[PATCH V2] mmc: core: try 1.8v signaling in ddr mode if host and device

[PATCH V2] mmc: core: try 1.8v signaling in ddr mode if host and device

[Chuanxiao Dong]

Even (e)MMC card can support 3.3v to 1.2v vccq in DDR, but not all
host controller can support this, like some of the SDHCI host
which connect to an eMMC device. Some of these host controller
still needs to use 1.8v vccq for supporting DDR mode.

So the sequence will be:
if (host and device can both support 1.2v IO)
	use 1.2v IO;
else if (host and device can both support 1.8v IO)
	use 1.8v IO;
so if host and device can only support 3.3v IO, this is the last choice.

Signed-off-by: Chuanxiao Dong <chuanxiao.dong@intel.com>
Signed-off-by: Yunpeng Gao <yunpeng.gao@intel.com>
---
Changelog V2:
    - For (e)MMC device switching to DDR mode, try 1.2v singaling first. Then
    try 1.8v. If 1.2v and 1.8v are both not supported, use the default 3.3v

 drivers/mmc/core/mmc.c |   20 ++++++++++++++++++--
 1 file changed, 18 insertions(+), 2 deletions(-)

diff --git a/drivers/mmc/core/mmc.c b/drivers/mmc/core/mmc.c
index 793c6f7..aa5180b 100644
--- a/drivers/mmc/core/mmc.c
+++ b/drivers/mmc/core/mmc.c
@@ -988,8 +988,19 @@ static int mmc_select_hs_ddr(struct mmc_card *card)
 	 * 1.8V vccq at 3.3V core voltage (vcc) is not required
 	 * in the JEDEC spec for DDR.
 	 *
-	 * Do not force change in vccq since we are obviously
-	 * working and no change to vccq is needed.
+	 * Even (e)MMC card can support 3.3v to 1.2v vccq, but not all
+	 * host controller can support this, like some of the SDHCI
+	 * controller which connect to an eMMC device. Some of these
+	 * host controller still needs to use 1.8v vccq for supporting
+	 * DDR mode.
+	 *
+	 * So the sequence will be:
+	 * if (host and device can both support 1.2v IO)
+	 *	use 1.2v IO;
+	 * else if (host and device can both support 1.8v IO)
+	 * 	use 1.8v IO;
+	 * so if host and device can only support 3.3v IO, this is the
+	 * last choice.
 	 *
 	 * WARNING: eMMC rules are NOT the same as SD DDR
 	 */
@@ -998,6 +1009,11 @@ static int mmc_select_hs_ddr(struct mmc_card *card)
 				MMC_SIGNAL_VOLTAGE_120);
 		if (err)
 			return err;
+	} else if (card->mmc_avail_type & EXT_CSD_CARD_TYPE_DDR_1_8V) {
+		err = __mmc_set_signal_voltage(host,
+				MMC_SIGNAL_VOLTAGE_180);
+		if (err)
+			return err;
 	}
 
 	mmc_set_timing(host, MMC_TIMING_MMC_DDR52);
-- 
1.7.10.4

Re: [PATCH V2] mmc: core: try 1.8v signaling in ddr mode if host and device

[Ulf Hansson]

On 14 August 2014 11:54, Chuanxiao Dong <chuanxiao.dong@intel.com> wrote:
> Even (e)MMC card can support 3.3v to 1.2v vccq in DDR, but not all
> host controller can support this, like some of the SDHCI host
> which connect to an eMMC device. Some of these host controller
> still needs to use 1.8v vccq for supporting DDR mode.
>
> So the sequence will be:
> if (host and device can both support 1.2v IO)
>         use 1.2v IO;
> else if (host and device can both support 1.8v IO)
>         use 1.8v IO;
> so if host and device can only support 3.3v IO, this is the last choice.
>
> Signed-off-by: Chuanxiao Dong <chuanxiao.dong@intel.com>
> Signed-off-by: Yunpeng Gao <yunpeng.gao@intel.com>
> ---
> Changelog V2:
>     - For (e)MMC device switching to DDR mode, try 1.2v singaling first. Then
>     try 1.8v. If 1.2v and 1.8v are both not supported, use the default 3.3v
>
>  drivers/mmc/core/mmc.c |   20 ++++++++++++++++++--
>  1 file changed, 18 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/mmc/core/mmc.c b/drivers/mmc/core/mmc.c
> index 793c6f7..aa5180b 100644
> --- a/drivers/mmc/core/mmc.c
> +++ b/drivers/mmc/core/mmc.c
> @@ -988,8 +988,19 @@ static int mmc_select_hs_ddr(struct mmc_card *card)
>          * 1.8V vccq at 3.3V core voltage (vcc) is not required
>          * in the JEDEC spec for DDR.
>          *
> -        * Do not force change in vccq since we are obviously
> -        * working and no change to vccq is needed.
> +        * Even (e)MMC card can support 3.3v to 1.2v vccq, but not all
> +        * host controller can support this, like some of the SDHCI
> +        * controller which connect to an eMMC device. Some of these
> +        * host controller still needs to use 1.8v vccq for supporting
> +        * DDR mode.
> +        *
> +        * So the sequence will be:
> +        * if (host and device can both support 1.2v IO)
> +        *      use 1.2v IO;
> +        * else if (host and device can both support 1.8v IO)
> +        *      use 1.8v IO;
> +        * so if host and device can only support 3.3v IO, this is the
> +        * last choice.
>          *
>          * WARNING: eMMC rules are NOT the same as SD DDR
>          */
> @@ -998,6 +1009,11 @@ static int mmc_select_hs_ddr(struct mmc_card *card)
>                                 MMC_SIGNAL_VOLTAGE_120);
>                 if (err)
>                         return err;
> +       } else if (card->mmc_avail_type & EXT_CSD_CARD_TYPE_DDR_1_8V) {

If we encounter errors switching to 1.2V, it would be nice to fall
back and to test with 1.8V.

You may get influenced by the code in mmc_select_hs200(), where a
similar approach is taken.


> +               err = __mmc_set_signal_voltage(host,
> +                               MMC_SIGNAL_VOLTAGE_180);
> +               if (err)
> +                       return err;
>         }
>
>         mmc_set_timing(host, MMC_TIMING_MMC_DDR52);
> --
> 1.7.10.4
>

Kind regards
Uffe