linux-kernel - Re: [PATCH 3/4] mtd: mchp23k256: add partitioning support

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Date:   Mon, 22 May 2017 04:52:34 +0000
From:   Chris Packham <Chris.Packham@...iedtelesis.co.nz>
To:     Boris Brezillon <boris.brezillon@...e-electrons.com>
CC:     "dwmw2@...radead.org" <dwmw2@...radead.org>,
        "computersforpeace@...il.com" <computersforpeace@...il.com>,
        "andrew@...n.ch" <andrew@...n.ch>,
        "linux-mtd@...ts.infradead.org" <linux-mtd@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Marek Vasut <marek.vasut@...il.com>,
        Richard Weinberger <richard@....at>,
        Cyrille Pitchen <cyrille.pitchen@...ev4u.fr>
Subject: Re: [PATCH 3/4] mtd: mchp23k256: add partitioning support

On 18/05/17 03:29, Boris Brezillon wrote:
> Hi Chris,
> 
> On Wed, 17 May 2017 17:39:07 +1200
> Chris Packham <chris.packham@...iedtelesis.co.nz> wrote:
> 
>> Setting the of_node for the mtd device allows the generic mtd code to
>> setup the partitions. Additionally we must specify a non-zero erasesize
>> for the partitions to be writeable.
>>
>> Signed-off-by: Chris Packham <chris.packham@...iedtelesis.co.nz>
>> ---
>>   drivers/mtd/devices/mchp23k256.c | 5 +++++
>>   1 file changed, 5 insertions(+)
>>
>> diff --git a/drivers/mtd/devices/mchp23k256.c b/drivers/mtd/devices/mchp23k256.c
>> index 2542f5b8b63f..02c6b9dcbd3e 100644
>> --- a/drivers/mtd/devices/mchp23k256.c
>> +++ b/drivers/mtd/devices/mchp23k256.c
>> @@ -143,6 +143,7 @@ static int mchp23k256_probe(struct spi_device *spi)
>>   
>>   	data = dev_get_platdata(&spi->dev);
>>   
>> +	mtd_set_of_node(&flash->mtd, spi->dev.of_node);
>>   	flash->mtd.dev.parent	= &spi->dev;
>>   	flash->mtd.type		= MTD_RAM;
>>   	flash->mtd.flags	= MTD_CAP_RAM;
>> @@ -151,6 +152,10 @@ static int mchp23k256_probe(struct spi_device *spi)
>>   	flash->mtd._read	= mchp23k256_read;
>>   	flash->mtd._write	= mchp23k256_write;
>>   
>> +	flash->mtd.erasesize = PAGE_SIZE;
>> +	while (flash->mtd.size & (flash->mtd.erasesize - 1))
>> +		flash->mtd.erasesize >>= 1;
>> +
> 
> Can we fix allocate_partition() to properly handle the
> master->erasesize == 0 case instead of doing that?
> 

Do you mean something like this?

diff --git a/drivers/mtd/mtdpart.c b/drivers/mtd/mtdpart.c
index ea5e5307f667..0cd20ed6b374 100644
--- a/drivers/mtd/mtdpart.c
+++ b/drivers/mtd/mtdpart.c
@@ -577,6 +577,7 @@ static struct mtd_part *allocate_partition(struct 
mtd_info *master,
                         part->name);
         }
         if ((slave->mtd.flags & MTD_WRITEABLE) &&
+           master->erasesize != 0 &&
             mtd_mod_by_eb(slave->mtd.size, &slave->mtd)) {
                 slave->mtd.flags &= ~MTD_WRITEABLE;


I'm happy to submit this as a formal patch but it could potentially 
affect a number of devices. Whereas the snippet I initially added is 
consistent with drivers/mtd/chips/map_ram.c.

For now I'll leave v2 as-is but I can send a v3 if needed.