[PATCH 1/1] Implementation for knowing speed_class of inserted SD card from user space

[PATCH 1/1] Implementation for knowing speed_class of inserted SD card from user space

[Mahadev Cholachagudda]

Dear All,

The below patch allows an application to know the speed_class of the
inserted SD card. Since the MMC cards do not specify speed_class, I'm
making the speed_class to indicate as 0xFF. The coding of the
speed_class is same as present in the SD Simplified specification.

simplified SD spec:
http://www.sdcard.org/developers/tech/sdcard/pls/Simplified_Physical_Layer_Spec.pdf

See page 65 and 66

SPEED_CLASS
This 8-bit field indicates the Speed Class and the value can be
calculated by Pw/2.
SPEED_CLASS Value Definition
00h Class 0
01h Class 2
02h Class 4
03h Class 6
04h – FFh Reserved
Table 4-38: Speed Class Code Field

The changes were tested in our platform, which displayed the proper
speed_class for inserted SD cards (6 of them were tested) and one
MMCMobile card.

The speed_class can be known by looking at sysfs entries at :
/sys/devices/platform/nx_sdiomc.0/mmc_host/mmc0/mmc0:XXXX/speed_class

	This file contains the speed class of the SD/MMC card that is
inserted. Please note that, speed_class is not applicable for MMC
cards. This file contains a hexadecimal number. Interpretation shall
be like as below:
0x00 à Class 0
0x01 à Class 2
0x02 à Class 4
0x03 à Class 6
0x04 to 0xFF à Reserved (currently, for MMC based cards, it is 0xFF)

(where in nx_sdiomc.0 is our platform driver for sdhci)

Let me know if you have any comments/suggestions?

Regards,
Mahadev K Cholachagudda

diff -urNd linux-orig/drivers/mmc/core/mmc.c
linux-current/drivers/mmc/core/mmc.c
--- linux-orig/drivers/mmc/core/mmc.c	2009-09-30 16:52:16.973273403 +0530
+++ linux-current/drivers/mmc/core/mmc.c	2009-09-30 17:06:48.321273501 +0530
@@ -258,6 +258,7 @@
 MMC_DEV_ATTR(name, "%s\n", card->cid.prod_name);
 MMC_DEV_ATTR(oemid, "0x%04x\n", card->cid.oemid);
 MMC_DEV_ATTR(serial, "0x%08x\n", card->cid.serial);
+MMC_DEV_ATTR(speed_class, "0x%02x\n", card->speed_class);

 static struct attribute *mmc_std_attrs[] = {
 	&dev_attr_cid.attr,
@@ -269,6 +270,7 @@
 	&dev_attr_name.attr,
 	&dev_attr_oemid.attr,
 	&dev_attr_serial.attr,
+	&dev_attr_speed_class.attr,
 	NULL,
 };

@@ -454,6 +456,12 @@
 		mmc_set_bus_width(card->host, bus_width);
 	}

+	/*
+	 * to indicate speed_class reserved, as MMC card do not indicate
+	 * any speed_class
+	 * */
+	card->speed_class = 0xFF;
+
 	if (!oldcard)
 		host->card = card;

diff -urNd linux-orig/drivers/mmc/core/sd.c linux-current/drivers/mmc/core/sd.c
--- linux-orig/drivers/mmc/core/sd.c	2009-09-30 16:52:10.588335882 +0530
+++ linux-current/drivers/mmc/core/sd.c	2009-09-30 17:03:59.458273462 +0530
@@ -294,6 +294,7 @@
 MMC_DEV_ATTR(name, "%s\n", card->cid.prod_name);
 MMC_DEV_ATTR(oemid, "0x%04x\n", card->cid.oemid);
 MMC_DEV_ATTR(serial, "0x%08x\n", card->cid.serial);
+MMC_DEV_ATTR(speed_class, "0x%02x\n", card->speed_class);


 static struct attribute *sd_std_attrs[] = {
@@ -307,6 +308,7 @@
 	&dev_attr_name.attr,
 	&dev_attr_oemid.attr,
 	&dev_attr_serial.attr,
+	&dev_attr_speed_class.attr,
 	NULL,
 };

@@ -508,6 +510,20 @@
 		}
 	}

+	if (!oldcard) {
+		/* get the speed class */
+		u8 *sd_status;
+		sd_status = kmalloc(64, GFP_KERNEL);
+		if(!sd_status)
+			goto free_card;
+
+		err = mmc_app_sd_status(card, sd_status);
+		card->speed_class = sd_status[8];
+		kfree(sd_status);
+		if(err)
+			goto free_card;
+	}
+
 	if (!oldcard)
 		host->card = card;

diff -urNd linux-orig/drivers/mmc/core/sd_ops.c
linux-current/drivers/mmc/core/sd_ops.c
--- linux-orig/drivers/mmc/core/sd_ops.c	2009-09-30 16:52:22.195336136 +0530
+++ linux-current/drivers/mmc/core/sd_ops.c	2009-09-30 17:01:11.901274205 +0530
@@ -348,3 +348,50 @@
 	return 0;
 }

+int mmc_app_sd_status(struct mmc_card *card, u8 *sd_status)
+{
+	int err;
+	struct mmc_request mrq;
+	struct mmc_command cmd;
+	struct mmc_data data;
+	struct scatterlist sg;
+
+	BUG_ON(!card);
+	BUG_ON(!card->host);
+	BUG_ON(!sd_status);
+
+	/* NOTE: caller guarantees sd_status is heap-allocated */
+	err = mmc_app_cmd(card->host, card);
+	if (err)
+		return err;
+
+	memset(&mrq, 0, sizeof(struct mmc_request));
+	memset(&cmd, 0, sizeof(struct mmc_command));
+	memset(&data, 0, sizeof(struct mmc_data));
+
+	mrq.cmd = &cmd;
+	mrq.data = &data;
+
+	cmd.opcode = 13;
+	cmd.arg = 0;
+	cmd.flags = MMC_RSP_SPI_R1 | MMC_RSP_R1 | MMC_CMD_ADTC;
+
+	data.blksz = 64;
+	data.blocks = 1;
+	data.flags = MMC_DATA_READ;
+	data.sg = &sg;
+	data.sg_len = 1;
+
+	sg_init_one(&sg, sd_status, 64);
+
+	mmc_set_data_timeout(&data, card);
+
+	mmc_wait_for_req(card->host, &mrq);
+
+	if (cmd.error)
+		return cmd.error;
+	if (data.error)
+		return data.error;
+	return 0;
+}
+
diff -urNd linux-orig/drivers/mmc/core/sd_ops.h
linux-current/drivers/mmc/core/sd_ops.h
--- linux-orig/drivers/mmc/core/sd_ops.h	2009-09-30 16:52:25.708273492 +0530
+++ linux-current/drivers/mmc/core/sd_ops.h	2009-09-30 16:59:04.767273889 +0530
@@ -19,6 +19,7 @@
 int mmc_app_send_scr(struct mmc_card *card, u32 *scr);
 int mmc_sd_switch(struct mmc_card *card, int mode, int group,
 	u8 value, u8 *resp);
+int mmc_app_sd_status(struct mmc_card *card, u8 *sd_status);

 #endif

diff -urNd linux-orig/include/linux/mmc/card.h
linux-current/include/linux/mmc/card.h
--- linux-orig/include/linux/mmc/card.h	2009-09-30 16:51:59.230273430 +0530
+++ linux-current/include/linux/mmc/card.h	2009-09-30 16:53:54.162273013 +0530
@@ -111,6 +111,7 @@
 	unsigned		num_info;	/* number of info strings */
 	const char		**info;		/* info strings */
 	struct sdio_func_tuple	*tuples;	/* unknown common tuples */
+	u32 speed_class; /* speed_class for SD cards, for MMC, it is always
reserved */

 	struct dentry		*debugfs_root;
 };

Re: [PATCH 1/1] Implementation for knowing speed_class of inserted SD card from user space

[Pierre Ossman]

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On Wed, 30 Sep 2009 17:22:14 +0530
Mahadev Cholachagudda <mgudda@gmail.com> wrote:

> 
> Let me know if you have any comments/suggestions?
> 

I have a few:

1. The obvious one; why? When does user space need to know the speed
rating, and is the speed rating still meaningful after all the layers
in the kernel? Userspace ABI stuff should be added with great care.

2. I think it's better to not show the attribute when it isn't relevant
rather than return 0xFF.

3. Isn't this a SD 2.0 feature? So you should check the version of the
card before populating/showing this field.

Rgds
-- 
     -- Pierre Ossman

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