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

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Message-ID: <Z9AnsaoxypL6qult@bogus>
Date: Tue, 11 Mar 2025 12:08:17 +0000
From: Sudeep Holla <sudeep.holla@....com>
To: "lihuisong (C)" <lihuisong@...wei.com>
Cc: <linux-acpi@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	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()

On Tue, Mar 11, 2025 at 07:47:39PM +0800, lihuisong (C) wrote:
>
> 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));
>

ioread32(&pcc_hdr->flags) just reads 4 byte flag instead of copying entire
header for no reason. It should be same as memcpy_fromio(.., .., 4)

--
Regards,
Sudeep