linux-kernel - Re: [PATCH 09/13] mtd: spinand: Add support for write volatile configuration register op

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Message-ID: <24b79a08-96fd-34eb-13d3-f707970aae95@ti.com>
Date:   Fri, 20 Aug 2021 17:00:03 +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 09/13] mtd: spinand: Add support for write volatile
 configuration register op

Hi Miquèl,

On 07/08/21 12:35 am, Miquel Raynal wrote:
> Hi Apurva,
> 
> Apurva Nandan <a-nandan@...com> wrote on Tue, 13 Jul 2021 13:05:34
> +0000:
> 
>> Volatile configuration register are a different set of configuration
>> registers, i.e. they differ from the status registers. A different
>> SPI instruction is required to write to these registers. Any changes
>> to the Volatile Configuration Register get transferred directly to
>> the Internal Configuration Register and instantly reflect on the
>> device operation.
>>
>> In Winbond W35N01JW, these volatile configuration register must be
>> configured in order to switch to Octal DTR SPI mode.
>>
>> Add support for writing to volatile configuration registers using a
>> new WRITE_VCR_OP template.
>>
>> Datasheet: https://www.winbond.com/export/sites/winbond/datasheet/W35N01JW_Datasheet_Brief.pdf
>>
>> Signed-off-by: Apurva Nandan <a-nandan@...com>
>> ---
>>   drivers/mtd/nand/spi/core.c    |  2 +-
>>   drivers/mtd/nand/spi/winbond.c | 28 ++++++++++++++++++++++++++++
>>   include/linux/mtd/spinand.h    |  1 +
>>   3 files changed, 30 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/mtd/nand/spi/core.c b/drivers/mtd/nand/spi/core.c
>> index 8711e887b795..f577e72da2c4 100644
>> --- a/drivers/mtd/nand/spi/core.c
>> +++ b/drivers/mtd/nand/spi/core.c
>> @@ -442,7 +442,7 @@ static void spinand_ondie_ecc_save_status(struct nand_device *nand, u8 status)
>>   		engine_conf->status = status;
>>   }
>>   
>> -static int spinand_write_enable_op(struct spinand_device *spinand)
>> +int spinand_write_enable_op(struct spinand_device *spinand)
>>   {
>>   	struct spi_mem_op op = SPINAND_WR_EN_DIS_OP(true);
>>   
>> diff --git a/drivers/mtd/nand/spi/winbond.c b/drivers/mtd/nand/spi/winbond.c
>> index 76684428354e..a7052a9ca171 100644
>> --- a/drivers/mtd/nand/spi/winbond.c
>> +++ b/drivers/mtd/nand/spi/winbond.c
>> @@ -7,6 +7,7 @@
>>    *	Boris Brezillon <boris.brezillon@...tlin.com>
>>    */
>>   
>> +#include <linux/delay.h>
>>   #include <linux/device.h>
>>   #include <linux/kernel.h>
>>   #include <linux/mtd/spinand.h>
>> @@ -114,6 +115,33 @@ static int winbond_spinand_init(struct spinand_device *spinand)
>>   	return 0;
>>   }
>>   
>> +static int winbond_write_vcr_op(struct spinand_device *spinand, u8 reg, u8 val)
> 
> Maybe a comment to tell people what vcr is?
> 

Okay sure!

>> +{
>> +	int ret;
>> +	struct spi_mem_op op = SPI_MEM_OP(SPI_MEM_OP_CMD(0x81, 1),
>> +					  SPI_MEM_OP_ADDR(3, reg, 1),
>> +					  SPI_MEM_OP_NO_DUMMY,
>> +					  SPI_MEM_OP_DATA_OUT(1, spinand->scratchbuf, 1));
>> +
>> +	*spinand->scratchbuf = val;
>> +
>> +	ret = spinand_write_enable_op(spinand);
>> +	if (ret)
>> +		return ret;
>> +
>> +	ret = spi_mem_exec_op(spinand->spimem, &op);
>> +	if (ret)
>> +		return ret;
>> +
>> +	/*
>> +	 * Write VCR operation doesn't set the busy bit in SR, so can't perform
>> +	 * a status poll. Minimum time of 50ns is needed to complete the write.
>> +	 * So, give thrice the minimum required delay.
> 
> Isn't there an official maximum time?
> 

No, there is only an official minimum time. No maximum time..

>> +	 */
>> +	ndelay(150);
>> +	return 0;
>> +}
>> +
>>   static const struct spinand_manufacturer_ops winbond_spinand_manuf_ops = {
>>   	.init = winbond_spinand_init,
>>   };
>> diff --git a/include/linux/mtd/spinand.h b/include/linux/mtd/spinand.h
>> index daa2ac5c3110..21a4e5adcd59 100644
>> --- a/include/linux/mtd/spinand.h
>> +++ b/include/linux/mtd/spinand.h
>> @@ -560,5 +560,6 @@ int spinand_match_and_init(struct spinand_device *spinand,
>>   
>>   int spinand_upd_cfg(struct spinand_device *spinand, u8 mask, u8 val);
>>   int spinand_select_target(struct spinand_device *spinand, unsigned int target);
>> +int spinand_write_enable_op(struct spinand_device *spinand);
>>   
>>   #endif /* __LINUX_MTD_SPINAND_H */
> 
> 
> 
> 
> Thanks,
> Miquèl
> 
> ______________________________________________________
> Linux MTD discussion mailing list
> http://lists.infradead.org/mailman/listinfo/linux-mtd/
> 

Thanks,
Apurva Nandan

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