Re: [PATCH 3/3] stmmac: Add AXI burst length support to platform device.

[Chen Baozi <cbz@baozis.org>]

On Mon, Feb 09, 2015 at 12:04:43PM +0000, Mark Rutland wrote:
> On Sat, Feb 07, 2015 at 05:07:16AM +0000, Chen Baozi wrote:
> > The AXI Bus Mode Register controls the AXI master behavior. It is mainly
> > used to control the burst splitting and the number of outstanding requests.
> > This register is present and valid only in GMAC-AXI configuration. The old
> > driver only supports this feature on PCI devices. This patch adds an
> > 'snps,apl' properties in DT to enable it on platform devices.
> > 
> > Signed-off-by: Chen Baozi <chenbaozi@kylinos.com.cn>
> > ---
> >  Documentation/devicetree/bindings/net/stmmac.txt      | 1 +
> >  drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c | 1 +
> >  2 files changed, 2 insertions(+)
> > 
> > diff --git a/Documentation/devicetree/bindings/net/stmmac.txt b/Documentation/devicetree/bindings/net/stmmac.txt
> > index c41afd9..8f3c834 100644
> > --- a/Documentation/devicetree/bindings/net/stmmac.txt
> > +++ b/Documentation/devicetree/bindings/net/stmmac.txt
> > @@ -43,6 +43,7 @@ Optional properties:
> >    available this clock is used for programming the Timestamp Addend Register.
> >    If not passed then the system clock will be used and this is fine on some
> >    platforms.
> > +- snps,abl: AXI Burst Length
> 
> This is not a good name (though I see it follows "snps,pbl", which is
> also not a good name)...

Any idea for a better name?

> 
> Why does this need to be in the DT? Is this required for correctness? Or
> performance?

This is required for correctness. Otherwise, the driver would write
'0' to the register by default, which makes the driver not work.

Cheers,

Baozi.

> 
> Thanks,
> Mark.
> 
> >  
> >  Examples:
> >  
> > diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c
> > index 3039de2..abbc897 100644
> > --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c
> > +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c
> > @@ -230,6 +230,7 @@ static int stmmac_probe_config_dt(struct platform_device *pdev,
> >  			return -ENOMEM;
> >  		plat->dma_cfg = dma_cfg;
> >  		of_property_read_u32(np, "snps,pbl", &dma_cfg->pbl);
> > +		of_property_read_u32(np, "snps,abl", &dma_cfg->burst_len);
> >  		dma_cfg->fixed_burst =
> >  			of_property_read_bool(np, "snps,fixed-burst");
> >  		dma_cfg->mixed_burst =
> > -- 
> > 2.1.4
> > 
> > 
> > _______________________________________________
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> > linux-arm-kernel@lists.infradead.org
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> > 
> 
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