[PATCH] mci: only write blocks when card out of programming mode
Ahmad Fatoum
a.fatoum at pengutronix.de
Tue Dec 13 06:12:04 PST 2022
eMMC Spec v5.1 (JEDEC Standard No. 84-B51) is quite clear that:
Due to legacy reasons, a Device may still treat CMD24/25 during
prg-state (while busy is active) as a legal or illegal command.
A host should not send CMD24/25 while the Device is in the prg
state and busy is active.
So far, we had never evaluated MMC_CMD_SEND_STATUS. This patch
corrects this and thereby resolves an issue of timed out writes
with the atmel_mci driver:
barebox at SAMA5D4:/ saveenv
ERROR: atmel_mci fc000000.mmc at fc000000.of: command/data timeout
ERROR: atmel_mci fc000000.mmc at fc000000.of: command/data timeout
These issues are not new, but were first reported in 2018[0] along
with a workaround suggesting a delay at the end of atmci_request:
if (cmdidx == MMC_CMD_STOP_TRANSMISSION)
mdelay(5)
Just before the command timing out, we read 0x00c00_0025 from the
status register, which is
CMDRDY | TXRDY | NOTBUSY | XFERDONE | FIFOEMPTY
which suggests the issue is not at the MCI host side, but rather at
the card side. With this patch applied and debugging enabled, this
seems to be confirmed:
barebox at SAMA5D4:/ saveenv
saving environment
mmc1: Ready polling took 0ms
mmc1: Ready polling took 4ms
I compared with AT91Bootstrap[1], U-Boot[2] and Trusted Firmware-A[3]
and all of them poll MCI status after block writes.
The sequence imported here is taken from U-Boot, but instead of doing
it after writes, we do it before them in hope that we need not always
incur the extra delay.
I don't have an answer why this was only necessary on the SAMA5D3/4 and
such issues weren't observed with other drivers. Card was operated
at 50MHz (SD HS) and I didn't observe differences when trying other
cards. I tested this change also on a Beaglebone Black where an
environment is also stored into FAT on a SD-Card operated with 50 MHz:
Ready polling took 0ms for each of the two writes.
[0]: https://lore.barebox.org/barebox/20181102091156.26476-1-s.hauer@pengutronix.de/
[1]: https://github.com/linux4sam/at91bootstrap/blob/v4.0.5/driver/mci_media.c#L1187
[2]: https://github.com/trini/u-boot/blob/v2023.01-rc3/drivers/mmc/mmc_write.c#L181
[3]: https://github.com/ARM-software/arm-trusted-firmware/blob/v2.8.0/drivers/mmc/mmc.c#L718
Signed-off-by: Ahmad Fatoum <a.fatoum at pengutronix.de>
---
For next, not master. I intend to test this change across more devices
in the coming weeks.
---
drivers/mci/mci-core.c | 96 ++++++++++++++++++++++++++++++++++++++++++
include/mci.h | 15 +++++++
2 files changed, 111 insertions(+)
diff --git a/drivers/mci/mci-core.c b/drivers/mci/mci-core.c
index 8cda07e71120..ec78bd33911c 100644
--- a/drivers/mci/mci-core.c
+++ b/drivers/mci/mci-core.c
@@ -74,6 +74,28 @@ static int mci_send_cmd(struct mci *mci, struct mci_cmd *cmd, struct mci_data *d
return host->send_cmd(mci->host, cmd, data);
}
+/**
+ * mci_send_cmd_retry() - send a command to the mmc device, retrying on error
+ *
+ * @dev: device to receive the command
+ * @cmd: command to send
+ * @data: additional data to send/receive
+ * @retries: how many times to retry; mci_send_cmd is always called at least
+ * once
+ * Return: 0 if ok, -ve on error
+ */
+static int mci_send_cmd_retry(struct mci *mci, struct mci_cmd *cmd,
+ struct mci_data *data, unsigned retries)
+{
+ int ret;
+
+ do
+ ret = mci_send_cmd(mci, cmd, data);
+ while (ret && retries--);
+
+ return ret;
+}
+
/**
* @param p Command definition to setup
* @param cmd Valid SD/MMC command (refer MMC_CMD_* / SD_CMD_*)
@@ -119,6 +141,69 @@ static int mci_set_blocklen(struct mci *mci, unsigned len)
static void *sector_buf;
+static int mci_send_status(struct mci *mci, unsigned int *status)
+{
+ struct mci_host *host = mci->host;
+ struct mci_cmd cmd;
+ int ret;
+
+ cmd.cmdidx = MMC_CMD_SEND_STATUS;
+ cmd.resp_type = MMC_RSP_R1;
+ if (!mmc_host_is_spi(host))
+ cmd.cmdarg = mci->rca << 16;
+
+ ret = mci_send_cmd_retry(mci, &cmd, NULL, 4);
+ if (!ret)
+ *status = cmd.response[0];
+
+ return ret;
+}
+
+static int mci_poll_until_ready(struct mci *mci, int timeout_ms)
+{
+ unsigned int status;
+ int err, retries = 0;
+
+ while (1) {
+ err = mci_send_status(mci, &status);
+ if (err)
+ return err;
+
+ /*
+ * Some cards mishandle the status bits, so make sure to
+ * check both the busy indication and the card state.
+ */
+ if ((status & R1_READY_FOR_DATA) &&
+ R1_CURRENT_STATE(status) != R1_STATE_PRG)
+ break;
+
+ if (status & R1_STATUS_MASK) {
+ dev_err(&mci->dev, "Status Error: 0x%08x\n", status);
+ return -EIO;
+ }
+
+ if (retries++ == timeout_ms)
+ break;
+
+ udelay(1000);
+ }
+
+ if (retries >= timeout_ms) {
+ dev_err(&mci->dev, "Timeout waiting card ready\n");
+ return -ETIMEDOUT;
+ }
+
+ /*
+ * With small UART FIFOs and slow CPUs, printing in the loop above
+ * may take enough time to render the polling loop above unnecessary
+ * falsifying the debugging info. Thus we report the retries here.
+ */
+ dev_info(&mci->dev, "Ready polling took %ums\n", retries);
+
+ return 0;
+}
+
+
/**
* Write one or several blocks of data to the card
* @param mci_dev MCI instance
@@ -136,6 +221,17 @@ static int mci_block_write(struct mci *mci, const void *src, int blocknum,
unsigned mmccmd;
int ret;
+ /*
+ * Quoting eMMC Spec v5.1 (JEDEC Standard No. 84-B51):
+ * Due to legacy reasons, a Device may still treat CMD24/25 during
+ * prg-state (while busy is active) as a legal or illegal command.
+ * A host should not send CMD24/25 while the Device is in the prg
+ * state and busy is active.
+ */
+ ret = mci_poll_until_ready(mci, 10 /* ms */);
+ if (ret)
+ return ret;
+
if (blocks > 1)
mmccmd = MMC_CMD_WRITE_MULTIPLE_BLOCK;
else
diff --git a/include/mci.h b/include/mci.h
index d949310fac30..1e53a09d71db 100644
--- a/include/mci.h
+++ b/include/mci.h
@@ -308,8 +308,23 @@
#define EXT_CSD_DDR_BUS_WIDTH_8 6 /* Card is in 8 bit DDR mode */
#define R1_ILLEGAL_COMMAND (1 << 22)
+#define R1_STATUS(x) (x & 0xFFF9A000)
+#define R1_CURRENT_STATE(x) ((x & 0x00001E00) >> 9) /* sx, b (4 bits) */
+#define R1_READY_FOR_DATA (1 << 8) /* sx, a */
#define R1_APP_CMD (1 << 5)
+#define R1_STATUS_MASK (~0x0206BF7F)
+
+#define R1_STATE_IDLE 0
+#define R1_STATE_READY 1
+#define R1_STATE_IDENT 2
+#define R1_STATE_STBY 3
+#define R1_STATE_TRAN 4
+#define R1_STATE_DATA 5
+#define R1_STATE_RCV 6
+#define R1_STATE_PRG 7
+#define R1_STATE_DIS 8
+
#define R1_SPI_IDLE (1 << 0)
#define R1_SPI_ERASE_RESET (1 << 1)
#define R1_SPI_ILLEGAL_COMMAND (1 << 2)
--
2.30.2
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