linux-kernel - Re: [PATCH 3/6] mailbox: pcc: Set txdone_irq/txdone

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Message-ID: <94ca016f-7c29-4339-9d52-7ca0a54ab6f2@amperemail.onmicrosoft.com>
Date: Fri, 17 Oct 2025 13:16:42 -0400
From: Adam Young <admiyo@...eremail.onmicrosoft.com>
To: Sudeep Holla <sudeep.holla@....com>, linux-acpi@...r.kernel.org,
 linux-kernel@...r.kernel.org
Cc: Adam Young <admiyo@...amperecomputing.com>,
 Robbie King <robbiek@...ghtlabs.com>, Huisong Li <lihuisong@...wei.com>,
 Jassi Brar <jassisinghbrar@...il.com>,
 Cristian Marussi <cristian.marussi@....com>
Subject: Re: [PATCH 3/6] mailbox: pcc: Set txdone_irq/txdone_poll based on
 PCCT flags

Tested-by: Adam Young <admiyo@...amperecomputing.com>

On 10/16/25 15:08, Sudeep Holla wrote:
> The PCC controller currently enables txdone via IRQ if the PCCT exposes
> platform capability to generate command completion interrupt, but it
> leaves txdone_poll unchanged. Make the behaviour explicit:
>
>    - If ACPI_PCCT_DOORBELL is present, use txdone_irq and disable polling.
>    - Otherwise, disable txdone_irq and fall back to txdone_poll.
>
> Configure the PCC mailbox to use interrupt-based completion for PCC types
> that signal completion via IRQ using TXDONE_BY_IRQ, and fall back to
> polling for others using TXDONE_BY_POLL.
>
> This ensures the PCC driver uses the appropriate completion mechanism
> according to the PCCT table definition and makes the completion mode
> unambiguous avoiding mixed signalling when the platform lacks a doorbell
> flag set.
>
> Signed-off-by: Sudeep Holla <sudeep.holla@....com>
> ---
>   drivers/mailbox/pcc.c | 7 ++++++-
>   1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/mailbox/pcc.c b/drivers/mailbox/pcc.c
> index 2b690c268cf0..327e022973db 100644
> --- a/drivers/mailbox/pcc.c
> +++ b/drivers/mailbox/pcc.c
> @@ -791,8 +791,13 @@ static int pcc_mbox_probe(struct platform_device *pdev)
>   		(unsigned long) pcct_tbl + sizeof(struct acpi_table_pcct));
>   
>   	acpi_pcct_tbl = (struct acpi_table_pcct *) pcct_tbl;
> -	if (acpi_pcct_tbl->flags & ACPI_PCCT_DOORBELL)
> +	if (acpi_pcct_tbl->flags & ACPI_PCCT_DOORBELL) {
>   		pcc_mbox_ctrl->txdone_irq = true;
> +		pcc_mbox_ctrl->txdone_poll = false;
> +	} else {
> +		pcc_mbox_ctrl->txdone_irq = false;
> +		pcc_mbox_ctrl->txdone_poll = true;
> +	}
>   
>   	for (i = 0; i < count; i++) {
>   		struct pcc_chan_info *pchan = chan_info + i;
>