct tcs_cmd *cmd;
>  	int i, j;
>  
>  	/* Convert all commands to RR when the request has wait_for_compl set */
>  	cmd_msgid |= msg->wait_for_compl ? CMD_MSGID_RESP_REQ : 0;
> -	if (!msg->is_read)
> -		cmd_msgid |= CMD_MSGID_WRITE;
> +	if (!msg->is_read) {
> +		cmd_msgid = CMD_MSGID_LEN | CMD_MSGID_WRITE;

I know this follows the current code, but CMD_MSGID_LEN doesn't seem
like a "fixed" part of this message anymore. It seems rather that
there's a few bits here which denotes the CMD_MSGID_LEN and the value
thereof is either 8 or 4.

If this is the case, I'd find it cleaner to define CMD_MSGID_LEN_MASK
and then just FIELD_PREP() to put a 4 or a 8 in the "length field" of
the command.

> +	} else {
> +		if (drv->ver.major >= 4 && drv->ver.minor >= 5)
> +			cmd_msgid = CMD_MSGID_LEN_READ_v4_5;

If I understand your commit message, this line says "on DRV 4.5 and
higher length is 4 otherwise it's 8" - but there's no way anyone can
read this line and come to that conclusion.

In contrast, this would actually say that:
  cmd_msgid |= FIELD_PREP(CMD_MSGID_LEN, 4);


Also, is this really supposed to apply to DRV versions such as 5.5, but
not 6.1?

Regards,
Bjorn

> +		else
> +			cmd_msgid = CMD_MSGID_LEN;
> +	}
>  
>  	for (i = 0, j = cmd_id; i < msg->num_cmds; i++, j++) {
>  		cmd = &msg->cmds[i];
> 
> -- 
> 2.43.0
>