linux-kernel - Re: [PATCH v4 1/3] mctp pcc: Check before sending MCTP PCC response ACK

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Message-ID: <20240703195232.GQ598357@kernel.org>
Date: Wed, 3 Jul 2024 20:52:32 +0100
From: Simon Horman <horms@...nel.org>
To: admiyo@...amperecomputing.com
Cc: Sudeep Holla <sudeep.holla@....com>,
	Jassi Brar <jassisinghbrar@...il.com>,
	Robert Moore <robert.moore@...el.com>,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	Len Brown <lenb@...nel.org>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, Jeremy Kerr <jk@...econstruct.com.au>,
	Matt Johnston <matt@...econstruct.com.au>,
	"David S . Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Jonathan Cameron <Jonathan.Cameron@...wei.com>,
	Huisong Li <lihuisong@...wei.com>
Subject: Re: [PATCH v4 1/3] mctp pcc: Check before sending MCTP PCC response
 ACK

On Tue, Jul 02, 2024 at 06:58:43PM -0400, admiyo@...amperecomputing.com wrote:
> From: Adam Young <admiyo@...amperecomputing.com>
> 
> Type 4 PCC channels have an option to send back a response
> to the platform when they are done processing the request.
> The flag to indicate whether or not to respond is inside
> the message body, and thus is not available to the pcc
> mailbox.
> 
> In order to read the flag, this patch maps the shared
> buffer to virtual memory.
> 
> Signed-off-by: Adam Young <admiyo@...amperecomputing.com>
> ---
>  drivers/mailbox/pcc.c | 31 +++++++++++++++++++++++--------
>  include/acpi/pcc.h    |  8 ++++++++
>  2 files changed, 31 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/mailbox/pcc.c b/drivers/mailbox/pcc.c
> index 94885e411085..cad6b5bc4b04 100644
> --- a/drivers/mailbox/pcc.c
> +++ b/drivers/mailbox/pcc.c
> @@ -107,6 +107,7 @@ struct pcc_chan_info {
>  	struct pcc_chan_reg cmd_complete;
>  	struct pcc_chan_reg cmd_update;
>  	struct pcc_chan_reg error;
> +	void __iomem *shmem_base_addr;

Hi Adam,

Please add an entry for shmem_base_addr to the Kernel doc for this
structure, which appears just above the structure.

Flagged by ./scripts/kernel-doc -none

>  	int plat_irq;
>  	u8 type;
>  	unsigned int plat_irq_flags;
> @@ -269,6 +270,24 @@ static bool pcc_mbox_cmd_complete_check(struct pcc_chan_info *pchan)
>  	return !!val;
>  }
>  
> +static void check_and_ack(struct pcc_chan_info *pchan, struct mbox_chan *chan)
> +{
> +	struct pcc_extended_type_hdr pcc_hdr;
> +
> +	if (pchan->type != ACPI_PCCT_TYPE_EXT_PCC_SLAVE_SUBSPACE)
> +		return;
> +	memcpy_fromio(&pcc_hdr, pchan->shmem_base_addr,
> +		      sizeof(struct pcc_extended_type_hdr));
> +	/*
> +	 * The PCC slave subspace channel needs to set the command complete bit
> +	 * and ring doorbell after processing message.
> +	 *
> +	 * The PCC master subspace channel clears chan_in_use to free channel.
> +	 */
> +	if (!!le32_to_cpup(&pcc_hdr.flags) & PCC_ACK_FLAG_MASK)

Should this be:

	if (!!(le32_to_cpup(&pcc_hdr.flags) & PCC_ACK_FLAG_MASK))

In which case I think it can be more simply expressed as:

	if (le32_to_cpup(&pcc_hdr.flags) & PCC_ACK_FLAG_MASK)

Flagged by Smatch and Sparse.

> +		pcc_send_data(chan, NULL);
> +}
> +
>  /**
>   * pcc_mbox_irq - PCC mailbox interrupt handler
>   * @irq:	interrupt number

...

> diff --git a/include/acpi/pcc.h b/include/acpi/pcc.h

...

> @@ -31,6 +38,7 @@ struct pcc_mbox_chan {
>  #define PCC_CMD_COMPLETION_NOTIFY	BIT(0)
>  
>  #define MAX_PCC_SUBSPACES	256
> +#define PCC_ACK_FLAG_MASK       0x1

nit: For consistency please follow the white-space pattern of the preceding
     line: please use a tab rathe rthan spaces between ...MASK and 0x1.

>  
>  #ifdef CONFIG_PCC
>  extern struct pcc_mbox_chan *
> -- 
> 2.34.1
> 
> 

-- 
pw-bot: changes-requested