lkml.org 
[lkml]   [2018]   [Oct]   [19]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
Subject[PATCH] mmc: sdhci-pci: Try "cd" for card-detect lookup before using NULL
From
Problem:

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

Details:

(Discussion: https://lkml.org/lkml/2018/9/25/1113)

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.

Fix:

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 <rajatja@google.com>
---
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;

--
2.19.1.568.g152ad8e336-goog
\
 
 \ /
  Last update: 2018-10-18 23:51    [W:0.097 / U:9.092 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site