[PATCH v3] mtd: atmel_nand: make PMECC lookup table and offset property optional

[PATCH v3] mtd: atmel_nand: make PMECC lookup table and offset property optional

[Josh Wu]

From: Josh Wu <Josh.wu-AIFe0yeh4nAAvxtiuMwx3w@public.gmane.org>

If there is no PMECC lookup table stored in ROM, or lookup table offset is
not specified, PMECC driver should build it in DDR by itself.

That make the PMECC driver work for some board which doesn't has PMECC
lookup table in ROM.

The PMECC use the BCH algorithm, so based on the build_gf_tables()
function in lib/bch.c, we can build the Galois Field lookup table.

For more information can refer to section 5.4 of PMECC controller
application note:
	http://www.atmel.com/images/doc11127.pdf

Signed-off-by: Josh Wu <josh.wu-AIFe0yeh4nAAvxtiuMwx3w@public.gmane.org>
Cc: devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
---
v1 -> v2:
  make create_lookup_table() static.

v2 -> v3:
  rewrite the build_gf_tables() function based on lib/bch.c.
  add error handling in create_lookup_table().

 .../devicetree/bindings/mtd/atmel-nand.txt         |  6 +-
 drivers/mtd/nand/atmel_nand.c                      | 81 ++++++++++++++++++++--
 drivers/mtd/nand/atmel_nand_ecc.h                  |  4 ++
 3 files changed, 85 insertions(+), 6 deletions(-)

diff --git a/Documentation/devicetree/bindings/mtd/atmel-nand.txt b/Documentation/devicetree/bindings/mtd/atmel-nand.txt
index 6edc3b6..1fe6dde 100644
--- a/Documentation/devicetree/bindings/mtd/atmel-nand.txt
+++ b/Documentation/devicetree/bindings/mtd/atmel-nand.txt
@@ -5,7 +5,9 @@ Required properties:
 - reg : should specify localbus address and size used for the chip,
 	and hardware ECC controller if available.
 	If the hardware ECC is PMECC, it should contain address and size for
-	PMECC, PMECC Error Location controller and ROM which has lookup tables.
+	PMECC and PMECC Error Location controller.
+	The PMECC lookup table address and size in ROM is optional. If not
+	specified, driver will build it in runtime.
 - atmel,nand-addr-offset : offset for the address latch.
 - atmel,nand-cmd-offset : offset for the command latch.
 - #address-cells, #size-cells : Must be present if the device has sub-nodes
@@ -27,7 +29,7 @@ Optional properties:
   are: 512, 1024.
 - atmel,pmecc-lookup-table-offset : includes two offsets of lookup table in ROM
   for different sector size. First one is for sector size 512, the next is for
-  sector size 1024.
+  sector size 1024. If not specified, driver will build the table in runtime.
 - nand-bus-width : 8 or 16 bus width if not present 8
 - nand-on-flash-bbt: boolean to enable on flash bbt option if not present false
 - Nand Flash Controller(NFC) is a slave driver under Atmel nand flash
diff --git a/drivers/mtd/nand/atmel_nand.c b/drivers/mtd/nand/atmel_nand.c
index 19d1e9d..5c1423a 100644
--- a/drivers/mtd/nand/atmel_nand.c
+++ b/drivers/mtd/nand/atmel_nand.c
@@ -127,6 +127,7 @@ struct atmel_nand_host {
 	bool			has_pmecc;
 	u8			pmecc_corr_cap;
 	u16			pmecc_sector_size;
+	bool			has_no_lookup_table;
 	u32			pmecc_lookup_table_offset;
 	u32			pmecc_lookup_table_offset_512;
 	u32			pmecc_lookup_table_offset_1024;
@@ -1112,12 +1113,66 @@ static int pmecc_choose_ecc(struct atmel_nand_host *host,
 	return 0;
 }
 
+static inline int deg(unsigned int poly)
+{
+	/* polynomial degree is the most-significant bit index */
+	return fls(poly) - 1;
+}
+
+static int build_gf_tables(int mm, unsigned int poly,
+		int16_t *index_of, int16_t *alpha_to)
+{
+	unsigned int i, x = 1;
+	const unsigned int k = 1 << deg(poly);
+	unsigned int nn = (1 << mm) - 1;
+
+	/* primitive polynomial must be of degree m */
+	if (k != (1u << mm))
+		return -EINVAL;
+
+	for (i = 0; i < nn; i++) {
+		alpha_to[i] = x;
+		index_of[x] = i;
+		if (i && (x == 1))
+			/* polynomial is not primitive (a^i=1 with 0<i<2^m-1) */
+			return -EINVAL;
+		x <<= 1;
+		if (x & k)
+			x ^= poly;
+	}
+	alpha_to[nn] = 1;
+	index_of[0] = 0;
+
+	return 0;
+}
+
+static uint16_t *create_lookup_table(struct device *dev, int sector_size)
+{
+	int degree = (sector_size == 512) ?
+			PMECC_GF_DIMENSION_13 :
+			PMECC_GF_DIMENSION_14;
+	unsigned int poly = (sector_size == 512) ?
+			PMECC_GF_13_PRIMITIVE_POLY :
+			PMECC_GF_14_PRIMITIVE_POLY;
+	int table_size = (sector_size == 512) ?
+			PMECC_LOOKUP_TABLE_SIZE_512 :
+			PMECC_LOOKUP_TABLE_SIZE_1024;
+
+	int16_t *addr = devm_kzalloc(dev, 2 * table_size * sizeof(uint16_t),
+			GFP_KERNEL);
+	if (addr && build_gf_tables(degree, poly, addr, addr + table_size))
+		return NULL;
+
+	return addr;
+}
+
 static int atmel_pmecc_nand_init_params(struct platform_device *pdev,
 					 struct atmel_nand_host *host)
 {
 	struct mtd_info *mtd = &host->mtd;
 	struct nand_chip *nand_chip = &host->nand_chip;
 	struct resource *regs, *regs_pmerr, *regs_rom;
+	uint16_t *galois_table;
 	int cap, sector_size, err_no;
 
 	err_no = pmecc_choose_ecc(host, &cap, &sector_size);
@@ -1163,8 +1218,24 @@ static int atmel_pmecc_nand_init_params(struct platform_device *pdev,
 	regs_rom = platform_get_resource(pdev, IORESOURCE_MEM, 3);
 	host->pmecc_rom_base = devm_ioremap_resource(&pdev->dev, regs_rom);
 	if (IS_ERR(host->pmecc_rom_base)) {
-		err_no = PTR_ERR(host->pmecc_rom_base);
-		goto err;
+		if (!host->has_no_lookup_table)
+			/* Don't display the information again */
+			dev_err(host->dev, "Can not get I/O resource for ROM, will build a lookup table in runtime!\n");
+
+		host->has_no_lookup_table = true;
+	}
+
+	if (host->has_no_lookup_table) {
+		/* Build the look-up table in runtime */
+		galois_table = create_lookup_table(host->dev, sector_size);
+		if (!galois_table) {
+			dev_err(host->dev, "Failed to build a lookup table in runtime!\n");
+			err_no = -EINVAL;
+			goto err;
+		}
+
+		host->pmecc_rom_base = (void __iomem *)galois_table;
+		host->pmecc_lookup_table_offset = 0;
 	}
 
 	nand_chip->ecc.size = sector_size;
@@ -1501,8 +1572,10 @@ static int atmel_of_init_port(struct atmel_nand_host *host,
 
 	if (of_property_read_u32_array(np, "atmel,pmecc-lookup-table-offset",
 			offset, 2) != 0) {
-		dev_err(host->dev, "Cannot get PMECC lookup table offset\n");
-		return -EINVAL;
+		dev_err(host->dev, "Cannot get PMECC lookup table offset, will build a lookup table in runtime.\n");
+		host->has_no_lookup_table = true;
+		/* Will build a lookup table and initialize the offset later */
+		return 0;
 	}
 	if (!offset[0] && !offset[1]) {
 		dev_err(host->dev, "Invalid PMECC lookup table offset\n");
diff --git a/drivers/mtd/nand/atmel_nand_ecc.h b/drivers/mtd/nand/atmel_nand_ecc.h
index 8a1e9a6..d4035e3 100644
--- a/drivers/mtd/nand/atmel_nand_ecc.h
+++ b/drivers/mtd/nand/atmel_nand_ecc.h
@@ -142,6 +142,10 @@
 #define PMECC_GF_DIMENSION_13			13
 #define PMECC_GF_DIMENSION_14			14
 
+/* Primitive Polynomial used by PMECC */
+#define PMECC_GF_13_PRIMITIVE_POLY		0x201b
+#define PMECC_GF_14_PRIMITIVE_POLY		0x4443
+
 #define PMECC_LOOKUP_TABLE_SIZE_512		0x2000
 #define PMECC_LOOKUP_TABLE_SIZE_1024		0x4000
 
-- 
1.9.1

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Re: [PATCH v3] mtd: atmel_nand: make PMECC lookup table and offset property optional

[Mark Rutland]

On Sat, Oct 11, 2014 at 11:01:50AM +0100, Josh Wu wrote:
> From: Josh Wu <Josh.wu-AIFe0yeh4nAAvxtiuMwx3w@public.gmane.org>
> 
> If there is no PMECC lookup table stored in ROM, or lookup table offset is
> not specified, PMECC driver should build it in DDR by itself.
> 
> That make the PMECC driver work for some board which doesn't has PMECC
> lookup table in ROM.
> 
> The PMECC use the BCH algorithm, so based on the build_gf_tables()
> function in lib/bch.c, we can build the Galois Field lookup table.
> 
> For more information can refer to section 5.4 of PMECC controller
> application note:
> 	http://www.atmel.com/images/doc11127.pdf
> 
> Signed-off-by: Josh Wu <josh.wu-AIFe0yeh4nAAvxtiuMwx3w@public.gmane.org>
> Cc: devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
> ---
> v1 -> v2:
>   make create_lookup_table() static.
> 
> v2 -> v3:
>   rewrite the build_gf_tables() function based on lib/bch.c.
>   add error handling in create_lookup_table().
> 
>  .../devicetree/bindings/mtd/atmel-nand.txt         |  6 +-
>  drivers/mtd/nand/atmel_nand.c                      | 81 ++++++++++++++++++++--
>  drivers/mtd/nand/atmel_nand_ecc.h                  |  4 ++
>  3 files changed, 85 insertions(+), 6 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/mtd/atmel-nand.txt b/Documentation/devicetree/bindings/mtd/atmel-nand.txt
> index 6edc3b6..1fe6dde 100644
> --- a/Documentation/devicetree/bindings/mtd/atmel-nand.txt
> +++ b/Documentation/devicetree/bindings/mtd/atmel-nand.txt
> @@ -5,7 +5,9 @@ Required properties:
>  - reg : should specify localbus address and size used for the chip,
>  	and hardware ECC controller if available.
>  	If the hardware ECC is PMECC, it should contain address and size for
> -	PMECC, PMECC Error Location controller and ROM which has lookup tables.
> +	PMECC and PMECC Error Location controller.
> +	The PMECC lookup table address and size in ROM is optional. If not
> +	specified, driver will build it in runtime.
>  - atmel,nand-addr-offset : offset for the address latch.
>  - atmel,nand-cmd-offset : offset for the command latch.
>  - #address-cells, #size-cells : Must be present if the device has sub-nodes
> @@ -27,7 +29,7 @@ Optional properties:
>    are: 512, 1024.
>  - atmel,pmecc-lookup-table-offset : includes two offsets of lookup table in ROM
>    for different sector size. First one is for sector size 512, the next is for
> -  sector size 1024.
> +  sector size 1024. If not specified, driver will build the table in runtime.

I'm not sure we need to mention this in the binding.

That said, if we can build this dynamically, can't we always do so, and
never need this property?

Mark.
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Re: [PATCH v3] mtd: atmel_nand: make PMECC lookup table and offset property optional

[Josh Wu]

Hi, Mark

On 10/13/2014 7:16 PM, Mark Rutland wrote:
> On Sat, Oct 11, 2014 at 11:01:50AM +0100, Josh Wu wrote:
>> From: Josh Wu <Josh.wu@atmel.com>
>>
>> If there is no PMECC lookup table stored in ROM, or lookup table offset is
>> not specified, PMECC driver should build it in DDR by itself.
>>
>> That make the PMECC driver work for some board which doesn't has PMECC
>> lookup table in ROM.
>>
>> The PMECC use the BCH algorithm, so based on the build_gf_tables()
>> function in lib/bch.c, we can build the Galois Field lookup table.
>>
>> For more information can refer to section 5.4 of PMECC controller
>> application note:
>> 	http://www.atmel.com/images/doc11127.pdf
>>
>> Signed-off-by: Josh Wu <josh.wu@atmel.com>
>> Cc: devicetree@vger.kernel.org
>> ---
>> v1 -> v2:
>>    make create_lookup_table() static.
>>
>> v2 -> v3:
>>    rewrite the build_gf_tables() function based on lib/bch.c.
>>    add error handling in create_lookup_table().
>>
>>   .../devicetree/bindings/mtd/atmel-nand.txt         |  6 +-
>>   drivers/mtd/nand/atmel_nand.c                      | 81 ++++++++++++++++++++--
>>   drivers/mtd/nand/atmel_nand_ecc.h                  |  4 ++
>>   3 files changed, 85 insertions(+), 6 deletions(-)
>>
>> diff --git a/Documentation/devicetree/bindings/mtd/atmel-nand.txt b/Documentation/devicetree/bindings/mtd/atmel-nand.txt
>> index 6edc3b6..1fe6dde 100644
>> --- a/Documentation/devicetree/bindings/mtd/atmel-nand.txt
>> +++ b/Documentation/devicetree/bindings/mtd/atmel-nand.txt
>> @@ -5,7 +5,9 @@ Required properties:
>>   - reg : should specify localbus address and size used for the chip,
>>   	and hardware ECC controller if available.
>>   	If the hardware ECC is PMECC, it should contain address and size for
>> -	PMECC, PMECC Error Location controller and ROM which has lookup tables.
>> +	PMECC and PMECC Error Location controller.
>> +	The PMECC lookup table address and size in ROM is optional. If not
>> +	specified, driver will build it in runtime.
>>   - atmel,nand-addr-offset : offset for the address latch.
>>   - atmel,nand-cmd-offset : offset for the command latch.
>>   - #address-cells, #size-cells : Must be present if the device has sub-nodes
>> @@ -27,7 +29,7 @@ Optional properties:
>>     are: 512, 1024.
>>   - atmel,pmecc-lookup-table-offset : includes two offsets of lookup table in ROM
>>     for different sector size. First one is for sector size 512, the next is for
>> -  sector size 1024.
>> +  sector size 1024. If not specified, driver will build the table in runtime.
> I'm not sure we need to mention this in the binding.
>
> That said, if we can build this dynamically, can't we always do so, and
> never need this property?

Since board like at91sam9x5, sama5d3xek has a rom lookup table. And the 
sama5d4ek has no rom lookup table.
To present this, I make this property as optional.

But yes, the pmecc lookup table related properties can be removed as 
driver can build it in runtime.
The cost is we need to use more memory to store the table.


>
> Mark.
Best Regards,
Josh Wu

______________________________________________________
Linux MTD discussion mailing list
http://lists.infradead.org/mailman/listinfo/linux-mtd/

Re: [PATCH v3] mtd: atmel_nand: make PMECC lookup table and offset property optional

[Josh Wu]

Hi, Mark

On 10/13/2014 7:31 PM, Josh Wu wrote:
> Hi, Mark
>
> On 10/13/2014 7:16 PM, Mark Rutland wrote:
>> On Sat, Oct 11, 2014 at 11:01:50AM +0100, Josh Wu wrote:
>>> From: Josh Wu <Josh.wu-AIFe0yeh4nAAvxtiuMwx3w@public.gmane.org>
>>>
>>> If there is no PMECC lookup table stored in ROM, or lookup table 
>>> offset is
>>> not specified, PMECC driver should build it in DDR by itself.
>>>
>>> That make the PMECC driver work for some board which doesn't has PMECC
>>> lookup table in ROM.
>>>
>>> The PMECC use the BCH algorithm, so based on the build_gf_tables()
>>> function in lib/bch.c, we can build the Galois Field lookup table.
>>>
>>> For more information can refer to section 5.4 of PMECC controller
>>> application note:
>>>     http://www.atmel.com/images/doc11127.pdf
>>>
>>> Signed-off-by: Josh Wu <josh.wu-AIFe0yeh4nAAvxtiuMwx3w@public.gmane.org>
>>> Cc: devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
>>> ---
>>> v1 -> v2:
>>>    make create_lookup_table() static.
>>>
>>> v2 -> v3:
>>>    rewrite the build_gf_tables() function based on lib/bch.c.
>>>    add error handling in create_lookup_table().
>>>
>>>   .../devicetree/bindings/mtd/atmel-nand.txt         |  6 +-
>>>   drivers/mtd/nand/atmel_nand.c                      | 81 
>>> ++++++++++++++++++++--
>>>   drivers/mtd/nand/atmel_nand_ecc.h                  |  4 ++
>>>   3 files changed, 85 insertions(+), 6 deletions(-)
>>>
>>> diff --git a/Documentation/devicetree/bindings/mtd/atmel-nand.txt 
>>> b/Documentation/devicetree/bindings/mtd/atmel-nand.txt
>>> index 6edc3b6..1fe6dde 100644
>>> --- a/Documentation/devicetree/bindings/mtd/atmel-nand.txt
>>> +++ b/Documentation/devicetree/bindings/mtd/atmel-nand.txt
>>> @@ -5,7 +5,9 @@ Required properties:
>>>   - reg : should specify localbus address and size used for the chip,
>>>       and hardware ECC controller if available.
>>>       If the hardware ECC is PMECC, it should contain address and 
>>> size for
>>> -    PMECC, PMECC Error Location controller and ROM which has lookup 
>>> tables.
>>> +    PMECC and PMECC Error Location controller.
>>> +    The PMECC lookup table address and size in ROM is optional. If not
>>> +    specified, driver will build it in runtime.
>>>   - atmel,nand-addr-offset : offset for the address latch.
>>>   - atmel,nand-cmd-offset : offset for the command latch.
>>>   - #address-cells, #size-cells : Must be present if the device has 
>>> sub-nodes
>>> @@ -27,7 +29,7 @@ Optional properties:
>>>     are: 512, 1024.
>>>   - atmel,pmecc-lookup-table-offset : includes two offsets of lookup 
>>> table in ROM
>>>     for different sector size. First one is for sector size 512, the 
>>> next is for
>>> -  sector size 1024.
>>> +  sector size 1024. If not specified, driver will build the table 
>>> in runtime.
>> I'm not sure we need to mention this in the binding.
>>
>> That said, if we can build this dynamically, can't we always do so, and
>> never need this property?
>
> Since board like at91sam9x5, sama5d3xek has a rom lookup table. And 
> the sama5d4ek has no rom lookup table.
> To present this, I make this property as optional.
>
> But yes, the pmecc lookup table related properties can be removed as 
> driver can build it in runtime.
> The cost is we need to use more memory to store the table.

In precisely, the table need to 32k bytes memory for 512-sector, and 64k 
bytes for 1024-sector.

Also I spend time to testing the performance of this version.
Compare with the version which use the SRAM rom lookup table, this 
version (build table in runtim) cost about 5~10ms more.

So I prefer to keep this property as optional.

Best Regards,
Josh Wu

>
>
>>
>> Mark.
> Best Regards,
> Josh Wu
>
> ______________________________________________________
> Linux MTD discussion mailing list
> http://lists.infradead.org/mailman/listinfo/linux-mtd/

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Re: [PATCH v3] mtd: atmel_nand: make PMECC lookup table and offset property optional

[Mark Rutland]

[...]

> >> That said, if we can build this dynamically, can't we always do so, and
> >> never need this property?
> >
> > Since board like at91sam9x5, sama5d3xek has a rom lookup table. And 
> > the sama5d4ek has no rom lookup table.
> > To present this, I make this property as optional.
> >
> > But yes, the pmecc lookup table related properties can be removed as 
> > driver can build it in runtime.
> > The cost is we need to use more memory to store the table.
> 
> In precisely, the table need to 32k bytes memory for 512-sector, and 64k 
> bytes for 1024-sector.
> 
> Also I spend time to testing the performance of this version.
> Compare with the version which use the SRAM rom lookup table, this 
> version (build table in runtim) cost about 5~10ms more.
> 
> So I prefer to keep this property as optional.

Sure. It sounds like it's always possible to ignore it later if we
choose to.

I just wouldn't mention what the driver should do in the binding --
whether or not the property is optional, the behaviour of the driver is
not a detail of the device.

Thanks,
Mark.
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Re: [PATCH v3] mtd: atmel_nand: make PMECC lookup table and offset property optional

[Josh Wu]

Hi,

Just a ping for this patch.

Best Regards,
Josh Wu

On 10/11/2014 6:01 PM, Josh Wu wrote:
> From: Josh Wu <Josh.wu-AIFe0yeh4nAAvxtiuMwx3w@public.gmane.org>
>
> If there is no PMECC lookup table stored in ROM, or lookup table offset is
> not specified, PMECC driver should build it in DDR by itself.
>
> That make the PMECC driver work for some board which doesn't has PMECC
> lookup table in ROM.
>
> The PMECC use the BCH algorithm, so based on the build_gf_tables()
> function in lib/bch.c, we can build the Galois Field lookup table.
>
> For more information can refer to section 5.4 of PMECC controller
> application note:
> 	http://www.atmel.com/images/doc11127.pdf
>
> Signed-off-by: Josh Wu <josh.wu-AIFe0yeh4nAAvxtiuMwx3w@public.gmane.org>
> Cc: devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
> ---
> v1 -> v2:
>    make create_lookup_table() static.
>
> v2 -> v3:
>    rewrite the build_gf_tables() function based on lib/bch.c.
>    add error handling in create_lookup_table().
>
>   .../devicetree/bindings/mtd/atmel-nand.txt         |  6 +-
>   drivers/mtd/nand/atmel_nand.c                      | 81 ++++++++++++++++++++--
>   drivers/mtd/nand/atmel_nand_ecc.h                  |  4 ++
>   3 files changed, 85 insertions(+), 6 deletions(-)
>
> diff --git a/Documentation/devicetree/bindings/mtd/atmel-nand.txt b/Documentation/devicetree/bindings/mtd/atmel-nand.txt
> index 6edc3b6..1fe6dde 100644
> --- a/Documentation/devicetree/bindings/mtd/atmel-nand.txt
> +++ b/Documentation/devicetree/bindings/mtd/atmel-nand.txt
> @@ -5,7 +5,9 @@ Required properties:
>   - reg : should specify localbus address and size used for the chip,
>   	and hardware ECC controller if available.
>   	If the hardware ECC is PMECC, it should contain address and size for
> -	PMECC, PMECC Error Location controller and ROM which has lookup tables.
> +	PMECC and PMECC Error Location controller.
> +	The PMECC lookup table address and size in ROM is optional. If not
> +	specified, driver will build it in runtime.
>   - atmel,nand-addr-offset : offset for the address latch.
>   - atmel,nand-cmd-offset : offset for the command latch.
>   - #address-cells, #size-cells : Must be present if the device has sub-nodes
> @@ -27,7 +29,7 @@ Optional properties:
>     are: 512, 1024.
>   - atmel,pmecc-lookup-table-offset : includes two offsets of lookup table in ROM
>     for different sector size. First one is for sector size 512, the next is for
> -  sector size 1024.
> +  sector size 1024. If not specified, driver will build the table in runtime.
>   - nand-bus-width : 8 or 16 bus width if not present 8
>   - nand-on-flash-bbt: boolean to enable on flash bbt option if not present false
>   - Nand Flash Controller(NFC) is a slave driver under Atmel nand flash
> diff --git a/drivers/mtd/nand/atmel_nand.c b/drivers/mtd/nand/atmel_nand.c
> index 19d1e9d..5c1423a 100644
> --- a/drivers/mtd/nand/atmel_nand.c
> +++ b/drivers/mtd/nand/atmel_nand.c
> @@ -127,6 +127,7 @@ struct atmel_nand_host {
>   	bool			has_pmecc;
>   	u8			pmecc_corr_cap;
>   	u16			pmecc_sector_size;
> +	bool			has_no_lookup_table;
>   	u32			pmecc_lookup_table_offset;
>   	u32			pmecc_lookup_table_offset_512;
>   	u32			pmecc_lookup_table_offset_1024;
> @@ -1112,12 +1113,66 @@ static int pmecc_choose_ecc(struct atmel_nand_host *host,
>   	return 0;
>   }
>   
> +static inline int deg(unsigned int poly)
> +{
> +	/* polynomial degree is the most-significant bit index */
> +	return fls(poly) - 1;
> +}
> +
> +static int build_gf_tables(int mm, unsigned int poly,
> +		int16_t *index_of, int16_t *alpha_to)
> +{
> +	unsigned int i, x = 1;
> +	const unsigned int k = 1 << deg(poly);
> +	unsigned int nn = (1 << mm) - 1;
> +
> +	/* primitive polynomial must be of degree m */
> +	if (k != (1u << mm))
> +		return -EINVAL;
> +
> +	for (i = 0; i < nn; i++) {
> +		alpha_to[i] = x;
> +		index_of[x] = i;
> +		if (i && (x == 1))
> +			/* polynomial is not primitive (a^i=1 with 0<i<2^m-1) */
> +			return -EINVAL;
> +		x <<= 1;
> +		if (x & k)
> +			x ^= poly;
> +	}
> +	alpha_to[nn] = 1;
> +	index_of[0] = 0;
> +
> +	return 0;
> +}
> +
> +static uint16_t *create_lookup_table(struct device *dev, int sector_size)
> +{
> +	int degree = (sector_size == 512) ?
> +			PMECC_GF_DIMENSION_13 :
> +			PMECC_GF_DIMENSION_14;
> +	unsigned int poly = (sector_size == 512) ?
> +			PMECC_GF_13_PRIMITIVE_POLY :
> +			PMECC_GF_14_PRIMITIVE_POLY;
> +	int table_size = (sector_size == 512) ?
> +			PMECC_LOOKUP_TABLE_SIZE_512 :
> +			PMECC_LOOKUP_TABLE_SIZE_1024;
> +
> +	int16_t *addr = devm_kzalloc(dev, 2 * table_size * sizeof(uint16_t),
> +			GFP_KERNEL);
> +	if (addr && build_gf_tables(degree, poly, addr, addr + table_size))
> +		return NULL;
> +
> +	return addr;
> +}
> +
>   static int atmel_pmecc_nand_init_params(struct platform_device *pdev,
>   					 struct atmel_nand_host *host)
>   {
>   	struct mtd_info *mtd = &host->mtd;
>   	struct nand_chip *nand_chip = &host->nand_chip;
>   	struct resource *regs, *regs_pmerr, *regs_rom;
> +	uint16_t *galois_table;
>   	int cap, sector_size, err_no;
>   
>   	err_no = pmecc_choose_ecc(host, &cap, &sector_size);
> @@ -1163,8 +1218,24 @@ static int atmel_pmecc_nand_init_params(struct platform_device *pdev,
>   	regs_rom = platform_get_resource(pdev, IORESOURCE_MEM, 3);
>   	host->pmecc_rom_base = devm_ioremap_resource(&pdev->dev, regs_rom);
>   	if (IS_ERR(host->pmecc_rom_base)) {
> -		err_no = PTR_ERR(host->pmecc_rom_base);
> -		goto err;
> +		if (!host->has_no_lookup_table)
> +			/* Don't display the information again */
> +			dev_err(host->dev, "Can not get I/O resource for ROM, will build a lookup table in runtime!\n");
> +
> +		host->has_no_lookup_table = true;
> +	}
> +
> +	if (host->has_no_lookup_table) {
> +		/* Build the look-up table in runtime */
> +		galois_table = create_lookup_table(host->dev, sector_size);
> +		if (!galois_table) {
> +			dev_err(host->dev, "Failed to build a lookup table in runtime!\n");
> +			err_no = -EINVAL;
> +			goto err;
> +		}
> +
> +		host->pmecc_rom_base = (void __iomem *)galois_table;
> +		host->pmecc_lookup_table_offset = 0;
>   	}
>   
>   	nand_chip->ecc.size = sector_size;
> @@ -1501,8 +1572,10 @@ static int atmel_of_init_port(struct atmel_nand_host *host,
>   
>   	if (of_property_read_u32_array(np, "atmel,pmecc-lookup-table-offset",
>   			offset, 2) != 0) {
> -		dev_err(host->dev, "Cannot get PMECC lookup table offset\n");
> -		return -EINVAL;
> +		dev_err(host->dev, "Cannot get PMECC lookup table offset, will build a lookup table in runtime.\n");
> +		host->has_no_lookup_table = true;
> +		/* Will build a lookup table and initialize the offset later */
> +		return 0;
>   	}
>   	if (!offset[0] && !offset[1]) {
>   		dev_err(host->dev, "Invalid PMECC lookup table offset\n");
> diff --git a/drivers/mtd/nand/atmel_nand_ecc.h b/drivers/mtd/nand/atmel_nand_ecc.h
> index 8a1e9a6..d4035e3 100644
> --- a/drivers/mtd/nand/atmel_nand_ecc.h
> +++ b/drivers/mtd/nand/atmel_nand_ecc.h
> @@ -142,6 +142,10 @@
>   #define PMECC_GF_DIMENSION_13			13
>   #define PMECC_GF_DIMENSION_14			14
>   
> +/* Primitive Polynomial used by PMECC */
> +#define PMECC_GF_13_PRIMITIVE_POLY		0x201b
> +#define PMECC_GF_14_PRIMITIVE_POLY		0x4443
> +
>   #define PMECC_LOOKUP_TABLE_SIZE_512		0x2000
>   #define PMECC_LOOKUP_TABLE_SIZE_1024		0x4000
>   

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Re: [PATCH v3] mtd: atmel_nand: make PMECC lookup table and offset property optional

[Brian Norris]

On Sat, Oct 11, 2014 at 06:01:50PM +0800, Josh Wu wrote:
> From: Josh Wu <Josh.wu-AIFe0yeh4nAAvxtiuMwx3w@public.gmane.org>
> 
> If there is no PMECC lookup table stored in ROM, or lookup table offset is
> not specified, PMECC driver should build it in DDR by itself.
> 
> That make the PMECC driver work for some board which doesn't has PMECC
> lookup table in ROM.
> 
> The PMECC use the BCH algorithm, so based on the build_gf_tables()
> function in lib/bch.c, we can build the Galois Field lookup table.
> 
> For more information can refer to section 5.4 of PMECC controller
> application note:
> 	http://www.atmel.com/images/doc11127.pdf
> 
> Signed-off-by: Josh Wu <josh.wu-AIFe0yeh4nAAvxtiuMwx3w@public.gmane.org>
> Cc: devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org

Applied to l2-mtd.git.

Brian
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