Re: [PATCH RFC 2/3] mmc: core: add new cap for 3.3V only DDR MMCs

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Am 11.08.2016 um 13:12 schrieb Jaehoon Chung:
On 08/07/2016 11:07 AM, Shawn Lin wrote:
在 2016/8/6 22:18, Stefan Wahren 写道:
Hi Marek,

Marek Vasut <marex@xxxxxxx> hat am 6. August 2016 um 15:14 geschrieben:


On 08/06/2016 02:55 PM, Stefan Wahren wrote:
This patch based on the work of Fabio Estevam:
"[PATCH v2] mmc: core: Do not set mmc voltage to 1.8V when
'no-1-8-v' is present"

It adds the support for 3.3V only DDR MMC hosts.

Do such cards even exist ? Do you have a link where I can find some ?

i never said anything about SD cards. I mean eMMC modules which usually have 8
data pins like this one [1].

Please don't blame me if it's not compatible to i.MX28. It's only an example.

[1] -
http://datasheet.octopart.com/THGBM3G4D1FBAIGH2H-Toshiba-datasheet-20748880.pdf


I download the datasheet you mentioned, and I explicitly see it
describe 1V8 everywhere, especially for the section of "ELECTRICAL
CHARACTERISTICS".

I never see one eMMC claiming DDR52 capability but doesn't support 1V8
so far. Could you kindly share me the part number of the eMMC you are
using? :)



Signed-off-by: Stefan Wahren <stefan.wahren@xxxxxxxx>
---
 drivers/mmc/core/host.c  |    2 ++
 drivers/mmc/core/mmc.c   |    6 ++++++
 include/linux/mmc/host.h |    1 +
 3 files changed, 9 insertions(+)

Changes to Fabio's patch:
- rebase to current linux-next
- rename DT property to mmc-ddr-3_3v
- use EXT_CSD_CARD_TYPE_DDR_52 instead of new define

diff --git a/drivers/mmc/core/host.c b/drivers/mmc/core/host.c
index 98f25ff..4c971de 100644
--- a/drivers/mmc/core/host.c
+++ b/drivers/mmc/core/host.c
@@ -301,6 +301,8 @@ int mmc_of_parse(struct mmc_host *host)
     if (of_property_read_bool(np, "wakeup-source") ||
         of_property_read_bool(np, "enable-sdio-wakeup")) /* legacy */
         host->pm_caps |= MMC_PM_WAKE_SDIO_IRQ;
+    if (of_property_read_bool(np, "mmc-ddr-3_3v"))
+        host->caps2 |= MMC_CAP2_3_3V_ONLY_DDR;
     if (of_property_read_bool(np, "mmc-ddr-1_8v"))
         host->caps |= MMC_CAP_1_8V_DDR;
     if (of_property_read_bool(np, "mmc-ddr-1_2v"))
diff --git a/drivers/mmc/core/mmc.c b/drivers/mmc/core/mmc.c
index f2d185c..8a933d5 100644
--- a/drivers/mmc/core/mmc.c
+++ b/drivers/mmc/core/mmc.c
@@ -210,6 +210,12 @@ static void mmc_select_card_type(struct mmc_card *card)
         avail_type |= EXT_CSD_CARD_TYPE_HS_52;
     }

+    if (caps2 & MMC_CAP2_3_3V_ONLY_DDR &&
+        card_type & EXT_CSD_CARD_TYPE_DDR_1_8V) {
+        hs_max_dtr = MMC_HIGH_DDR_MAX_DTR;
+        avail_type |= EXT_CSD_CARD_TYPE_DDR_52;
+    }

did you know EXT_CSD_CARD_TYPE_DDR_52 -> TYPE_DDR_1_8V and TYPE_DDR_1_2V?

Thanks for pointing out. Fabio's patch was better here.

As i wrote to Shawn the subject line is incorrect. I want to add 3.3V only support for hosts not for "card".

According to the comments EXT_CSD_CARD_TYPE_DDR_1_8V stands for 1.8V or 3.3V. So i better add EXT_CSD_CARD_TYPE_DDR_3_3V_ONLY even the "card" supports 1.8V.

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