Re: [PATCH] sdhci: Add support for hosts that are only capable of 1-bit transfers

On Sat, Jun 13, 2009 at 09:40:02AM -0600, Grant Likely wrote:

On Thu, Jun 11, 2009 at 2:15 PM, Anton
Vorontsov[off-list ref] wrote:

quoted

Some hosts (hardware configurations, or particular SD/MMC slots) may
not support 4-bit bus. For example, on MPC8569E-MDS boards we can
switch between serial (1-bit only) and nibble (4-bit) modes, thought
we have to disable more peripherals to work in 4-bit mode.

Along with some small core changes, this patch modifies sdhci-of
driver, so that now it looks for "mode" property in the device-tree.

Signed-off-by: Anton Vorontsov <redacted>
---

Pierre, I'm not sure if a quirk would be appropriate here. If so,
I can redo the patch with FORCE_1_BIT_DATA quirk.

Thanks,

 Documentation/powerpc/dts-bindings/fsl/esdhc.txt |    2 ++
 drivers/mmc/host/sdhci-of.c                      |    7 +++++++
 drivers/mmc/host/sdhci-pci.c                     |    1 +
 drivers/mmc/host/sdhci.c                         |    2 +-
 4 files changed, 11 insertions(+), 1 deletions(-)

diff --git a/Documentation/powerpc/dts-bindings/fsl/esdhc.txt b/Documentation/powerpc/dts-bindings/fsl/esdhc.txt
index 5093ddf..298b865 100644
--- a/Documentation/powerpc/dts-bindings/fsl/esdhc.txt
+++ b/Documentation/powerpc/dts-bindings/fsl/esdhc.txt

@@ -10,6 +10,8 @@ Required properties:

  - interrupts : should contain eSDHC interrupt.
  - interrupt-parent : interrupt source phandle.
  - clock-frequency : specifies eSDHC base clock frequency.
+  - mode : specifies eSDHC mode, valid values are: "1-bit" and "4-bit".
+    If mode is unspecified, then 4-bit mode is assumed.

In light of Pierre's comment that 4-bit is mandatory and this is a
deviation, perhaps it would be better to define an empty property to
indicate that only 1-bit transfers work.  Maybe something along the
lines of "sdhc-1-bit-only"?

Yeah, since it turned up to be a quirk, we'd better use a named
property.

(I think that by convention we should use commas for
controller-specific properties, i.e. "sdhci,property".)


Thanks!

-- 
Anton Vorontsov
email: cbouatmailru@gmail.com
irc://irc.freenode.net/bd2