Re: [PATCH v2 03/25] hw/sd: ssi-sd: Fix incorrect card response sequence

[Philippe Mathieu-Daudé]

On 1/23/21 11:39 AM, Bin Meng wrote:
> From: Bin Meng <bin.meng@windriver.com>
> 
> Per the "Physical Layer Specification Version 8.00" chapter 7.5.1,
> "Command/Response", there is a minimum 8 clock cycles (Ncr) before
> the card response shows up on the data out line. However current
> implementation jumps directly to the sending response state after
> all 6 bytes command is received, which is a spec violation.
> 
> Add a new state PREP_RESP in the ssi-sd state machine to handle it.
> 
> Fixes: 775616c3ae8c ("Partial SD card SPI mode support")
> Signed-off-by: Bin Meng <bin.meng@windriver.com>
> Reviewed-by: Pragnesh Patel <pragnesh.patel@sifive.com>
> Tested-by: Pragnesh Patel <pragnesh.patel@sifive.com>
> 
> ---
> 
> Changes in v2:
> - Add a debug printf in the state handling codes
> 
>  hw/sd/ssi-sd.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/hw/sd/ssi-sd.c b/hw/sd/ssi-sd.c
> index 9a75e0095c..043e270066 100644
> --- a/hw/sd/ssi-sd.c
> +++ b/hw/sd/ssi-sd.c
> @@ -36,6 +36,7 @@ do { fprintf(stderr, "ssi_sd: error: " fmt , ## 
> __VA_ARGS__);} while (0)
>  typedef enum {
>      SSI_SD_CMD = 0,
>      SSI_SD_CMDARG,
> +    SSI_SD_PREP_RESP,

Another migration change.

Otherwise (trusting you with the spec):
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>

>      SSI_SD_RESPONSE,
>      SSI_SD_DATA_START,
>      SSI_SD_DATA_READ,
> @@ -163,12 +164,16 @@ static uint32_t ssi_sd_transfer(SSIPeripheral *dev, 
> uint32_t val)
>                  s->response[1] = status;
>                  DPRINTF("Card status 0x%02x\n", status);
>              }
> -            s->mode = SSI_SD_RESPONSE;
> +            s->mode = SSI_SD_PREP_RESP;
>              s->response_pos = 0;
>          } else {
>              s->cmdarg[s->arglen++] = val;
>          }
>          return 0xff;
> +    case SSI_SD_PREP_RESP:
> +        DPRINTF("Prepare card response (Ncr)\n");
> +        s->mode = SSI_SD_RESPONSE;
> +        return 0xff;
>      case SSI_SD_RESPONSE:
>          if (s->stopping) {
>              s->stopping = 0;
>