linux-kernel - Re: [PATCH v2 5/6] powerpc/pseries/iommu: Make use of DDW even if it does not map the partition

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Date:   Wed, 01 Jul 2020 16:57:48 -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 v2 5/6] powerpc/pseries/iommu: Make use of DDW even if
 it does not map the partition

On Wed, 2020-07-01 at 18:16 +1000, Alexey Kardashevskiy wrote:
> 
> On 24/06/2020 16:24, Leonardo Bras wrote:
> > As of today, if a DDW is created and can't map the whole partition, it's
> > removed and the default DMA window "ibm,dma-window" is used instead.
> > 
> > Usually this DDW is bigger than the default DMA window, so it would be
> > better to make use of it instead.
> > 
> > Signed-off-by: Leonardo Bras <leobras.c@...il.com>
> > ---
> >  arch/powerpc/platforms/pseries/iommu.c | 28 +++++++++++++++++---------
> >  1 file changed, 19 insertions(+), 9 deletions(-)
> > 
> > diff --git a/arch/powerpc/platforms/pseries/iommu.c b/arch/powerpc/platforms/pseries/iommu.c
> > index 4fcf00016fb1..2d217cda4075 100644
> > --- a/arch/powerpc/platforms/pseries/iommu.c
> > +++ b/arch/powerpc/platforms/pseries/iommu.c
> > @@ -685,7 +685,7 @@ static void pci_dma_bus_setup_pSeriesLP(struct pci_bus *bus)
> >  	struct iommu_table *tbl;
> >  	struct device_node *dn, *pdn;
> >  	struct pci_dn *ppci;
> > -	const __be32 *dma_window = NULL;
> > +	const __be32 *dma_window = NULL, *alt_dma_window = NULL;
> >  
> >  	dn = pci_bus_to_OF_node(bus);
> >  
> > @@ -699,8 +699,13 @@ static void pci_dma_bus_setup_pSeriesLP(struct pci_bus *bus)
> >  			break;
> >  	}
> >  
> > +	/* If there is a DDW available, use it instead */
> > +	alt_dma_window = of_get_property(pdn, DIRECT64_PROPNAME, NULL);
> 
> It is not necessarily "direct" anymore as the name suggests, you may
> want to change that. DMA64_PROPNAME, may be. Thanks,
> 

Yeah, you are right.
I will change this for next version, also changing the string name to
reflect this.

-#define DIRECT64_PROPNAME "linux,direct64-ddr-window-info"
+#define DMA64_PROPNAME "linux,dma64-ddr-window-info"

Is that ok?

Thank you for helping!