linux-kernel - Re: [PATCH v2] mtd: rawnand: meson: fix bitmask for length in command word

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Date:   Wed, 29 Mar 2023 11:33:38 +0300
From:   Arseniy Krasnov <avkrasnov@...rdevices.ru>
To:     Tudor Ambarus <tudor.ambarus@...aro.org>,
        Liang Yang <liang.yang@...ogic.com>,
        Miquel Raynal <miquel.raynal@...tlin.com>,
        Richard Weinberger <richard@....at>,
        Vignesh Raghavendra <vigneshr@...com>,
        Neil Armstrong <neil.armstrong@...aro.org>,
        Kevin Hilman <khilman@...libre.com>,
        Jerome Brunet <jbrunet@...libre.com>,
        Martin Blumenstingl <martin.blumenstingl@...glemail.com>,
        Jianxin Pan <jianxin.pan@...ogic.com>,
        Yixun Lan <yixun.lan@...ogic.com>
CC:     <linux-mtd@...ts.infradead.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-amlogic@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <kernel@...rdevices.ru>,
        <oxffffaa@...il.com>
Subject: Re: [PATCH v2] mtd: rawnand: meson: fix bitmask for length in command
 word



On 29.03.2023 11:09, Tudor Ambarus wrote:
> 
> 
> On 3/29/23 08:47, Arseniy Krasnov wrote:
>> Valid mask is 0x3FFF, without this patch the following problems were
>> found:
>>
>> 1) [    0.938914] Could not find a valid ONFI parameter page, trying
>>                   bit-wise majority to recover it
>>    [    0.947384] ONFI parameter recovery failed, aborting
>>
>> 2) Read with disabled ECC mode was broken.
>>
>> Fixes: 8fae856c5350 ("mtd: rawnand: meson: add support for Amlogic NAND flash controller")
>> Cc: <Stable@...r.kernel.org>
>> Signed-off-by: Arseniy Krasnov <AVKrasnov@...rdevices.ru>
>> ---
>>  drivers/mtd/nand/raw/meson_nand.c | 6 +++---
>>  1 file changed, 3 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/mtd/nand/raw/meson_nand.c b/drivers/mtd/nand/raw/meson_nand.c
>> index a28574c00900..074e14225c06 100644
>> --- a/drivers/mtd/nand/raw/meson_nand.c
>> +++ b/drivers/mtd/nand/raw/meson_nand.c
>> @@ -280,7 +280,7 @@ static void meson_nfc_cmd_access(struct nand_chip *nand, int raw, bool dir,
>>  
>>  	if (raw) {
>>  		len = mtd->writesize + mtd->oobsize;
>> -		cmd = (len & GENMASK(5, 0)) | scrambler | DMA_DIR(dir);
>> +		cmd = (len & GENMASK(13, 0)) | scrambler | DMA_DIR(dir);
> 
> What happens when len > GENMASK(13, 0)? Do you check this somewhere?

'len' will be trimmed. I'm not sure that this case is possible here, because GENMASK(13, 0)
is hardware limit for this NAND controller, so 'writesize' and 'oobsize' will be initialized
to fit this value. Moreover GENMASK(13, 0) is 16Kb - i think it is big enough for single
read. Also i'm not sure that it is good approach to check 'len' here - we are in the middle
of NAND read processing.

> 
> Please introduce a macro/field for GENMASK(13, 0), having such mask
> scattered along the code looks hackish and doesn't help readability.
> You'll get to use FIELD_PREP as well.

Ack, i'll do it in v3

Thanks, Arseniy

> 
>>  		writel(cmd, nfc->reg_base + NFC_REG_CMD);
>>  		return;
>>  	}
>> @@ -544,7 +544,7 @@ static int meson_nfc_read_buf(struct nand_chip *nand, u8 *buf, int len)
>>  	if (ret)
>>  		goto out;
>>  
>> -	cmd = NFC_CMD_N2M | (len & GENMASK(5, 0));
>> +	cmd = NFC_CMD_N2M | (len & GENMASK(13, 0));
>>  	writel(cmd, nfc->reg_base + NFC_REG_CMD);
>>  
>>  	meson_nfc_drain_cmd(nfc);
>> @@ -568,7 +568,7 @@ static int meson_nfc_write_buf(struct nand_chip *nand, u8 *buf, int len)
>>  	if (ret)
>>  		return ret;
>>  
>> -	cmd = NFC_CMD_M2N | (len & GENMASK(5, 0));
>> +	cmd = NFC_CMD_M2N | (len & GENMASK(13, 0));
>>  	writel(cmd, nfc->reg_base + NFC_REG_CMD);
>>  
>>  	meson_nfc_drain_cmd(nfc);