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#n263

Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
---
Eventually we should add the ADMA changes Igor sent in this patch:
https://patchwork.ozlabs.org/patch/181854/
They might solve the boot timing issues when using SD cards.
---
 hw/sd/sdhci.c         | 65 +++++++++++++++++++++++++++++++++++++++++++
 include/hw/sd/sdhci.h |  2 ++
 2 files changed, 67 insertions(+)

diff --git a/hw/sd/sdhci.c b/hw/sd/sdhci.c
index 82ec5c1b4a..88404d0e9d 100644
--- a/hw/sd/sdhci.c
+++ b/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)
diff --git a/include/hw/sd/sdhci.h b/include/hw/sd/sdhci.h
index cbf415e43a..c6868c9699 100644
--- a/include/hw/sd/sdhci.h
+++ b/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 */
-- 
2.20.1

On Sat, Oct 05, 2019 at 05:47:46PM +0200, Philippe Mathieu-Daudé wrote:
> 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.

The CONTROL2  has also few other settings, not clock related, but they
can be skipped as well.

Reviewed-by: Krzysztof Kozlowski <krzk@kernel.org>

Best regards,
Krzysztof

> 
> [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#n263
> 
> Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
> ---
> Eventually we should add the ADMA changes Igor sent in this patch:
> https://patchwork.ozlabs.org/patch/181854/
> They might solve the boot timing issues when using SD cards.
> ---
>  hw/sd/sdhci.c         | 65 +++++++++++++++++++++++++++++++++++++++++++
>  include/hw/sd/sdhci.h |  2 ++
>  2 files changed, 67 insertions(+)
>