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From: Rajat Jain <>
To: Adrian Hunter <>,
	Ulf Hansson <>,,
	Linus Walleij <>
Cc: Rajat Jain <>,,,
	Mika Westerberg <>,
	Andy Shevchenko <>,
	Dmitry Torokhov <>,,
Subject: [PATCH] mmc: sdhci-pci: Try "cd" for card-detect lookup before using NULL
Date: Thu, 18 Oct 2018 14:51:01 -0700	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>


The card detect IRQ does not work with modern BIOS (that want
to use DSD to provide the card detect GPIO to the driver).



The mmc core provides the mmc_gpiod_request_cd() API to let host drivers
request the gpio descriptor for the "card detect" (or carrier detect?) pin.
This pin is specified in the ACPI for the SDHC device:

 * Either as a resource using _CRS. This is a method used by legacy BIOS.
   (The driver needs to tell which resource index).

 * Or as a named property ("cd-gpio") in DSD (which may internally point
   to an entry in _CRS). This way, the driver can lookup using a string.
   This is what modern BIOS prefer to use.

This API finally results in a call to the following code:

struct gpio_desc *acpi_find_gpio(..., const char *con_id,...)
   /* Lookup gpio (using "<con_id>-gpio") in the _DSD */
   if (!acpi_can_fallback_to_crs(adev, con_id))
          return ERR_PTR(-ENOENT);
   /* Falling back to _CRS is allowed, Lookup gpio in the _CRS */

Note that this means that if the ACPI has _DSD properties, the kernel
will never use _CRS for the lookup (Because acpi_can_fallback_to_crs()
will always be false for any device hat has _DSD entries).

The SDHCI driver is thus currently broken on a modern BIOS (even if
BIOS provides both _CRS and DSD entries, either of which could be used for
a successful lookup). Ironically, none of these will be used for the
lookup currently because:

* Since the con_id is NULL, acpi_find_gpio() does not find a matching
  entry in DSDT. (The DSDT entry has the property name = "cd-gpio")

* Because ACPI contains DSDT entries, thus acpi_can_fallback_to_crs()
  returns false (because device properties have been populated from
  DSD), thus the _CRS is never used for the lookup.


Try "cd" for lookup in the _DSD before falling back to using NULL so
as to try looking up in the _CRS.

I've tested this patch successfully with both Legacy BIOS (that
provide only _CRS method) as well as modern BIOS (that provide both
_CRS and DSD). Also the use of "cd" also appears to be farly consistent
across other users of this API (other MMC host controller drivers).

Signed-off-by: Rajat Jain <>
 drivers/mmc/host/sdhci-pci-core.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/mmc/host/sdhci-pci-core.c b/drivers/mmc/host/sdhci-pci-core.c
index 7bfd366d970d..e53333c695b3 100644
--- a/drivers/mmc/host/sdhci-pci-core.c
+++ b/drivers/mmc/host/sdhci-pci-core.c
@@ -1762,8 +1762,13 @@ static struct sdhci_pci_slot *sdhci_pci_probe_slot(
 		device_init_wakeup(&pdev->dev, true);
 	if (slot->cd_idx >= 0) {
-		ret = mmc_gpiod_request_cd(host->mmc, NULL, slot->cd_idx,
+		ret = mmc_gpiod_request_cd(host->mmc, "cd", slot->cd_idx,
 					   slot->cd_override_level, 0, NULL);
+		if (ret && ret != -EPROBE_DEFER)
+			ret = mmc_gpiod_request_cd(host->mmc, NULL,
+						   slot->cd_idx,
+						   slot->cd_override_level,
+						   0, NULL);
 		if (ret == -EPROBE_DEFER)
 			goto remove;

  reply	other threads:[~2018-10-18 21:51 UTC|newest]

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-09-25 20:54 sdhci driver card-detect is broken because gpiolib can't fallback to _CRS? Rajat Jain
2018-09-26  7:47 ` Mika Westerberg
2018-09-26  8:42   ` Andy Shevchenko
2018-09-26 19:25     ` Rajat Jain
2018-09-27  7:26       ` Andy Shevchenko
2018-09-27 17:56         ` Rajat Jain
2018-09-28  8:42           ` Linus Walleij
2018-09-28 12:34             ` Rajat Jain
2018-09-28 13:13               ` Linus Walleij
2018-10-18 21:51                 ` Rajat Jain [this message]
2018-10-19  9:13                   ` [PATCH] mmc: sdhci-pci: Try "cd" for card-detect lookup before using NULL Andy Shevchenko
2018-10-22 23:34                     ` Rajat Jain
2018-10-24 10:02                       ` Andy Shevchenko
2018-10-24 18:03                         ` Dmitry Torokhov
2018-10-29 15:23                           ` Andy Shevchenko
2018-10-29 17:22                             ` Rajat Jain
2018-10-29 17:43                               ` Andy Shevchenko
2018-10-29 19:43                                 ` Rajat Jain
2018-10-29 22:17                                   ` [PATCH v2] " Rajat Jain
2018-10-30  7:53                                     ` Adrian Hunter
2018-11-12 11:05                                     ` Ulf Hansson
2018-11-12 11:25                                       ` Andy Shevchenko
2018-11-13  1:26                                         ` Rajat Jain

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