Re: [PATCH 07/22] hw/sd: ssi-sd: Suffix a data block with CRC16

[Alistair Francis]

On Thu, Dec 31, 2020 at 3:38 AM Bin Meng <bmeng.cn@gmail.com> wrote:
>
> From: Bin Meng <bin.meng@windriver.com>
>
> Per the SD spec, a valid data block is suffixed with a 16-bit CRC
> generated by the standard CCITT polynomial x16+x12+x5+1. This part
> is currently missing in the ssi-sd state machine. Without it, all
> data block transfer fails in guest software because the expected
> CRC16 is missing on the data out line.
>
> Fixes: 775616c3ae8c ("Partial SD card SPI mode support")
> Signed-off-by: Bin Meng <bin.meng@windriver.com>

Acked-by: Alistair Francis <alistair.francis@wdc.com>

Alistair

> ---
>
>  hw/sd/ssi-sd.c | 17 +++++++++++++++++
>  1 file changed, 17 insertions(+)
>
> diff --git a/hw/sd/ssi-sd.c b/hw/sd/ssi-sd.c
> index 228ce4ddc7..10b0ac2eaf 100644
> --- a/hw/sd/ssi-sd.c
> +++ b/hw/sd/ssi-sd.c
> @@ -17,6 +17,7 @@
>  #include "hw/qdev-properties.h"
>  #include "hw/sd/sd.h"
>  #include "qapi/error.h"
> +#include "qemu/crc-ccitt.h"
>  #include "qemu/module.h"
>  #include "qom/object.h"
>
> @@ -40,6 +41,7 @@ typedef enum {
>      SSI_SD_RESPONSE,
>      SSI_SD_DATA_START,
>      SSI_SD_DATA_READ,
> +    SSI_SD_DATA_CRC16,
>  } ssi_sd_mode;
>
>  struct ssi_sd_state {
> @@ -48,6 +50,7 @@ struct ssi_sd_state {
>      int cmd;
>      uint8_t cmdarg[4];
>      uint8_t response[5];
> +    uint16_t crc16;
>      int32_t arglen;
>      int32_t response_pos;
>      int32_t stopping;
> @@ -193,12 +196,24 @@ static uint32_t ssi_sd_transfer(SSIPeripheral *dev, 
> uint32_t val)
>      case SSI_SD_DATA_START:
>          DPRINTF("Start read block\n");
>          s->mode = SSI_SD_DATA_READ;
> +        s->response_pos = 0;
>          return 0xfe;
>      case SSI_SD_DATA_READ:
>          val = sdbus_read_byte(&s->sdbus);
> +        s->crc16 = crc_ccitt_false(s->crc16, (uint8_t *)&val, 1);
>          if (!sdbus_data_ready(&s->sdbus)) {
>              DPRINTF("Data read end\n");
> +            s->mode = SSI_SD_DATA_CRC16;
> +        }
> +        return val;
> +    case SSI_SD_DATA_CRC16:
> +        val = (s->crc16 & 0xff00) >> 8;
> +        s->crc16 <<= 8;
> +        s->response_pos++;
> +        if (s->response_pos == 2) {
> +            DPRINTF("CRC16 read end\n");
>              s->mode = SSI_SD_CMD;
> +            s->response_pos = 0;
>          }
>          return val;
>      }
> @@ -236,6 +251,7 @@ static const VMStateDescription vmstate_ssi_sd = {
>          VMSTATE_INT32(cmd, ssi_sd_state),
>          VMSTATE_UINT8_ARRAY(cmdarg, ssi_sd_state, 4),
>          VMSTATE_UINT8_ARRAY(response, ssi_sd_state, 5),
> +        VMSTATE_UINT16(crc16, ssi_sd_state),
>          VMSTATE_INT32(arglen, ssi_sd_state),
>          VMSTATE_INT32(response_pos, ssi_sd_state),
>          VMSTATE_INT32(stopping, ssi_sd_state),
> @@ -287,6 +303,7 @@ static void ssi_sd_reset(DeviceState *dev)
>      s->cmd = 0;
>      memset(s->cmdarg, 0, sizeof(s->cmdarg));
>      memset(s->response, 0, sizeof(s->response));
> +    s->crc16 = 0;
>      s->arglen = 0;
>      s->response_pos = 0;
>      s->stopping = 0;
> --
> 2.25.1
>
>