[PATCH 1/2] mmc: core: enable CMD19 tuning for DDR50 mode

[Barry Song]

2015-08-25 20:05 GMT+08:00 Ulf Hansson <ulf.hansson at linaro.org>:
> On 20 August 2015 at 02:16, Barry Song <21cnbao at gmail.com> wrote:
>> 2015-08-18 1:11 GMT+08:00 Ulf Hansson <ulf.hansson at linaro.org>:
>>> On 11 August 2015 at 10:41, Barry Song <21cnbao at gmail.com> wrote:
>>>> From: Weijun Yang <york.yang at csr.com>
>>>>
>>>> As SD Specifications Part1 Physical Layer Specification Version
>>>> 3.01 says, CMD19 tuning is available for unlocked cards in transfer
>>>> state of 1.8V signaling mode. The small difference between v3.00
>>>> and 3.01 spec means that CMD19 tuning is also available for DDR50
>>>> mode.
>>>
>>> So what happens with cards following the 3.0 spec version, those
>>> doesn't need to support the tuning CMD right? Perhaps that needs to be
>>> addressed in this patch well!?
>>
>> from HW registers of the card, we cann't know whether the HW needs
>> tuning. it is said 3.0.x need tuning, but 3.0 doesn't need.  @weijun,
>> pls fix me if i am wrong.
>> if so, it seems we need a static flag somewhere to indicate whether
>> the tuning is needed. we can't detect to find the tuning requirement.
>
> Another way is to always try doing the tuning for DDR50, but in case
> of errors just ignore them and print a debug/info message!?

Uffe, do you mean something like below:

diff --git a/drivers/mmc/core/sd.c b/drivers/mmc/core/sd.c
index 4e7366a..d4df9f0 100644
--- a/drivers/mmc/core/sd.c
+++ b/drivers/mmc/core/sd.c
@@ -629,8 +629,23 @@ static int mmc_sd_init_uhs_card(struct mmc_card *card)
      */
     if (!mmc_host_is_spi(card->host) &&
         (card->sd_bus_speed == UHS_SDR50_BUS_SPEED ||
-         card->sd_bus_speed == UHS_SDR104_BUS_SPEED))
+         card->sd_bus_speed == UHS_DDR50_BUS_SPEED ||
+         card->sd_bus_speed == UHS_SDR104_BUS_SPEED)) {
         err = mmc_execute_tuning(card);
+
+        /*
+         * As SD Specifications Part1 Physical Layer Specification Version
+         * 3.01 says, CMD19 tuning is available for unlocked cards in transfer
+         * state of 1.8V signaling mode. The small difference between v3.00
+         * and 3.01 spec means that CMD19 tuning is also available for DDR50
+         * mode.
+         */
+        if (err && (card->sd_bus_speed == UHS_DDR50_BUS_SPEED))
+            pr_err("%s: ddr50 tuning failed\n", mmc_hostname(card->host));
+            kfree(status);
+            return 0;
+        }
+    }
 out:
     kfree(status);

diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
index 64b7fdb..382810d 100644
--- a/drivers/mmc/host/sdhci.c
+++ b/drivers/mmc/host/sdhci.c
@@ -1915,6 +1915,7 @@ static int sdhci_execute_tuning(struct mmc_host
*mmc, u32 opcode)
         break;

     case MMC_TIMING_UHS_SDR104:
+    case MMC_TIMING_UHS_DDR50:
         break;

     case MMC_TIMING_UHS_SDR50:

>
> Kind regards
> Uffe

-barry