Date:   Wed, 20 Apr 2022 11:18:21 +0200
From:   Michael Walle <michael@...le.cc>
To:     Pratyush Yadav <p.yadav@...com>
Cc:     Tudor Ambarus <tudor.ambarus@...rochip.com>,
        Miquel Raynal <miquel.raynal@...tlin.com>,
        Richard Weinberger <richard@....at>,
        Vignesh Raghavendra <vigneshr@...com>,
        linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH RFC v1 2/2] mtd: spi-nor: expose internal parameters via
 debugfs

Am 2022-04-20 07:23, schrieb Pratyush Yadav:
> On 18/04/22 02:10PM, Michael Walle wrote:
>> There is no way to gather all information to verify support for a new
>> flash chip. Also if you want to convert an existing flash chip to the
>> new SFDP parsing, there is not enough information to determine if the
>> flash will work like before. To ease this development, expose internal
>> parameters via the debugfs.
> 
> A big +1 for this patch from me. I have too often added prints in the
> driver to find out all this information. This won't be very useful in
> case the probe fails, but I don't suppose we can do much about that.

That might get better with the "generic sfdp driver" fallback though.

>> Signed-off-by: Michael Walle <michael@...le.cc>
>> ---
>>  drivers/mtd/spi-nor/Makefile  |   1 +
>>  drivers/mtd/spi-nor/core.c    |   4 +
>>  drivers/mtd/spi-nor/core.h    |   8 ++
>>  drivers/mtd/spi-nor/debugfs.c | 241 
>> ++++++++++++++++++++++++++++++++++
>>  include/linux/mtd/spi-nor.h   |   2 +
>>  5 files changed, 256 insertions(+)
>>  create mode 100644 drivers/mtd/spi-nor/debugfs.c
>> 
>> diff --git a/drivers/mtd/spi-nor/Makefile 
>> b/drivers/mtd/spi-nor/Makefile
>> index 6b904e439372..e347b435a038 100644
>> --- a/drivers/mtd/spi-nor/Makefile
>> +++ b/drivers/mtd/spi-nor/Makefile
>> @@ -17,6 +17,7 @@ spi-nor-objs			+= sst.o
>>  spi-nor-objs			+= winbond.o
>>  spi-nor-objs			+= xilinx.o
>>  spi-nor-objs			+= xmc.o
>> +spi-nor-$(CONFIG_DEBUG_FS)	+= debugfs.o
>>  obj-$(CONFIG_MTD_SPI_NOR)	+= spi-nor.o
>> 
>>  obj-$(CONFIG_MTD_SPI_NOR)	+= controllers/
>> diff --git a/drivers/mtd/spi-nor/core.c b/drivers/mtd/spi-nor/core.c
>> index 80d65cfcb88d..302331695d96 100644
>> --- a/drivers/mtd/spi-nor/core.c
>> +++ b/drivers/mtd/spi-nor/core.c
>> @@ -3117,6 +3117,8 @@ static int spi_nor_probe(struct spi_mem *spimem)
>>  	if (ret)
>>  		return ret;
>> 
>> +	spi_nor_debugfs_register(nor);
> 
> I think you should register this after mtd_device_register() to be sure
> the probe would not fail with these debugfs entries still in place. Or
> clean up before returning errors in the code below. Otherwise access to
> the debugfs entires would cause you to access a nor struct that is no
> longer there.

Ohh, you are right. I'll probaly drop the unregister altogether and use
devm_add_action().

>> +
>>  	/*
>>  	 * None of the existing parts have > 512B pages, but let's play safe
>>  	 * and add this logic so that if anyone ever adds support for such
>> @@ -3148,6 +3150,8 @@ static int spi_nor_remove(struct spi_mem 
>> *spimem)
>>  {
>>  	struct spi_nor *nor = spi_mem_get_drvdata(spimem);
>> 
>> +	spi_nor_debugfs_unregister(nor);
>> +
>>  	spi_nor_restore(nor);
>> 
>>  	/* Clean up MTD stuff. */
>> diff --git a/drivers/mtd/spi-nor/core.h b/drivers/mtd/spi-nor/core.h
>> index 81c4bb7d3193..d042d745a1f6 100644
>> --- a/drivers/mtd/spi-nor/core.h
>> +++ b/drivers/mtd/spi-nor/core.h
>> @@ -589,4 +589,12 @@ static inline struct spi_nor 
>> *mtd_to_spi_nor(struct mtd_info *mtd)
>>  	return container_of(mtd, struct spi_nor, mtd);
>>  }
>> 
>> +#ifdef CONFIG_DEBUG_FS
>> +void spi_nor_debugfs_register(struct spi_nor *nor);
>> +void spi_nor_debugfs_unregister(struct spi_nor *nor);
>> +#else
>> +static inline void spi_nor_debugfs_register(struct spi_nor *nor) {}
>> +static inline void spi_nor_debugfs_unregister(struct spi_nor *nor) {}
>> +#endif
>> +
>>  #endif /* __LINUX_MTD_SPI_NOR_INTERNAL_H */
>> diff --git a/drivers/mtd/spi-nor/debugfs.c 
>> b/drivers/mtd/spi-nor/debugfs.c
>> new file mode 100644
>> index 000000000000..61d6d90eda13
>> --- /dev/null
>> +++ b/drivers/mtd/spi-nor/debugfs.c
>> @@ -0,0 +1,241 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +
>> +#include <linux/mtd/spi-nor.h>
>> +#include <linux/spi/spi.h>
>> +#include <linux/spi/spi-mem.h>
>> +#include <linux/debugfs.h>
>> +
>> +#include "core.h"
>> +
>> +static struct dentry *rootdir;
>> +
>> +#define SNOR_F_NAME(name) [ilog2(SNOR_F_##name)] = #name
>> +static const char *const snor_f_names[] = {
>> +	SNOR_F_NAME(HAS_SR_TB),
>> +	SNOR_F_NAME(NO_OP_CHIP_ERASE),
>> +	SNOR_F_NAME(BROKEN_RESET),
>> +	SNOR_F_NAME(4B_OPCODES),
>> +	SNOR_F_NAME(HAS_4BAIT),
>> +	SNOR_F_NAME(HAS_LOCK),
>> +	SNOR_F_NAME(HAS_16BIT_SR),
>> +	SNOR_F_NAME(NO_READ_CR),
>> +	SNOR_F_NAME(HAS_SR_TB_BIT6),
>> +	SNOR_F_NAME(HAS_4BIT_BP),
>> +	SNOR_F_NAME(HAS_SR_BP3_BIT6),
>> +	SNOR_F_NAME(IO_MODE_EN_VOLATILE),
>> +	SNOR_F_NAME(SOFT_RESET),
>> +	SNOR_F_NAME(SWP_IS_VOLATILE),
>> +};
>> +#undef SNOR_F_NAME
> 
> Huh, clever! Took me some time to get what this is doing. But I wonder
> if there is a way to do this so we don't have to update in 2 locations
> when adding a new flag. If not, please at least add a comment on enum
> spi_nor_option_flags to remind people to also add the flag here.

Sure can add a comment.

> 
> But I wonder if we really need this instead of doing just:
> 
> 	static const char *snor_f_names[] = {
> 		"HAS_SR_TB",
> 		"NO_OP_CHIP_ERASE",
> 		...
> 	};
> 
> Since if we have to keep this and enum spi_nor_option_flags in sync,
> might as well keep things simple.

But then the compiler wont help us catching renames and reorders.

>> +
>> +static const char *spi_nor_protocol_name(enum spi_nor_protocol proto)
>> +{
>> +	switch (proto) {
>> +	case SNOR_PROTO_1_1_1:     return "1S-1S-1S";
>> +	case SNOR_PROTO_1_1_2:     return "1S-1S-2S";
>> +	case SNOR_PROTO_1_1_4:     return "1S-1S-4S";
>> +	case SNOR_PROTO_1_1_8:     return "1S-1S-8S";
>> +	case SNOR_PROTO_1_2_2:     return "1S-2S-2S";
>> +	case SNOR_PROTO_1_4_4:     return "1S-4S-4S";
>> +	case SNOR_PROTO_1_8_8:     return "1S-8S-8S";
>> +	case SNOR_PROTO_2_2_2:     return "2S-2S-2S";
>> +	case SNOR_PROTO_4_4_4:     return "4S-4S-4S";
>> +	case SNOR_PROTO_8_8_8:     return "8S-8S-8S";
>> +	case SNOR_PROTO_1_1_1_DTR: return "1D-1D-1D";
>> +	case SNOR_PROTO_1_2_2_DTR: return "1D-2D-2D";
>> +	case SNOR_PROTO_1_4_4_DTR: return "1D-4D-4D";
>> +	case SNOR_PROTO_1_8_8_DTR: return "1D-8D-8D";
>> +	case SNOR_PROTO_8_8_8_DTR: return "8D-8D-8D";
> 
> Okay. Though this reminds me that we have no way to specify mixed DTR
> modes like 1S-8D-8D. But that is a problem for another time.
> 
>> +	}
>> +
>> +	return "<unknown>";
>> +}
>> +
>> +static void spi_nor_print_flags(struct seq_file *s, unsigned long 
>> flags,
>> +				const char *const *names, int names_len)
> 
> Do you see a need to make this generic? Why not just use snor_f_names
> directly?

There might be more flags in the future, so why should I make
this unnecessarily specific? ;)

>> +{
>> +	bool sep = false;
>> +	int i;
>> +
>> +	for (i = 0; i < sizeof(flags) * BITS_PER_BYTE; i++) {
>> +		if (!(flags & BIT(i)))
>> +			continue;
>> +		if (sep)
>> +			seq_puts(s, "|");
> 
> I have not tried running this yet, but I think putting spaces around 
> the
> '|' would make things easier to read.

Yeah and there are also no linewraps, it's just for debugging.
No need to win a beauty contest ;)

flags		HAS_16BIT_SR|NO_READ_CR|SOFT_RESET
vs
flags		HAS_16BIT_SR | NO_READ_CR | SOFT_RESET

I'm fine with either. Can add the spaces.

>> +		sep = true;
>> +		if (i < names_len && names[i])
>> +			seq_puts(s, names[i]);
>> +		else
>> +			seq_printf(s, "1<<%d", i);
> 
> Okay, so this is in case we _don't_ keep snor_f_names in sync.
> 
>> +	}
>> +}
>> +
>> +static int spi_nor_params_show(struct seq_file *s, void *data)
>> +{
>> +	struct spi_nor *nor = s->private;
>> +	struct spi_nor_flash_parameter *params = nor->params;
>> +	struct spi_nor_erase_map *erase_map = &params->erase_map;
>> +	struct spi_nor_erase_region *region;
>> +	const struct flash_info *info = nor->info;
>> +	char buf[16], *str;
>> +	int i;
>> +
>> +	seq_printf(s, "name\t\t%s\n", info->name);
>> +	seq_printf(s, "id\t\t%*phN\n", info->id_len, nor->info->id);
>> +	string_get_size(params->size, 1, STRING_UNITS_2, buf, sizeof(buf));
>> +	seq_printf(s, "size\t\t%s\n", buf);
>> +	seq_printf(s, "write size\t%u\n", params->writesize);
>> +	seq_printf(s, "page size\t%u\n", params->page_size);
>> +	seq_printf(s, "address width\t%u\n", nor->addr_width);
>> +
>> +	seq_puts(s, "flags\t\t");
>> +	spi_nor_print_flags(s, nor->flags, snor_f_names, 
>> sizeof(snor_f_names));
>> +	seq_puts(s, "\n");
>> +
>> +	seq_puts(s, "\nopcodes\n");
>> +	seq_printf(s, " read\t\t%02x\n", nor->read_opcode);
> 
> Should you prefix hex numbers with "0x" to clarify their base? If
> someone sees opcode is 12 they might not be sure if this is in decimal
> or hex. I am not sure what the convention for this usually is, if there
> even is one. Same for other hex numbers printed below.

Yeah, I wasn't sure about that either. The target audience are
developers so I just dropped the prefix (or suffix 'h'). I'll
re-add the prefix, though.

>> +	seq_printf(s, "  dummy cycles\t%d\n", nor->read_dummy);
>> +	seq_printf(s, " erase\t\t%02x\n", nor->erase_opcode);
>> +	seq_printf(s, " program\t%02x\n", nor->program_opcode);

.. esp. because the bases are mixed here.

>> +
>> +	switch (nor->cmd_ext_type) {
>> +	case SPI_NOR_EXT_NONE:
>> +		str = "none";
>> +		break;
>> +	case SPI_NOR_EXT_REPEAT:
>> +		str = "repeat";
>> +		break;
>> +	case SPI_NOR_EXT_INVERT:
>> +		str = "invert";
>> +		break;
>> +	default:
>> +		str = "<unknown>";
>> +		break;
>> +	}
>> +	seq_printf(s, " 8D extension\t%s\n", str);
> 
> You might only want to print this if the flash is 8D capable to avoid
> confusion. But I am not sure how easy/difficult that would be, so I
> leave that up to you.

This is parsed from the SFDP regardless of the mode, so it might be
helpful even if it's unused. I reckon upon the knowledge of the
developer :)

>> +
>> +	seq_puts(s, "\nprotocols\n");
>> +	seq_printf(s, " read\t\t%s\n",
>> +		   spi_nor_protocol_name(nor->read_proto));
>> +	seq_printf(s, " write\t\t%s\n",
>> +		   spi_nor_protocol_name(nor->write_proto));
>> +	seq_printf(s, " register\t%s\n",
>> +		   spi_nor_protocol_name(nor->reg_proto));
>> +
>> +	seq_puts(s, "\nerase commands\n");
>> +	for (i = 0; i < SNOR_ERASE_TYPE_MAX; i++) {
>> +		struct spi_nor_erase_type *et = &erase_map->erase_type[i];
>> +
>> +		if (et->size) {
>> +			string_get_size(et->size, 1, STRING_UNITS_2, buf,
>> +					sizeof(buf));
>> +			seq_printf(s, " %02x (%s) [%d]\n", et->opcode, buf, i);
>> +		}
>> +	}
>> +
>> +	if (!(nor->flags & SNOR_F_NO_OP_CHIP_ERASE)) {
>> +		string_get_size(params->size, 1, STRING_UNITS_2, buf, sizeof(buf));
>> +		seq_printf(s, " %02x (%s)\n", SPINOR_OP_CHIP_ERASE, buf);
>> +	}
>> +
>> +	seq_puts(s, "\nsector map\n");
>> +	seq_puts(s, " region              | erase mask | flags\n");
>> +	seq_puts(s, " --------------------+------------+----------\n");
>> +	for (region = erase_map->regions;
>> +	     region;
>> +	     region = spi_nor_region_next(region)) {
>> +		u64 start = region->offset & ~SNOR_ERASE_FLAGS_MASK;
>> +		u64 flags = region->offset & SNOR_ERASE_FLAGS_MASK;
>> +		u64 end = start + region->size - 1;
>> +
>> +		seq_printf(s, " %08llx - %08llx |     [%c%c%c%c] | %s\n",
>> +			   start, end,
>> +			   flags & BIT(0) ? '0' : ' ',
>> +			   flags & BIT(1) ? '1' : ' ',
>> +			   flags & BIT(2) ? '2' : ' ',
>> +			   flags & BIT(3) ? '3' : ' ',
>> +			   flags & SNOR_OVERLAID_REGION ? "overlaid" : "");
>> +	}
>> +
>> +	return 0;
>> +}
>> +DEFINE_SHOW_ATTRIBUTE(spi_nor_params);
>> +
>> +static void spi_nor_print_read_cmd(struct seq_file *s, u32 cap,
>> +				   struct spi_nor_read_command *cmd)
>> +{
>> +	seq_printf(s, "%s%s\n", spi_nor_protocol_name(cmd->proto),
>> +		   cap == SNOR_HWCAPS_READ_FAST ? " (fast read)" : "");
>> +	seq_printf(s, "  opcode\t%02x\n", cmd->opcode);
>> +	seq_printf(s, "  mode cycles\t%02x\n", cmd->num_mode_clocks);
>> +	seq_printf(s, "  dummy cycles\t%02x\n", cmd->num_wait_states);
>> +}
>> +
>> +static void spi_nor_print_pp_cmd(struct seq_file *s,
>> +				 struct spi_nor_pp_command *cmd)
>> +{
>> +	seq_printf(s, "%s\n", spi_nor_protocol_name(cmd->proto));
>> +	seq_printf(s, "  opcode\t%02x\n", cmd->opcode);
>> +}
>> +
>> +static int spi_nor_capabilities_show(struct seq_file *s, void *data)
>> +{
>> +	struct spi_nor *nor = s->private;
>> +	struct spi_nor_flash_parameter *params = nor->params;
>> +	u32 hwcaps = params->hwcaps.mask;
>> +	int i, cmd;
>> +
>> +	seq_puts(s, "Supported read modes by the flash\n");
>> +	for (i = 0; i < sizeof(hwcaps) * BITS_PER_BYTE; i++) {
>> +		if (!(hwcaps & BIT(i)))
>> +			continue;
>> +
>> +		cmd = spi_nor_hwcaps_read2cmd(BIT(i));
>> +		if (cmd < 0)
>> +			continue;
>> +
>> +		spi_nor_print_read_cmd(s, BIT(i), &params->reads[cmd]);
>> +		hwcaps &= ~BIT(i);
>> +	}
>> +
>> +	seq_puts(s, "\nSupported page program modes by the flash\n");
>> +	for (i = 0; i < sizeof(hwcaps) * BITS_PER_BYTE; i++) {
>> +		if (!(hwcaps & BIT(i)))
>> +			continue;
>> +
>> +		cmd = spi_nor_hwcaps_pp2cmd(BIT(i));
>> +		if (cmd < 0)
>> +			continue;
>> +
>> +		spi_nor_print_pp_cmd(s, &params->page_programs[cmd]);
>> +		hwcaps &= ~BIT(i);
>> +	}
>> +
>> +	if (hwcaps)
>> +		seq_printf(s, "\nunknown hwcaps %x\n", hwcaps);
>> +
>> +	return 0;
>> +}
>> +DEFINE_SHOW_ATTRIBUTE(spi_nor_capabilities);
>> +
>> +void spi_nor_debugfs_register(struct spi_nor *nor)
>> +{
>> +	struct dentry *d;
>> +
>> +	/* Create rootdir once. Will never be deleted again. */
>> +	if (!rootdir)
>> +		rootdir = debugfs_create_dir("spi-nor", NULL);
>> +
>> +	d = debugfs_create_dir(dev_name(nor->dev), rootdir);
>> +	nor->debugfs_root = d;
>> +
>> +	debugfs_create_file("params", 0444, d, nor, &spi_nor_params_fops);
>> +	debugfs_create_file("capabilities", 0444, d, nor,
>> +			    &spi_nor_capabilities_fops);
>> +}
>> +
>> +void spi_nor_debugfs_unregister(struct spi_nor *nor)
>> +{
>> +	debugfs_remove(nor->debugfs_root);
>> +	nor->debugfs_root = NULL;
>> +}
>> diff --git a/include/linux/mtd/spi-nor.h b/include/linux/mtd/spi-nor.h
>> index 5e25a7b75ae2..7d43447768ee 100644
>> --- a/include/linux/mtd/spi-nor.h
>> +++ b/include/linux/mtd/spi-nor.h
>> @@ -365,6 +365,7 @@ struct spi_nor_flash_parameter;
>>   * @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
>> + * @debugfs_root:	pointer to the debugfs directory
>>   * @controller_ops:	SPI NOR controller driver specific operations.
>>   * @params:		[FLASH-SPECIFIC] SPI NOR flash parameters and settings.
>>   *                      The structure includes legacy flash 
>> parameters and
>> @@ -394,6 +395,7 @@ struct spi_nor {
>>  	u32			flags;
>>  	enum spi_nor_cmd_ext	cmd_ext_type;
>>  	struct sfdp		*sfdp;
>> +	struct dentry		*debugfs_root;
>> 
>>  	const struct spi_nor_controller_ops *controller_ops;
>> 
>> --
>> 2.30.2
>> 

-- 
-michael

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