On 7 January 2013 16:10, Johan Rudholm <johan.rudholm@xxxxxxxxxxxxxx> wrote:
> When switching SD and SDIO cards from 3.3V to 1.8V signal levels, the
> clock should be gated for 5 ms during the step. After enabling the
> clock, the host should wait for at least 1 ms before checking for
> failure. Failure by the card to switch is indicated by dat[0:3] being
> pulled low. The host should check for this condition and power-cycle
> the card if failure is indicated.
>
> Add a retry mechanism for the SDIO case.
>
> If the voltage switch fails repeatedly, give up and continue the
> initialization using the original voltage.
>
> This patch places a couple of requirements on the host driver:
>
> 1) mmc_set_ios with ios.clock = 0 must gate the clock
> 2) mmc_power_off must actually cut the power to the card
> 3) The card_busy host_ops member must be implemented
>
> if these requirements are not fulfilled, the 1.8V signal voltage switch
> will still be attempted but may not be successful.
>
> Signed-off-by: Johan Rudholm <johan.rudholm@xxxxxxxxxxxxxx>
> Signed-off-by: Kevin Liu <kliu5@xxxxxxxxxxx>
> Signed-off-by: Ulf Hansson <ulf.hansson@xxxxxxxxxx>
> ---
> drivers/mmc/core/core.c | 83 +++++++++++++++++++++++++++++++++++++++++------
> drivers/mmc/core/sd.c | 21 +++++++++---
> drivers/mmc/core/sdio.c | 20 ++++++++++--
> 3 files changed, 107 insertions(+), 17 deletions(-)
>
> diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
> index 90f8e11..0894a2f 100644
> --- a/drivers/mmc/core/core.c
> +++ b/drivers/mmc/core/core.c
> @@ -1238,6 +1238,7 @@ int mmc_set_signal_voltage(struct mmc_host *host, int signal_voltage)
> {
> struct mmc_command cmd = {0};
> int err = 0;
> + u32 clock;
>
> BUG_ON(!host);
>
> @@ -1245,20 +1246,82 @@ int mmc_set_signal_voltage(struct mmc_host *host, int signal_voltage)
> * Send CMD11 only if the request is to switch the card to
> * 1.8V signalling.
> */
> - if (signal_voltage != MMC_SIGNAL_VOLTAGE_330) {
> - cmd.opcode = SD_SWITCH_VOLTAGE;
> - cmd.arg = 0;
> - cmd.flags = MMC_RSP_R1 | MMC_CMD_AC;
> + if (signal_voltage == MMC_SIGNAL_VOLTAGE_330)
> + return __mmc_set_signal_voltage(host, signal_voltage);
>
> - err = mmc_wait_for_cmd(host, &cmd, 0);
> - if (err)
> - return err;
> + /*
> + * If we cannot switch voltages, return failure so the caller
> + * can continue without UHS mode
> + */
> + if (!host->ops->start_signal_voltage_switch)
> + return -EPERM;
> + if (!host->ops->card_busy)
> + pr_warning("%s: cannot verify signal voltage switch\n",
> + mmc_hostname(host));
> +
> + cmd.opcode = SD_SWITCH_VOLTAGE;
> + cmd.arg = 0;
> + cmd.flags = MMC_RSP_R1 | MMC_CMD_AC;
> +
> + err = mmc_wait_for_cmd(host, &cmd, 0);
> + if (err)
> + return err;
>
> - if (!mmc_host_is_spi(host) && (cmd.resp[0] & R1_ERROR))
> - return -EIO;
> + if (!mmc_host_is_spi(host) && (cmd.resp[0] & R1_ERROR))
> + return -EIO;
> +
> + mmc_host_clk_hold(host);
> + /*
> + * The card should drive cmd and dat[0:3] low immediately
> + * after the response of cmd11, but wait 1 ms to be sure
> + */
> + mmc_delay(1);
> + if (host->ops->card_busy && !host->ops->card_busy(host)) {
> + err = -EAGAIN;
> + goto power_cycle;
> }
> + /*
> + * During a signal voltage level switch, the clock must be gated
> + * for 5 ms according to the SD spec
> + */
> + clock = host->ios.clock;
> + host->ios.clock = 0;
> + mmc_set_ios(host);
>
> - return __mmc_set_signal_voltage(host, signal_voltage);
> + if (__mmc_set_signal_voltage(host, signal_voltage)) {
> + /*
> + * Voltages may not have been switched, but we've already
> + * sent CMD11, so a power cycle is required anyway
> + */
> + err = -EAGAIN;
> + goto power_cycle;
> + }
> +
> + /* Keep clock gated for at least 5 ms */
> + mmc_delay(5);
> + host->ios.clock = clock;
> + mmc_set_ios(host);
> +
> + /* Wait for at least 1 ms according to spec */
> + mmc_delay(1);
> +
> + /*
> + * Failure to switch is indicated by the card holding
> + * dat[0:3] low
> + */
> + if (host->ops->card_busy && host->ops->card_busy(host))
> + err = -EAGAIN;
> +
> +power_cycle:
> + if (err) {
> + pr_debug("%s: Signal voltage switch failed, "
> + "power cycling card\n", mmc_hostname(host));
> + mmc_power_cycle(host);
> + }
> +
> + mmc_host_clk_release(host);
> +
> + return err;
> }
>
> /*
> diff --git a/drivers/mmc/core/sd.c b/drivers/mmc/core/sd.c
> index 0cc1b26..f5729b0 100644
> --- a/drivers/mmc/core/sd.c
> +++ b/drivers/mmc/core/sd.c
> @@ -713,6 +713,14 @@ int mmc_sd_get_cid(struct mmc_host *host, u32 ocr, u32 *cid, u32 *rocr)
> {
> int err;
> u32 max_current;
> + int retries = 10;
> +
> +try_again:
> + if (!retries) {
> + ocr &= ~SD_OCR_S18R;
> + pr_warning("%s: Skipping voltage switch\n",
> + mmc_hostname(host));
> + }
>
> /*
> * Since we're changing the OCR value, we seem to
> @@ -734,9 +742,10 @@ int mmc_sd_get_cid(struct mmc_host *host, u32 ocr, u32 *cid, u32 *rocr)
>
> /*
> * If the host supports one of UHS-I modes, request the card
> - * to switch to 1.8V signaling level.
> + * to switch to 1.8V signaling level. If the card has failed
> + * repeatedly to switch however, skip this.
> */
> - if (host->caps & (MMC_CAP_UHS_SDR12 | MMC_CAP_UHS_SDR25 |
> + if (retries && host->caps & (MMC_CAP_UHS_SDR12 | MMC_CAP_UHS_SDR25 |
> MMC_CAP_UHS_SDR50 | MMC_CAP_UHS_SDR104 | MMC_CAP_UHS_DDR50))
> ocr |= SD_OCR_S18R;
>
> @@ -748,7 +757,6 @@ int mmc_sd_get_cid(struct mmc_host *host, u32 ocr, u32 *cid, u32 *rocr)
> if (max_current > 150)
> ocr |= SD_OCR_XPC;
>
> -try_again:
> err = mmc_send_app_op_cond(host, ocr, rocr);
> if (err)
> return err;
> @@ -760,8 +768,11 @@ try_again:
> if (!mmc_host_is_spi(host) && rocr &&
> ((*rocr & 0x41000000) == 0x41000000)) {
> err = mmc_set_signal_voltage(host, MMC_SIGNAL_VOLTAGE_180);
> - if (err) {
> - ocr &= ~SD_OCR_S18R;
> + if (err == -EAGAIN) {
> + retries--;
> + goto try_again;
> + } else if (err) {
> + retries = 0;
> goto try_again;
> }
> }
> diff --git a/drivers/mmc/core/sdio.c b/drivers/mmc/core/sdio.c
> index 0c84e0f..494569b 100644
> --- a/drivers/mmc/core/sdio.c
> +++ b/drivers/mmc/core/sdio.c
> @@ -583,10 +583,19 @@ static int mmc_sdio_init_card(struct mmc_host *host, u32 ocr,
> {
> struct mmc_card *card;
> int err;
> + int retries = 10;
>
> BUG_ON(!host);
> WARN_ON(!host->claimed);
>
> +try_again:
> + if (!retries) {
> + pr_warning("%s: Skipping voltage switch\n",
> + mmc_hostname(host));
> + ocr &= ~R4_18V_PRESENT;
> + host->ocr &= ~R4_18V_PRESENT;
> + }
> +
> /*
> * Inform the card of the voltage
> */
> @@ -645,13 +654,20 @@ static int mmc_sdio_init_card(struct mmc_host *host, u32 ocr,
> * systems that claim 1.8v signalling in fact do not support
> * it.
> */
> - if ((ocr & R4_18V_PRESENT) &&
> + if (!powered_resume && (ocr & R4_18V_PRESENT) &&
> (host->caps &
> (MMC_CAP_UHS_SDR12 | MMC_CAP_UHS_SDR25 |
> MMC_CAP_UHS_SDR50 | MMC_CAP_UHS_SDR104 |
> MMC_CAP_UHS_DDR50))) {
> err = mmc_set_signal_voltage(host, MMC_SIGNAL_VOLTAGE_180);
> - if (err) {
> + if (err == -EAGAIN) {
> + sdio_reset(host);
> + mmc_go_idle(host);
> + mmc_send_if_cond(host, host->ocr_avail);
> + mmc_remove_card(card);
> + retries--;
> + goto try_again;
> + } else if (err) {
> ocr &= ~R4_18V_PRESENT;
> host->ocr &= ~R4_18V_PRESENT;
> }
> --
> 1.7.10
>
This looks good Johan, nice work!
Kind regards
Ulf Hansson
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