linux-kernel - Re: [EXT] Re: [PATCH v2] PCI: endpoint: pci-epf-{,v}ntb: fix a check for no epc alignment constraint

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Date:   Fri, 28 Oct 2022 19:56:15 +0900
From:   Shunsuke Mie <mie@...l.co.jp>
To:     Frank Li <frank.li@....com>
Cc:     Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
        Jon Mason <jdmason@...zu.us>,
        Dave Jiang <dave.jiang@...el.com>,
        Allen Hubbe <allenbh@...il.com>,
        "kishon@...nel.org" <kishon@...nel.org>,
        Lorenzo Pieralisi <lpieralisi@...nel.org>,
        Krzysztof Wilczyński <kw@...ux.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        "ntb@...ts.linux.dev" <ntb@...ts.linux.dev>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [EXT] Re: [PATCH v2] PCI: endpoint: pci-epf-{,v}ntb: fix a check
 for no epc alignment constraint

2022年10月28日(金) 1:25 Frank Li <frank.li@....com>:
>
>
>
> > -----Original Message-----
> > From: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
> > Sent: Thursday, October 27, 2022 11:10 AM
> > To: Frank Li <frank.li@....com>
> > Cc: Shunsuke Mie <mie@...l.co.jp>; Jon Mason <jdmason@...zu.us>; Dave
> > Jiang <dave.jiang@...el.com>; Allen Hubbe <allenbh@...il.com>;
> > kishon@...nel.org; Lorenzo Pieralisi <lpieralisi@...nel.org>; Krzysztof
> > Wilczyński <kw@...ux.com>; Bjorn Helgaas <bhelgaas@...gle.com>;
> > ntb@...ts.linux.dev; linux-pci@...r.kernel.org; linux-kernel@...r.kernel.org
> > Subject: Re: [EXT] Re: [PATCH v2] PCI: endpoint: pci-epf-{,v}ntb: fix a check for
> > no epc alignment constraint
> >
> > Caution: EXT Email
> >
> > [Added Kishon's new email address and removed the old one]
> >
> > On Thu, Oct 27, 2022 at 03:34:11PM +0000, Frank Li wrote:
> > >
> > >
> > > > -----Original Message-----
> > > > From: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
> > > > Sent: Thursday, October 27, 2022 10:12 AM
> > > > To: Frank Li <frank.li@....com>
> > > > Cc: Shunsuke Mie <mie@...l.co.jp>; Jon Mason <jdmason@...zu.us>;
> > Dave
> > > > Jiang <dave.jiang@...el.com>; Allen Hubbe <allenbh@...il.com>;
> > Kishon
> > > > Vijay Abraham I <kishon@...com>; Lorenzo Pieralisi
> > <lpieralisi@...nel.org>;
> > > > Krzysztof Wilczyński <kw@...ux.com>; Bjorn Helgaas
> > > > <bhelgaas@...gle.com>; ntb@...ts.linux.dev; linux-pci@...r.kernel.org;
> > > > linux-kernel@...r.kernel.org
> > > > Subject: Re: [EXT] Re: [PATCH v2] PCI: endpoint: pci-epf-{,v}ntb: fix a check
> > for
> > > > no epc alignment constraint
> > > >
> > > > Caution: EXT Email
> > > >
> > > > On Thu, Oct 27, 2022 at 02:35:56PM +0000, Frank Li wrote:
> > > > >
> > > > >
> > > > > > -----Original Message-----
> > > > > > From: Shunsuke Mie <mie@...l.co.jp>
> > > > > > Sent: Wednesday, October 26, 2022 8:43 PM
> > > > > > To: Frank Li <frank.li@....com>
> > > > > > Cc: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>;
> > Jon
> > > > > > Mason <jdmason@...zu.us>; Dave Jiang <dave.jiang@...el.com>;
> > Allen
> > > > > > Hubbe <allenbh@...il.com>; Kishon Vijay Abraham I
> > <kishon@...com>;
> > > > > > Lorenzo Pieralisi <lpieralisi@...nel.org>; Krzysztof Wilczyński
> > > > > > <kw@...ux.com>; Bjorn Helgaas <bhelgaas@...gle.com>;
> > > > > > ntb@...ts.linux.dev; linux-pci@...r.kernel.org; linux-
> > > > kernel@...r.kernel.org
> > > > > > Subject: Re: [EXT] Re: [PATCH v2] PCI: endpoint: pci-epf-{,v}ntb: fix a
> > check
> > > > for
> > > > > > no epc alignment constraint
> > > > > >
> > > > > > Caution: EXT Email
> > > > > >
> > > > > > Hi Frank,
> > > > > >
> > > > > > 2022年10月26日(水) 1:07 Frank Li <frank.li@....com>:
> > > > > > >
> > > > > > >
> > > > > > >
> > > > > > > > -----Original Message-----
> > > > > > > > From: Manivannan Sadhasivam
> > <manivannan.sadhasivam@...aro.org>
> > > > > > > > Sent: Tuesday, October 25, 2022 9:22 AM
> > > > > > > > To: Shunsuke Mie <mie@...l.co.jp>
> > > > > > > > Cc: Jon Mason <jdmason@...zu.us>; Dave Jiang
> > > > <dave.jiang@...el.com>;
> > > > > > > > Allen Hubbe <allenbh@...il.com>; Kishon Vijay Abraham I
> > > > > > > > <kishon@...com>; Lorenzo Pieralisi <lpieralisi@...nel.org>;
> > Krzysztof
> > > > > > > > Wilczyński <kw@...ux.com>; Bjorn Helgaas
> > <bhelgaas@...gle.com>;
> > > > > > > > ntb@...ts.linux.dev; linux-pci@...r.kernel.org; linux-
> > > > > > kernel@...r.kernel.org
> > > > > > > > Subject: [EXT] Re: [PATCH v2] PCI: endpoint: pci-epf-{,v}ntb: fix a
> > check
> > > > for
> > > > > > no
> > > > > > > > epc alignment constraint
> > > > > > > >
> > > > > > > > Caution: EXT Email
> > > > > > > >
> > > > > > > > On Thu, Sep 22, 2022 at 06:23:57PM +0900, Shunsuke Mie wrote:
> > > > > > > > > Some PCI endpoint controllers have no alignment constraints,
> > and
> > > > the
> > > > > > > > > epc_features->align becomes 0. In this case, IS_ALIGNED() in
> > > > > > >
> > > > > > > [Frank Li] why not set epc_features->align 1
> > > > > > > no alignment constraints should mean align to byte.
> > > > > > It is one of the solutions too I think. But in that case,  we need to
> > > > > > write epc_features->align = 1 to all epc drivers, dwc, qcom, rcar,
> > > > > > tegra, and etc.
> > > > > >
> > > > > > I think that my change is better.
> > > > >
> > > > > I think it should be based on what original term defined.
> > > > > It should be fixed at where make mistake.
> > > > >
> > > >
> > > > 1byte is the default alignment that drivers can assume, why do you want
> > > > drivers
> > > > to set them explicitly when they do not want any special alignment?
> > >
> > > What's definition of not alignment by align variable?
> > > Using both 0 and 1 as no alignment is not good enough.
> > >
> > > I grep whole kernel driver directory, not one use
> > >       If (align && IS_ALIGNED(x, align))  statement.
> >
> > I can see multiple hits:
> >
> > lib/ubsan.c
> > drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
> > drivers/gpu/drm/i915/i915_vma.c
> > drivers/nvdimm/pfn_devs.c
> > drivers/misc/pci_endpoint_test.c
> >
> > But in most of the places, the alignment is guaranteed to be set by the client
> > drivers because they might be read from the hardware register or fixed for
> > an
> > IP. But in this case, I don't think we should _force_ the drivers to set
> > alignment to 1 (default) if they don't really care about it.
>
> I keep my opinion.  I think EP controller have not reported correct data.
> Hardware register also can be set 0 as no alignment means.
> It broken "align" conversion.
It is certainly true. In addition, I don't think it is a good design
for the framework to
require the same check for all ep function drivers. like this patch.

But I can't be determined, so I'm going to look into other
drivers/subsystems to find a
common and better way.

> If most people prefer this way, I suggest change api document at
> Include/linux/pci-epc.h to explicitly said 0 is validate option.
Yes. If we take the way, I'll add the explanation.
> >
> > Thanks,
> > Mani
> >
> > >
> > > There are a common convention, align is 2^n
> > >
> > >
> > > >
> > > > I think this patch is fine.
> > > >
> > > > Thanks,
> > > > Mani
> > > >
> > > > > Are there other place use align == 0 means no alignment in kernel?
> > > > >
> > > > > >
> > > > > > > > > epf_ntb_config_spad_bar_alloc() doesn't work well. Check for
> > this
> > > > > > before
> > > > > > > > > IS_ALIGNED().
> > > > > > > > >
> > > > > > > > > Signed-off-by: Shunsuke Mie <mie@...l.co.jp>
> > > > > > > >
> > > > > > > > Reviewed-by: Manivannan Sadhasivam
> > > > > > > > <manivannan.sadhasivam@...aro.org>
> > > > > > > >
> > > > > > > > Thanks,
> > > > > > > > Mani
> > > > > > > >
> > > > > > > > > ---
> > > > > > > > > Changes in v2:
> > > > > > > > > * Fix the commit message in phrasings and words.
> > > > > > > > > ---
> > > > > > > > > ---
> > > > > > > > >  drivers/pci/endpoint/functions/pci-epf-ntb.c  | 2 +-
> > > > > > > > >  drivers/pci/endpoint/functions/pci-epf-vntb.c | 2 +-
> > > > > > > > >  2 files changed, 2 insertions(+), 2 deletions(-)
> > > > > > > > >
> > > > > > > > > diff --git a/drivers/pci/endpoint/functions/pci-epf-ntb.c
> > > > > > > > b/drivers/pci/endpoint/functions/pci-epf-ntb.c
> > > > > > > > > index 9a00448c7e61..f74155ee8d72 100644
> > > > > > > > > --- a/drivers/pci/endpoint/functions/pci-epf-ntb.c
> > > > > > > > > +++ b/drivers/pci/endpoint/functions/pci-epf-ntb.c
> > > > > > > > > @@ -1021,7 +1021,7 @@ static int
> > > > > > epf_ntb_config_spad_bar_alloc(struct
> > > > > > > > epf_ntb *ntb,
> > > > > > > > >       peer_size = peer_epc_features->bar_fixed_size[peer_barno];
> > > > > > > > >
> > > > > > > > >       /* Check if epc_features is populated incorrectly */
> > > > > > > > > -     if ((!IS_ALIGNED(size, align)))
> > > > > > > > > +     if (align && (!IS_ALIGNED(size, align)))
> > > > > > > > >               return -EINVAL;
> > > > > > > > >
> > > > > > > > >       spad_count = ntb->spad_count;
> > > > > > > > > diff --git a/drivers/pci/endpoint/functions/pci-epf-vntb.c
> > > > > > > > b/drivers/pci/endpoint/functions/pci-epf-vntb.c
> > > > > > > > > index 0ea85e1d292e..5e346c0a0f05 100644
> > > > > > > > > --- a/drivers/pci/endpoint/functions/pci-epf-vntb.c
> > > > > > > > > +++ b/drivers/pci/endpoint/functions/pci-epf-vntb.c
> > > > > > > > > @@ -418,7 +418,7 @@ static int
> > > > epf_ntb_config_spad_bar_alloc(struct
> > > > > > > > epf_ntb *ntb)
> > > > > > > > >       size = epc_features->bar_fixed_size[barno];
> > > > > > > > >       align = epc_features->align;
> > > > > > > > >
> > > > > > > > > -     if ((!IS_ALIGNED(size, align)))
> > > > > > > > > +     if (align && !IS_ALIGNED(size, align))
> > > > > > > > >               return -EINVAL;
> > > > > > > > >
> > > > > > > > >       spad_count = ntb->spad_count;
> > > > > > > > > --
> > > > > > > > > 2.17.1
> > > > > > > > >
> > > > > > > >
> > > > > > > > --
> > > > > > > > மணிவண்ணன் சதாசிவம்
> > > > > >
> > > > > > Best,
> > > > > > Shunsuke
> > > >
> > > > --
> > > > மணிவண்ணன் சதாசிவம்
> >
> > --
> > மணிவண்ணன் சதாசிவம்

Best,
Shunsuke