[PATCH 1/2] mtd: spi-nor: sfdp: save a copy of the SFDP data
Michael Walle
michael at walle.cc
Mon Mar 22 15:32:49 GMT 2021
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 at 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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