linux-kernel - Re: [PATCH 2/4] powerpc/pseries/iommu: Implement ibm,reset-pe-dma-windows rtas call

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Date:   Mon, 22 Jun 2020 23:20:08 -0300
From:   Leonardo Bras <leobras.c@...il.com>
To:     Alexey Kardashevskiy <aik@...abs.ru>,
        Michael Ellerman <mpe@...erman.id.au>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Thiago Jung Bauermann <bauerman@...ux.ibm.com>,
        Ram Pai <linuxram@...ibm.com>
Cc:     linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/4] powerpc/pseries/iommu: Implement
 ibm,reset-pe-dma-windows rtas call

On Tue, 2020-06-23 at 11:11 +1000, Alexey Kardashevskiy wrote:
> 
> On 23/06/2020 04:58, Leonardo Bras wrote:
> > Hello Alexey, thanks for the feedback!
> > 
> > On Mon, 2020-06-22 at 20:02 +1000, Alexey Kardashevskiy wrote:
> > > On 19/06/2020 15:06, Leonardo Bras wrote:
> > > > Platforms supporting the DDW option starting with LoPAR level 2.7 implement
> > > > ibm,ddw-extensions. The first extension available (index 2) carries the
> > > > token for ibm,reset-pe-dma-windows rtas call, which is used to restore
> > > > the default DMA window for a device, if it has been deleted.
> > > > 
> > > > It does so by resetting the TCE table allocation for the PE to it's
> > > > boot time value, available in "ibm,dma-window" device tree node.
> > > > 
> > > > Signed-off-by: Leonardo Bras <leobras.c@...il.com>
> > > > ---
> > > >  arch/powerpc/platforms/pseries/iommu.c | 33 ++++++++++++++++++++++++++
> > > >  1 file changed, 33 insertions(+)
> > > > 
> > > > diff --git a/arch/powerpc/platforms/pseries/iommu.c b/arch/powerpc/platforms/pseries/iommu.c
> > > > index e5a617738c8b..5e1fbc176a37 100644
> > > > --- a/arch/powerpc/platforms/pseries/iommu.c
> > > > +++ b/arch/powerpc/platforms/pseries/iommu.c
> > > > @@ -1012,6 +1012,39 @@ static phys_addr_t ddw_memory_hotplug_max(void)
> > > >  	return max_addr;
> > > >  }
> > > >  
> > > > +/*
> > > > + * Platforms supporting the DDW option starting with LoPAR level 2.7 implement
> > > > + * ibm,ddw-extensions, which carries the rtas token for
> > > > + * ibm,reset-pe-dma-windows.
> > > > + * That rtas-call can be used to restore the default DMA window for the device.
> > > > + */
> > > > +static void reset_dma_window(struct pci_dev *dev, struct device_node *par_dn)
> > > > +{
> > > > +	int ret;
> > > > +	u32 cfg_addr, ddw_ext[3];
> > > > +	u64 buid;
> > > > +	struct device_node *dn;
> > > > +	struct pci_dn *pdn;
> > > > +
> > > > +	ret = of_property_read_u32_array(par_dn, "ibm,ddw-extensions",
> > > > +					 &ddw_ext[0], 3);
> > > 
> > > s/3/2/ as for the reset extension you do not need the "64bit largest
> > > block" extension.
> > 
> > Sure, I will update this.
> > 
> > > 
> > > > +	if (ret)
> > > > +		return;
> > > > +
> > > > +	dn = pci_device_to_OF_node(dev);
> > > > +	pdn = PCI_DN(dn);
> > > > +	buid = pdn->phb->buid;
> > > > +	cfg_addr = ((pdn->busno << 16) | (pdn->devfn << 8));
> > > > +
> > > > +	ret = rtas_call(ddw_ext[1], 3, 1, NULL, cfg_addr,
> > > 
> > > Here the "reset" extention is in ddw_ext[1]. Hm. 1/4 has a bug then.
> > 
> > Humm, in 1/4 I used dd_ext[0] (how many extensions) and ddw_ext[2] (64-
> > bit largest window count). I fail to see the bug here.
> 
> There is none, my bad :)
> 
> 
> > > And I am pretty sure it won't compile as reset_dma_window() is not used
> > > and it is static so fold it into one the next patches. Thanks,
> > 
> > Sure, I will do that. 
> > I was questioning myself about this and thought it would be better to
> > split for easier revision.
> 
> People separate things when a patch is really huge but even then I miss
> the point - I'd really like to see a new function _and_ its uses in the
> same patch, otherwise I either need to jump between mails or apply the
> series, either is little but extra work :) Thanks,


Sure, that makes sense.
I will keep that in mind for future patchsets (and v2).

Thank you!

> 
> 
> > > 
> > > > +			BUID_HI(buid), BUID_LO(buid));
> > > > +	if (ret)
> > > > +		dev_info(&dev->dev,
> > > > +			 "ibm,reset-pe-dma-windows(%x) %x %x %x returned %d ",
> > > > +			 ddw_ext[1], cfg_addr, BUID_HI(buid), BUID_LO(buid),
> > > > +			 ret);
> > > > +}
> > > > +
> > > >  /*
> > > >   * If the PE supports dynamic dma windows, and there is space for a table
> > > >   * that can map all pages in a linear offset, then setup such a table,
> > > > 
> > 
> > Best regards,
> > Leonardo
> >