hw/sd/sdhci: Add dummy Samsung SDHCI controller

The Linux kernel access few S3C-specific registers [1] to set some
clock. We don't care about this part for device emulation [2]. Add
a dummy device to properly ignore these accesses, so we can focus
on the important registers missing.

[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/mmc/host/sdhci-s3c-regs.h?h=cc014f3
[2] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/mmc/host/sdhci-s3c.c?h=v5.3#n263Signed-off-by: NPhilippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: NKrzysztof Kozlowski <krzk@kernel.org>
Message-id: 20191005154748.21718-4-f4bug@amsat.org
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>

hw/sd/sdhci.c

@@ -1761,11 +1761,76 @@ static const TypeInfo imx_usdhc_info = {
     .instance_init = imx_usdhc_init,
 };
 
+/* --- qdev Samsung s3c --- */
+
+#define S3C_SDHCI_CONTROL2      0x80
+#define S3C_SDHCI_CONTROL3      0x84
+#define S3C_SDHCI_CONTROL4      0x8c
+
+static uint64_t sdhci_s3c_read(void *opaque, hwaddr offset, unsigned size)
+{
+    uint64_t ret;
+
+    switch (offset) {
+    case S3C_SDHCI_CONTROL2:
+    case S3C_SDHCI_CONTROL3:
+    case S3C_SDHCI_CONTROL4:
+        /* ignore */
+        ret = 0;
+        break;
+    default:
+        ret = sdhci_read(opaque, offset, size);
+        break;
+    }
+
+    return ret;
+}
+
+static void sdhci_s3c_write(void *opaque, hwaddr offset, uint64_t val,
+                            unsigned size)
+{
+    switch (offset) {
+    case S3C_SDHCI_CONTROL2:
+    case S3C_SDHCI_CONTROL3:
+    case S3C_SDHCI_CONTROL4:
+        /* ignore */
+        break;
+    default:
+        sdhci_write(opaque, offset, val, size);
+        break;
+    }
+}
+
+static const MemoryRegionOps sdhci_s3c_mmio_ops = {
+    .read = sdhci_s3c_read,
+    .write = sdhci_s3c_write,
+    .valid = {
+        .min_access_size = 1,
+        .max_access_size = 4,
+        .unaligned = false
+    },
+    .endianness = DEVICE_LITTLE_ENDIAN,
+};
+
+static void sdhci_s3c_init(Object *obj)
+{
+    SDHCIState *s = SYSBUS_SDHCI(obj);
+
+    s->io_ops = &sdhci_s3c_mmio_ops;
+}
+
+static const TypeInfo sdhci_s3c_info = {
+    .name = TYPE_S3C_SDHCI  ,
+    .parent = TYPE_SYSBUS_SDHCI,
+    .instance_init = sdhci_s3c_init,
+};
+
 static void sdhci_register_types(void)
 {
     type_register_static(&sdhci_sysbus_info);
     type_register_static(&sdhci_bus_info);
     type_register_static(&imx_usdhc_info);
+    type_register_static(&sdhci_s3c_info);
 }
 
 type_init(sdhci_register_types)

include/hw/sd/sdhci.h

@@ -116,4 +116,6 @@ typedef struct SDHCIState {
 
 #define TYPE_IMX_USDHC "imx-usdhc"
 
+#define TYPE_S3C_SDHCI "s3c-sdhci"
+
 #endif /* SDHCI_H */