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Message-ID: <5a6f6764-6779-42b0-b6c6-3f638b85ef78@linaro.org>
Date: Mon, 11 Dec 2023 09:35:21 +0000
From: Tudor Ambarus <tudor.ambarus@...aro.org>
To: "Mahapatra, Amit Kumar" <amit.kumar-mahapatra@....com>,
"broonie@...nel.org" <broonie@...nel.org>,
"pratyush@...nel.org" <pratyush@...nel.org>,
"miquel.raynal@...tlin.com" <miquel.raynal@...tlin.com>,
"richard@....at" <richard@....at>,
"vigneshr@...com" <vigneshr@...com>,
"sbinding@...nsource.cirrus.com" <sbinding@...nsource.cirrus.com>,
"lee@...nel.org" <lee@...nel.org>,
"james.schulman@...rus.com" <james.schulman@...rus.com>,
"david.rhodes@...rus.com" <david.rhodes@...rus.com>,
"rf@...nsource.cirrus.com" <rf@...nsource.cirrus.com>,
"perex@...ex.cz" <perex@...ex.cz>,
"tiwai@...e.com" <tiwai@...e.com>
Cc: "linux-spi@...r.kernel.org" <linux-spi@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"michael@...le.cc" <michael@...le.cc>,
"linux-mtd@...ts.infradead.org" <linux-mtd@...ts.infradead.org>,
"nicolas.ferre@...rochip.com" <nicolas.ferre@...rochip.com>,
"alexandre.belloni@...tlin.com" <alexandre.belloni@...tlin.com>,
"claudiu.beznea@...on.dev" <claudiu.beznea@...on.dev>,
"Simek, Michal" <michal.simek@....com>,
"linux-arm-kernel@...ts.infradead.org"
<linux-arm-kernel@...ts.infradead.org>,
"alsa-devel@...a-project.org" <alsa-devel@...a-project.org>,
"patches@...nsource.cirrus.com" <patches@...nsource.cirrus.com>,
"linux-sound@...r.kernel.org" <linux-sound@...r.kernel.org>,
"git (AMD-Xilinx)" <git@....com>,
"amitrkcian2002@...il.com" <amitrkcian2002@...il.com>
Subject: Re: [PATCH v11 07/10] mtd: spi-nor: Add stacked memories support in
spi-nor
On 12/11/23 06:56, Mahapatra, Amit Kumar wrote:
>
>
>> -----Original Message-----
>> From: Tudor Ambarus <tudor.ambarus@...aro.org>
>> Sent: Monday, December 11, 2023 9:03 AM
>> To: Mahapatra, Amit Kumar <amit.kumar-mahapatra@....com>;
>> broonie@...nel.org; pratyush@...nel.org; miquel.raynal@...tlin.com;
>> richard@....at; vigneshr@...com; sbinding@...nsource.cirrus.com;
>> lee@...nel.org; james.schulman@...rus.com; david.rhodes@...rus.com;
>> rf@...nsource.cirrus.com; perex@...ex.cz; tiwai@...e.com
>> Cc: linux-spi@...r.kernel.org; linux-kernel@...r.kernel.org;
>> michael@...le.cc; linux-mtd@...ts.infradead.org;
>> nicolas.ferre@...rochip.com; alexandre.belloni@...tlin.com;
>> claudiu.beznea@...on.dev; Simek, Michal <michal.simek@....com>; linux-
>> arm-kernel@...ts.infradead.org; alsa-devel@...a-project.org;
>> patches@...nsource.cirrus.com; linux-sound@...r.kernel.org; git (AMD-
>> Xilinx) <git@....com>; amitrkcian2002@...il.com
>> Subject: Re: [PATCH v11 07/10] mtd: spi-nor: Add stacked memories support
>> in spi-nor
>>
>>
>>
>> On 12/8/23 17:05, Mahapatra, Amit Kumar wrote:
>>> Hello Tudor,
>>
>> Hi!
>
> Hello Tudor,
>
Hi!
>>
>>>
>>>> -----Original Message-----
>>>> From: Tudor Ambarus <tudor.ambarus@...aro.org>
>>>> Sent: Wednesday, December 6, 2023 8:00 PM
>>>> To: Mahapatra, Amit Kumar <amit.kumar-mahapatra@....com>;
>>>> broonie@...nel.org; pratyush@...nel.org; miquel.raynal@...tlin.com;
>>>> richard@....at; vigneshr@...com; sbinding@...nsource.cirrus.com;
>>>> lee@...nel.org; james.schulman@...rus.com; david.rhodes@...rus.com;
>>>> rf@...nsource.cirrus.com; perex@...ex.cz; tiwai@...e.com
>>>> Cc: linux-spi@...r.kernel.org; linux-kernel@...r.kernel.org;
>>>> michael@...le.cc; linux-mtd@...ts.infradead.org;
>>>> nicolas.ferre@...rochip.com; alexandre.belloni@...tlin.com;
>>>> claudiu.beznea@...on.dev; Simek, Michal <michal.simek@....com>;
>>>> linux- arm-kernel@...ts.infradead.org; alsa-devel@...a-project.org;
>>>> patches@...nsource.cirrus.com; linux-sound@...r.kernel.org; git (AMD-
>>>> Xilinx) <git@....com>; amitrkcian2002@...il.com
>>>> Subject: Re: [PATCH v11 07/10] mtd: spi-nor: Add stacked memories
>>>> support in spi-nor
>>>>
>>>> Hi, Amit,
>>>>
>>>> On 11/25/23 09:21, Amit Kumar Mahapatra wrote:
>>>>> Each flash that is connected in stacked mode should have a separate
>>>>> parameter structure. So, the flash parameter member(*params) of the
>>>>> spi_nor structure is changed to an array (*params[2]). The array is
>>>>> used to store the parameters of each flash connected in stacked
>>>> configuration.
>>>>>
>>>>> The current implementation assumes that a maximum of two flashes are
>>>>> connected in stacked mode and both the flashes are of same make but
>>>>> can differ in sizes. So, except the sizes all other flash parameters
>>>>> of both the flashes are identical.
>>>>
>>>> Do you plan to add support for different flashes in stacked mode? If
>>>> not,
>>>
>>> No, according to the current implementation, in stacked mode, both
>>> flashes must be of the same make.
>>>
>>>> wouldn't it be simpler to have just an array of flash sizes instead
>>>> of duplicating the entire params struct?
>>>
>>> Yes, that is accurate. In alignment with our current stacked support
>>> use case we can have an array of flash sizes instead.
>>> The primary purpose of having an array of params struct was to
>>> facilitate potential future extensions, allowing the addition of
>>> stacked support for different flashes
>>>
>>
>> right. Don't do this change yet, let's decide on the overall architecture first.
>
> Sure.
>>
>>>>
>>>>>
>>>>> SPI-NOR is not aware of the chip_select values, for any incoming
>>>>> request SPI-NOR will decide the flash index with the help of
>>>>> individual flash size and the configuration type (single/stacked).
>>>>> SPI-NOR will pass on the flash index information to the SPI core &
>>>>> SPI driver by setting the appropriate bit in
>>>>> nor->spimem->spi->cs_index_mask. For example, if nth bit of
>>>>> nor->spimem->spi->cs_index_mask is set then the driver would
>>>>> assert/de-assert spi->chip_slect[n].
>>>>>
>>>>> Signed-off-by: Amit Kumar Mahapatra <amit.kumar-
>> mahapatra@....com>
>>>>> ---
>>>>> drivers/mtd/spi-nor/core.c | 272 +++++++++++++++++++++++++++++-----
>> --
>>>>> drivers/mtd/spi-nor/core.h | 4 +
>>>>> include/linux/mtd/spi-nor.h | 15 +-
>>>>> 3 files changed, 240 insertions(+), 51 deletions(-)
>>>>>
>>>>> diff --git a/drivers/mtd/spi-nor/core.c b/drivers/mtd/spi-nor/core.c
>>>>> index 93ae69b7ff83..e990be7c7eb6 100644
>>>>> --- a/drivers/mtd/spi-nor/core.c
>>>>> +++ b/drivers/mtd/spi-nor/core.c
>>>>
>>>> cut
>>>>
>>>>> @@ -2905,7 +3007,10 @@ static void spi_nor_init_fixup_flags(struct
>>>>> spi_nor *nor) static int spi_nor_late_init_params(struct spi_nor
>>>>> *nor) {
>>>>> struct spi_nor_flash_parameter *params = spi_nor_get_params(nor,
>>>> 0);
>>>>> - int ret;
>>>>> + struct device_node *np = spi_nor_get_flash_node(nor);
>>>>> + u64 flash_size[SNOR_FLASH_CNT_MAX];
>>>>> + u32 idx = 0;
>>>>> + int rc, ret;
>>>>>
>>>>> if (nor->manufacturer && nor->manufacturer->fixups &&
>>>>> nor->manufacturer->fixups->late_init) { @@ -2937,6 +3042,44 @@
>>>>> static int spi_nor_late_init_params(struct spi_nor *nor)
>>>>> if (params->n_banks > 1)
>>>>> params->bank_size = div64_u64(params->size, params-
>> n_banks);
>>>>>
>>>>> + nor->num_flash = 0;
>>>>> +
>>>>> + /*
>>>>> + * The flashes that are connected in stacked mode should be of
>>>>> +same
>>>> make.
>>>>> + * Except the flash size all other properties are identical for all the
>>>>> + * flashes connected in stacked mode.
>>>>> + * The flashes that are connected in parallel mode should be identical.
>>>>> + */
>>>>> + while (idx < SNOR_FLASH_CNT_MAX) {
>>>>> + rc = of_property_read_u64_index(np, "stacked-memories",
>>>> idx,
>>>>> +&flash_size[idx]);
>>>>
>>>> This is a little late in my opinion, as we don't have any sanity
>>>> check on the flashes that are stacked on top of the first. We shall
>>>> at least read and compare the ID for all.
>>>
>>> Alright, I will incorporate a sanity check for reading and comparing
>>> the ID of the stacked flash. Subsequently, I believe this stacked
>>> logic should be relocated to spi_nor_get_flash_info() where we
>>> identify the first flash. Please share your thoughts on this.
>>> Additionally, do you
>>
>> I'm wondering whether we can add a layer on top of the flash type to handle
>
> When you mention "on top," are you referring to incorporating it into
> the MTD layer? Initially, Miquel had submitted this patch to address
I mean something above SPI MEM flashes, be it NOR, NANDs or whatever.
Instead of treating the stacked flashes as a monolithic device and treat
in SPI NOR some array of flashes, to have a layer above which probes the
SPI MEM flash driver for each stacked flash. In your case SPI NOR would
be probed twice, as you use 2 SPI NOR flashes.
> stacked/parallel handling in the MTD layer.
> https://lore.kernel.org/linux-mtd/20200114191052.0a16d116@xps13/t/
> However, the Device Tree bindings were initially not accepted.
Okay, thanks for the pointer. I'll take a look.
> Following a series of discussions, the below bindings were
> eventually merged.
> https://lore.kernel.org/all/20220126112608.955728-4-miquel.raynal@bootlin.com/
I saw, thanks.
>
>> the stacked/parallel modes. This way everything will become flash type
>> independent. Would it be possible to stack 2 SPI NANDs? How about a SPI
>> NOR and a SPI NAND?
>>
>> Is the datasheet of the controller public?
>
> Yes, https://docs.xilinx.com/r/en-US/am011-versal-acap-trm/Quad-SPI-Controller
>
Wonderful, I'll take a look. I see two clocks there. Does this mean that
the stacked flashes can be operated at different frequencies? Do you
know if we can combine a SPI NOR with a SPI NAND in stacked configuration?
I need to study this a bit. I'll try to involve Michael and Pratyush too.
Cheers,
ta
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