Re: [PATCH 1/2] mtd: dataflash: Make use of "extened device information"

From: Andrey Smirnov
Date: Wed Apr 12 2017 - 10:59:03 EST

On Tue, Apr 11, 2017 at 11:29 AM, Marek Vasut <marek.vasut@xxxxxxxxx> wrote:
> On 04/11/2017 06:17 PM, Andrey Smirnov wrote:
>> In anticipation of supporting chips that need it, extend the size of
>> struct flash_info's 'jedec_id' field to make room 2 byte of extended
>> device information as well as add code to fetch this data during
>> jedec_probe().
>>
>> Cc: cphealy@xxxxxxxxx
>> Cc: David Woodhouse <dwmw2@xxxxxxxxxxxxx>
>> Cc: Brian Norris <computersforpeace@xxxxxxxxx>
>> Cc: Boris Brezillon <boris.brezillon@xxxxxxxxxxxxxxxxxx>
>> Cc: Marek Vasut <marek.vasut@xxxxxxxxx>
>> Cc: Richard Weinberger <richard@xxxxxx>
>> Cc: Cyrille Pitchen <cyrille.pitchen@xxxxxxxxx>
>> Cc: linux-kernel@xxxxxxxxxxxxxxx
>> Signed-off-by: Andrey Smirnov <andrew.smirnov@xxxxxxxxx>
>> ---
>> drivers/mtd/devices/mtd_dataflash.c | 113 +++++++++++++++++++++---------------
>> 1 file changed, 66 insertions(+), 47 deletions(-)
>>
>> diff --git a/drivers/mtd/devices/mtd_dataflash.c b/drivers/mtd/devices/mtd_dataflash.c
>> index f9e9bd1..9a98cdc 100644
>> --- a/drivers/mtd/devices/mtd_dataflash.c
>> +++ b/drivers/mtd/devices/mtd_dataflash.c
>> @@ -689,7 +689,7 @@ struct flash_info {
>> /* JEDEC id has a high byte of zero plus three data bytes:
>> * the manufacturer id, then a two byte device id.
>> */
>> - uint32_t jedec_id;
>> + uint64_t jedec_id;
>>
>> /* The size listed here is what works with OP_ERASE_PAGE. */
>> unsigned nr_pages;
>> @@ -712,61 +712,35 @@ static struct flash_info dataflash_data[] = {
>> * These newer chips also support 128-byte security registers (with
>> * 64 bytes one-time-programmable) and software write-protection.
>> */
>> - { "AT45DB011B", 0x1f2200, 512, 264, 9, SUP_POW2PS},
>> - { "at45db011d", 0x1f2200, 512, 256, 8, SUP_POW2PS | IS_POW2PS},
>> + { "AT45DB011B", 0x1f22000000, 512, 264, 9, SUP_POW2PS},
>> + { "at45db011d", 0x1f22000000, 512, 256, 8, SUP_POW2PS | IS_POW2PS},
>>
>> - { "AT45DB021B", 0x1f2300, 1024, 264, 9, SUP_POW2PS},
>> - { "at45db021d", 0x1f2300, 1024, 256, 8, SUP_POW2PS | IS_POW2PS},
>> + { "AT45DB021B", 0x1f23000000, 1024, 264, 9, SUP_POW2PS},
>> + { "at45db021d", 0x1f23000000, 1024, 256, 8, SUP_POW2PS | IS_POW2PS},
>>
>> - { "AT45DB041x", 0x1f2400, 2048, 264, 9, SUP_POW2PS},
>> - { "at45db041d", 0x1f2400, 2048, 256, 8, SUP_POW2PS | IS_POW2PS},
>> + { "AT45DB041x", 0x1f24000000, 2048, 264, 9, SUP_POW2PS},
>> + { "at45db041d", 0x1f24000000, 2048, 256, 8, SUP_POW2PS | IS_POW2PS},
>>
>> - { "AT45DB081B", 0x1f2500, 4096, 264, 9, SUP_POW2PS},
>> - { "at45db081d", 0x1f2500, 4096, 256, 8, SUP_POW2PS | IS_POW2PS},
>> + { "AT45DB081B", 0x1f25000000, 4096, 264, 9, SUP_POW2PS},
>> + { "at45db081d", 0x1f25000000, 4096, 256, 8, SUP_POW2PS | IS_POW2PS},
>>
>> - { "AT45DB161x", 0x1f2600, 4096, 528, 10, SUP_POW2PS},
>> - { "at45db161d", 0x1f2600, 4096, 512, 9, SUP_POW2PS | IS_POW2PS},
>> + { "AT45DB161x", 0x1f26000000, 4096, 528, 10, SUP_POW2PS},
>> + { "at45db161d", 0x1f26000000, 4096, 512, 9, SUP_POW2PS | IS_POW2PS},
>>
>> - { "AT45DB321x", 0x1f2700, 8192, 528, 10, 0}, /* rev C */
>> + { "AT45DB321x", 0x1f27000000, 8192, 528, 10, 0}, /* rev C */
>>
>> - { "AT45DB321x", 0x1f2701, 8192, 528, 10, SUP_POW2PS},
>> - { "at45db321d", 0x1f2701, 8192, 512, 9, SUP_POW2PS | IS_POW2PS},
>> + { "AT45DB321x", 0x1f27010000, 8192, 528, 10, SUP_POW2PS},
>> + { "at45db321d", 0x1f27010000, 8192, 512, 9, SUP_POW2PS | IS_POW2PS},
>>
>> - { "AT45DB642x", 0x1f2800, 8192, 1056, 11, SUP_POW2PS},
>> - { "at45db642d", 0x1f2800, 8192, 1024, 10, SUP_POW2PS | IS_POW2PS},
>> + { "AT45DB642x", 0x1f28000000, 8192, 1056, 11, SUP_POW2PS},
>> + { "at45db642d", 0x1f28000000, 8192, 1024, 10, SUP_POW2PS | IS_POW2PS},
>> };
>>
>> -static struct flash_info *jedec_probe(struct spi_device *spi)
>> +static struct flash_info *jedec_lookup(struct spi_device *spi,
>> + uint64_t jedec)
>
> const u64 (not uint64_t , this is NOT userspace). Fix globally.
>

I am not sure what this has to do with userspace. There's plenty of
kernel code that uses standard C99 types, coding style guide calls
them out as being OK

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/process/coding-style.rst?id=refs/tags/v4.11-rc6#n364

but more to the point, the rest of this file uses nothing but C99
types. Why should this function be any different?


>> {
>> - int tmp;
>> - uint8_t code = OP_READ_ID;
>> - uint8_t id[3];
>> - uint32_t jedec;
>> - struct flash_info *info;
>> - int status;
>> -
>> - /* JEDEC also defines an optional "extended device information"
>> - * string for after vendor-specific data, after the three bytes
>> - * we use here. Supporting some chips might require using it.
>> - *
>> - * If the vendor ID isn't Atmel's (0x1f), assume this call failed.
>> - * That's not an error; only rev C and newer chips handle it, and
>> - * only Atmel sells these chips.
>> - */
>> - tmp = spi_write_then_read(spi, &code, 1, id, 3);
>> - if (tmp < 0) {
>> - pr_debug("%s: error %d reading JEDEC ID\n",
>> - dev_name(&spi->dev), tmp);
>> - return ERR_PTR(tmp);
>> - }
>> - if (id[0] != 0x1f)
>> - return NULL;
>> -
>> - jedec = id[0];
>> - jedec = jedec << 8;
>> - jedec |= id[1];
>> - jedec = jedec << 8;
>> - jedec |= id[2];
>> + int tmp, status;
>> + struct flash_info *info;
>>
>> for (tmp = 0, info = dataflash_data;
>> tmp < ARRAY_SIZE(dataflash_data);
>> @@ -796,12 +770,57 @@ static struct flash_info *jedec_probe(struct spi_device *spi)
>> }
>> }
>>
>> + return NULL;
>> +}
>> +
>> +static struct flash_info *jedec_probe(struct spi_device *spi)
>> +{
>> + int tmp;
>> + uint8_t code = OP_READ_ID;
>> + uint8_t id[8] = {0};
>> + const unsigned int id_size = 5;
>> + const unsigned int first_byte = sizeof(id) - id_size;
>> + const uint64_t eid_mask = GENMASK_ULL(63, 16);
>
> Can we have some macro, like DATAFLASH_ID_BYTES and derive all the masks
> and crap from it instead of having this stack of variables ?
>

Can you give me an example of what you have in mind? A macro that
would simplify this code is not very obvious to me.

>> + uint64_t jedec;
>> + struct flash_info *info;
>
> Replace the tab after the type with space please.

Why? This code was originally using tabs, the only thing I changed was
type of 'jedec' variable from uint32_t to uint64_t.

>
>> + /* JEDEC also defines an optional "extended device information"
>
> Multi-line comment format:
>
> /*
> * foo
> * bar
> */
>

This is how the code was before my patch. I just moved this block
without changing it, so I'd prefer to not make that fact less clear by
doing re-formatting.

>> + * string for after vendor-specific data, after the three bytes
>> + * we use here. Supporting some chips might require using it.
>> + *
>> + * If the vendor ID isn't Atmel's (0x1f), assume this call failed.
>> + * That's not an error; only rev C and newer chips handle it, and
>> + * only Atmel sells these chips.
>> + */
>> + tmp = spi_write_then_read(spi, &code, 1, &id[first_byte], id_size);
>> + if (tmp < 0) {
>
> Use ret instead of tmp.

Ditto.

>
>> + pr_debug("%s: error %d reading JEDEC ID\n",
>> + dev_name(&spi->dev), tmp);
>> + return ERR_PTR(tmp);
>> + }
>
> newline

Ditto.

>
>> + if (id[first_byte] != 0x1f)
>
> Use a macro, like CFI_MFR_ATMEL ?
>

Ditto.

>> + return NULL;
>> +
>> + jedec = be64_to_cpup((__be64 *)id);
>> +
>> + info = jedec_lookup(spi, jedec);
>> + if (info)
>> + return info;
>> + /*
>> + * Clear extended id bits and try to find a match again
>> + */
>
> This could be a single-line comment.

OK, I'll change that.

Thanks,
Andrey Smirnov