* [PATCH] mmc: implement driver stage register handling
@ 2014-05-23 13:34 Sascha Hauer
2014-06-16 11:36 ` Ulf Hansson
0 siblings, 1 reply; 3+ messages in thread
From: Sascha Hauer @ 2014-05-23 13:34 UTC (permalink / raw)
To: linux-arm-kernel
The eMMC and the SD-Card specifications describe the optional SET_DSR command.
During measurements at our lab we found that some cards implementing this feature
having really strong driver strengts per default. This can lead to voltage peaks
above the specification of the host on signal edges for data sent from a card to
the host.
Since availability of a given card type may be shorter than the time a certain
hardware will be produced it is useful to have support for this command (Alternative
would be changing termination resistors and adapting the driver strength of the
host to the used card.)
As the value of the dsr register is board specific this adds a 'dsr' devicetree
property which is handled in mmc_of_parse.
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
---
Documentation/devicetree/bindings/mmc/mmc.txt | 3 +++
drivers/mmc/core/host.c | 3 +++
drivers/mmc/core/mmc.c | 4 ++++
drivers/mmc/core/mmc_ops.c | 17 +++++++++++++++++
drivers/mmc/core/mmc_ops.h | 1 +
include/linux/mmc/card.h | 3 ++-
include/linux/mmc/host.h | 2 ++
7 files changed, 32 insertions(+), 1 deletion(-)
diff --git a/Documentation/devicetree/bindings/mmc/mmc.txt b/Documentation/devicetree/bindings/mmc/mmc.txt
index 9dce540..737203e 100644
--- a/Documentation/devicetree/bindings/mmc/mmc.txt
+++ b/Documentation/devicetree/bindings/mmc/mmc.txt
@@ -38,6 +38,9 @@ Optional properties:
- mmc-highspeed-ddr-1_2v: eMMC high-speed DDR mode(1.2V I/O) is supported
- mmc-hs200-1_8v: eMMC HS200 mode(1.8V I/O) is supported
- mmc-hs200-1_2v: eMMC HS200 mode(1.2V I/O) is supported
+- dsr: Content of the optional driver stage register (DSR) as described
+ in JEDEC Standard No. 84-A44, 12.4: Programmable card output driver. Not
+ all MMC cards implement this register and the actual value is card specific.
*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 fdea825..eea272e 100644
--- a/drivers/mmc/core/host.c
+++ b/drivers/mmc/core/host.c
@@ -447,6 +447,7 @@ int mmc_of_parse(struct mmc_host *host)
host->caps2 |= MMC_CAP2_HS200_1_8V_SDR;
if (of_find_property(np, "mmc-hs200-1_2v", &len))
host->caps2 |= MMC_CAP2_HS200_1_2V_SDR;
+ of_property_read_u32(np, "dsr", &host->dsr);
return 0;
@@ -515,6 +516,8 @@ struct mmc_host *mmc_alloc_host(int extra, struct device *dev)
host->max_blk_size = 512;
host->max_blk_count = PAGE_CACHE_SIZE / 512;
+ host->dsr = 0xffffffff;
+
return host;
free:
diff --git a/drivers/mmc/core/mmc.c b/drivers/mmc/core/mmc.c
index 1ab5f3a..0ab1c44 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);
@@ -970,6 +971,9 @@ static int mmc_init_card(struct mmc_host *host, u32 ocr,
goto free_card;
}
+ if (card->csd.dsr_imp && (host->dsr & 0xffff) == host->dsr)
+ mmc_set_dsr(host);
+
/*
* Select card, as all following commands rely on that.
*/
diff --git a/drivers/mmc/core/mmc_ops.c b/drivers/mmc/core/mmc_ops.c
index f51b5ba..f8af72a 100644
--- a/drivers/mmc/core/mmc_ops.c
+++ b/drivers/mmc/core/mmc_ops.c
@@ -93,6 +93,23 @@ int mmc_deselect_cards(struct mmc_host *host)
return _mmc_select_card(host, NULL);
}
+int mmc_set_dsr(struct mmc_host *host)
+{
+ int err;
+ struct mmc_command cmd = {0};
+
+ cmd.opcode = MMC_SET_DSR;
+
+ cmd.arg = (host->dsr << 16) | 0xffff;
+ cmd.flags = MMC_RSP_NONE | MMC_CMD_AC;
+
+ err = mmc_wait_for_cmd(host, &cmd, MMC_CMD_RETRIES);
+ if (err)
+ return err;
+
+ return 0;
+}
+
int mmc_go_idle(struct mmc_host *host)
{
int err;
diff --git a/drivers/mmc/core/mmc_ops.h b/drivers/mmc/core/mmc_ops.h
index 80ae9f4..390dac6 100644
--- a/drivers/mmc/core/mmc_ops.h
+++ b/drivers/mmc/core/mmc_ops.h
@@ -14,6 +14,7 @@
int mmc_select_card(struct mmc_card *card);
int mmc_deselect_cards(struct mmc_host *host);
+int mmc_set_dsr(struct mmc_host *host);
int mmc_go_idle(struct mmc_host *host);
int mmc_send_op_cond(struct mmc_host *host, u32 ocr, u32 *rocr);
int mmc_all_send_cid(struct mmc_host *host, u32 *cid);
diff --git a/include/linux/mmc/card.h b/include/linux/mmc/card.h
index b730272..ced116f 100644
--- a/include/linux/mmc/card.h
+++ b/include/linux/mmc/card.h
@@ -42,7 +42,8 @@ struct mmc_csd {
unsigned int read_partial:1,
read_misalign:1,
write_partial:1,
- write_misalign:1;
+ write_misalign:1,
+ dsr_imp:1;
};
struct mmc_ext_csd {
diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h
index cb61ea4..d8d9d68 100644
--- a/include/linux/mmc/host.h
+++ b/include/linux/mmc/host.h
@@ -358,6 +358,8 @@ struct mmc_host {
unsigned int slotno; /* used for sdio acpi binding */
+ u32 dsr; /* optional driver stage register (dsr) value */
+
unsigned long private[0] ____cacheline_aligned;
};
--
2.0.0.rc0
^ permalink raw reply related [flat|nested] 3+ messages in thread
* [PATCH] mmc: implement driver stage register handling
2014-05-23 13:34 [PATCH] mmc: implement driver stage register handling Sascha Hauer
@ 2014-06-16 11:36 ` Ulf Hansson
2014-06-16 11:48 ` Russell King - ARM Linux
0 siblings, 1 reply; 3+ messages in thread
From: Ulf Hansson @ 2014-06-16 11:36 UTC (permalink / raw)
To: linux-arm-kernel
On 23 May 2014 15:34, Sascha Hauer <s.hauer@pengutronix.de> wrote:
> The eMMC and the SD-Card specifications describe the optional SET_DSR command.
> During measurements at our lab we found that some cards implementing this feature
> having really strong driver strengts per default. This can lead to voltage peaks
> above the specification of the host on signal edges for data sent from a card to
> the host.
>
> Since availability of a given card type may be shorter than the time a certain
> hardware will be produced it is useful to have support for this command (Alternative
> would be changing termination resistors and adapting the driver strength of the
> host to the used card.)
>
> As the value of the dsr register is board specific this adds a 'dsr' devicetree
> property which is handled in mmc_of_parse.
>
> Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
> ---
> Documentation/devicetree/bindings/mmc/mmc.txt | 3 +++
> drivers/mmc/core/host.c | 3 +++
> drivers/mmc/core/mmc.c | 4 ++++
> drivers/mmc/core/mmc_ops.c | 17 +++++++++++++++++
> drivers/mmc/core/mmc_ops.h | 1 +
> include/linux/mmc/card.h | 3 ++-
> include/linux/mmc/host.h | 2 ++
> 7 files changed, 32 insertions(+), 1 deletion(-)
>
> diff --git a/Documentation/devicetree/bindings/mmc/mmc.txt b/Documentation/devicetree/bindings/mmc/mmc.txt
> index 9dce540..737203e 100644
> --- a/Documentation/devicetree/bindings/mmc/mmc.txt
> +++ b/Documentation/devicetree/bindings/mmc/mmc.txt
> @@ -38,6 +38,9 @@ Optional properties:
> - mmc-highspeed-ddr-1_2v: eMMC high-speed DDR mode(1.2V I/O) is supported
> - mmc-hs200-1_8v: eMMC HS200 mode(1.8V I/O) is supported
> - mmc-hs200-1_2v: eMMC HS200 mode(1.2V I/O) is supported
> +- dsr: Content of the optional driver stage register (DSR) as described
> + in JEDEC Standard No. 84-A44, 12.4: Programmable card output driver. Not
> + all MMC cards implement this register and the actual value is card specific.
I get the impression of that this is (e)MMC specific, but this is
relevant for SD cards as well, right!?
I don't find the part's that should be implemented for sd/sdio, could
we add that in this patch as well?
>
> *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 fdea825..eea272e 100644
> --- a/drivers/mmc/core/host.c
> +++ b/drivers/mmc/core/host.c
> @@ -447,6 +447,7 @@ int mmc_of_parse(struct mmc_host *host)
> host->caps2 |= MMC_CAP2_HS200_1_8V_SDR;
> if (of_find_property(np, "mmc-hs200-1_2v", &len))
> host->caps2 |= MMC_CAP2_HS200_1_2V_SDR;
> + of_property_read_u32(np, "dsr", &host->dsr);
>
> return 0;
>
> @@ -515,6 +516,8 @@ struct mmc_host *mmc_alloc_host(int extra, struct device *dev)
> host->max_blk_size = 512;
> host->max_blk_count = PAGE_CACHE_SIZE / 512;
>
> + host->dsr = 0xffffffff;
> +
Why is this needed?
> return host;
>
> free:
> diff --git a/drivers/mmc/core/mmc.c b/drivers/mmc/core/mmc.c
> index 1ab5f3a..0ab1c44 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);
> @@ -970,6 +971,9 @@ static int mmc_init_card(struct mmc_host *host, u32 ocr,
> goto free_card;
> }
>
> + if (card->csd.dsr_imp && (host->dsr & 0xffff) == host->dsr)
To clarify, maybe add an extra pair of parentheses around the above expression?
Additionally I don't quite understand the comparison? Couldn't we just
use a "u16" to simplify this?
> + mmc_set_dsr(host);
> +
> /*
> * Select card, as all following commands rely on that.
> */
> diff --git a/drivers/mmc/core/mmc_ops.c b/drivers/mmc/core/mmc_ops.c
> index f51b5ba..f8af72a 100644
> --- a/drivers/mmc/core/mmc_ops.c
> +++ b/drivers/mmc/core/mmc_ops.c
> @@ -93,6 +93,23 @@ int mmc_deselect_cards(struct mmc_host *host)
> return _mmc_select_card(host, NULL);
> }
>
> +int mmc_set_dsr(struct mmc_host *host)
> +{
> + int err;
> + struct mmc_command cmd = {0};
> +
> + cmd.opcode = MMC_SET_DSR;
> +
> + cmd.arg = (host->dsr << 16) | 0xffff;
> + cmd.flags = MMC_RSP_NONE | MMC_CMD_AC;
I think it should be MMC_CMD_BC instead of MMC_CMD_AC.
> +
> + err = mmc_wait_for_cmd(host, &cmd, MMC_CMD_RETRIES);
> + if (err)
> + return err;
> +
> + return 0;
> +}
> +
> int mmc_go_idle(struct mmc_host *host)
> {
> int err;
> diff --git a/drivers/mmc/core/mmc_ops.h b/drivers/mmc/core/mmc_ops.h
> index 80ae9f4..390dac6 100644
> --- a/drivers/mmc/core/mmc_ops.h
> +++ b/drivers/mmc/core/mmc_ops.h
> @@ -14,6 +14,7 @@
>
> int mmc_select_card(struct mmc_card *card);
> int mmc_deselect_cards(struct mmc_host *host);
> +int mmc_set_dsr(struct mmc_host *host);
> int mmc_go_idle(struct mmc_host *host);
> int mmc_send_op_cond(struct mmc_host *host, u32 ocr, u32 *rocr);
> int mmc_all_send_cid(struct mmc_host *host, u32 *cid);
> diff --git a/include/linux/mmc/card.h b/include/linux/mmc/card.h
> index b730272..ced116f 100644
> --- a/include/linux/mmc/card.h
> +++ b/include/linux/mmc/card.h
> @@ -42,7 +42,8 @@ struct mmc_csd {
> unsigned int read_partial:1,
> read_misalign:1,
> write_partial:1,
> - write_misalign:1;
> + write_misalign:1,
> + dsr_imp:1;
> };
>
> struct mmc_ext_csd {
> diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h
> index cb61ea4..d8d9d68 100644
> --- a/include/linux/mmc/host.h
> +++ b/include/linux/mmc/host.h
> @@ -358,6 +358,8 @@ struct mmc_host {
>
> unsigned int slotno; /* used for sdio acpi binding */
>
> + u32 dsr; /* optional driver stage register (dsr) value */
Again, the DSR register is 16 bits. Couldn't we use u16 instead?
Moreover, feel free to to move this further up in the struct. I would
put it between ocr_avail and f_init, since it's more related to these.
Kind regards
Uffe
> +
> unsigned long private[0] ____cacheline_aligned;
> };
>
> --
> 2.0.0.rc0
>
> --
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^ permalink raw reply [flat|nested] 3+ messages in thread
* [PATCH] mmc: implement driver stage register handling
2014-06-16 11:36 ` Ulf Hansson
@ 2014-06-16 11:48 ` Russell King - ARM Linux
0 siblings, 0 replies; 3+ messages in thread
From: Russell King - ARM Linux @ 2014-06-16 11:48 UTC (permalink / raw)
To: linux-arm-kernel
On Mon, Jun 16, 2014 at 01:36:38PM +0200, Ulf Hansson wrote:
> On 23 May 2014 15:34, Sascha Hauer <s.hauer@pengutronix.de> wrote:
> > @@ -970,6 +971,9 @@ static int mmc_init_card(struct mmc_host *host, u32 ocr,
> > goto free_card;
> > }
> >
> > + if (card->csd.dsr_imp && (host->dsr & 0xffff) == host->dsr)
>
> To clarify, maybe add an extra pair of parentheses around the above expression?
To which I say, don't you bloody dare. It's perfectly readable as it
is, it doesn't need any additional parenthesis.
Additional useless parenthesis detracts from readability. Don't encourage
stuch stuff.
--
FTTC broadband for 0.8mile line: now at 9.7Mbps down 460kbps up... slowly
improving, and getting towards what was expected from it.
^ permalink raw reply [flat|nested] 3+ messages in thread
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