Hello Ulf,

On Fri, Aug 15, 2014 at 11:05:39AM +0200, Ulf Hansson wrote:

On 15 August 2014 10:38, Uwe Kleine-K?nig
[off-list ref] wrote:

quoted

From: Sascha Hauer <s.hauer@pengutronix.de>

Some eMMC and SD cards implement a DSR register that allows to tune
raise/fall times and drive strength of the CMD and DATA outputs.
The values to use depend on the card in use and the host.
It might be needed to reduce the drive strength to prevent voltage peaks
above the host's specification.

Implement a 'dsr' devicetree property that allows to specify the value
to set the DSR to. For non-dt setups the new members of mmc_host can be
set by board code.

This patch was initially authored by Sascha Hauer. It contains
improvements authored by Markus Niebel and Uwe Kleine-K?nig.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Markus Niebel <redacted>
Signed-off-by: Uwe Kleine-K?nig <redacted>
---
Changes since v3:

 - fix a compiler warning about err not being used.
 - clearified valid range. I didn't write "16-bit value" because the
   value is still expected to be written as 32-bit value in the device
   tree.
 - make host->dsr an u32, which simplified parsing the device tree and
   also makes casting in mmc_set_dsr unnecessary.
---
 Documentation/devicetree/bindings/mmc/mmc.txt |  2 ++
 drivers/mmc/core/host.c                       |  8 ++++++++
 drivers/mmc/core/mmc.c                        |  8 ++++++++
 drivers/mmc/core/mmc_ops.c                    | 20 ++++++++++++++++++++
 drivers/mmc/core/mmc_ops.h                    |  1 +
 drivers/mmc/core/sd.c                         |  8 ++++++++
 include/linux/mmc/card.h                      |  3 ++-
 include/linux/mmc/host.h                      |  3 +++
 8 files changed, 52 insertions(+), 1 deletion(-)

diff --git a/Documentation/devicetree/bindings/mmc/mmc.txt b/Documentation/devicetree/bindings/mmc/mmc.txt
index 3c18001dfd5d..a3fe21f2b709 100644
--- a/Documentation/devicetree/bindings/mmc/mmc.txt
+++ b/Documentation/devicetree/bindings/mmc/mmc.txt

@@ -40,6 +40,8 @@ Optional properties:
 - mmc-hs200-1_2v: eMMC HS200 mode(1.2V I/O) is supported
 - mmc-hs400-1_8v: eMMC HS400 mode(1.8V I/O) is supported
 - mmc-hs400-1_2v: eMMC HS400 mode(1.2V I/O) is supported
+- dsr: Value the card's (optional) Driver Stage Register (DSR) should be
+  programmed with. Valid range: [0 .. 0xffff].

 *NOTE* on CD and WP polarity. To use common for all SD/MMC host controllers line
 polarity properties, we have to fix the meaning of the "normal" and "inverted"

diff --git a/drivers/mmc/core/host.c b/drivers/mmc/core/host.c
index 95cceae96944..6442eecb672e 100644
--- a/drivers/mmc/core/host.c
+++ b/drivers/mmc/core/host.c

@@ -452,6 +452,14 @@ int mmc_of_parse(struct mmc_host *host)
        if (of_find_property(np, "mmc-hs400-1_2v", &len))
                host->caps2 |= MMC_CAP2_HS400_1_2V | MMC_CAP2_HS200_1_2V_SDR;

+       host->dsr_req = of_property_read_u32(np, "dsr", &host->dsr);
+       if (host->dsr_req && (host->dsr & ~0xffff)) {

This doesn't look correct.
I guess what you want is: if (!host->dsr_req && (host->dsr & ~0xffff))

Ah, you're right. I thought that of_property_read_u32 returned true if
it worked and false if not. But it returns 0 for success and -ESOMETHING
otherwise.

So I want host->dsr_req = !of_property_read_u32(np, "dsr", &host->dsr);

I now have some working hardware again, will test again and send an v5.

quoted

+               dev_err(host->parent,
+                       "device tree specified broken value for DSR: 0x%x, ignoring\n",
+                       host->dsr);
+               host->dsr_req = 0;
+       }
+
        return 0;

 out:

diff --git a/drivers/mmc/core/mmc.c b/drivers/mmc/core/mmc.c
index 793c6f7ddb04..fdc1ac1360c4 100644
--- a/drivers/mmc/core/mmc.c
+++ b/drivers/mmc/core/mmc.c

@@ -162,6 +162,7 @@ static int mmc_decode_csd(struct mmc_card *card)
        csd->read_partial = UNSTUFF_BITS(resp, 79, 1);
        csd->write_misalign = UNSTUFF_BITS(resp, 78, 1);
        csd->read_misalign = UNSTUFF_BITS(resp, 77, 1);
+       csd->dsr_imp = UNSTUFF_BITS(resp, 76, 1);
        csd->r2w_factor = UNSTUFF_BITS(resp, 26, 3);
        csd->write_blkbits = UNSTUFF_BITS(resp, 22, 4);
        csd->write_partial = UNSTUFF_BITS(resp, 21, 1);

@@ -1273,6 +1274,13 @@ static int mmc_init_card(struct mmc_host *host, u32 ocr,
        }

        /*
+        * handling only for cards supporting DSR and hosts requesting
+        * DSR configuration
+        */
+       if (card->csd.dsr_imp && host->dsr_req)

if (card->csd.dsr_imp && !host->dsr_req)

With the above change my line is correct.

quoted

 struct mmc_ext_csd {

diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h
index 7960424d0bc0..8acaebd866a7 100644
--- a/include/linux/mmc/host.h
+++ b/include/linux/mmc/host.h

@@ -319,6 +319,7 @@ struct mmc_host {
 #ifdef CONFIG_MMC_DEBUG
        unsigned int            removed:1;      /* host is being removed */
 #endif
+       unsigned int            dsr_req:1;      /* DSR is requested for Host */

Should be an int instead.

I don't care much, can change to int.

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-K?nig            |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |