[PATCH] mci: only write blocks when card out of programming mode
Ahmad Fatoum
a.fatoum at pengutronix.de
Wed Dec 14 01:47:10 PST 2022
On 13.12.22 15:12, Ahmad Fatoum wrote:
> 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);
This should've been a dev_dbg...
> +
> + 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)
--
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