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Date:	Mon, 28 Jul 2014 22:53:26 +0530
From:	punnaiah choudary kalluri <punnaia@...inx.com>
To:	Borislav Petkov <bp@...en8.de>
Cc:	Punnaiah Choudary Kalluri <punnaiah.choudary.kalluri@...inx.com>,
	dougthompson@...ssion.com,
	"robh+dt@...nel.org" <robh+dt@...nel.org>,
	"pawel.moll@....com" <pawel.moll@....com>,
	"michal.simek@...inx.com" <michal.simek@...inx.com>,
	"mark.rutland@....com" <mark.rutland@....com>,
	"ijc+devicetree@...lion.org.uk" <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	Rob Landley <rob@...dley.net>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
	linux-edac@...r.kernel.org,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	linux-arm-kernel@...ts.infradead.org,
	Punnaiah Choudary <kpc528@...il.com>, anirudh@...inx.com,
	svemula@...inx.com
Subject: Re: [RFC PATCH v3] edac: synps: Added EDAC support for zynq ddr ecc controller

Hi Boris,

On Mon, Jul 28, 2014 at 5:04 PM, Borislav Petkov <bp@...en8.de> wrote:
> On Sun, Jul 27, 2014 at 12:10:52AM +0530, Punnaiah Choudary Kalluri wrote:
>> Added EDAC support for reporting the ecc errors of synopsys ddr controller.
>> The ddr ecc controller corrects single bit errors and detects double bit
>> errors.
>>
>> Signed-off-by: Punnaiah Choudary Kalluri <punnaia@...inx.com>
>> ---
>> Changes for v3:
>> - Updated maintainer information
>> - Driver cleanup as per the review comments
>> - Shortened the prefix "sysnopsys" to "synps"
>
> This is not a good idea, IMO. "synopsys" is much more understandable
> instead of "synps". And synopsys-edac is just fine.

Ok. I thought of keeping file name and function name prefixes in sync
will be good and shortening
the prefix would save alignment issues at some places.

As you said i will revert the file name and still i will use "synps"
as prefix for functions.
Hope this will be ok for you.

>
>> Changes for v2:
>> - Updated the commit header and message
>> - Renamed the filenames to synopsys_edac
>> - Corrected the compatilble string, commnets
>> - Renamed the macros,fucntions and data structures
>> ---
>>
>>  .../devicetree/bindings/edac/synps_edac.txt        |   18 +
>>  MAINTAINERS                                        |    1 +
>>  drivers/edac/Kconfig                               |    7 +
>>  drivers/edac/Makefile                              |    1 +
>>  drivers/edac/synps_edac.c                          |  554 ++++++++++++++++++++
>>  5 files changed, 581 insertions(+), 0 deletions(-)
>>  create mode 100644 Documentation/devicetree/bindings/edac/synps_edac.txt
>>  create mode 100644 drivers/edac/synps_edac.c
>>
>> diff --git a/Documentation/devicetree/bindings/edac/synps_edac.txt b/Documentation/devicetree/bindings/edac/synps_edac.txt
>> new file mode 100644
>> index 0000000..c4a559b
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/edac/synps_edac.txt
>> @@ -0,0 +1,18 @@
>> +Synopsys EDAC driver, it does reports the DDR ECC single bit errors that are
>> +corrected and double bit ecc errors that are detected by the DDR ECC controller.
>> +ECC support for DDR is available in half-bus width(16 bit) configuration only.
>> +
>> +Required properties:
>> +- compatible: Should be "xlnx,zynq-ddrc-1.04"
>> +- reg: Should contain DDR controller registers location and length.
>> +
>> +Example:
>> +++++++++
>> +
>> +ddrc0: ddrc@...06000 {
>> +     compatible = "xlnx,zynq-ddrc-1.04";
>> +     reg = <0xf8006000 0x1000>;
>> +};
>
> I'd need an ack from device tree people about the DT bits.
>
>> +
>> +Synopsys EDAC driver detects the DDR ECC enable state by reading the appropriate
>> +control register.
>> diff --git a/MAINTAINERS b/MAINTAINERS
>> index d76e077..984b5a7 100644
>> --- a/MAINTAINERS
>> +++ b/MAINTAINERS
>> @@ -1479,6 +1479,7 @@ N:      xilinx
>>  F:   drivers/clocksource/cadence_ttc_timer.c
>>  F:   drivers/i2c/busses/i2c-cadence.c
>>  F:   drivers/mmc/host/sdhci-of-arasan.c
>> +F:   drivers/edac/synps_edac.c
>>
>>  ARM SMMU DRIVER
>>  M:   Will Deacon <will.deacon@....com>
>> diff --git a/drivers/edac/Kconfig b/drivers/edac/Kconfig
>> index 878f090..f628a2b 100644
>> --- a/drivers/edac/Kconfig
>> +++ b/drivers/edac/Kconfig
>> @@ -368,4 +368,11 @@ config EDAC_OCTEON_PCI
>>         Support for error detection and correction on the
>>         Cavium Octeon family of SOCs.
>>
>> +config EDAC_SYNPS
>> +     tristate "Synopsys DDR Memory Controller"
>> +     depends on EDAC_MM_EDAC && ARCH_ZYNQ
>> +     help
>> +       Support for EDAC on the ECC memory used with the Synopsys DDR
>> +       memory controller.
>> +
>>  endif # EDAC
>> diff --git a/drivers/edac/Makefile b/drivers/edac/Makefile
>> index 4154ed6..0af900f 100644
>> --- a/drivers/edac/Makefile
>> +++ b/drivers/edac/Makefile
>> @@ -64,3 +64,4 @@ obj-$(CONFIG_EDAC_OCTEON_PC)                += octeon_edac-pc.o
>>  obj-$(CONFIG_EDAC_OCTEON_L2C)                += octeon_edac-l2c.o
>>  obj-$(CONFIG_EDAC_OCTEON_LMC)                += octeon_edac-lmc.o
>>  obj-$(CONFIG_EDAC_OCTEON_PCI)                += octeon_edac-pci.o
>> +obj-$(CONFIG_EDAC_SYNPS)             += synps_edac.o
>> diff --git a/drivers/edac/synps_edac.c b/drivers/edac/synps_edac.c
>> new file mode 100644
>> index 0000000..a9417fe
>> --- /dev/null
>> +++ b/drivers/edac/synps_edac.c
>> @@ -0,0 +1,554 @@
>> +/*
>> + * Synopsys DDR ECC Driver
>> + * This driver is based on ppc4xx_edac.c drivers
>> + *
>> + * Copyright (C) 2012 - 2014 Xilinx, Inc.
>> + *
>> + * This program is free software: you can redistribute it and/or modify
>> + * it under the terms of the GNU General Public License as published by
>> + * the Free Software Foundation, either version 2 of the License, or
>> + * (at your option) any later version.
>> + *
>> + * This program is distributed in the hope that it will be useful,
>> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
>> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
>> + * GNU General Public License for more details.
>> + *
>> + * This file is subject to the terms and conditions of the GNU General Public
>> + * License.  See the file "COPYING" in the main directory of this archive
>> + * for more details
>> + */
>> +
>> +#include <linux/edac.h>
>> +#include <linux/module.h>
>> +#include <linux/platform_device.h>
>> +
>> +#include "edac_core.h"
>> +
>> +/* Number of cs_rows needed per memory controller */
>> +#define SYNPS_EDAC_NR_CSROWS 1
>> +
>> +/* Number of channels per memory controller */
>> +#define SYNPS_EDAC_NR_CHANS  1
>> +
>> +/* Granularity of reported error in bytes */
>> +#define SYNPS_EDAC_ERR_GRAIN 1
>> +
>> +#define SYNPS_EDAC_MSG_SIZE  256
>> +
>> +#define SYNPS_EDAC_MOD_STRING        "synps_edac"
>> +#define SYNPS_EDAC_MOD_VER   "1"
>> +
>> +/* Synopsys DDR memory controller registers that are relevant to ECC */
>> +#define SYNPS_DDRC_CTRL_REG_OFST     0x0
>> +#define SYNPS_DDRC_T_ZQ_REG_OFST     0xA4
>> +
>> +/* ECC control register */
>> +#define SYNPS_DDRC_ECC_CTRL_REG_OFST         0xC4
>> +/* ECC log register */
>> +#define SYNPS_DDRC_ECC_CE_LOG_REG_OFST               0xC8
>> +/* ECC address register */
>> +#define SYNPS_DDRC_ECC_CE_ADDR_REG_OFST              0xCC
>> +/* ECC data[31:0] register */
>> +#define SYNPS_DDRC_ECC_CE_DATA_31_0_REG_OFST 0xD0
>> +
>> +/* Uncorrectable error info regsisters */
>> +#define SYNPS_DDRC_ECC_UE_LOG_REG_OFST               0xDC
>> +#define SYNPS_DDRC_ECC_UE_ADDR_REG_OFST              0xE0
>> +#define SYNPS_DDRC_ECC_UE_DATA_31_0_REG_OFST 0xE4
>> +
>> +#define SYNPS_DDRC_ECC_STAT_REG_OFST         0xF0
>> +#define SYNPS_DDRC_ECC_SCRUB_REG_OFST                0xF4
>> +
>> +/* Control regsiter bitfield definitions */
>> +#define SYNPS_DDRC_CTRLREG_BUSWIDTH_MASK     0xC
>> +#define SYNPS_DDRC_CTRLREG_BUSWIDTH_SHIFT    2
>> +
>> +#define SYNPS_DDRCTL_WDTH_16 1
>> +#define SYNPS_DDRCTL_WDTH_32 0
>> +
>> +/* ZQ register bitfield definitions */
>> +#define SYNPS_DDRC_T_ZQ_REG_DDRMODE_MASK     0x2
>> +
>> +/* ECC control register bitfield definitions */
>> +#define SYNPS_DDRC_ECCCTRL_CLR_CE_ERR                0x2
>> +#define SYNPS_DDRC_ECCCTRL_CLR_UE_ERR                0x1
>> +
>> +/* ECC correctable/uncorrectable error log register definitions */
>> +#define SYNPS_DDRC_ECC_CE_LOGREG_VALID               0x1
>> +#define SYNPS_DDRC_ECC_CE_LOGREG_BITPOS_MASK 0xFE
>> +#define SYNPS_DDRC_ECC_CE_LOGREG_BITPOS_SHIFT        1
>> +
>> +/* ECC correctable/uncorrectable error address register definitions */
>> +#define SYNPS_DDRC_ECC_ADDRREG_COL_MASK              0xFFF
>> +#define SYNPS_DDRC_ECC_ADDRREG_ROW_MASK              0xFFFF000
>> +#define SYNPS_DDRC_ECC_ADDRREG_ROW_SHIFT     12
>> +#define SYNPS_DDRC_ECC_ADDRREG_BANK_MASK     0x70000000
>> +#define SYNPS_DDRC_ECC_ADDRREG_BANK_SHIFT    28
>> +
>> +/* ECC statistic regsiter definitions */
>> +#define SYNPS_DDRC_ECC_STATREG_UECNT_MASK    0xFF
>> +#define SYNPS_DDRC_ECC_STATREG_CECNT_MASK    0xFF00
>> +#define SYNPS_DDRC_ECC_STATREG_CECNT_SHIFT   8
>> +
>> +/* ECC scrub regsiter definitions */
>> +#define SYNPS_DDRC_ECC_SCRUBREG_ECC_MODE_MASK        0x7
>> +#define SYNPS_DDRC_ECC_SCRUBREG_ECCMODE_SECDED       0x4
>
> Now those are certainly too long: having the
> SYNPS_EDAC/SYNPS_DDRC{,_ECC}* prefix for defines used only in this file
> is certainly making the code unreadable. Here's what it could look like,
> for example:
>
>      regval = readl(base + STAT_OFST) & (STAT_UECNT_MASK | STAT_CECNT_MASK);
>
> so you have STAT which is the register name, followed by a name of the
> bit or bits. I think this is perfectly fine instead of those heavy names
> which all start with the same prefix and you have to go look at the end
> to find out what they actually are.

I can agree with you that we can use shorter names.But ZYNQ has
programmable logic next to
processing system where one can add soft memory controller in the same
system and may use
different driver. So, the edac driver for zynq may include multiple
drivers for different
memory controllers in the same file. In this case it is difficult to
maintain generic macros as you
suggested above.

Also the current edac framework for edac memory controllers is
expecting the mc_num from the
driver while allocating the memory controller instance using the
edac_mc_alloc function. This
requirement mandates that if the system contains two different memory
controllers then the
corresponding  edac drivers should be in single file.

Regards,
Punnaiah
>
> --
> Regards/Gruss,
>     Boris.
>
> Sent from a fat crate under my desk. Formatting is fine.
> --
--
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