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Message-ID: <6ca33c39-e425-ff8b-f50a-3ce30b6c2d34@ti.com>
Date: Thu, 19 Oct 2017 17:11:34 +0300
From: Roger Quadros <rogerq@...com>
To: Boris Brezillon <boris.brezillon@...e-electrons.com>
CC: <richard@....at>, <tony@...mide.com>,
<linux-mtd@...ts.infradead.org>, <linux-omap@...r.kernel.org>,
<linux-kernel@...r.kernel.org>,
"# v4 . 12+" <stable@...r.kernel.org>
Subject: Re: [PATCH] mtd: nand: omap2: Fix subpage write
On 19/10/17 16:51, Boris Brezillon wrote:
> On Thu, 19 Oct 2017 11:41:29 +0300
> Roger Quadros <rogerq@...com> wrote:
>
>> Since v4.12, NAND subpage writes were causing a NULL pointer
>> dereference on OMAP platforms (omap2-nand) using OMAP_ECC_BCH4_CODE_HW,
>> OMAP_ECC_BCH8_CODE_HW and OMAP_ECC_BCH16_CODE_HW.
>>
>> This is because for those ECC modes, omap_calculate_ecc_bch()
>> generates ECC bytes for the entire (multi-sector) page and this can
>> overflow the ECC buffer provided by nand_write_subpage_hwecc()
>> as it expects ecc.calculate() to return ECC bytes for just one sector.
>>
>> However, the root cause of the problem is present much before
>> v4.12 but was not seen then as NAND buffers were being allocated
>> as one big chunck prior to
>> commit 3deb9979c731 ("mtd: nand: allocate aligned buffers if NAND_OWN_BUFFERS is unset")
>>
>> Fix the issue by providing a OMAP optimized write_subpage() implementation.
>>
>> cc: <stable@...r.kernel.org> # v4.12+
>> Signed-off-by: Roger Quadros <rogerq@...com>
>> ---
>> drivers/mtd/nand/omap2.c | 338 +++++++++++++++++++++++++++++++----------------
>> 1 file changed, 225 insertions(+), 113 deletions(-)
>>
>> diff --git a/drivers/mtd/nand/omap2.c b/drivers/mtd/nand/omap2.c
>> index 54540c8..a0bd456 100644
>> --- a/drivers/mtd/nand/omap2.c
>> +++ b/drivers/mtd/nand/omap2.c
>> @@ -1133,129 +1133,172 @@ static u8 bch8_polynomial[] = {0xef, 0x51, 0x2e, 0x09, 0xed, 0x93, 0x9a, 0xc2,
>> 0x97, 0x79, 0xe5, 0x24, 0xb5};
>>
<snip>
>> +
>> +/**
>> * omap_read_page_bch - BCH ecc based page read function for entire page
>> * @mtd: mtd info structure
>> * @chip: nand chip info structure
>> @@ -2044,7 +2153,7 @@ static int omap_nand_probe(struct platform_device *pdev)
>> nand_chip->ecc.strength = 4;
>> nand_chip->ecc.hwctl = omap_enable_hwecc_bch;
>> nand_chip->ecc.correct = nand_bch_correct_data;
>> - nand_chip->ecc.calculate = omap_calculate_ecc_bch;
>> + nand_chip->ecc.calculate = omap_calculate_ecc_bch_sw;
>> mtd_set_ooblayout(mtd, &omap_sw_ooblayout_ops);
>> /* Reserve one byte for the OMAP marker */
>> oobbytes_per_step = nand_chip->ecc.bytes + 1;
>> @@ -2066,9 +2175,10 @@ static int omap_nand_probe(struct platform_device *pdev)
>> nand_chip->ecc.strength = 4;
>> nand_chip->ecc.hwctl = omap_enable_hwecc_bch;
>> nand_chip->ecc.correct = omap_elm_correct_data;
>> - nand_chip->ecc.calculate = omap_calculate_ecc_bch;
>> + nand_chip->ecc.calculate = omap_calculate_ecc_bch_multi;
>> nand_chip->ecc.read_page = omap_read_page_bch;
>> nand_chip->ecc.write_page = omap_write_page_bch;
>> + nand_chip->ecc.write_subpage = omap_write_subpage_bch;
>> mtd_set_ooblayout(mtd, &omap_ooblayout_ops);
>> oobbytes_per_step = nand_chip->ecc.bytes;
>>
>> @@ -2087,7 +2197,7 @@ static int omap_nand_probe(struct platform_device *pdev)
>> nand_chip->ecc.strength = 8;
>> nand_chip->ecc.hwctl = omap_enable_hwecc_bch;
>> nand_chip->ecc.correct = nand_bch_correct_data;
>> - nand_chip->ecc.calculate = omap_calculate_ecc_bch;
>> + nand_chip->ecc.calculate = omap_calculate_ecc_bch_sw;
>> mtd_set_ooblayout(mtd, &omap_sw_ooblayout_ops);
>> /* Reserve one byte for the OMAP marker */
>> oobbytes_per_step = nand_chip->ecc.bytes + 1;
>> @@ -2109,9 +2219,10 @@ static int omap_nand_probe(struct platform_device *pdev)
>> nand_chip->ecc.strength = 8;
>> nand_chip->ecc.hwctl = omap_enable_hwecc_bch;
>> nand_chip->ecc.correct = omap_elm_correct_data;
>> - nand_chip->ecc.calculate = omap_calculate_ecc_bch;
>> + nand_chip->ecc.calculate = omap_calculate_ecc_bch_multi;
>
> Hm, it still looks wrong. omap_calculate_ecc_bch_multi() will generate
> the same overflow when called by the core, or am I missing something?
>
In the current setup core will never call ecc.calculate as we're overriding every op
that can be used.
The thing is that omap driver code uses these hooks as is so I wasn't sure
if I should change the caller code to call the multi versions directly and fix these
hooks to single sector versions.
Alternatively, is it OK to set them to NULL?
>> nand_chip->ecc.read_page = omap_read_page_bch;
>> nand_chip->ecc.write_page = omap_write_page_bch;
>> + nand_chip->ecc.write_subpage = omap_write_subpage_bch;
>> mtd_set_ooblayout(mtd, &omap_ooblayout_ops);
>> oobbytes_per_step = nand_chip->ecc.bytes;
>>
>> @@ -2131,9 +2242,10 @@ static int omap_nand_probe(struct platform_device *pdev)
>> nand_chip->ecc.strength = 16;
>> nand_chip->ecc.hwctl = omap_enable_hwecc_bch;
>> nand_chip->ecc.correct = omap_elm_correct_data;
>> - nand_chip->ecc.calculate = omap_calculate_ecc_bch;
>> + nand_chip->ecc.calculate = omap_calculate_ecc_bch_multi;
>> nand_chip->ecc.read_page = omap_read_page_bch;
>> nand_chip->ecc.write_page = omap_write_page_bch;
>> + nand_chip->ecc.write_subpage = omap_write_subpage_bch;
>> mtd_set_ooblayout(mtd, &omap_ooblayout_ops);
>> oobbytes_per_step = nand_chip->ecc.bytes;
>>
>
--
cheers,
-roger
Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki. Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki
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