linux-kernel - Re: [PATCH V2 2/9] platform/x86/intel/sdsi: Combine read and write mailbox flows

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Message-ID: <2dba47561b467c483263b65606aa3e79c05c91a3.camel@linux.intel.com>
Date: Wed, 28 Feb 2024 10:10:11 -0800
From: "David E. Box" <david.e.box@...ux.intel.com>
To: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>,
  rajvi.jingar@...ux.intel.com, platform-driver-x86@...r.kernel.org, 
 linux-kernel@...r.kernel.org, hdegoede@...hat.com,
 ilpo.jarvinen@...ux.intel.com
Subject: Re: [PATCH V2 2/9] platform/x86/intel/sdsi: Combine read and write
 mailbox flows

On Tue, 2024-02-27 at 18:38 -0800, Kuppuswamy Sathyanarayanan wrote:
> 
> On 2/27/24 4:00 PM, David E. Box wrote:
> > The current mailbox commands are either read-only or write-only and the
> > flow is different for each. New commands will need to send and receive
> > data. In preparation for these commands, create a common polling function
> > to handle sending data and receiving in the same transaction.
> > 
> > Signed-off-by: David E. Box <david.e.box@...ux.intel.com>
> > ---
> > 
> > V2 - In sdsi_cmd_read() remove unnecessary check for non-zero packet_size
> >      in do loop since the loop is exited earlier when packet_size is
> >      zero.
> > 
> >  drivers/platform/x86/intel/sdsi.c | 79 +++++++++++++++++--------------
> >  1 file changed, 44 insertions(+), 35 deletions(-)
> > 
> > diff --git a/drivers/platform/x86/intel/sdsi.c
> > b/drivers/platform/x86/intel/sdsi.c
> > index a70c071de6e2..d80c2dc0ce71 100644
> > --- a/drivers/platform/x86/intel/sdsi.c
> > +++ b/drivers/platform/x86/intel/sdsi.c
> > @@ -15,6 +15,7 @@
> >  #include <linux/iopoll.h>
> >  #include <linux/kernel.h>
> >  #include <linux/module.h>
> > +#include <linux/overflow.h>
> >  #include <linux/pci.h>
> >  #include <linux/slab.h>
> >  #include <linux/sysfs.h>
> > @@ -156,8 +157,8 @@ static int sdsi_status_to_errno(u32 status)
> >  	}
> >  }
> >  
> > -static int sdsi_mbox_cmd_read(struct sdsi_priv *priv, struct sdsi_mbox_info
> > *info,
> > -			      size_t *data_size)
> > +static int sdsi_mbox_poll(struct sdsi_priv *priv, struct sdsi_mbox_info
> > *info,
> > +			  size_t *data_size)
> >  {
> >  	struct device *dev = priv->dev;
> >  	u32 total, loop, eom, status, message_size;
> > @@ -166,18 +167,10 @@ static int sdsi_mbox_cmd_read(struct sdsi_priv *priv,
> > struct sdsi_mbox_info *inf
> >  
> >  	lockdep_assert_held(&priv->mb_lock);
> >  
> > -	/* Format and send the read command */
> > -	control = FIELD_PREP(CTRL_EOM, 1) |
> > -		  FIELD_PREP(CTRL_SOM, 1) |
> > -		  FIELD_PREP(CTRL_RUN_BUSY, 1) |
> > -		  FIELD_PREP(CTRL_PACKET_SIZE, info->size);
> > -	writeq(control, priv->control_addr);
> > -
> >  	/* For reads, data sizes that are larger than the mailbox size are
> > read in packets. */
> >  	total = 0;
> >  	loop = 0;
> >  	do {
> > -		void *buf = info->buffer + (SDSI_SIZE_MAILBOX * loop);
> >  		u32 packet_size;
> >  
> >  		/* Poll on ready bit */
> > @@ -195,6 +188,11 @@ static int sdsi_mbox_cmd_read(struct sdsi_priv *priv,
> > struct sdsi_mbox_info *inf
> >  		if (ret)
> >  			break;
> >  
> > +		if (!packet_size) {
> > +			sdsi_complete_transaction(priv);
> > +			break;
> > +		}
> > +
> >  		/* Only the last packet can be less than the mailbox size.
> > */
> >  		if (!eom && packet_size != SDSI_SIZE_MAILBOX) {
> >  			dev_err(dev, "Invalid packet size\n");
> > @@ -208,9 +206,13 @@ static int sdsi_mbox_cmd_read(struct sdsi_priv *priv,
> > struct sdsi_mbox_info *inf
> >  			break;
> >  		}
> >  
> > -		sdsi_memcpy64_fromio(buf, priv->mbox_addr,
> > round_up(packet_size, SDSI_SIZE_CMD));
> > +		if (info->buffer) {
> > +			void *buf = info->buffer +
> > array_size(SDSI_SIZE_MAILBOX, loop);
> >  
> > -		total += packet_size;
> > +			sdsi_memcpy64_fromio(buf, priv->mbox_addr,
> > +					     round_up(packet_size,
> > SDSI_SIZE_CMD));
> > +			total += packet_size;
> > +		}
> >  
> >  		sdsi_complete_transaction(priv);
> >  	} while (!eom && ++loop < MBOX_MAX_PACKETS);
> > @@ -230,16 +232,33 @@ static int sdsi_mbox_cmd_read(struct sdsi_priv *priv,
> > struct sdsi_mbox_info *inf
> >  		dev_warn(dev, "Read count %u differs from expected count
> > %u\n",
> >  			 total, message_size);
> >  
> > -	*data_size = total;
> > +	if (data_size)
> > +		*data_size = total;
> >  
> 
> Is there a chance for it to be NULL with current callers?

Yes. Write only callers set this to NULL.

David