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

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Date:   Wed, 29 Mar 2023 13:55:29 +0300
From:   Arseniy Krasnov <avkrasnov@...rdevices.ru>
To:     Miquel Raynal <miquel.raynal@...tlin.com>
CC:     Tudor Ambarus <tudor.ambarus@...aro.org>,
        Liang Yang <liang.yang@...ogic.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>,
        <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 12:00, Miquel Raynal wrote:
> Hi Arseniy,
> 
> avkrasnov@...rdevices.ru wrote on Wed, 29 Mar 2023 11:33:38 +0300:
> 
>> 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.
> 
> No, you should check the page size will not exceed this limit in the
> attach hook, likely.
> 
> You should also refuse exec_op operations with a data length bigger
> than 16k (either with a manual check in your own parser or just by
> providing the max size to the parser table, depending on what's used).
>

 
Ok, I see.

Thanks, Arseniy

>>
>>>
>>> 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);  
> 
> 
> Thanks,
> Miquèl