linux-kernel - Re: [PATCH 1/3] mtd: spi-nor: sst: fix write support for SST

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Message-ID: <7cee3de0-19ee-d9f7-fd04-7f0771f73da5@microchip.com>
Date:   Wed, 16 Sep 2020 09:36:20 +0000
From:   <Tudor.Ambarus@...rochip.com>
To:     <vigneshr@...com>, <m.felsch@...gutronix.de>,
        <miquel.raynal@...tlin.com>, <richard@....at>,
        <sergei.shtylyov@...entembedded.com>,
        <boris.brezillon@...labora.com>, <michael@...le.cc>,
        <j.neuschaefer@....net>
CC:     <linux-mtd@...ts.infradead.org>, <kernel@...gutronix.de>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/3] mtd: spi-nor: sst: fix write support for SST_WRITE
 marked devices

On 9/14/20 3:00 PM, Vignesh Raghavendra wrote:
> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
> 
> On 9/11/20 8:17 PM, Marco Felsch wrote:
>> The sst write support for devices using the special SST_WRITE routine
>> is broken since commit commit df5c21002cf4 ("mtd: spi-nor: use spi-mem
>> dirmap API") because the spi_nor_create_write_dirmap() function checks
>> SPINOR_OP_AAI_WP and sst_write_second. These checks are not valid during
>> probe. The check seems also to be broken since the "op->addr.nbytes = 0"
>> causes the devm_spi_mem_dirmap_create() function to return
>> PTR_ERR(-EINVAL) and the probe() function will fail.
>>
>> It seems that the commit only copy'n'pasted the existing logic. Use the
>> correct SST_WRITE flag and return 0 to fix both issues.
>>
>> Fixes: df5c21002cf4 ("mtd: spi-nor: use spi-mem dirmap API")
>> Signed-off-by: Marco Felsch <m.felsch@...gutronix.de>
>> ---
>>  drivers/mtd/spi-nor/core.c | 12 +++++++++---
>>  1 file changed, 9 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/mtd/spi-nor/core.c b/drivers/mtd/spi-nor/core.c
>> index 65eff4ce6ab1..31869ac245a8 100644
>> --- a/drivers/mtd/spi-nor/core.c
>> +++ b/drivers/mtd/spi-nor/core.c
>> @@ -3289,15 +3289,21 @@ static int spi_nor_create_write_dirmap(struct spi_nor *nor)
>>       };
>>       struct spi_mem_op *op = &info.op_tmpl;
>>
>> +     /*
>> +      * Most SST SPI-NOR's have a special write routine.which should so
> 
> s/SPI-NOR/SPI NOR.
> 
>> +      * dirmap.wdesc is not supported for these.
> 
> Or How about more readable version:
> 
> "Most SST flashes have special sequence for writing data to the flash
> and therefore cannot support writes through direct mapping APIs."
> 
>> +      */
>> +     if (nor->info->flags & SST_WRITE) {
>> +             nor->dirmap.wdesc = NULL;
> 
> nor->dirmap.wdesc is known to be NULL at this point. So no need to set
> to NULL again.
> 
>> +             return 0;
>> +     }
>> +
>>       /* get transfer protocols. */
>>       op->cmd.buswidth = spi_nor_get_protocol_inst_nbits(nor->write_proto);
>>       op->addr.buswidth = spi_nor_get_protocol_addr_nbits(nor->write_proto);
>>       op->dummy.buswidth = op->addr.buswidth;
>>       op->data.buswidth = spi_nor_get_protocol_data_nbits(nor->write_proto);
>>
>> -     if (nor->program_opcode == SPINOR_OP_AAI_WP && nor->sst_write_second)
>> -             op->addr.nbytes = 0;
>> -
>>       nor->dirmap.wdesc = devm_spi_mem_dirmap_create(nor->dev, nor->spimem,
>>                                                      &info);
>>       return PTR_ERR_OR_ZERO(nor->dirmap.wdesc);
>>

With Vignesh's comments addressed, one can add:
Reviewed-by: Tudor Ambarus <tudor.ambarus@...rochip.com>