linux-kernel - Re: [PATCH 3/3] edac: altera: Add SDRAM EDAC support for CycloneV/ArriaV

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Message-ID: <20140408124541.GA16054@pengutronix.de>
Date:	Tue, 8 Apr 2014 14:45:41 +0200
From:	Steffen Trumtrar <s.trumtrar@...gutronix.de>
To:	Mark Rutland <mark.rutland@....com>
Cc:	"tthayer@...era.com" <tthayer@...era.com>,
	"robherring2@...il.com" <robherring2@...il.com>,
	"dougthompson@...ssion.com" <dougthompson@...ssion.com>,
	"grant.likely@...aro.org" <grant.likely@...aro.org>,
	Pawel Moll <Pawel.Moll@....com>,
	"ijc+devicetree@...lion.org.uk" <ijc+devicetree@...lion.org.uk>,
	"galak@...eaurora.org" <galak@...eaurora.org>,
	"rob@...dley.net" <rob@...dley.net>,
	"linux@....linux.org.uk" <linux@....linux.org.uk>,
	"dinguyen@...era.com" <dinguyen@...era.com>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-edac@...r.kernel.org" <linux-edac@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/3] edac: altera: Add SDRAM EDAC support for
 CycloneV/ArriaV

On Tue, Apr 08, 2014 at 11:45:25AM +0100, Mark Rutland wrote:
> On Mon, Apr 07, 2014 at 10:54:09PM +0100, tthayer@...era.com wrote:
> > From: Thor Thayer <tthayer@...era.com>
> > 
> > Added EDAC support for reporting ECC errors of CycloneV
> > and ArriaV SDRAM controller.
> > - The SDRAM Controller registers are used by the FPGA bridge so
> >   these are accessed through the syscon interface.
> > - The configuration of the SDRAM memory size for the EDAC framework
> >   is discovered from the memory node of the device tree.
> > - Documentation of the bindings in devicetree/bindings/arm/altera/
> >   socfpga-sdram-edac.txt
> > - Correction of single bit errors, detection of double bit errors.
> > 
> > Signed-off-by: Thor Thayer <tthayer@...era.com>
> > To: Rob Herring <robherring2@...il.com>
> > To: Doug Thompson <dougthompson@...ssion.com>
> > To: Grant Likely <grant.likely@...aro.org>
> > Cc: Dinh Nguyen <dinguyen@...era.com>
> > Cc: devicetree@...r.kernel.org
> > Cc: linux-edac@...r.kernel.org
> > Cc: linux-kernel@...r.kernel.org
> > ---
> >  drivers/edac/Kconfig          |    9 ++
> >  drivers/edac/Makefile         |    2 +
> >  drivers/edac/altera_mc_edac.c |  360 +++++++++++++++++++++++++++++++++++++++++
> >  3 files changed, 371 insertions(+)
> >  create mode 100644 drivers/edac/altera_mc_edac.c
> 
> [...]
> 
> > +/* Get total memory size from Open Firmware DTB */
> > +static u32 altr_sdram_get_total_mem_size(void)
> > +{
> > +       struct device_node *np;
> > +       u32 retcode, reg_array[2];
> > +
> > +       np = of_find_node_by_type(NULL, "memory");
> > +       if (!np)
> > +               return 0;
> > +
> > +       retcode = of_property_read_u32_array(np, "reg",
> > +                                            reg_array, ARRAY_SIZE(reg_array));
> 
> There's no requirement that #address-cells = <1> or #size-cells = <1>,
> even if any values in either would fit into 32 bits. If we must read
> this from the DTB rather than elsewhere, please check
> of_n_{addr,size}_cells.
> 
> Additionally, it's possible that the physical memory might be described
> over multiple reg entries, or multiple memory nodes for some arbitrary
> reason.
> 
> Can we not get this info from elsewhere rather than having to parse the
> memory node within a driver?
> 

It should be possible to calculate this from the dramaddrw register in the
SDRAM controller.

Regards,
Steffen

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