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 [thread overview]
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
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next prev parent reply other threads:[~2019-08-05 10:38 UTC|newest]
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
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