[Qemu-devel] [PATCH 1/3] sd: sdhci: Delete over-zealous power check

[Andrew Baumann <Andrew.Baumann@microsoft.com>]

This check was conditionalising SD card operation on the card being
powered by the SDHCI host controller. It is however possible
(particularly in embedded systems) for the power control of the SD card
to be managed outside of SDHCI. This can be as trivial as hard-wiring
the SD slot VCC to a constant power-rail.

This means the guest SDHCI can validly opt-out of the SDHCI power
control feature while still using the card. So delete this check to
allow operation of the card with SDHCI power control.

This is needed for at least Xilinx Zynq and also makes Freescale i.MX25
work for me. The digilent Zybo board has a public schematic
which shows SD VCC hardwiring:

http://digilentinc.com/Data/Products/ZYBO/ZYBO_sch_VB.3.pdf
bottom of page 3.

Signed-off-by: Peter Crosthwaite <crosthwaite.peter@gmail.com>
Reviewed-by: Sai Pavan Boddu <sai.pavan.boddu@xilinx.com>
Signed-off-by: Andrew Baumann <Andrew.Baumann@microsoft.com>
---

Notes:
    This is exactly equivalent to Peter's patch here:
    https://lists.gnu.org/archive/html/qemu-devel/2015-11/msg06271.html
    ... which is why I've copied the signed-off-by lines (I assume that is
    legit; if not, my apologies!). It is also needed for Pi.

 hw/sd/sdhci.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/hw/sd/sdhci.c b/hw/sd/sdhci.c
index 8612760..bc39d48 100644
--- a/hw/sd/sdhci.c
+++ b/hw/sd/sdhci.c
@@ -831,7 +831,7 @@ static void sdhci_data_transfer(void *opaque)
 
 static bool sdhci_can_issue_command(SDHCIState *s)
 {
-    if (!SDHC_CLOCK_IS_ON(s->clkcon) || !(s->pwrcon & SDHC_POWER_ON) ||
+    if (!SDHC_CLOCK_IS_ON(s->clkcon) ||
         (((s->prnsts & SDHC_DATA_INHIBIT) || s->stopped_state) &&
         ((s->cmdreg & SDHC_CMD_DATA_PRESENT) ||
         ((s->cmdreg & SDHC_CMD_RESPONSE) == SDHC_CMD_RSP_WITH_BUSY &&
-- 
2.5.3