Double the MMCSD_IDLE_DELAY from 50ms to 100ms because I found one card that needs this to work after initial CMD0.
/* Timing (all in units of microseconds) */
#define MMCSD_POWERUP_DELAY ((useconds_t)250) /* 74 clock cycles @ 400KHz = 185uS */
-#define MMCSD_IDLE_DELAY ((useconds_t)50000) /* Short delay to allow change to IDLE state */
+#define MMCSD_IDLE_DELAY ((useconds_t)100000) /* Short delay to allow change to IDLE state */
#define MMCSD_DSR_DELAY ((useconds_t)100000) /* Time to wait after setting DSR */
#define MMCSD_CLK_DELAY ((useconds_t)5000) /* Delay after changing clock speeds */
