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Subject: Re: [PATCH 11/13] mtd: spinand: Add support for Power-on-Reset (PoR)
 instruction
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>
References: <20210713130538.646-1-a-nandan@ti.com>
 <20210713130538.646-12-a-nandan@ti.com> <20210806210840.65c06b67@xps13>
From:   Apurva Nandan <a-nandan@ti.com>
Message-ID: <403a2b26-fd95-31ab-8992-a6e6862249e6@ti.com>
Date:   Fri, 20 Aug 2021 17:09:07 +0530
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Hi Miquèl,

On 07/08/21 12:38 am, Miquel Raynal wrote:
> Hi Apurva,
> 
> Apurva Nandan <a-nandan@ti.com> wrote on Tue, 13 Jul 2021 13:05:36
> +0000:
> 
>> Manufacturers like Gigadevice and Winbond are adding Power-on-Reset
>> functionality in their SPI NAND flash chips. PoR instruction consists
>> of a 66h command followed by 99h command, and is different from the FFh
>> reset. The reset command FFh just clears the status only registers,
>> while the PoR command erases all the configurations written to the
>> flash and is equivalent to a power-down -> power-up cycle.
>>
>> Add support for the Power-on-Reset command for any flash that provides
>> this feature.
>>
>> Datasheet: https://www.winbond.com/export/sites/winbond/datasheet/W35N01JW_Datasheet_Brief.pdf
>>
>> Signed-off-by: Apurva Nandan <a-nandan@ti.com>
>> ---
> 
> [...]
> 				\
>> @@ -218,6 +230,8 @@ struct spinand_device;
>>    * reading/programming/erasing when the RESET occurs. Since we always
>>    * issue a RESET when the device is IDLE, 5us is selected for both initial
>>    * and poll delay.
>> + * Power on Reset can take max upto 500 us to complete, so sleep for 1000 us
> 
> s/max upto/up to/
> 

Okay!

>> + * to 1200 us safely.
> 
> I don't really get why, if the maximum is 500, then let's wait for
> 500us.
> 

Generally we keep some margin from the maximum time, no?

>>    */
>>   #define SPINAND_READ_INITIAL_DELAY_US	6
>>   #define SPINAND_READ_POLL_DELAY_US	5
>> @@ -227,6 +241,8 @@ struct spinand_device;
>>   #define SPINAND_WRITE_POLL_DELAY_US	15
>>   #define SPINAND_ERASE_INITIAL_DELAY_US	250
>>   #define SPINAND_ERASE_POLL_DELAY_US	50
>> +#define SPINAND_POR_MIN_DELAY_US	1000
>> +#define SPINAND_POR_MAX_DELAY_US	1200
>>   
>>   #define SPINAND_WAITRDY_TIMEOUT_MS	400
>>   
>> @@ -351,6 +367,7 @@ struct spinand_ecc_info {
>>   #define SPINAND_HAS_QE_BIT		BIT(0)
>>   #define SPINAND_HAS_CR_FEAT_BIT		BIT(1)
>>   #define SPINAND_HAS_OCTAL_DTR_BIT	BIT(2)
>> +#define SPINAND_HAS_POR_CMD_BIT		BIT(3)
>>   
>>   /**
>>    * struct spinand_ondie_ecc_conf - private SPI-NAND on-die ECC engine structure
> 
> 
> 
> 
> Thanks,
> Miquèl
> 
> ______________________________________________________
> Linux MTD discussion mailing list
> http://lists.infradead.org/mailman/listinfo/linux-mtd/
> 

Thanks,
Apurva Nandan