SD cards which conform to Physical Layer Spec v3.01 can support
additional Bus Speed Modes, Driver Strength, and Current Limit
other than the default values. We use CMD6 mode 0 to read these
additional card functions. The values read here will be used
during UHS-I initialization steps.
Signed-off-by: Arindam Nath <arindam.nath@xxxxxxx>
Reviewed-by: Philip Rakity <prakity@xxxxxxxxxxx>
Tested-by: Philip Rakity <prakity@xxxxxxxxxxx>
---
drivers/mmc/core/sd.c | 69 ++++++++++++++++++++++++++++++++++++++++-----
include/linux/mmc/card.h | 4 ++
2 files changed, 65 insertions(+), 8 deletions(-)
diff --git a/drivers/mmc/core/sd.c b/drivers/mmc/core/sd.c
index b0cd285..d4410c9 100644
--- a/drivers/mmc/core/sd.c
+++ b/drivers/mmc/core/sd.c
@@ -189,6 +189,9 @@ static int mmc_decode_scr(struct mmc_card *card)
scr->sda_vsn = UNSTUFF_BITS(resp, 56, 4);
scr->bus_widths = UNSTUFF_BITS(resp, 48, 4);
+ if (scr->sda_vsn == SCR_SPEC_VER_2)
+ /* Check if Physical Layer Spec v3.0 is supported*/
+ scr->sda_spec3 = UNSTUFF_BITS(resp, 47, 1);
if (UNSTUFF_BITS(resp, 55, 1))
card->erased_byte = 0xFF;
@@ -278,25 +281,75 @@ static int mmc_read_switch(struct mmc_card *card)
return -ENOMEM;
}
+ /* Find out the supported Bus Speed Modes. */
err = mmc_sd_switch(card, 0, 0, 1, status);
if (err) {
- /* If the host or the card can't do the switch,
- * fail more gracefully. */
+ /*
+ * If the host or the card can't do the switch,
+ * fail more gracefully.
+ */
if ((err != -EINVAL)
- && (err != -ENOSYS)
- && (err != -EFAULT))
+ && (err != -ENOSYS)
+ && (err != -EFAULT))
goto out;
- printk(KERN_WARNING "%s: problem reading switch "
- "capabilities, performance might suffer.\n",
+ printk(KERN_WARNING "%s: problem reading Bus Speed modes.\n",
mmc_hostname(card->host));
err = 0;
goto out;
}
- if (status[13] & 0x02)
- card->sw_caps.hs_max_dtr = 50000000;
+ if (card->scr.sda_spec3) {
+ card->sw_caps.sd3_bus_mode = status[13];
+
+ /* Find out Driver Strengths supported by the card */
+ err = mmc_sd_switch(card, 0, 2, 1, status);
+ if (err) {
+ /*
+ * If the host or the card can't do the switch,
+ * fail more gracefully.
+ */
+ if ((err != -EINVAL)
+ && (err != -ENOSYS)
+ && (err != -EFAULT))
+ goto out;
+
+ printk(KERN_WARNING "%s: problem reading "
+ "Driver Strength.\n",
+ mmc_hostname(card->host));
+ err = 0;
+
+ goto out;
+ }
+
+ card->sw_caps.sd3_drv_type = status[9];
+
+ /* Find out Current Limits supported by the card */
+ err = mmc_sd_switch(card, 0, 3, 1, status);
+ if (err) {
+ /*
+ * If the host or the card can't do the switch,
+ * fail more gracefully.
+ */
+ if ((err != -EINVAL)
+ && (err != -ENOSYS)
+ && (err != -EFAULT))
+ goto out;
+
+ printk(KERN_WARNING "%s: problem reading "
+ "Current Limit.\n",
+ mmc_hostname(card->host));
+ err = 0;
+
+ goto out;
+ }
+
+ card->sw_caps.sd3_curr_limit = status[7];
+ } else {
+ if (status[13] & 0x02)
+ card->sw_caps.hs_max_dtr = 50000000;
+ }
out:
kfree(status);
diff --git a/include/linux/mmc/card.h b/include/linux/mmc/card.h
index 72a9868..56f4d92 100644
--- a/include/linux/mmc/card.h
+++ b/include/linux/mmc/card.h
@@ -67,6 +67,7 @@ struct mmc_ext_csd {
struct sd_scr {
unsigned char sda_vsn;
+ unsigned char sda_spec3;
unsigned char bus_widths;
#define SD_SCR_BUS_WIDTH_1 (1<<0)
#define SD_SCR_BUS_WIDTH_4 (1<<2)
@@ -80,6 +81,9 @@ struct sd_ssr {
struct sd_switch_caps {
unsigned int hs_max_dtr;
+ unsigned int sd3_bus_mode;
+ unsigned int sd3_drv_type;
+ unsigned int sd3_curr_limit;
};
struct sdio_cccr {
--
1.7.1
--
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