Linux-mtd Archive on lore.kernel.org
 help / color / Atom feed
From: Vignesh Raghavendra <vigneshr@ti.com>
To: <Tudor.Ambarus@microchip.com>, <miquel.raynal@bootlin.com>,
	<richard@nod.at>
Cc: marek.vasut@gmail.com, linux-mtd@lists.infradead.org,
	linux-kernel@vger.kernel.org, tmaimon77@gmail.com,
	bbrezillon@kernel.org
Subject: Re: [PATCH v4 1/3] mtd: spi-nor: always use bounce buffer for register read/writes
Date: Mon, 5 Aug 2019 16:08:57 +0530
Message-ID: <2b10c18a-e955-31b8-b3e0-c3df83508756@ti.com> (raw)
In-Reply-To: <b125bf29-f1fd-6d33-4a7c-49cb94ef1488@microchip.com>



On 05/08/19 2:36 PM, Tudor.Ambarus@microchip.com wrote:
> 
> 
> On 08/01/2019 07:22 PM, Vignesh Raghavendra wrote:
>> External E-Mail
>>
>>
>> spi-mem layer expects all buffers passed to it to be DMA'able. But
>> spi-nor layer mostly allocates buffers on stack for reading/writing to
>> registers and therefore are not DMA'able. Introduce bounce buffer to be
>> used to read/write to registers. This ensures that buffer passed to
>> spi-mem layer during register read/writes is DMA'able. With this change
>> nor->cmd-buf is no longer used, so drop it.
>>
>> Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
>> Signed-off-by: Vignesh Raghavendra <vigneshr@ti.com>
>> ---
>>
>> v4:
>> Avoid memcpy during READID
>>
>> v3: new patch
>>
>>  drivers/mtd/spi-nor/spi-nor.c | 70 ++++++++++++++++++++---------------
>>  include/linux/mtd/spi-nor.h   |  7 +++-
>>  2 files changed, 45 insertions(+), 32 deletions(-)
>>
>> diff --git a/drivers/mtd/spi-nor/spi-nor.c b/drivers/mtd/spi-nor/spi-nor.c
>> index 03cc788511d5..e02376e1127b 100644
>> --- a/drivers/mtd/spi-nor/spi-nor.c
>> +++ b/drivers/mtd/spi-nor/spi-nor.c
> 
> cut
> 
>>  /**
>> @@ -1404,9 +1401,11 @@ static int write_sr_cr(struct spi_nor *nor, u8 *sr_cr)
>>  {
>>  	int ret;
>>  
>> +	memcpy(nor->bouncebuf, sr_cr, 2);
> 
> I'm thinking out loud. This can be avoided by forcing all the callers to use
> nor->bouncebuf. That would result in a:
> 

I can make this change and make all callers use nor->bouncebuf in next
version.

> static int write_sr(struct spi_nor *nor, size_t len)
> 
> write_sr_cr() can be removed. Memcopying 2 bytes is a small price to pay, we can
> keep things as they are, to not be too invasive. But if you think that this idea
> is worth it, tell.
> 

Sounds good to me. But replacing write_sr_cr() with above defintion of
write_sr() should be a patch IMO>

>> +
>>  	write_enable(nor);
>>  
>> -	ret = nor->write_reg(nor, SPINOR_OP_WRSR, sr_cr, 2);
>> +	ret = nor->write_reg(nor, SPINOR_OP_WRSR, nor->bouncebuf, 2);
>>  	if (ret < 0) {
>>  		dev_err(nor->dev,
>>  			"error while writing configuration register\n");
> 
> cut
> 
>> @@ -2177,9 +2176,10 @@ static const struct flash_info spi_nor_ids[] = {
>>  static const struct flash_info *spi_nor_read_id(struct spi_nor *nor)
>>  {
>>  	int			tmp;
>> -	u8			id[SPI_NOR_MAX_ID_LEN];
>> +	u8			*id;
>>  	const struct flash_info	*info;
>>  
>> +	id = nor->bouncebuf;
> 
> nit: do init at declaration.
> 

Ok.

> Also, you missed a place in which you can use the bouncebuf, search by "read_reg(":
> ret = nor->read_reg(nor, SPINOR_OP_XRDSR, &val, 1);
> 

Indeed, will fix in next version!

> Cheers,
> ta
> 

-- 
Regards
Vignesh

______________________________________________________
Linux MTD discussion mailing list
http://lists.infradead.org/mailman/listinfo/linux-mtd/

  reply index

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-01 16:22 [PATCH v4 0/3] Merge m25p80 into spi-nor Vignesh Raghavendra
2019-08-01 16:22 ` [PATCH v4 1/3] mtd: spi-nor: always use bounce buffer for register read/writes Vignesh Raghavendra
2019-08-05  9:06   ` Tudor.Ambarus
2019-08-05 10:38     ` Vignesh Raghavendra [this message]
2019-08-05 11:24       ` Tudor.Ambarus
2019-08-01 16:22 ` [PATCH v4 2/3] mtd: spi-nor: Move m25p80 code in spi-nor.c Vignesh Raghavendra
2019-08-05 10:25   ` Tudor.Ambarus
2019-08-05 11:10     ` Vignesh Raghavendra
2019-08-05 11:51       ` Tudor.Ambarus
2019-08-05 12:31         ` Vignesh Raghavendra
2019-08-01 16:22 ` [PATCH v4 3/3] mtd: spi-nor: Rework hwcaps selection for the spi-mem case Vignesh Raghavendra
2019-08-05 17:45   ` Tudor.Ambarus

Reply instructions:

You may reply publically to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=2b10c18a-e955-31b8-b3e0-c3df83508756@ti.com \
    --to=vigneshr@ti.com \
    --cc=Tudor.Ambarus@microchip.com \
    --cc=bbrezillon@kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mtd@lists.infradead.org \
    --cc=marek.vasut@gmail.com \
    --cc=miquel.raynal@bootlin.com \
    --cc=richard@nod.at \
    --cc=tmaimon77@gmail.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

Linux-mtd Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-mtd/0 linux-mtd/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-mtd linux-mtd/ https://lore.kernel.org/linux-mtd \
		linux-mtd@lists.infradead.org linux-mtd@archiver.kernel.org
	public-inbox-index linux-mtd

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.infradead.lists.linux-mtd


AGPL code for this site: git clone https://public-inbox.org/ public-inbox