Re: [PATCH RFC] ARM: dts: mxs: leave card detect out of common mmcpins config

From: Hector Palacios
Date: Tue Apr 09 2013 - 05:00:29 EST

Dear Marek Vasut,

On 04/09/2013 10:15 AM, Marek Vasut wrote:
Dear Hector Palacios,

Dear Marek Vasut,

On 04/08/2013 06:28 PM, Marek Vasut wrote:
Dear Shawn Guo,

On Mon, Apr 08, 2013 at 03:58:05PM +0200, Hector Palacios wrote:
On 04/08/2013 02:48 PM, Shawn Guo wrote:
On Mon, Apr 08, 2013 at 12:12:20PM +0200, Hector Palacios wrote:
MicroSD card sockets don't usually have card detect line. This pin
is actually not needed for the MMC to work and it is more of a
platform design decission to have it.
The card detect pin already has a configuration entry of its own:
'mmc0_cd_cfg' so we complete the iomux configuration here and let
platforms to include it or not depending on whether the card detect
line is routed to the SD socket.

Sounds sensible.

Signed-off-by: Hector Palacios <hector.palacios@xxxxxxxx>


All imx28 based platforms except 'bluegiga,apx4devkit' and
'schulercontrol,imx28-sps1', use 'mmc0_cd_cfg' in their mmc
configuration so please check whether this patch would break these

I just tested the patch on imx28-evk and card-detection still works.
So patches applied, thanks.

The EVK and most platforms will work because they are using
'mmc0_cd_cfg' so actually this patch does not change anything on
Platforms 'bluegiga,apx4devkit' and 'schulercontrol,imx28-sps1'
however are not referencing 'mmc0_cd_cfg' so after applying this
patch they will have unconfigured CD line and they may break.

Ah, yes. I thought that any board that has CD support has to reference
'mmc0_cd_cfg'. That's not necessarily true.

The driver will call get_cd() upon probing, which returns the status of
the CD line. Please check these two platforms before applying.

Ok, let's wait for people owning the boards to confirm.

Maybe you want to use MMC_CAP_NEEDS_POLL as was noted by someone before
on the olinuxino -- the slot is there, it's just the CD line that's

I'm not sure of what you mean. The mxs-mmc.c driver already sets the
MMC_CAP_NEEDS_POLL flag by default in the probe() function. My platform
does not even route the CD line because the microSD socket does not have
So what I have done is modify the driver to parse the property
'non-removable' from the device tree in order to set the

Yes, I get it. I have two remarks still:
1) The card is removable (you can pull it out from olinuxino's slot)

True, I misunderstood the use of 'non-removable'. So I guess I could use 'broken-cd' property instead, right?

2) Why is the NEEDS_POLL set by default ?

Because the CD line cannot cause an interrupt in this controller.

3) Does the NEEDS_POLL not solve the issue with missing CD line?

No. CD polling relies on the status register. The field CARD_DETECT in HW_SSP_STATUS register directly reflects the state of the SSP_DETECT input pin. If the pin is not connected it can have any value, so I guess we need a custom flag on the driver:

diff --git a/drivers/mmc/host/mxs-mmc.c b/drivers/mmc/host/mxs-mmc.c
index 206fe49..ec0874b 100644
--- a/drivers/mmc/host/mxs-mmc.c
+++ b/drivers/mmc/host/mxs-mmc.c
@@ -72,6 +72,7 @@ struct mxs_mmc_host {
int sdio_irq_en;
int wp_gpio;
bool wp_inverted;
+ bool cd_broken;

static int mxs_mmc_get_ro(struct mmc_host *mmc)
@@ -95,6 +96,9 @@ static int mxs_mmc_get_cd(struct mmc_host *mmc)
struct mxs_mmc_host *host = mmc_priv(mmc);
struct mxs_ssp *ssp = &host->ssp;

+ if (host->cd_broken)
+ return 1;
return !(readl(ssp->base + HW_SSP_STATUS(ssp)) &
@@ -686,8 +690,11 @@ static int mxs_mmc_probe(struct platform_device *pdev)
mmc->caps |= MMC_CAP_4_BIT_DATA;
else if (bus_width == 8)
mmc->caps |= MMC_CAP_4_BIT_DATA | MMC_CAP_8_BIT_DATA;
- host->wp_gpio = of_get_named_gpio_flags(np, "wp-gpios", 0, &flags);

+ if (of_find_property(np, "broken-cd", NULL))
+ host->cd_broken = 1;
+ host->wp_gpio = of_get_named_gpio_flags(np, "wp-gpios", 0, &flags);
if (flags & OF_GPIO_ACTIVE_LOW)
host->wp_inverted = 1;

Thank you for your comments.
Héctor Palacios
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