Message-ID: <20150817212452.GA3816@codeaurora.org>
Date:	Mon, 17 Aug 2015 14:24:52 -0700
From:	Mathieu Olivari <mathieu@...eaurora.org>
To:	Bjorn Andersson <bjorn.andersson@...ymobile.com>
Cc:	"robh+dt@...nel.org" <robh+dt@...nel.org>,
	"pawel.moll@....com" <pawel.moll@....com>,
	"mark.rutland@....com" <mark.rutland@....com>,
	"ijc+devicetree@...lion.org.uk" <ijc+devicetree@...lion.org.uk>,
	"galak@...eaurora.org" <galak@...eaurora.org>,
	"linux@....linux.org.uk" <linux@....linux.org.uk>,
	"dwmw2@...radead.org" <dwmw2@...radead.org>,
	"computersforpeace@...il.com" <computersforpeace@...il.com>,
	"agross@...eaurora.org" <agross@...eaurora.org>,
	"sboyd@...eaurora.org" <sboyd@...eaurora.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-mtd@...ts.infradead.org" <linux-mtd@...ts.infradead.org>
Subject: Re: [PATCH 3/3] mtd: add SMEM parser for QCOM platforms

On Fri, Aug 14, 2015 at 10:48:17PM -0700, Bjorn Andersson wrote:
> On Fri 14 Aug 17:46 PDT 2015, Mathieu Olivari wrote:
> 
> > On QCOM platforms using MTD devices storage (such as IPQ806x), SMEM is
> > used to store partition layout. This new parser can now be used to read
> > SMEM and use it to register an MTD layout according to its content.
> > 
> 
> Nice to see another user of the smem code :)
> 
> > diff --git a/drivers/mtd/qcom_smem_part.c b/drivers/mtd/qcom_smem_part.c
> [..]
> > +
> > +/* Processor/host identifier for the application processor */
> > +#define SMEM_HOST_APPS			0
> 
> This makes me wonder if there will ever be an apps partition. I would
> have picked QCOM_SMEM_HOST_ANY, but I don't know what future platforms
> might hold for us.
> 
> 
> And as a side note, I think I will propose that we rename that define
> QCOM_SMEM_GLOBAL.
OK; I'll rename it in QCOM_SMEM_GLOBAL then to be in sync.
> 
> > +
> > +/* SMEM items index */
> > +#define SMEM_AARM_PARTITION_TABLE	9
> > +#define SMEM_BOOT_FLASH_TYPE		421
> > +#define SMEM_BOOT_FLASH_BLOCK_SIZE	424
> > +
> > +/* SMEM Flash types */
> > +#define SMEM_FLASH_NAND			2
> > +#define SMEM_FLASH_SPI			6
> > +
> > +#define SMEM_PART_NAME_SZ		16
> > +#define SMEM_PARTS_MAX			32
> > +
> > +struct smem_partition {
> > +	char name[SMEM_PART_NAME_SZ];
> > +	__le32 start;
> > +	__le32 size;
> > +	__le32 attr;
> > +};
> > +
> > +struct smem_partition_table {
> > +	u8 magic[8];
> > +	__le32 version;
> > +	__le32 len;
> > +	struct smem_partition parts[SMEM_PARTS_MAX];
> > +};
> > +
> > +/* SMEM Magic values in partition table */
> > +static const u8 SMEM_PTABLE_MAGIC[] = {
> > +	0xaa, 0x73, 0xee, 0x55,
> > +	0xdb, 0xbd, 0x5e, 0xe3,
> > +};
> > +
> > +static int qcom_smem_get_flash_blksz(u64 **smem_blksz)
> 
> Instead of passing pointers around I think you should just make this
> function return < 0 for errors and >= 0 for the requested data. You can
> probably still have it as an int, as the current values are well below
> the size of the int.
Good point. Thanks. I'll report it.
> 
> > +{
> > +	int ret;
> > +	size_t size;
> > +
> > +	ret = qcom_smem_get(SMEM_HOST_APPS, SMEM_BOOT_FLASH_BLOCK_SIZE,
> > +			    (void **) smem_blksz, &size);
> > +
> > +	if (ret < 0) {
> > +		pr_err("Unable to read flash blksz from SMEM\n");
> > +		return -ENOENT;
> > +	}
> > +
> > +	if (size != sizeof(**smem_blksz)) {
> > +		pr_err("Invalid flash blksz size in SMEM\n");
> > +		return -EINVAL;
> > +	}
> > +
> > +	return 0;
> > +}
> > +
> > +static int qcom_smem_get_flash_type(u64 **smem_flash_type)
> 
> Same as above.
OK.
> 
> > +{
> > +	int ret;
> > +	size_t size;
> > +
> > +	ret = qcom_smem_get(SMEM_HOST_APPS, SMEM_BOOT_FLASH_TYPE,
> > +			    (void **) smem_flash_type, &size);
> > +
> > +	if (ret < 0) {
> > +		pr_err("Unable to read flash type from SMEM\n");
> > +		return -ENOENT;
> > +	}
> > +
> > +	if (size != sizeof(**smem_flash_type)) {
> > +		pr_err("Invalid flash type size in SMEM\n");
> > +		return -EINVAL;
> > +	}
> > +
> > +	return 0;
> > +}
> > +
> > +static int qcom_smem_get_flash_partitions(struct smem_partition_table **pparts)
> > +{
> > +	int ret;
> > +	size_t size;
> > +
> > +	ret = qcom_smem_get(SMEM_HOST_APPS, SMEM_AARM_PARTITION_TABLE,
> > +			    (void **) pparts, &size);
> > +
> 
> If you don't care about the size just pass NULL as the last argument.
OK.
> 
> > +	if (ret < 0) {
> > +		pr_err("Unable to read partition table from SMEM\n");
> > +		return -ENOENT;
> > +	}
> 
> I think it would be cleaner if you had this function check the magic and
> version and then return the partition pointer. That is:
> 
> static smem_partition *qcom_smem_get_flash_partitions(size_t *count)
> 
> 
> And make *count = le32_to_cpu(table->len); so you don't have to care
> about that below.
> 
> (And use NULL or ERR_PTR for the error paths)
Same; good idea. I'll make the mod.
> 
> > +
> > +	return 0;
> > +}
> > +
> > +static int of_dev_node_match(struct device *dev, void *data)
> > +{
> > +	return dev->of_node == data;
> > +}
> > +
> > +static bool is_spi_device(struct device_node *np)
> > +{
> > +	struct device *dev;
> > +
> > +	dev = bus_find_device(&spi_bus_type, NULL, np, of_dev_node_match);
> > +	if (!dev)
> > +		return false;
> > +
> > +	put_device(dev);
> > +	return true;
> > +}
> > +
> > +static int parse_qcom_smem_partitions(struct mtd_info *master,
> > +				      struct mtd_partition **pparts,
> > +				      struct mtd_part_parser_data *data)
> > +{
> > +	struct smem_partition_table *smem_parts;
> > +	u64 *smem_flash_type, *smem_blksz;
> > +	struct mtd_partition *mtd_parts;
> > +	struct device_node *of_node = data->of_node;
> > +	int i, ret;
> > +
> > +	/*
> > +	 * SMEM will only store the partition table of the boot device.
> > +	 * If this is not the boot device, do not return any partition.
> > +	 */
> 
> I guess this is the result of below checks, but it's not describing
> what's actually done here. I think it should say "only parse
> partitions on the specified memory type" or something like that.
OK.
> 
> > +	ret = qcom_smem_get_flash_type(&smem_flash_type);
> > +	if (ret < 0)
> > +		return ret;
> > +
> > +	if ((*smem_flash_type == SMEM_FLASH_NAND && !mtd_type_is_nand(master))
> > +	    || (*smem_flash_type == SMEM_FLASH_SPI && !is_spi_device(of_node)))
> > +		return 0;
> > +
> > +	/*
> > +	 * Just for sanity purpose, make sure the block size in SMEM matches the
> > +	 * block size of the MTD device
> > +	 */
> 
> Well, this is not only for sanity purpose, as you multiply all sizes
> with this number below...
I'll update the comment.
> 
> > +	ret = qcom_smem_get_flash_blksz(&smem_blksz);
> > +	if (ret < 0)
> > +		return ret;
> > +
> > +	if (*smem_blksz != master->erasesize) {
> > +		pr_err("SMEM block size differs from MTD block size\n");
> > +		return -EINVAL;
> > +	}
> > +
> > +	/* Get partition pointer from SMEM */
> > +	ret = qcom_smem_get_flash_partitions(&smem_parts);
> > +	if (ret < 0)
> > +		return ret;
> > +
> > +	if (memcmp(SMEM_PTABLE_MAGIC, smem_parts->magic,
> > +		   sizeof(SMEM_PTABLE_MAGIC))) {
> > +		pr_err("SMEM partition magic invalid\n");
> > +		return -EINVAL;
> > +	}
> > +
> > +	/* Allocate and populate the mtd structures */
> > +	mtd_parts = kcalloc(le32_to_cpu(smem_parts->len), sizeof(*mtd_parts),
> > +			    GFP_KERNEL);
> > +	if (!mtd_parts)
> > +		return -ENOMEM;
> > +
> > +	for (i = 0; i < smem_parts->len; i++) {
> 
> This might have the wrong endian...
Right. I'll do a le32_to_cpu()
> 
> > +		struct smem_partition *s_part = &smem_parts->parts[i];
> > +		struct mtd_partition *m_part = &mtd_parts[i];
> 
> I think Stephens suggestion was that you assign *pparts before looping
> and then you simply do:
> 
> *pparts = mtd_parts;
> 
> while (len--) {
> 	..
> 
> 	s_part++;
> 	mtd_parts++;
> }
> 
> > +
> > +		m_part->name = s_part->name;
> 
> I tried to follow the mtd code, and I believe that this pointer might
> be freed in free_partition(). If so you must kstrdup it here.
OK.
> 
> > +		m_part->size = le32_to_cpu(s_part->size) * (*smem_blksz);
> > +		m_part->offset = le32_to_cpu(s_part->start) * (*smem_blksz);
> > +
> > +		/*
> > +		 * The last SMEM partition may have its size marked as
> > +		 * something like 0xffffffff, which means "until the end of the
> > +		 * flash device". In this case, truncate it.
> > +		 */
> > +		if (m_part->offset + m_part->size > master->size)
> > +			m_part->size = master->size - m_part->offset;
> > +	}
> > +
> > +	*pparts = mtd_parts;
> > +
> > +	return smem_parts->len;
> 
> Again, this might be in the wrong endian.
Yes.
> 
> > +}
> > +
> > +static struct mtd_part_parser qcom_smem_parser = {
> > +	.owner = THIS_MODULE,
> > +	.parse_fn = parse_qcom_smem_partitions,
> > +	.name = "qcom-smem",
> > +};
> > +
> > +static int __init qcom_smem_parser_init(void)
> > +{
> > +	register_mtd_parser(&qcom_smem_parser);
> > +	return 0;
> > +}
> > +
> > +static void __exit qcom_smem_parser_exit(void)
> > +{
> > +	deregister_mtd_parser(&qcom_smem_parser);
> > +}
> > +
> > +module_init(qcom_smem_parser_init);
> > +module_exit(qcom_smem_parser_exit);
> 
> Mostly unrelated to this patch; This makes me appreciate the
> module_platform_driver() macro, would be nice to see a patch that
> introduces something similar for partition parsers.
> 
> > +
> > +MODULE_LICENSE("GPL");
> 
> Are you sure you don't mean "GPL v2" here?
I'll update it.
> 
> > +MODULE_AUTHOR("Mathieu Olivari <mathieu@...eaurora.org>");
> > +MODULE_DESCRIPTION("Parsing code for SMEM based partition tables");
> 
> Regards,
> Bjorn
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