linux-kernel - Re: [PATCH v2 08/13] mailbox: pcc: Refactor and simplify check_and

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Message-ID: <34bdfee2-4780-f45b-7891-e845b13fdd2f@huawei.com>
Date: Tue, 11 Mar 2025 19:47:39 +0800
From: "lihuisong (C)" <lihuisong@...wei.com>
To: Sudeep Holla <sudeep.holla@....com>, <linux-acpi@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>
CC: Jassi Brar <jassisinghbrar@...il.com>, Adam Young
	<admiyo@...amperecomputing.com>, Robbie King <robbiek@...ghtlabs.com>
Subject: Re: [PATCH v2 08/13] mailbox: pcc: Refactor and simplify
 check_and_ack()


在 2025/3/6 0:38, Sudeep Holla 写道:
> The existing check_and_ack() function had unnecessary complexity. The
> logic could be streamlined to improve code readability and maintainability.
>
> The command update register needs to be updated in order to acknowledge
> the platform notification through type 4 channel. So it can be done
> unconditionally. Currently it is complicated just to make use of
> pcc_send_data() which also executes the same updation.
>
> In order to simplify, let us just ring the doorbell directly from
> check_and_ack() instead of calling into pcc_send_data(). While at it,
> rename it into pcc_chan_check_and_ack() to maintain consistency in the
> driver.
LGTM except for some trivial,
Acked-by: Huisong Li <lihuisong@...wei.com>
>
> Signed-off-by: Sudeep Holla <sudeep.holla@....com>
> ---
>   drivers/mailbox/pcc.c | 37 +++++++++++++------------------------
>   1 file changed, 13 insertions(+), 24 deletions(-)
>
> diff --git a/drivers/mailbox/pcc.c b/drivers/mailbox/pcc.c
> index b3d133170aac7f8acfd1999564c69b7fe4f6d582..90d6f5e24df7e796f8c29705808eb6df2806c1f2 100644
> --- a/drivers/mailbox/pcc.c
> +++ b/drivers/mailbox/pcc.c
> @@ -117,8 +117,6 @@ struct pcc_chan_info {
>   static struct pcc_chan_info *chan_info;
>   static int pcc_chan_count;
>   
> -static int pcc_send_data(struct mbox_chan *chan, void *data);
> -
>   /*
>    * PCC can be used with perf critical drivers such as CPPC
>    * So it makes sense to locally cache the virtual address and
> @@ -288,33 +286,24 @@ static int pcc_mbox_error_check_and_clear(struct pcc_chan_info *pchan)
>   	return 0;
>   }
>   
> -static void check_and_ack(struct pcc_chan_info *pchan, struct mbox_chan *chan)
> +static void pcc_chan_check_and_ack(struct pcc_chan_info *pchan)
How about use pcc_chan_ack?
>   {
> -	struct acpi_pcct_ext_pcc_shared_memory pcc_hdr;
> +	struct acpi_pcct_ext_pcc_shared_memory __iomem *pcc_hdr;
>   
>   	if (pchan->type != ACPI_PCCT_TYPE_EXT_PCC_SLAVE_SUBSPACE)
>   		return;
> -	/* If the memory region has not been mapped, we cannot
> -	 * determine if we need to send the message, but we still
> -	 * need to set the cmd_update flag before returning.
> -	 */
> -	if (pchan->chan.shmem == NULL) {
> -		pcc_chan_reg_read_modify_write(&pchan->cmd_update);
> -		return;
> -	}
> -	memcpy_fromio(&pcc_hdr, pchan->chan.shmem,
> -		      sizeof(struct acpi_pcct_ext_pcc_shared_memory));
> +
> +	pcc_chan_reg_read_modify_write(&pchan->cmd_update);
> +
> +	pcc_hdr = pchan->chan.shmem;

Should use the original code?

memcpy_fromio(&pcc_hdr, pchan->chan.shmem,
		      sizeof(struct acpi_pcct_ext_pcc_shared_memory));

> +
>   	/*
> -	 * The PCC slave subspace channel needs to set the command complete bit
> -	 * after processing message. If the PCC_ACK_FLAG is set, it should also
> -	 * ring the doorbell.
> -	 *
> -	 * The PCC master subspace channel clears chan_in_use to free channel.
> +	 * The PCC slave subspace channel needs to set the command
> +	 * complete bit after processing message. If the PCC_ACK_FLAG
> +	 * is set, it should also ring the doorbell.
>   	 */
> -	if (pcc_hdr.flags & PCC_CMD_COMPLETION_NOTIFY)
> -		pcc_send_data(chan, NULL);
> -	else
> -		pcc_chan_reg_read_modify_write(&pchan->cmd_update);
> +	if (ioread32(&pcc_hdr->flags) & PCC_CMD_COMPLETION_NOTIFY)
> +		pcc_chan_reg_read_modify_write(&pchan->db);
>   }
>   
>   /**
> @@ -352,7 +341,7 @@ static irqreturn_t pcc_mbox_irq(int irq, void *p)
>   	pchan->chan_in_use = false;
>   	mbox_chan_received_data(chan, NULL);
>   
> -	check_and_ack(pchan, chan);
> +	pcc_chan_check_and_ack(pchan);
>   
>   	return IRQ_HANDLED;
>   }
>