Avoid hardcoding 1MiB boot size in EXT_CSD_BOOT_MULT,
expose it as QOM property.

By default, do not use any size. The board is responsible
to set the boot size property.

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
---
 hw/sd/sd.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/hw/sd/sd.c b/hw/sd/sd.c
index e6f1cc2066..57a9eb91d0 100644
--- a/hw/sd/sd.c
+++ b/hw/sd/sd.c
@@ -135,6 +135,7 @@ struct SDState {
     /* Static properties */
 
     uint8_t spec_version;
+    uint64_t boot_part_size;
     BlockBackend *blk;
 
     const SDProto *proto;
@@ -492,7 +493,8 @@ static void mmc_set_ext_csd(SDState *sd, uint64_t size)
     /* Properties segment (RO) */
     sd->ext_csd[EXT_CSD_S_CMD_SET] = 0b1; /* supported command sets */
     sd->ext_csd[EXT_CSD_BOOT_INFO] = 0x0; /* Boot information */
-    sd->ext_csd[EXT_CSD_BOOT_MULT] = 0x8; /* Boot partition size. 128KB unit */
+                                     /* Boot partition size. 128KB unit */
+    sd->ext_csd[EXT_CSD_BOOT_MULT] = sd->boot_part_size / (128 * KiB);
     sd->ext_csd[EXT_CSD_ACC_SIZE] = 0x1; /* Access size */
     sd->ext_csd[EXT_CSD_HC_ERASE_GRP_SIZE] = 0x01; /* HC Erase unit size */
     sd->ext_csd[EXT_CSD_ERASE_TIMEOUT_MULT] = 0x01; /* HC erase timeout */
@@ -2704,6 +2706,7 @@ static Property sd_properties[] = {
 };
 
 static Property emmc_properties[] = {
+    DEFINE_PROP_UINT64("boot-size", SDState, boot_part_size, 0),
     DEFINE_PROP_END_OF_LIST()
 };
 
-- 
2.41.0