Messages in this thread | | | Date | Mon, 05 Apr 2021 17:07:42 +0200 | From | Michael Walle <> | Subject | Re: [PATCH 1/2] mtd: spi-nor: sfdp: save a copy of the SFDP data |
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Hi,
Am 2021-04-05 15:11, schrieb Tudor.Ambarus@microchip.com: > On 3/18/21 11:24 AM, Michael Walle wrote: >> EXTERNAL EMAIL: Do not click links or open attachments unless you know >> the content is safe >> >> Due to possible mode switching to 8D-8D-8D, it might not be possible >> to >> read the SFDP after the initial probe. To be able to dump the SFDP via >> sysfs afterwards, make a complete copy of it. >> >> Signed-off-by: Michael Walle <michael@walle.cc> >> --- >> drivers/mtd/spi-nor/core.h | 10 ++++++++ >> drivers/mtd/spi-nor/sfdp.c | 49 >> +++++++++++++++++++++++++++++++++++++ >> include/linux/mtd/spi-nor.h | 3 +++ >> 3 files changed, 62 insertions(+) >> >> diff --git a/drivers/mtd/spi-nor/core.h b/drivers/mtd/spi-nor/core.h >> index 4a3f7f150b5d..668f22011b1d 100644 >> --- a/drivers/mtd/spi-nor/core.h >> +++ b/drivers/mtd/spi-nor/core.h >> @@ -407,6 +407,16 @@ struct spi_nor_manufacturer { >> const struct spi_nor_fixups *fixups; >> }; >> >> +/** >> + * struct sfdp - SFDP data >> + * @num_dwords: number of entries in the dwords array >> + * @dwords: array of double words of the SFDP data >> + */ >> +struct sfdp { >> + size_t num_dwords; >> + u32 *dwords; >> +}; >> + >> /* Manufacturer drivers. */ >> extern const struct spi_nor_manufacturer spi_nor_atmel; >> extern const struct spi_nor_manufacturer spi_nor_catalyst; >> diff --git a/drivers/mtd/spi-nor/sfdp.c b/drivers/mtd/spi-nor/sfdp.c >> index 25142ec4737b..2b6c96e02532 100644 >> --- a/drivers/mtd/spi-nor/sfdp.c >> +++ b/drivers/mtd/spi-nor/sfdp.c >> @@ -16,6 +16,7 @@ >> (((p)->parameter_table_pointer[2] << 16) | \ >> ((p)->parameter_table_pointer[1] << 8) | \ >> ((p)->parameter_table_pointer[0] << 0)) >> +#define SFDP_PARAM_HEADER_PARAM_LEN(p) ((p)->length * 4) >> >> #define SFDP_BFPT_ID 0xff00 /* Basic Flash Parameter Table >> */ >> #define SFDP_SECTOR_MAP_ID 0xff81 /* Sector Map Table */ >> @@ -1263,6 +1264,8 @@ int spi_nor_parse_sfdp(struct spi_nor *nor, >> struct sfdp_parameter_header *param_headers = NULL; >> struct sfdp_header header; >> struct device *dev = nor->dev; >> + struct sfdp *sfdp; >> + size_t sfdp_size; >> size_t psize; >> int i, err; >> >> @@ -1285,6 +1288,9 @@ int spi_nor_parse_sfdp(struct spi_nor *nor, >> bfpt_header->major != SFDP_JESD216_MAJOR) >> return -EINVAL; >> >> + sfdp_size = SFDP_PARAM_HEADER_PTP(bfpt_header) + >> + SFDP_PARAM_HEADER_PARAM_LEN(bfpt_header); >> + >> /* >> * Allocate memory then read all parameter headers with a >> single >> * Read SFDP command. These parameter headers will actually be >> parsed >> @@ -1311,6 +1317,49 @@ int spi_nor_parse_sfdp(struct spi_nor *nor, >> } >> } >> >> + /* >> + * Cache the complete SFDP data. It is not (easily) possible >> to fetch >> + * SFDP after probe time and we need it for the sysfs access. >> + */ >> + for (i = 0; i < header.nph; i++) { >> + param_header = ¶m_headers[i]; >> + sfdp_size = max_t(size_t, sfdp_size, >> + SFDP_PARAM_HEADER_PTP(param_header) >> + >> + >> SFDP_PARAM_HEADER_PARAM_LEN(param_header)); >> + } > > Michael, I like the idea of saving the SFDP data, but I think this can > be > improved a little. For example, it is not mandatory for the tables to > be > continuous in memory, there can be some gaps between BFPT and SMPT for > example, > thus we can improve the memory allocation logic.
I want to parse the SFDP as little as possible. Keep in mind, that this should help to debug SFDP (errors). Therefore, I don't want to rely on the SFDP saying "hey there is a hole, please skip it". Who knows if there is some useful data?
> Also, we can make the saved sfdp > data table-agnostic so that we don't duplicate the reads in > parse_bfpt/smpt/4bait.
This falls into the same category as above. While it might be reused, the primary use case is to have the SFDP data available to a developer/user. Eg. what will you do with some holes in the sysfs read()? Return zeros?
FWIW I'm planning to refactor the read code so the cached values are used.
-michael
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