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Re: [Qemu-devel] [PATCH-for-4.1 v6 3/5] hw/block/pflash_cfi01: Extract p


From: Alistair Francis
Subject: Re: [Qemu-devel] [PATCH-for-4.1 v6 3/5] hw/block/pflash_cfi01: Extract pflash_mode_read_array()
Date: Tue, 16 Jul 2019 15:53:36 -0700

On Tue, Jul 16, 2019 at 3:16 PM Philippe Mathieu-Daudé
<address@hidden> wrote:
>
> The same pattern is used when setting the flash in READ_ARRAY mode:
> - Set the state machine command to READ_ARRAY
> - Reset the write_cycle counter
> - Reset the memory region in ROMD
>
> Refactor the current code by extracting this pattern.
> It is used three times:
>
> - On a read access (on invalid command).
>
>   Note this default case is not reachable by the state machine
>   updates in pflash_data_write(). However we might reach this
>   case migrating from a future QEMU version that would implement
>   newer commands, without incrementing the migration version.
>   Since we never know, we keep this default case.
>
>   Previous to this patch, an invalid read command would not reset
>   the memory region in ROMD mode, so:
>
>   . A further read access would keep going into I/O mode, calling
>   the same switch in pflash_read(). Undefined behaviour, probably
>   unexpected.
>   . A further write access in I/O mode. Since the default case set
>   (wcycle=0, cmd=0x00), we jump to reset_flash which set the flash
>   in READ_ARRAY.
>
>   After this patch, if we get an invalid read command we directly
>   set (wcycle=0, cmd=0x00) and put the device in ROMD mode.
>   Further I/O access are now properly handled.
>
> - On a write access (on command failure, error, or explicitly asked)
>
> - When the device is initialized. Here the ROMD mode is hidden
>   by the memory_region_init_rom_device() call.
>
> Signed-off-by: Philippe Mathieu-Daudé <address@hidden>

Reviewed-by: Alistair Francis <address@hidden>

Alistair

> ---
> v6: split of the label rename to ease review
>     the pattern is used 3 times (was 2 times previously)
>     describe the 3rd time and reset the review tags :(
> ---
>  hw/block/pflash_cfi01.c | 31 +++++++++++++++----------------
>  hw/block/trace-events   |  1 +
>  2 files changed, 16 insertions(+), 16 deletions(-)
>
> diff --git a/hw/block/pflash_cfi01.c b/hw/block/pflash_cfi01.c
> index 6838e8a1ab..a28d0f8cc7 100644
> --- a/hw/block/pflash_cfi01.c
> +++ b/hw/block/pflash_cfi01.c
> @@ -112,6 +112,18 @@ static const VMStateDescription vmstate_pflash = {
>      }
>  };
>
> +static void pflash_mode_read_array(PFlashCFI01 *pfl)
> +{
> +    trace_pflash_mode_read_array();
> +    /*
> +     * The command 0x00 is not assigned by the CFI open standard,
> +     * but QEMU historically uses it for the READ_ARRAY command (0xff).
> +     */
> +    pfl->cmd = 0x00;
> +    pfl->wcycle = 0;
> +    memory_region_rom_device_set_romd(&pfl->mem, true);
> +}
> +
>  /* Perform a CFI query based on the bank width of the flash.
>   * If this code is called we know we have a device_width set for
>   * this flash.
> @@ -276,12 +288,7 @@ static uint32_t pflash_read(PFlashCFI01 *pfl, hwaddr 
> offset,
>      default:
>          /* This should never happen : reset state & treat it as a read */
>          DPRINTF("%s: unknown command state: %x\n", __func__, pfl->cmd);
> -        pfl->wcycle = 0;
> -        /*
> -         * The command 0x00 is not assigned by the CFI open standard,
> -         * but QEMU historically uses it for the READ_ARRAY command (0xff).
> -         */
> -        pfl->cmd = 0x00;
> +        pflash_mode_read_array(pfl);
>          /* fall through to read code */
>      case 0x00: /* This model reset value for READ_ARRAY (not CFI compliant) 
> */
>          /* Flash area read */
> @@ -646,10 +653,7 @@ static void pflash_write(PFlashCFI01 *pfl, hwaddr offset,
>                    "\n", __func__, offset, pfl->wcycle, pfl->cmd, value);
>
>   reset_flash:
> -    trace_pflash_reset();
> -    memory_region_rom_device_set_romd(&pfl->mem, true);
> -    pfl->wcycle = 0;
> -    pfl->cmd = 0x00; /* This model reset value for READ_ARRAY (not CFI) */
> +    pflash_mode_read_array(pfl);
>  }
>
>
> @@ -764,12 +768,7 @@ static void pflash_cfi01_realize(DeviceState *dev, Error 
> **errp)
>          pfl->max_device_width = pfl->device_width;
>      }
>
> -    pfl->wcycle = 0;
> -    /*
> -     * The command 0x00 is not assigned by the CFI open standard,
> -     * but QEMU historically uses it for the READ_ARRAY command (0xff).
> -     */
> -    pfl->cmd = 0x00;
> +    pflash_mode_read_array(pfl);
>      pfl->status = 0x80; /* WSM ready */
>      /* Hardcoded CFI table */
>      /* Standard "QRY" string */
> diff --git a/hw/block/trace-events b/hw/block/trace-events
> index 13d1b21dd4..91a8a106c0 100644
> --- a/hw/block/trace-events
> +++ b/hw/block/trace-events
> @@ -7,6 +7,7 @@ fdc_ioport_write(uint8_t reg, uint8_t value) "write reg 
> 0x%02x val 0x%02x"
>  # pflash_cfi02.c
>  # pflash_cfi01.c
>  pflash_reset(void) "reset"
> +pflash_mode_read_array(void) "mode: read array"
>  pflash_timer_expired(uint8_t cmd) "command 0x%02x done"
>  pflash_io_read(uint64_t offset, int width, int fmt_width, uint32_t value, 
> uint8_t cmd, uint8_t wcycle) "offset:0x%04"PRIx64" width:%d value:0x%0*x 
> cmd:0x%02x wcycle:%u"
>  pflash_io_write(uint64_t offset, int width, int fmt_width, uint32_t value, 
> uint8_t wcycle) "offset:0x%04"PRIx64" width:%d value:0x%0*x wcycle:%u"
> --
> 2.20.1
>
>



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