[Qemu-devel] [PULL 28/36] hw/sd: model a power-up delay, as a workaround for an EDK2 bug

[Peter Maydell]

From: Andrew Baumann <address@hidden>

The SD spec for ACMD41 says that a zero argument is an "inquiry"
ACMD41, which does not start initialisation and is used only for
retrieving the OCR. However, Tianocore EDK2 (UEFI) has a bug [1]: it
first sends an inquiry (zero) ACMD41. If that first request returns an
OCR value with the power up bit (0x80000000) set, it assumes the card
is ready and continues, leaving the card in the wrong state. (My
assumption is that this works on hardware, because no real card is
immediately powered up upon reset.)

This change models a delay of 0.5ms from the first ACMD41 to the power
being up. However, it also immediately sets the power on upon seeing a
non-zero (non-enquiry) ACMD41. This speeds up UEFI boot, it should
also account for guests that simply delay after card reset and then
issue an ACMD41 that they expect will succeed.

[1] 
https://github.com/tianocore/edk2/blob/master/EmbeddedPkg/Universal/MmcDxe/MmcIdentification.c#L279
(This is the loop starting with "We need to wait for the MMC or SD
card is ready")

Reviewed-by: Peter Maydell <address@hidden>
Signed-off-by: Andrew Baumann <address@hidden>
Message-id: address@hidden
Signed-off-by: Peter Maydell <address@hidden>
---
 hw/sd/sd.c | 81 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++----
 1 file changed, 76 insertions(+), 5 deletions(-)

diff --git a/hw/sd/sd.c b/hw/sd/sd.c
index 8dd6f39..bef6c0f 100644
--- a/hw/sd/sd.c
+++ b/hw/sd/sd.c
@@ -37,6 +37,7 @@
 #include "qemu/bitmap.h"
 #include "hw/qdev-properties.h"
 #include "qemu/error-report.h"
+#include "qemu/timer.h"
 
 //#define DEBUG_SD 1
 
@@ -47,7 +48,9 @@ do { fprintf(stderr, "SD: " fmt , ## __VA_ARGS__); } while (0)
 #define DPRINTF(fmt, ...) do {} while(0)
 #endif
 
-#define ACMD41_ENQUIRY_MASK 0x00ffffff
+#define ACMD41_ENQUIRY_MASK     0x00ffffff
+#define OCR_POWER_UP            0x80000000
+#define OCR_POWER_DELAY_NS      500000 /* 0.5ms */
 
 typedef enum {
     sd_r0 = 0,    /* no response */
@@ -86,6 +89,7 @@ struct SDState {
     uint32_t mode;    /* current card mode, one of SDCardModes */
     int32_t state;    /* current card state, one of SDCardStates */
     uint32_t ocr;
+    QEMUTimer *ocr_power_timer;
     uint8_t scr[8];
     uint8_t cid[16];
     uint8_t csd[16];
@@ -200,8 +204,17 @@ static uint16_t sd_crc16(void *message, size_t width)
 
 static void sd_set_ocr(SDState *sd)
 {
-    /* All voltages OK, card power-up OK, Standard Capacity SD Memory Card */
-    sd->ocr = 0x80ffff00;
+    /* All voltages OK, Standard Capacity SD Memory Card, not yet powered up */
+    sd->ocr = 0x00ffff00;
+}
+
+static void sd_ocr_powerup(void *opaque)
+{
+    SDState *sd = opaque;
+
+    /* Set powered up bit in OCR */
+    assert(!(sd->ocr & OCR_POWER_UP));
+    sd->ocr |= OCR_POWER_UP;
 }
 
 static void sd_set_scr(SDState *sd)
@@ -476,10 +489,44 @@ static const BlockDevOps sd_block_ops = {
     .change_media_cb = sd_cardchange,
 };
 
+static bool sd_ocr_vmstate_needed(void *opaque)
+{
+    SDState *sd = opaque;
+
+    /* Include the OCR state (and timer) if it is not yet powered up */
+    return !(sd->ocr & OCR_POWER_UP);
+}
+
+static const VMStateDescription sd_ocr_vmstate = {
+    .name = "sd-card/ocr-state",
+    .version_id = 1,
+    .minimum_version_id = 1,
+    .needed = sd_ocr_vmstate_needed,
+    .fields = (VMStateField[]) {
+        VMSTATE_UINT32(ocr, SDState),
+        VMSTATE_TIMER_PTR(ocr_power_timer, SDState),
+        VMSTATE_END_OF_LIST()
+    },
+};
+
+static int sd_vmstate_pre_load(void *opaque)
+{
+    SDState *sd = opaque;
+
+    /* If the OCR state is not included (prior versions, or not
+     * needed), then the OCR must be set as powered up. If the OCR state
+     * is included, this will be replaced by the state restore.
+     */
+    sd_ocr_powerup(sd);
+
+    return 0;
+}
+
 static const VMStateDescription sd_vmstate = {
     .name = "sd-card",
     .version_id = 1,
     .minimum_version_id = 1,
+    .pre_load = sd_vmstate_pre_load,
     .fields = (VMStateField[]) {
         VMSTATE_UINT32(mode, SDState),
         VMSTATE_INT32(state, SDState),
@@ -506,7 +553,11 @@ static const VMStateDescription sd_vmstate = {
         VMSTATE_BUFFER_POINTER_UNSAFE(buf, SDState, 1, 512),
         VMSTATE_BOOL(enable, SDState),
         VMSTATE_END_OF_LIST()
-    }
+    },
+    .subsections = (const VMStateDescription*[]) {
+        &sd_ocr_vmstate,
+        NULL
+    },
 };
 
 /* Legacy initialization function for use by non-qdevified callers */
@@ -1323,9 +1374,28 @@ static sd_rsp_type_t sd_app_command(SDState *sd,
         }
         switch (sd->state) {
         case sd_idle_state:
+            /* If it's the first ACMD41 since reset, we need to decide
+             * whether to power up. If this is not an enquiry ACMD41,
+             * we immediately report power on and proceed below to the
+             * ready state, but if it is, we set a timer to model a
+             * delay for power up. This works around a bug in EDK2
+             * UEFI, which sends an initial enquiry ACMD41, but
+             * assumes that the card is in ready state as soon as it
+             * sees the power up bit set. */
+            if (!(sd->ocr & OCR_POWER_UP)) {
+                if ((req.arg & ACMD41_ENQUIRY_MASK) != 0) {
+                    timer_del(sd->ocr_power_timer);
+                    sd_ocr_powerup(sd);
+                } else if (!timer_pending(sd->ocr_power_timer)) {
+                    timer_mod_ns(sd->ocr_power_timer,
+                                 (qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL)
+                                  + OCR_POWER_DELAY_NS));
+                }
+            }
+
             /* We accept any voltage.  10000 V is nothing.
              *
-             * We don't model init delay so just advance straight to ready 
state
+             * Once we're powered up, we advance straight to ready state
              * unless it's an enquiry ACMD41 (bits 23:0 == 0).
              */
             if (req.arg & ACMD41_ENQUIRY_MASK) {
@@ -1837,6 +1907,7 @@ static void sd_instance_init(Object *obj)
     SDState *sd = SD_CARD(obj);
 
     sd->enable = true;
+    sd->ocr_power_timer = timer_new_ns(QEMU_CLOCK_VIRTUAL, sd_ocr_powerup, sd);
 }
 
 static void sd_realize(DeviceState *dev, Error **errp)
-- 
1.9.1