linux-kernel - Re: [PATCH 1/4] of/fdt: Update zone_dma

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Message-ID: <20201001172320.GQ21544@gaia>
Date:   Thu, 1 Oct 2020 18:23:21 +0100
From:   Catalin Marinas <catalin.marinas@....com>
To:     Nicolas Saenz Julienne <nsaenzjulienne@...e.de>
Cc:     devicetree@...r.kernel.org, will@...nel.org,
        Frank Rowand <frowand.list@...il.com>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        iommu@...ts.linux-foundation.org, robh+dt@...nel.org,
        linux-rpi-kernel@...ts.infradead.org, robin.murphy@....com,
        hch@....de, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 1/4] of/fdt: Update zone_dma_bits when running in bcm2711

On Thu, Oct 01, 2020 at 06:15:01PM +0100, Catalin Marinas wrote:
> Hi Nicolas,
> 
> Thanks for putting this together.
> 
> On Thu, Oct 01, 2020 at 06:17:37PM +0200, Nicolas Saenz Julienne wrote:
> > diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
> > index 4602e467ca8b..cd0d115ef329 100644
> > --- a/drivers/of/fdt.c
> > +++ b/drivers/of/fdt.c
> > @@ -25,6 +25,7 @@
> >  #include <linux/serial_core.h>
> >  #include <linux/sysfs.h>
> >  #include <linux/random.h>
> > +#include <linux/dma-direct.h>	/* for zone_dma_bits */
> >  
> >  #include <asm/setup.h>  /* for COMMAND_LINE_SIZE */
> >  #include <asm/page.h>
> > @@ -1198,6 +1199,14 @@ void __init early_init_dt_scan_nodes(void)
> >  	of_scan_flat_dt(early_init_dt_scan_memory, NULL);
> >  }
> >  
> > +void __init early_init_dt_update_zone_dma_bits(void)
> > +{
> > +	unsigned long dt_root = of_get_flat_dt_root();
> > +
> > +	if (of_flat_dt_is_compatible(dt_root, "brcm,bcm2711"))
> > +		zone_dma_bits = 30;
> > +}
> 
> I think we could keep this entirely in the arm64 setup_machine_fdt() and
> not pollute the core code with RPi4-specific code.

Actually, even better, could we not move the check to
arm64_memblock_init() when we initialise zone_dma_bits?

-- 
Catalin