[PATCH v1 1/5] mtd: spi-nor: Added way to rescan spi-nor device
Kamal Dasu
kdasu.kdev at gmail.com
Mon Feb 6 12:32:28 PST 2017
On Mon, Feb 6, 2017 at 6:46 AM, Cyrille Pitchen
<cyrille.pitchen at atmel.com> wrote:
> Hi Kamal,
>
> Le 04/02/2017 à 00:31, Kamal Dasu a écrit :
>> On pm resume op spi-nor flash may need to be reconfigured on a power
>> reset, however there is no need to go through a full spi_nor_scan().
>> The driver might need to disable protection, program the address width and
>> transfer mode where applicable. The spi-nor framework has all the generic
>> code to do this. Refactored a few pieces and added a spi_nor_pm_rescan()
>> to be called by the mtd device driver's pm resume() op.
>>
>> Signed-off-by: Kamal Dasu <kdasu.kdev at gmail.com>
>> ---
>> drivers/mtd/spi-nor/spi-nor.c | 93 +++++++++++++++++++++++++++++++++++++------
>> include/linux/mtd/spi-nor.h | 17 ++++++++
>> 2 files changed, 98 insertions(+), 12 deletions(-)
>>
>> diff --git a/drivers/mtd/spi-nor/spi-nor.c b/drivers/mtd/spi-nor/spi-nor.c
>> index da7cd69..e72233b 100644
>> --- a/drivers/mtd/spi-nor/spi-nor.c
>> +++ b/drivers/mtd/spi-nor/spi-nor.c
>> @@ -1312,26 +1312,28 @@ static int spi_nor_check(struct spi_nor *nor)
>> return 0;
>> }
>>
>> -int spi_nor_scan(struct spi_nor *nor, const char *name, enum read_mode mode)
>> +static const struct flash_info *spi_nor_get_flash_info(struct spi_nor *nor,
>> + const char *name,
>> + int *retval)
>> +
>> {
>> const struct flash_info *info = NULL;
>> struct device *dev = nor->dev;
>> - struct mtd_info *mtd = &nor->mtd;
>> - struct device_node *np = spi_nor_get_flash_node(nor);
>> - int ret;
>> - int i;
>> + int ret = 0;
>>
>> ret = spi_nor_check(nor);
>> if (ret)
>> - return ret;
>> + goto info_out;
>>
>> if (name)
>> info = spi_nor_match_id(name);
>> /* Try to auto-detect if chip name wasn't specified or not found */
>> if (!info)
>> info = spi_nor_read_id(nor);
>> - if (IS_ERR_OR_NULL(info))
>> - return -ENOENT;
>> + if (IS_ERR_OR_NULL(info)) {
>> + ret = -ENOENT;
>> + goto info_out;
>> + }
>>
>> /*
>> * If caller has specified name of flash model that can normally be
>> @@ -1342,7 +1344,8 @@ int spi_nor_scan(struct spi_nor *nor, const char *name, enum read_mode mode)
>>
>> jinfo = spi_nor_read_id(nor);
>> if (IS_ERR(jinfo)) {
>> - return PTR_ERR(jinfo);
>> + ret = PTR_ERR(jinfo);
>> + goto info_out;
>> } else if (jinfo != info) {
>> /*
>> * JEDEC knows better, so overwrite platform ID. We
>> @@ -1357,8 +1360,15 @@ int spi_nor_scan(struct spi_nor *nor, const char *name, enum read_mode mode)
>> }
>> }
>>
>> - mutex_init(&nor->lock);
>> +info_out:
>> +
>> + *retval = ret;
>> + return info;
>> +}
>>
>> +static void spi_nor_unprotect(struct spi_nor *nor,
>> + const struct flash_info *info)
>> +{
>> /*
>> * Atmel, SST, Intel/Numonyx, and others serial NOR tend to power up
>> * with the software protection bits set
>> @@ -1372,6 +1382,35 @@ int spi_nor_scan(struct spi_nor *nor, const char *name, enum read_mode mode)
>> write_sr(nor, 0);
>> spi_nor_wait_till_ready(nor);
>> }
>> +}
>> +
>> +static inline void spi_nor_print_flash_info(struct spi_nor *nor,
>> + const struct flash_info *info)
>> +{
>> + struct mtd_info *mtd = &nor->mtd;
>> + struct device *dev = nor->dev;
>> +
>> + dev_info(dev, "%s (%lld Kbytes)\n", info->name,
>> + (long long)mtd->size >> 10);
>> +
>> +}
>> +
>> +int spi_nor_scan(struct spi_nor *nor, const char *name, enum read_mode mode)
>> +{
>> + const struct flash_info *info;
>> + struct device *dev = nor->dev;
>> + struct mtd_info *mtd = &nor->mtd;
>> + struct device_node *np = spi_nor_get_flash_node(nor);
>> + int ret;
>> + int i;
>> +
>> + info = spi_nor_get_flash_info(nor, name, &ret);
>> + if (ret)
>> + return ret;
>> +
>> + mutex_init(&nor->lock);
>> +
>> + spi_nor_unprotect(nor, info);
>>
>> if (!mtd->name)
>> mtd->name = dev_name(dev);
>> @@ -1517,8 +1556,7 @@ int spi_nor_scan(struct spi_nor *nor, const char *name, enum read_mode mode)
>>
>> nor->read_dummy = spi_nor_read_dummy_cycles(nor);
>>
>> - dev_info(dev, "%s (%lld Kbytes)\n", info->name,
>> - (long long)mtd->size >> 10);
>> + spi_nor_print_flash_info(nor, info);
>>
>> dev_dbg(dev,
>> "mtd .name = %s, .size = 0x%llx (%lldMiB), "
>> @@ -1540,6 +1578,37 @@ int spi_nor_scan(struct spi_nor *nor, const char *name, enum read_mode mode)
>> }
>> EXPORT_SYMBOL_GPL(spi_nor_scan);
>>
>> +int spi_nor_pm_rescan(struct spi_nor *nor, const char *name)
>> +{
>> + int ret = 0;
>> + const struct flash_info *info;
>> + struct device *dev = nor->dev;
>> +
>> + info = spi_nor_get_flash_info(nor, name, &ret);
>> + if (ret)
>> + return ret;
>
> Why don't we save the info pointer in the spi_nor structure from
> spi_nor_scan()?
>
> in include/linux/mtd/spi-nor.h
>
> +struct flash_info;
>
> struct spi_nor {
> + const struct flash_info *info;
> struct mtd_info mtd;
> struct mutex lock;
>
> I would avoid scanning the SPI flash again and again just to always
> retrieve the very same settings.
>
> Besides, when the parsing of the SFDP tables will be added, the scan
> procedure will cost more than a single Read JEDEC ID command.
>
> Hence if we can skip this step I guess it would be better!
>
That's a great suggestion. I will make the necessary changes.
>> +
>> + spi_nor_unprotect(nor, info);
>> +
>> + if (nor->flash_read == SPI_NOR_QUAD) {
>> + ret = set_quad_mode(nor, info);
>> + if (ret) {
>> + dev_err(dev, "quad mode not supported\n");
>> + return ret;
>> + }
>> + }
>> +
>> + if (nor->addr_width == 4 && JEDEC_MFR(info) != CFI_MFR_AMD)
>> + set_4byte(nor, info, 1);
>
> You have forgotten the case where spi_nor_set_4byte_opcodes() is to be
> called instead of set_4byte(), that is when we want to use the stateless
> 4-byte address instruction set instead of the stateful 4-byte address mode.
>
Actually instruction set applies to SNOR_MFR_SPANSION only and is set
in the spi-nor structure. Is there a need to implement and call
spi_nor_set_4byte_opcodes().
>> +
>> + spi_nor_print_flash_info(nor, info);
>
> IMHO, there is no reason to print this message a second time. It has
> already been displayed from spi_nor_scan() then I guess it's enough.
> Nothing has changed since spi_nor_scan().
>
>> + dev_dbg(dev, "addr width %d read mode %d",
>> + nor->addr_width, nor->flash_read);
>
> Why should we display those settings here in spi_nor_pm_rescan() but not in
> spi_nor_scan() ?
>
Will fix this in v2 version as well.
>> +
>> + return ret;
>> +}
>> +EXPORT_SYMBOL_GPL(spi_nor_pm_rescan);
>> +
>
> Actually most of the spi_nor_pm_rescan() code can be removed. We only need
> to keep:
> - unlock the flash
> - check the Quad Enable requirement
> - for memory > 128 Mbit, either make it enter its 4-byte address mode or
> use the 4-byte address instruction set.
>
Yes I agree the above is all that is needed on reset.
> Moreover, for the ease of the maintenance, I think something like
>
>
> int spi_nor_reset(...)
> {
> /* unlock the flash */
> ...
>
> /* check the Quad Enable requirement */
> ...
>
> /* handle memory > 128 Mbit */
> ...
> }
> EXPORT_SYMBOL_GPL(spi_nor_reset);
>
> int spi_nor_scan(...)
> {
> /* scan */
> ...
>
> /* reset */
> spi_nor_reset();
>
> ...
> }
> EXPORT_SYMBOL_GPL(spi_nor_scan);
>
> could be better than
>
I can get rid of unnecessary refactoring and implement a single
> int func1()
> {
>
> }
>
> int func2()
> {
>
> }
>
> int func3()
> {
>
> }
>
> int func4()
> {
>
> }
>
> int spi_nor_scan(...)
> {
> func1();
> func2();
> func3();
> func4();
> ...
> }
> EXPORT_SYMBOL_GPL(spi_nor_scan);
>
> int spi_nor_pm_rescan(...)
> {
> func2();
> func3();
> }
> EXPORT_SYMBOL_GPL(spi_nor_pm_rescan);
>
> because in the 2nd case it's more difficult to figure out whether some
> piece of code should be called from either spi_nor_scan() or
> spi_nor_pm_rescan() only or from both.
>
> For instance, you have forgotten to call spi_nor_set_4byte_opcodes() when
> needed from spi_nor_pm_rescan().
>
> The reset function should only be a subset of spi_nor_scan().
>
> IMHO, the spi_nor_pm_rescan() approach is a little bit more confusing.
>
>
I will make the necessary changes. Thanks for the detailed review and
explanation.
> Best regards,
>
> Cyrille
>
Thanks
Kamal
>> static const struct flash_info *spi_nor_match_id(const char *name)
>> {
>> const struct flash_info *id = spi_nor_ids;
>> diff --git a/include/linux/mtd/spi-nor.h b/include/linux/mtd/spi-nor.h
>> index c425c7b..487b473 100644
>> --- a/include/linux/mtd/spi-nor.h
>> +++ b/include/linux/mtd/spi-nor.h
>> @@ -213,4 +213,21 @@ static inline struct device_node *spi_nor_get_flash_node(struct spi_nor *nor)
>> */
>> int spi_nor_scan(struct spi_nor *nor, const char *name, enum read_mode mode);
>>
>> +/**
>> + * spi_nor_pm_rescan() - rescan the SPI NOR
>> + * @nor: the spi_nor structure
>> + * @name: the chip type name
>> + *
>> + * The drivers can use this function to set the SPI NOR flash device to
>> + * its initial scanned state, it shall use all nor information set on poweron
>> + * for the read mode, address width and enabling write mode for certain
>> + * manufacturers. This would be needed to be called for flash devices that are
>> + * reset during power management.
>> + *
>> + * The chip type name can be provided through the @name parameter.
>> + *
>> + * Return: 0 for success, others for failure.
>> + */
>> +int spi_nor_pm_rescan(struct spi_nor *nor, const char *name);
>> +
>> #endif
>>
>
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