Re: [Qemu-devel] [PATCH v3] aspeed/smc: handle dummy bytes when doing fast reads in command mode

["mar.krzeminski" <mar.krzeminski@gmail.com>]

W dniu 18.01.2017 o 16:01, Cédric Le Goater pisze:
> When doing fast read, a certain amount of dummy bytes should be sent
> before the read. This number is configurable in the controler CE0
> Control Register and needs to be modeled using fake transfers to the
> flash module.
>
> This only supports command mode. User mode requires more work and a
> possible extension of the m25p80 device model.
>
> Signed-off-by: Cédric Le Goater <clg@kaod.org>
> ---
>
>   Changes since v2:
>
>   - handled dummies under read routine and removed the test on the spi
>     command READ_FAST (0xb)
>
>   hw/ssi/aspeed_smc.c | 21 +++++++++++++++++++++
>   1 file changed, 21 insertions(+)
>
> diff --git a/hw/ssi/aspeed_smc.c b/hw/ssi/aspeed_smc.c
> index a0a816407fc1..fc3cccec0566 100644
> --- a/hw/ssi/aspeed_smc.c
> +++ b/hw/ssi/aspeed_smc.c
> @@ -69,7 +69,9 @@
>   #define R_CTRL0           (0x10 / 4)
>   #define   CTRL_CMD_SHIFT           16
>   #define   CTRL_CMD_MASK            0xff
> +#define   CTRL_DUMMY_HIGH_SHIFT    14
>   #define   CTRL_AST2400_SPI_4BYTE   (1 << 13)
> +#define   CTRL_DUMMY_LOW_SHIFT     6 /* 2 bits [7:6] */
>   #define   CTRL_CE_STOP_ACTIVE      (1 << 2)
>   #define   CTRL_CMD_MODE_MASK       0x3
>   #define     CTRL_READMODE          0x0
> @@ -490,6 +492,16 @@ static uint32_t aspeed_smc_check_segment_addr(const AspeedSMCFlash *fl,
>       return addr;
>   }
>   
> +static int aspeed_smc_flash_dummies(const AspeedSMCFlash *fl)
> +{
> +    const AspeedSMCState *s = fl->controller;
> +    uint32_t r_ctrl0 = s->regs[s->r_ctrl0 + fl->id];
> +    uint32_t dummy_high = (r_ctrl0 >> CTRL_DUMMY_HIGH_SHIFT) & 0x1;
> +    uint32_t dummy_low = (r_ctrl0 >> CTRL_DUMMY_LOW_SHIFT) & 0x3;
> +
> +    return ((dummy_high << 2) | dummy_low) * 8;
> +}
> +
>   static void aspeed_smc_flash_send_addr(AspeedSMCFlash *fl, uint32_t addr)
>   {
>       const AspeedSMCState *s = fl->controller;
> @@ -526,6 +538,15 @@ static uint64_t aspeed_smc_flash_read(void *opaque, hwaddr addr, unsigned size)
>           aspeed_smc_flash_select(fl);
>           aspeed_smc_flash_send_addr(fl, addr);
>   
> +        /*
> +         * Use fake transfers to model dummy bytes. The value should
> +         * be configured to some non-zero value in fast read mode and
> +         * zero in read mode.
> +         */
> +        for (i = 0; i < aspeed_smc_flash_dummies(fl); i++) {
> +            ssi_transfer(fl->controller->spi, 0xFF);
> +        }
> +
>           for (i = 0; i < size; i++) {
>               ret |= ssi_transfer(s->spi, 0x0) << (8 * i);
>           }
If it does not break CTRL_WRITEMODE then:
Acked-by: Marcin Krzemiński <mar.krzeminski@gmail.com>