Messages in this thread | | | Date | Mon, 22 Mar 2021 16:32:49 +0100 | From | Michael Walle <> | Subject | Re: [PATCH 1/2] mtd: spi-nor: sfdp: save a copy of the SFDP data |
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Am 2021-03-22 15:21, schrieb Pratyush Yadav: > On 18/03/21 10:24AM, Michael Walle wrote: >> 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)); > > *sigh* If BFPT header was not made a part of the main SFDP header, two > "sfdp_size = ..." would not be needed, and we could do it all in one > place. > > You can do that refactor if you're feeling like it, but I won't insist > on it.
I think that could be refactored when we also use the SFDP cache for the remaining parsing.
> >> + } >> + >> + /* >> + * Limit the total size to a reasonable value to avoid allocating >> too >> + * much memory just of because the flash returned some insane >> values. >> + */ >> + if (sfdp_size > PAGE_SIZE) { >> + dev_dbg(dev, "SFDP data (%zu) too big, truncating\n", >> + sfdp_size); >> + sfdp_size = PAGE_SIZE; > > Ok. 4K should be large enough for any reasonable SFDP table. > >> + } >> + >> + sfdp = devm_kzalloc(dev, sizeof(*sfdp), GFP_KERNEL); >> + if (!sfdp) { >> + err = -ENOMEM; >> + goto exit; >> + } > > I assume you made nor->sfdp a pointer and not an embedded struct so it > can easily indicate if SFDP was found or not, correct?
Correct.
> >> + >> + sfdp->num_dwords = DIV_ROUND_UP(sfdp_size, sizeof(*sfdp->dwords)); > > The SFDP spec says that Parameter Table Pointer should be DWORD aligned > and Parameter Table length is specified in number of DWORDs. So, > sfdp_size should always be a multiple of 4. Any SFDP table where this > is > not true is an invalid one. > > Also, the spec says "Device behavior when the Read SFDP command crosses > the SFDP structure boundary is not defined". > > So I think this should be a check for alignment instead of a round-up.
Well, that woundn't help for debugging. I.e. you also want the SFDP data in cases like this. IMHO we should try hard enough to actually get a reasonable dump.
OTOH we also rely on the header and the pointers in the header. Any other ideas, but just to chicken out?
>> + sfdp->dwords = devm_kcalloc(dev, sfdp->num_dwords, >> + sizeof(*sfdp->dwords), GFP_KERNEL); >> + if (!sfdp->dwords) { >> + err = -ENOMEM; > > Free sfdp here since it won't be used any longer.
I see, spi_nor_parse_sfdp() is optional and won't fail the probe. Nice catch.
> >> + goto exit; >> + } >> + >> + err = spi_nor_read_sfdp_dma_unsafe(nor, 0, sfdp_size, sfdp->dwords); >> + if (err < 0) { >> + dev_dbg(dev, "failed to read SFDP data\n"); >> + goto exit; > > Free sfdp and sfdp->dwords here since they won't be used any longer. > >> + } >> + >> + nor->sfdp = sfdp; >> + >> /* >> * Check other parameter headers to get the latest revision of >> * the basic flash parameter table. >> diff --git a/include/linux/mtd/spi-nor.h b/include/linux/mtd/spi-nor.h >> index a0d572855444..55c550208949 100644 >> --- a/include/linux/mtd/spi-nor.h >> +++ b/include/linux/mtd/spi-nor.h >> @@ -351,6 +351,7 @@ enum spi_nor_cmd_ext { >> struct flash_info; >> struct spi_nor_manufacturer; >> struct spi_nor_flash_parameter; >> +struct sfdp; > > nor->sfdp is a pointer. This should not be needed. > >> >> /** >> * struct spi_nor - Structure for defining the SPI NOR layer >> @@ -375,6 +376,7 @@ struct spi_nor_flash_parameter; >> * @read_proto: the SPI protocol for read operations >> * @write_proto: the SPI protocol for write operations >> * @reg_proto: the SPI protocol for read_reg/write_reg/erase >> operations >> + * @sfdp: the SFDP data of the flash >> * @controller_ops: SPI NOR controller driver specific operations. >> * @params: [FLASH-SPECIFIC] SPI NOR flash parameters and settings. >> * The structure includes legacy flash >> parameters and >> @@ -404,6 +406,7 @@ struct spi_nor { >> bool sst_write_second; >> u32 flags; >> enum spi_nor_cmd_ext cmd_ext_type; >> + struct sfdp *sfdp; >> >> const struct spi_nor_controller_ops *controller_ops; >> >> -- >> 2.20.1 >>
-- -michael
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