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:   Thu, 27 Oct 2022 16:25:01 +0000
From:   Frank Li <frank.li@....com>
To:     Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
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" <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



> -----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.  

If most people prefer this way, I suggest change api document at 
Include/linux/pci-epc.h to explicitly said 0 is validate option.  

> 
> 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