linux-kernel - Re: [PATCH 08/13] mtd: spinand: Reject 8D-8D-8D op_templates if octal_dtr_enale() is missing in manufacturer_op

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Message-ID: <68eb2817-1df8-464b-aef8-15e9c9adfead@ti.com>
Date:   Fri, 20 Aug 2021 21:23:25 +0530
From:   Apurva Nandan <a-nandan@...com>
To:     Miquel Raynal <miquel.raynal@...tlin.com>
CC:     Richard Weinberger <richard@....at>,
        Vignesh Raghavendra <vigneshr@...com>,
        Mark Brown <broonie@...nel.org>,
        Patrice Chotard <patrice.chotard@...s.st.com>,
        Boris Brezillon <boris.brezillon@...labora.com>,
        <linux-mtd@...ts.infradead.org>, <linux-kernel@...r.kernel.org>,
        <linux-spi@...r.kernel.org>, Pratyush Yadav <p.yadav@...com>
Subject: Re: [PATCH 08/13] mtd: spinand: Reject 8D-8D-8D op_templates if
 octal_dtr_enale() is missing in manufacturer_op

Hi Miquèl,

On 20/08/21 8:08 pm, Miquel Raynal wrote:
> Hi Apurva,
> 
> Apurva Nandan <a-nandan@...com> wrote on Fri, 20 Aug 2021 19:24:34
> +0530:
> 
>> Hi Miquèl,
>>
>> On 20/08/21 5:44 pm, Miquel Raynal wrote:
>>> Hi Apurva,
>>>
>>> Apurva Nandan <a-nandan@...com> wrote on Fri, 20 Aug 2021 16:56:50
>>> +0530:
>>>    
>>>> On 07/08/21 12:31 am, Miquel Raynal wrote:
>>>>> Hi Apurva,
>>>>>
>>>>> Apurva Nandan <a-nandan@...com> wrote on Tue, 13 Jul 2021 13:05:33
>>>>> +0000:
>>>>>     >>>> The SPI NAND core doesn't know how to switch the flash to Octal DTR
>>>>>> mode (i.e. which operations to perform). If the manufacturer hasn't
>>>>>> implemented the octal_dtr_enable() manufacturer_op, the SPI NAND core
>>>>>> wouldn't be able to switch to 8D-8D-8D mode and will also not be able
>>>>>> to run in 1S-1S-1S mode due to already selected 8D-8D-8D read/write
>>>>>> cache op_templates.
>>>>>>
>>>>>> So, avoid choosing a Octal DTR SPI op_template for read_cache,
>>>>>> write_cache and update_cache operations, if the manufacturer_op
>>>>>> octal_dtr_enable() is missing.
>>>>>
>>>>> After looking at your previous commit I don't see why this patch would
>>>>> be needed. octal_dtr_enable() only updates the mode when it succeeds so
>>>>> I don't think this patch is really needed.
>>>>>     >>
>>>> I added it to prevent any errors happening dues to a missing implementation of octal_dtr_enable() from manufacturer driver side.
>>>> So, if the manufacturers skips the octal_dtr_enable() implementation, we want the spinand core to run in 1s-1s-1s mode.
>>>
>>> I still don't get the point: you fail the probe if the octal bit is
>>> enabled but the manufacturer did not implement octal_dtr_enable(), so
>>> how could we have issues? Maybe I am overlooking something though, but
>>> this seemed completely redundant to my eyes so far.
>>>    
>>
>> Okay, I feel this may be redundant. This is for the case when the manufacturer has added Octal DTR read/write/update cache variants but hasn't implemented the octal_dtr_enable() method.
>>
>> Without this patch, the probe would fail, if the manufacturer did not implement octal_dtr_enable(). But after using this patch, spinand can still use the chip in 1s-1s-1s mode in that case and just skip the Octal DTR op variants during the selection. And also the probe would succeed.
> 
> Unless I am overlooking something with this series applied
> (with or without this patch) the possibilities are:
> - no octal bit -> continue as before
> - octal bit and vendor callback -> uses octal mode
> - octal bit and no vendor callback -> will return an error from
> spinand_init_octal_dtr_enable() which will fail the probe (patch 7)
> 
> Anyway we have a choice:
> - Either we consider the tables describing chips as pure descriptions
>    and we can support these chips in mode 1-1-1 (will require changes in
>    your series as this is not what you support as far as I understand
>    the code)
> - Or we consider these tables as "what is currently supported" and in
>    this case we just fail if one adds the octal bit without any callback
>    implementation.
> 
> I think the latter is better for now. We can update this choice later
> if needed anyway.
> 

Yes, I fully agree with the latter. I will drop this patch in the v2. 
Thanks!

>>
>>>>
>>>> Read/write/update op variant selection happens in select_op_variant(), much before octal_dtr_enable(). So just check if there is a definition of octal_dtr_enable in manufacturer ops and then only use 8D op variants.
>>>>
>>>> Removing this wouldn't break anything in the current implementation.
>>>> Do you think we should drop this?
>>>>   
>>>>>>
>>>>>> Signed-off-by: Apurva Nandan <a-nandan@...com>
>>>>>> ---
>>>>>>     drivers/mtd/nand/spi/core.c | 7 ++++++-
>>>>>>     1 file changed, 6 insertions(+), 1 deletion(-)
>>>>>>
>>>>>> diff --git a/drivers/mtd/nand/spi/core.c b/drivers/mtd/nand/spi/core.c
>>>>>> index 19d8affac058..8711e887b795 100644
>>>>>> --- a/drivers/mtd/nand/spi/core.c
>>>>>> +++ b/drivers/mtd/nand/spi/core.c
>>>>>> @@ -1028,6 +1028,8 @@ static int spinand_manufacturer_match(struct spinand_device *spinand,
>>>>>>     		if (id[0] != manufacturer->id)
>>>>>>     			continue;
>>>>>>     >> +		spinand->manufacturer = manufacturer;
>>>>>> +
>>>>>>     		ret = spinand_match_and_init(spinand,
>>>>>>     					     manufacturer->chips,
>>>>>>     					     manufacturer->nchips,
>>>>>> @@ -1035,7 +1037,6 @@ static int spinand_manufacturer_match(struct spinand_device *spinand,
>>>>>>     		if (ret < 0)
>>>>>>     			continue;
>>>>>>     >> -		spinand->manufacturer = manufacturer;
>>>>>>     		return 0;
>>>>>>     	}
>>>>>>     	return -ENOTSUPP;
>>>>>> @@ -1097,6 +1098,10 @@ spinand_select_op_variant(struct spinand_device *spinand,
>>>>>>     		unsigned int nbytes;
>>>>>>     		int ret;
>>>>>>     >> +		if (spinand_op_is_octal_dtr(&op) &&
>>>>>> +		    !spinand->manufacturer->ops->octal_dtr_enable)
>>>>>> +			continue;
>>>>>> +
>>>>>>     		nbytes = nanddev_per_page_oobsize(nand) +
>>>>>>     			 nanddev_page_size(nand);
>>>>>>     > > Thanks,
>>>>> Miquèl
>>>>>
>>>>> ______________________________________________________
>>>>> Linux MTD discussion mailing list
>>>>> http://lists.infradead.org/mailman/listinfo/linux-mtd/
>>>>>     >>
>>>> Thanks,
>>>> Apurva Nandan
>>>
>>>
>>>
>>>
>>> Thanks,
>>> Miquèl
>>>    
>>
>> Thanks,
>> Apurva Nandan
> 
> Thanks,
> Miquèl
> 

Thanks,
Apurva Nandan

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