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Date:   Fri, 9 Jun 2023 15:59:26 +0800
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Subject: Re: [PATCH v2] mtd: rawnand: meson: check buffer length
To:     Miquel Raynal <miquel.raynal@bootlin.com>
Cc:     Arseniy Krasnov <avkrasnov@sberdevices.ru>,
        Richard Weinberger <richard@nod.at>,
        Vignesh Raghavendra <vigneshr@ti.com>,
        Neil Armstrong <neil.armstrong@linaro.org>,
        Kevin Hilman <khilman@baylibre.com>,
        Jerome Brunet <jbrunet@baylibre.com>,
        Martin Blumenstingl <martin.blumenstingl@googlemail.com>,
        oxffffaa@gmail.com, kernel@sberdevices.ru,
        linux-mtd@lists.infradead.org,
        linux-arm-kernel@lists.infradead.org,
        linux-amlogic@lists.infradead.org, linux-kernel@vger.kernel.org
References: <20230606101644.3297859-1-AVKrasnov@sberdevices.ru>
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 <20230608152114.3a1d82ac@xps-13>
From:   Liang Yang <liang.yang@amlogic.com>
In-Reply-To: <20230608152114.3a1d82ac@xps-13>
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Hi Miquel,

On 2023/6/8 21:21, Miquel Raynal wrote:
> [ EXTERNAL EMAIL ]
> 
> Hi Liang,
> 
> liang.yang@amlogic.com wrote on Thu, 8 Jun 2023 20:37:14 +0800:
> 
>> Hi Arseniy and Miquel,
>>
>> On 2023/6/8 15:12, Liang Yang wrote:
>>> Hi Miquel,
>>>
>>> On 2023/6/8 14:54, Miquel Raynal wrote:
>>>> [ EXTERNAL EMAIL ]
>>>>
>>>> Hi Liang,
>>>>
>>>> liang.yang@amlogic.com wrote on Thu, 8 Jun 2023 14:42:53 +0800:
>>>>
>>>>> Hi Arseniy,
>>>>>
>>>>> On 2023/6/8 5:17, Arseniy Krasnov wrote:
>>>>>> [ EXTERNAL EMAIL ]
>>>>>>
>>>>>> Hi again Miquel, Liang!
>>>>>>
>>>>>> What do You think about this patch?
>>>>>>
>>>>>> Thanks, Arseniy
>>>>>>
>>>>>> On 06.06.2023 19:29, Arseniy Krasnov wrote:
>>>>>>> Sorry, here is changelog:
>>>>>>> v1 -> v2:
>>>>>>> * Move checks from 'switch/case' which executes commands in >>>>> 'meson_nfc_exec_op()' to a special
>>>>>>>      separated function 'meson_nfc_check_op()' which is called >>>>> before commands processing.
>>>>>>>
>>>>>>> On 06.06.2023 13:16, Arseniy Krasnov wrote:
>>>>>>>> Meson NAND controller has limited buffer length, so check it before
>>>>>>>> command execution to avoid length trim. Also check MTD write size on
>>>>>>>> chip attach.
>>>>>>>>
>>>>>>>> Signed-off-by: Arseniy Krasnov <AVKrasnov@sberdevices.ru>
>>>>>>>> ---
>>>>>>>>     drivers/mtd/nand/raw/meson_nand.c | 47 >>>>>> +++++++++++++++++++++++++++----
>>>>>>>>     1 file changed, 42 insertions(+), 5 deletions(-)
>>>>>>>>
>>>>>>>> diff --git a/drivers/mtd/nand/raw/meson_nand.c >>>>>> b/drivers/mtd/nand/raw/meson_nand.c
>>>>>>>> index 23a73268421b..db6b18753071 100644
>>>>>>>> --- a/drivers/mtd/nand/raw/meson_nand.c
>>>>>>>> +++ b/drivers/mtd/nand/raw/meson_nand.c
>>>>>>>> @@ -111,6 +111,8 @@
>>>>>>>>
>>>>>>>>     #define PER_INFO_BYTE               8
>>>>>>>>
>>>>>>>> +#define NFC_CMD_RAW_LEN     GENMASK(13, 0)
>>>>>>>> +
>>>>>>>>     struct meson_nfc_nand_chip {
>>>>>>>>         struct list_head node;
>>>>>>>>         struct nand_chip nand;
>>>>>>>> @@ -284,7 +286,7 @@ static void meson_nfc_cmd_access(struct >>>>>> nand_chip *nand, int raw, bool dir,
>>>>>>>>
>>>>>>>>         if (raw) {
>>>>>>>>                 len = mtd->writesize + mtd->oobsize;
>>>>>>>> -            cmd = (len & GENMASK(13, 0)) | scrambler | DMA_DIR(dir);
>>>>>>>> +            cmd = len | scrambler | DMA_DIR(dir);
>>>>>>>>                 writel(cmd, nfc->reg_base + NFC_REG_CMD);
>>>>>
>>>>> I think we could keep "& GENMASK(13, 0)". it is better here to >>> indicate how many bits of length in this command and don't destory >>> the command once we don't check the "len" outside of this function. >>> or the code "if (len >  NFC_CMD_RAW_LEN)" is better to put inside >>> this function nearly. Thanks.
>>>>
>>>> It depends who calls this helper. If only used inside >> exec_op,write_page_raw() and read_page_raw() also call >> meson_nfc_cmd_access(), > but i don't find where constrain the "len".
>>
>> Is the helper "meson_nfc_check_op()" needed by exec_op() after the constraint in attach_chip()? the length passed in exec_op() seems smaller than "mtd->writesize + mtd->oobsize" now.
> 
> exec_op() is primarily dedicated to performing side commands than page
> accesses, typically the parameter page is X bytes, you might want to
> read it 3 times, depending on the capabilities of the controller, you
> might need to split the operation or not, so the core checks what are
> the controller capabilities before doing the operation. So yes, the
> check_op() thing is necessary.

ok, i get it. thanks

@Arseniy I have no other questions about this patch.
> 
>>
>> @Arseniy if it does need, I think the same constraint is needed by
>> "meson_nfc_cmd_access()"
>>
>>>
>>>> it's not useful. If used outside, then if you want to clarify
>>>> things you may want to use:
>>>>
>>>> #define NFC_CMD_OP_LEN(cmd) FIELD_PREP(GENMASK(13, 0), (cmd))
>>>>
>>>> This is by far my favorite construction. Could apply to many other
>>>> fields, like DMA_DIR, scrambler, etc.
>>
>> @Miquel, FIELD_PREP() is better, but i have no idea whether we should add FIELD_PREP() in this patch, or keep the previous code.
>>
>>>>
>>>>>>>>                 return;
>>>>>>>>         }
>>>>>>>> @@ -573,7 +575,7 @@ static int meson_nfc_read_buf(struct nand_chip >>>>>> *nand, u8 *buf, int len)
>>>>>>>>         if (ret)
>>>>>>>>                 goto out;
>>>>>>>>
>>>>>>>> -    cmd = NFC_CMD_N2M | (len & GENMASK(13, 0));
>>>>>>>> +    cmd = NFC_CMD_N2M | len;
>>>>>>>>         writel(cmd, nfc->reg_base + NFC_REG_CMD);
>>>>>>>>
>>>>>>>>         meson_nfc_drain_cmd(nfc);
>>>>>>>> @@ -597,7 +599,7 @@ static int meson_nfc_write_buf(struct >>>>>> nand_chip *nand, u8 *buf, int len)
>>>>>>>>         if (ret)
>>>>>>>>                 return ret;
>>>>>>>>
>>>>>>>> -    cmd = NFC_CMD_M2N | (len & GENMASK(13, 0));
>>>>>>>> +    cmd = NFC_CMD_M2N | len;
>>>>>>>>         writel(cmd, nfc->reg_base + NFC_REG_CMD);
>>>>>>>>
>>>>>>>>         meson_nfc_drain_cmd(nfc);
>>>>>>>> @@ -1007,6 +1009,31 @@ meson_nand_op_put_dma_safe_output_buf(const >>>>>> struct nand_op_instr *instr,
>>>>>>>>                 kfree(buf);
>>>>>>>>     }
>>>>>>>>
>>>>>>>> +static int meson_nfc_check_op(struct nand_chip *chip,
>>>>>>>> +                          const struct nand_operation *op)
>>>>>>>> +{
>>>>>>>> +    int op_id;
>>>>>>>> +
>>>>>>>> +    for (op_id = 0; op_id < op->ninstrs; op_id++) {
>>>>>>>> +            const struct nand_op_instr *instr;
>>>>>>>> +
>>>>>>>> +            instr = &op->instrs[op_id];
>>>>>>>> +
>>>>>>>> +            switch (instr->type) {
>>>>>>>> +            case NAND_OP_DATA_IN_INSTR:
>>>>>>>> +            case NAND_OP_DATA_OUT_INSTR:
>>>>>>>> +                    if (instr->ctx.data.len > NFC_CMD_RAW_LEN)
>>>>>>>> +                            return -ENOTSUPP;
>>>>>>>> +
>>>>>>>> +                    break;
>>>>>>>> +            default:
>>>>>>>> +                    break;
>>>>>>>> +            }
>>>>>>>> +    }
>>>>>>>> +
>>>>>>>> +    return 0;
>>>>>>>> +}
>>>>>>>> +
>>>>>>>>     static int meson_nfc_exec_op(struct nand_chip *nand,
>>>>>>>>                              const struct nand_operation *op, bool >>>>>> check_only)
>>>>>>>>     {
>>>>>>>> @@ -1015,10 +1042,12 @@ static int meson_nfc_exec_op(struct >>>>>> nand_chip *nand,
>>>>>>>>         const struct nand_op_instr *instr = NULL;
>>>>>>>>         void *buf;
>>>>>>>>         u32 op_id, delay_idle, cmd;
>>>>>>>> +    int err;
>>>>>>>>         int i;
>>>>>>>>
>>>>>>>> -    if (check_only)
>>>>>>>> -            return 0;
>>>>>>>> +    err = meson_nfc_check_op(nand, op);
>>>>>>>> +    if (err || check_only)
>>>>>>>> +            return err;
>>>>>>>>
>>>>>>>>         meson_nfc_select_chip(nand, op->cs);
>>>>>>>>         for (op_id = 0; op_id < op->ninstrs; op_id++) {
>>>>>>>> @@ -1293,6 +1322,7 @@ static int meson_nand_attach_chip(struct >>>>>> nand_chip *nand)
>>>>>>>>         struct meson_nfc_nand_chip *meson_chip = to_meson_nand(nand);
>>>>>>>>         struct mtd_info *mtd = nand_to_mtd(nand);
>>>>>>>>         int nsectors = mtd->writesize / 1024;
>>>>>>>> +    int raw_writesize;
>>>>>>>>         int ret;
>>>>>>>>
>>>>>>>>         if (!mtd->name) {
>>>>>>>> @@ -1304,6 +1334,13 @@ static int meson_nand_attach_chip(struct >>>>>> nand_chip *nand)
>>>>>>>>                         return -ENOMEM;
>>>>>>>>         }
>>>>>>>>
>>>>>>>> +    raw_writesize = mtd->writesize + mtd->oobsize;
>>>>>>>> +    if (raw_writesize > NFC_CMD_RAW_LEN) {
>>>>>>>> +            dev_err(nfc->dev, "too big write size in raw mode: %d >>>>>> > %ld\n",
>>>>>>>> +                    raw_writesize, NFC_CMD_RAW_LEN);
>>>>>>>> +            return -EINVAL;
>>>>>>>> +    }
>>>>>>>> +
>>>>>>>>         if (nand->bbt_options & NAND_BBT_USE_FLASH)
>>>>>>>>                 nand->bbt_options |= NAND_BBT_NO_OOB;
>>>>>>>>
>>>>
>>>>
>>>> Thanks,
>>>> Miquèl
> 
> 
> Thanks,
> Miquèl