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

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Message-ID: <4180fd9bb0409a9c7009fef3ccae8eb2ad46d0a2.camel@gmail.com>
Date:   Mon, 22 Jun 2020 15:58:50 -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

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.

> 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.

> 
> 
> > +			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