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

From: Apurva Nandan <a-nandan@ti.com>
To: Miquel Raynal <miquel.raynal@bootlin.com>
Cc: Richard Weinberger <richard@nod.at>,
	Vignesh Raghavendra <vigneshr@ti.com>,
	Mark Brown <broonie@kernel.org>,
	Patrice Chotard <patrice.chotard@foss.st.com>,
	Boris Brezillon <boris.brezillon@collabora.com>,
	<linux-mtd@lists.infradead.org>, <linux-kernel@vger.kernel.org>,
	<linux-spi@vger.kernel.org>, Pratyush Yadav <p.yadav@ti.com>
Subject: Re: [PATCH 08/13] mtd: spinand: Reject 8D-8D-8D op_templates if octal_dtr_enale() is missing in manufacturer_op
Date: Fri, 20 Aug 2021 19:24:34 +0530	[thread overview]
Message-ID: <11d173f2-2011-d029-e905-a10fdd0f2b85@ti.com> (raw)
In-Reply-To: <20210820141413.6c519255@xps13>

Hi Miquèl,

On 20/08/21 5:44 pm, Miquel Raynal wrote:
> Hi Apurva,
> 
> Apurva Nandan <a-nandan@ti.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@ti.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.

>>
>> 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@ti.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