Re: [PATCH v2 1/2] hw: m25p80: add WP# pin and SRWD bit for write protection

[Francisco Iglesias <frasse.iglesias@gmail.com>]

Hi Iris,

Looks good some, a couple of comments below.

On [2022 Jun 08] Wed 20:13:19, Iris Chen wrote:
> From: Iris Chen <irischenlj@gmail.com>
> 
> Signed-off-by: Iris Chen <irischenlj@gmail.com>
> ---
> Addressed all comments from V1. The biggest change: removed object_class_property_add.
> 
>  hw/block/m25p80.c             | 37 +++++++++++++++++++++++++++++++++++
>  tests/qtest/aspeed_smc-test.c |  2 ++
>  2 files changed, 39 insertions(+)
> 
> diff --git a/hw/block/m25p80.c b/hw/block/m25p80.c
> index 81ba3da4df..1a20bd55d4 100644
> --- a/hw/block/m25p80.c
> +++ b/hw/block/m25p80.c
> @@ -27,12 +27,14 @@
>  #include "hw/qdev-properties.h"
>  #include "hw/qdev-properties-system.h"
>  #include "hw/ssi/ssi.h"
> +#include "hw/irq.h"
>  #include "migration/vmstate.h"
>  #include "qemu/bitops.h"
>  #include "qemu/log.h"
>  #include "qemu/module.h"
>  #include "qemu/error-report.h"
>  #include "qapi/error.h"
> +#include "qapi/visitor.h"
>  #include "trace.h"
>  #include "qom/object.h"
>  
> @@ -472,11 +474,13 @@ struct Flash {
>      uint8_t spansion_cr2v;
>      uint8_t spansion_cr3v;
>      uint8_t spansion_cr4v;
> +    bool wp_level;
>      bool write_enable;
>      bool four_bytes_address_mode;
>      bool reset_enable;
>      bool quad_enable;
>      bool aai_enable;
> +    bool status_register_write_disabled;
>      uint8_t ear;
>  
>      int64_t dirty_page;
> @@ -723,6 +727,21 @@ static void complete_collecting_data(Flash *s)
>          flash_erase(s, s->cur_addr, s->cmd_in_progress);
>          break;
>      case WRSR:
> +        /*
> +         * If WP# is low and status_register_write_disabled is high,
> +         * status register writes are disabled.
> +         * This is also called "hardware protected mode" (HPM). All other
> +         * combinations of the two states are called "software protected mode"
> +         * (SPM), and status register writes are permitted.
> +         */
> +        if ((s->wp_level == 0 && s->status_register_write_disabled)
> +            || !s->write_enable) {

'write_enable' needs to be true in 'decode_new_cmd' when issueing the WRSR
command, otherwise the state machinery will not advance to this function
(meaning that above check for !s->write_enable will never hit as far as I can
tell). A suggestion is to move the check for wp_level and
status_reg_wr_disabled into 'decode_new_cmd' to for keeping it consistent.

> +            qemu_log_mask(LOG_GUEST_ERROR,
> +                          "M25P80: Status register write is disabled!\n");
> +            break;
> +        }
> +        s->status_register_write_disabled = extract32(s->data[0], 7, 1);
> +
>          switch (get_man(s)) {
>          case MAN_SPANSION:
>              s->quad_enable = !!(s->data[1] & 0x02);
> @@ -1195,6 +1214,8 @@ static void decode_new_cmd(Flash *s, uint32_t value)
>  
>      case RDSR:
>          s->data[0] = (!!s->write_enable) << 1;
> +        s->data[0] |= (!!s->status_register_write_disabled) << 7;
> +
>          if (get_man(s) == MAN_MACRONIX || get_man(s) == MAN_ISSI) {
>              s->data[0] |= (!!s->quad_enable) << 6;
>          }
> @@ -1484,6 +1505,14 @@ static uint32_t m25p80_transfer8(SSIPeripheral *ss, uint32_t tx)
>      return r;
>  }
>  
> +static void m25p80_write_protect_pin_irq_handler(void *opaque, int n, int level)
> +{
> +    Flash *s = M25P80(opaque);
> +    /* WP# is just a single pin. */
> +    assert(n == 0);
> +    s->wp_level = !!level;
> +}
> +
>  static void m25p80_realize(SSIPeripheral *ss, Error **errp)
>  {
>      Flash *s = M25P80(ss);
> @@ -1515,12 +1544,18 @@ static void m25p80_realize(SSIPeripheral *ss, Error **errp)
>          s->storage = blk_blockalign(NULL, s->size);
>          memset(s->storage, 0xFF, s->size);
>      }
> +
> +    qdev_init_gpio_in_named(DEVICE(s),
> +                            m25p80_write_protect_pin_irq_handler, "WP#", 1);
>  }
>  
>  static void m25p80_reset(DeviceState *d)
>  {
>      Flash *s = M25P80(d);
>  
> +    s->wp_level = true;
> +    s->status_register_write_disabled = false;
> +
>      reset_memory(s);
>  }
>  
> @@ -1601,6 +1636,8 @@ static const VMStateDescription vmstate_m25p80 = {
>          VMSTATE_UINT8(needed_bytes, Flash),
>          VMSTATE_UINT8(cmd_in_progress, Flash),
>          VMSTATE_UINT32(cur_addr, Flash),
> +        VMSTATE_BOOL(wp_level, Flash),
> +        VMSTATE_BOOL(status_register_write_disabled, Flash),

Above needs to be added through a subsection, you can see commit 465ef47abe3
for an example an also read about this in docs/devel/migration.rst.

Thank you,
Best regads,
Francisco Iglesias


>          VMSTATE_BOOL(write_enable, Flash),
>          VMSTATE_BOOL(reset_enable, Flash),
>          VMSTATE_UINT8(ear, Flash),
> diff --git a/tests/qtest/aspeed_smc-test.c b/tests/qtest/aspeed_smc-test.c
> index ec233315e6..c5d97d4410 100644
> --- a/tests/qtest/aspeed_smc-test.c
> +++ b/tests/qtest/aspeed_smc-test.c
> @@ -56,7 +56,9 @@ enum {
>      BULK_ERASE = 0xc7,
>      READ = 0x03,
>      PP = 0x02,
> +    WRSR = 0x1,
>      WREN = 0x6,
> +    SRWD = 0x80,
>      RESET_ENABLE = 0x66,
>      RESET_MEMORY = 0x99,
>      EN_4BYTE_ADDR = 0xB7,
> -- 
> 2.30.2
> 
>