linux-kernel - Re: [RFC PATCH v2 03/27] NTB: epf: Handle mwN

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Message-ID: <dwejbrb2ow7l2q3ndtiwvffzipiog3ebe3pgzccyt3662s6yrk@mxag5rmqopkn>
Date: Tue, 2 Dec 2025 15:23:48 +0900
From: Koichiro Den <den@...inux.co.jp>
To: Frank Li <Frank.li@....com>
Cc: ntb@...ts.linux.dev, linux-pci@...r.kernel.org, 
	dmaengine@...r.kernel.org, linux-kernel@...r.kernel.org, mani@...nel.org, 
	kwilczynski@...nel.org, kishon@...nel.org, bhelgaas@...gle.com, corbet@....net, 
	vkoul@...nel.org, jdmason@...zu.us, dave.jiang@...el.com, allenbh@...il.com, 
	Basavaraj.Natikar@....com, Shyam-sundar.S-k@....com, kurt.schwemmer@...rosemi.com, 
	logang@...tatee.com, jingoohan1@...il.com, lpieralisi@...nel.org, robh@...nel.org, 
	jbrunet@...libre.com, fancer.lancer@...il.com, arnd@...db.de, pstanner@...hat.com, 
	elfring@...rs.sourceforge.net
Subject: Re: [RFC PATCH v2 03/27] NTB: epf: Handle mwN_offset for inbound MW
 regions

On Mon, Dec 01, 2025 at 02:14:03PM -0500, Frank Li wrote:
> On Sun, Nov 30, 2025 at 01:03:41AM +0900, Koichiro Den wrote:
> > Add and use new fields in the common control register to convey both
> > offset and size for each memory window (MW), so that it can correctly
> > handle flexible MW layouts and support partial BAR mappings.
> >
> > Signed-off-by: Koichiro Den <den@...inux.co.jp>
> > ---
> >  drivers/ntb/hw/epf/ntb_hw_epf.c | 27 ++++++++++++++++-----------
> >  1 file changed, 16 insertions(+), 11 deletions(-)
> >
> > diff --git a/drivers/ntb/hw/epf/ntb_hw_epf.c b/drivers/ntb/hw/epf/ntb_hw_epf.c
> > index d3ecf25a5162..91d3f8e05807 100644
> > --- a/drivers/ntb/hw/epf/ntb_hw_epf.c
> > +++ b/drivers/ntb/hw/epf/ntb_hw_epf.c
> > @@ -36,12 +36,13 @@
> >  #define NTB_EPF_LOWER_SIZE	0x18
> >  #define NTB_EPF_UPPER_SIZE	0x1C
> >  #define NTB_EPF_MW_COUNT	0x20
> > -#define NTB_EPF_MW1_OFFSET	0x24
> > -#define NTB_EPF_SPAD_OFFSET	0x28
> > -#define NTB_EPF_SPAD_COUNT	0x2C
> > -#define NTB_EPF_DB_ENTRY_SIZE	0x30
> > -#define NTB_EPF_DB_DATA(n)	(0x34 + (n) * 4)
> > -#define NTB_EPF_DB_OFFSET(n)	(0xB4 + (n) * 4)
> > +#define NTB_EPF_MW_OFFSET(n)	(0x24 + (n) * 4)
> > +#define NTB_EPF_MW_SIZE(n)	(0x34 + (n) * 4)
> > +#define NTB_EPF_SPAD_OFFSET	0x44
> > +#define NTB_EPF_SPAD_COUNT	0x48
> > +#define NTB_EPF_DB_ENTRY_SIZE	0x4C
> > +#define NTB_EPF_DB_DATA(n)	(0x50 + (n) * 4)
> > +#define NTB_EPF_DB_OFFSET(n)	(0xD0 + (n) * 4)
> 
> You need check difference version for register layout change. EP and RC
> side's software are not necessary to run the same kernel. Maybe EP side
> running at old version, RC side run at new version.

That totally makes sense, I'll do so. Thank you.

-Koichiro

> 
> Frank
> 
> >
> >  #define NTB_EPF_MIN_DB_COUNT	3
> >  #define NTB_EPF_MAX_DB_COUNT	31
> > @@ -451,11 +452,12 @@ static int ntb_epf_peer_mw_get_addr(struct ntb_dev *ntb, int idx,
> >  				    phys_addr_t *base, resource_size_t *size)
> >  {
> >  	struct ntb_epf_dev *ndev = ntb_ndev(ntb);
> > -	u32 offset = 0;
> > +	resource_size_t bar_sz;
> > +	u32 offset, sz;
> >  	int bar;
> >
> > -	if (idx == 0)
> > -		offset = readl(ndev->ctrl_reg + NTB_EPF_MW1_OFFSET);
> > +	offset = readl(ndev->ctrl_reg + NTB_EPF_MW_OFFSET(idx));
> > +	sz = readl(ndev->ctrl_reg + NTB_EPF_MW_SIZE(idx));
> >
> >  	bar = ntb_epf_mw_to_bar(ndev, idx);
> >  	if (bar < 0)
> > @@ -464,8 +466,11 @@ static int ntb_epf_peer_mw_get_addr(struct ntb_dev *ntb, int idx,
> >  	if (base)
> >  		*base = pci_resource_start(ndev->ntb.pdev, bar) + offset;
> >
> > -	if (size)
> > -		*size = pci_resource_len(ndev->ntb.pdev, bar) - offset;
> > +	if (size) {
> > +		bar_sz = pci_resource_len(ndev->ntb.pdev, bar);
> > +		*size = sz ? min_t(resource_size_t, sz, bar_sz - offset)
> > +			   : (bar_sz > offset ? bar_sz - offset : 0);
> > +	}
> >
> >  	return 0;
> >  }
> > --
> > 2.48.1
> >