Re: [PATCH 1/2] q800: fix mac_via RTC PRAM commands

[Mark Cave-Ayland]

On 19/12/2019 20:14, Laurent Vivier wrote:

> The command byte is not decoded correctly.
> 
> This patch reworks the RTC/PRAM interface and fixes the problem.
> It adds a comment before the function to explain how are encoded commands
> and some trace-events to ease debugging.
> 
> Bug: https://bugs.launchpad.net/qemu/+bug/1856549
> Fixes: 6dca62a000 ("hw/m68k: add VIA support")
> Signed-off-by: Laurent Vivier <address@hidden>
> ---
>  hw/misc/mac_via.c    | 274 ++++++++++++++++++++++++++++++-------------
>  hw/misc/trace-events |  19 +++
>  2 files changed, 210 insertions(+), 83 deletions(-)
> 
> diff --git a/hw/misc/mac_via.c b/hw/misc/mac_via.c
> index f3f130ad96..e5658af922 100644
> --- a/hw/misc/mac_via.c
> +++ b/hw/misc/mac_via.c
> @@ -27,7 +27,7 @@
>  #include "sysemu/runstate.h"
>  #include "qapi/error.h"
>  #include "qemu/cutils.h"
> -
> +#include "trace.h"
>  
>  /*
>   * VIAs: There are two in every machine,
> @@ -278,6 +278,21 @@
>  /* VIA returns time offset from Jan 1, 1904, not 1970 */
>  #define RTC_OFFSET 2082844800
>  
> +enum {
> +    REG_0,
> +    REG_1,
> +    REG_2,
> +    REG_3,
> +    REG_TEST,
> +    REG_WPROTECT,
> +    REG_PRAM_ADDR,
> +    REG_PRAM_ADDR_LAST = REG_PRAM_ADDR + 19,
> +    REG_PRAM_SECT,
> +    REG_PRAM_SECT_LAST = REG_PRAM_SECT + 7,
> +    REG_INVALID,
> +    REG_EMPTY = 0xff,
> +};
> +
>  static void via1_VBL_update(MOS6522Q800VIA1State *v1s)
>  {
>      MOS6522State *s = MOS6522(v1s);
> @@ -360,10 +375,62 @@ static void via2_irq_request(void *opaque, int irq, int 
> level)
>      mdc->update_irq(s);
>  }
>  
> +/*
> + * RTC Commands
> + *
> + * Command byte    Register addressed by the command
> + *
> + * z0000001        Seconds register 0 (lowest-order byte)
> + * z0000101        Seconds register 1
> + * z0001001        Seconds register 2
> + * z0001101        Seconds register 3 (highest-order byte)
> + * 00110001        Test register (write-only)
> + * 00110101        Write-Protect Register (write-only)
> + * z010aa01        RAM address 100aa ($10-$13) (first 20 bytes only)
> + * z1aaaa01        RAM address 0aaaa ($00-$0F) (first 20 bytes only)
> + * z0111aaa        Extended memory designator and sector number
> + *
> + * For a read request, z=1, for a write z=0
> + * The letter a indicates bits whose value depend on what parameter
> + * RAM byte you want to address
> + */
> +static int via1_rtc_compact_cmd(uint8_t value)
> +{
> +    uint8_t read = value & 0x80;
> +
> +    value &= 0x7f;
> +
> +    /* the last 2 bits of a command byte must always be 0b01 ... */
> +    if ((value & 0x78) == 0x38) {
> +        /* except for the extended memory designator */
> +        return read | (REG_PRAM_SECT + (value & 0x07));
> +    }
> +    if ((value & 0x03) == 0x01) {
> +        value >>= 2;
> +        if ((value & 0x1c) == 0) {
> +            /* seconds registers */
> +            return read | (REG_0 + (value & 0x03));
> +        } else if ((value == 0x0c) && !read) {
> +            return REG_TEST;
> +        } else if ((value == 0x0d) && !read) {
> +            return REG_WPROTECT;
> +        } else if ((value & 0x1c) == 0x08) {
> +            /* RAM address 0x10 to 0x13 */
> +            return read | (REG_PRAM_ADDR + 0x10 + (value & 0x03));
> +        } else if ((value & 0x43) == 0x41) {
> +            /* RAM address 0x00 to 0x0f */
> +            return read | (REG_PRAM_ADDR + (value & 0x0f));
> +        }
> +    }
> +    return REG_INVALID;
> +}
> +
>  static void via1_rtc_update(MacVIAState *m)
>  {
>      MOS6522Q800VIA1State *v1s = &m->mos6522_via1;
>      MOS6522State *s = MOS6522(v1s);
> +    int cmd, sector, addr;
> +    uint32_t time;
>  
>      if (s->b & VIA1B_vRTCEnb) {
>          return;
> @@ -376,7 +443,9 @@ static void via1_rtc_update(MacVIAState *m)
>              m->data_out |= s->b & VIA1B_vRTCData;
>              m->data_out_cnt++;
>          }
> +        trace_via1_rtc_update_data_out(m->data_out_cnt, m->data_out);
>      } else {
> +        trace_via1_rtc_update_data_in(m->data_in_cnt, m->data_in);
>          /* receive bits from the RTC */
>          if ((v1s->last_b & VIA1B_vRTCClk) &&
>              !(s->b & VIA1B_vRTCClk) &&
> @@ -386,96 +455,132 @@ static void via1_rtc_update(MacVIAState *m)
>              m->data_in <<= 1;
>              m->data_in_cnt--;
>          }
> +        return;
>      }
>  
> -    if (m->data_out_cnt == 8) {
> -        m->data_out_cnt = 0;
> -
> -        if (m->cmd == 0) {
> -            if (m->data_out & 0x80) {
> -                /* this is a read command */
> -                uint32_t time = m->tick_offset +
> -                               (qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) /
> -                               NANOSECONDS_PER_SECOND);
> -                if (m->data_out == 0x81) {        /* seconds register 0 */
> -                    m->data_in = time & 0xff;
> -                    m->data_in_cnt = 8;
> -                } else if (m->data_out == 0x85) { /* seconds register 1 */
> -                    m->data_in = (time >> 8) & 0xff;
> -                    m->data_in_cnt = 8;
> -                } else if (m->data_out == 0x89) { /* seconds register 2 */
> -                    m->data_in = (time >> 16) & 0xff;
> -                    m->data_in_cnt = 8;
> -                } else if (m->data_out == 0x8d) { /* seconds register 3 */
> -                    m->data_in = (time >> 24) & 0xff;
> -                    m->data_in_cnt = 8;
> -                } else if ((m->data_out & 0xf3) == 0xa1) {
> -                    /* PRAM address 0x10 -> 0x13 */
> -                    int addr = (m->data_out >> 2) & 0x03;
> -                    m->data_in = v1s->PRAM[addr];
> -                    m->data_in_cnt = 8;
> -                } else if ((m->data_out & 0xf3) == 0xa1) {
> -                    /* PRAM address 0x00 -> 0x0f */
> -                    int addr = (m->data_out >> 2) & 0x0f;
> -                    m->data_in = v1s->PRAM[addr];
> -                    m->data_in_cnt = 8;
> -                } else if ((m->data_out & 0xf8) == 0xb8) {
> -                    /* extended memory designator and sector number */
> -                    m->cmd = m->data_out;
> -                }
> -            } else {
> -                /* this is a write command */
> -                m->cmd = m->data_out;
> +    if (m->data_out_cnt != 8) {
> +        return;
> +    }
> +
> +    m->data_out_cnt = 0;
> +
> +    trace_via1_rtc_internal_status(m->cmd, m->alt, m->data_out);
> +    /* first byte: it's a command */
> +    if (m->cmd == REG_EMPTY) {
> +
> +        cmd = via1_rtc_compact_cmd(m->data_out);
> +        trace_via1_rtc_internal_cmd(cmd);
> +
> +        if (cmd == REG_INVALID) {
> +            trace_via1_rtc_cmd_invalid(m->data_out);
> +            return;
> +        }
> +
> +        if (cmd & 0x80) { /* this is a read command */
> +            switch (cmd & 0x7f) {
> +            case REG_0...REG_3: /* seconds registers */
> +                /*
> +                 * register 0 is lowest-order byte
> +                 * register 3 is highest-order byte
> +                 */
> +
> +                time = m->tick_offset + 
> (qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL)
> +                       / NANOSECONDS_PER_SECOND);
> +                trace_via1_rtc_internal_time(time);
> +                m->data_in = (time >> ((cmd & 0x03) << 3)) & 0xff;
> +                m->data_in_cnt = 8;
> +                trace_via1_rtc_cmd_seconds_read((cmd & 0x7f) - REG_0,
> +                                                m->data_in);
> +                break;
> +            case REG_PRAM_ADDR...REG_PRAM_ADDR_LAST:
> +                /* PRAM address 0x00 -> 0x13 */
> +                m->data_in = v1s->PRAM[(cmd & 0x7f) - REG_PRAM_ADDR];
> +                m->data_in_cnt = 8;
> +                trace_via1_rtc_cmd_pram_read((cmd & 0x7f) - REG_PRAM_ADDR,
> +                                             m->data_in);
> +                break;
> +            case REG_PRAM_SECT...REG_PRAM_SECT_LAST:
> +                /*
> +                 * extended memory designator and sector number
> +                 * the only two-byte read command
> +                 */
> +                trace_via1_rtc_internal_set_cmd(cmd);
> +                m->cmd = cmd;
> +                break;
> +            default:
> +                g_assert_not_reached();
> +                break;
>              }
> +            return;
> +        }
> +
> +        /* this is a write command, needs a parameter */
> +        if (cmd == REG_WPROTECT || !m->wprotect) {
> +            trace_via1_rtc_internal_set_cmd(cmd);
> +            m->cmd = cmd;
>          } else {
> +            trace_via1_rtc_internal_ignore_cmd(cmd);
> +        }
> +        return;
> +    }
> +
> +    /* second byte: it's a parameter */
> +    if (m->alt == REG_EMPTY) {
> +        switch (m->cmd & 0x7f) {
> +        case REG_0...REG_3: /* seconds register */
> +            /* FIXME */
> +            trace_via1_rtc_cmd_seconds_write(m->cmd - REG_0, m->data_out);
> +            m->cmd = REG_EMPTY;
> +            break;
> +        case REG_TEST:
> +            /* device control: nothing to do */
> +            trace_via1_rtc_cmd_test_write(m->data_out);
> +            m->cmd = REG_EMPTY;
> +            break;
> +        case REG_WPROTECT:
> +            /* Write Protect register */
> +            trace_via1_rtc_cmd_wprotect_write(m->data_out);
> +            m->wprotect = !!(m->data_out & 0x80);
> +            m->cmd = REG_EMPTY;
> +            break;
> +        case REG_PRAM_ADDR...REG_PRAM_ADDR_LAST:
> +            /* PRAM address 0x00 -> 0x13 */
> +            trace_via1_rtc_cmd_pram_write(m->cmd - REG_PRAM_ADDR, 
> m->data_out);
> +            v1s->PRAM[m->cmd - REG_PRAM_ADDR] = m->data_out;
> +            m->cmd = REG_EMPTY;
> +            break;
> +        case REG_PRAM_SECT...REG_PRAM_SECT_LAST:
> +            addr = (m->data_out >> 2) & 0x1f;
> +            sector = (m->cmd & 0x7f) - REG_PRAM_SECT;
>              if (m->cmd & 0x80) {
> -                if ((m->cmd & 0xf8) == 0xb8) {
> -                    /* extended memory designator and sector number */
> -                    int sector = m->cmd & 0x07;
> -                    int addr = (m->data_out >> 2) & 0x1f;
> -
> -                    m->data_in = v1s->PRAM[sector * 8 + addr];
> -                    m->data_in_cnt = 8;
> -                }
> -            } else if (!m->wprotect) {
> -                /* this is a write command */
> -                if (m->alt != 0) {
> -                    /* extended memory designator and sector number */
> -                    int sector = m->cmd & 0x07;
> -                    int addr = (m->alt >> 2) & 0x1f;
> -
> -                    v1s->PRAM[sector * 8 + addr] = m->data_out;
> -
> -                    m->alt = 0;
> -                } else if (m->cmd == 0x01) { /* seconds register 0 */
> -                    /* FIXME */
> -                } else if (m->cmd == 0x05) { /* seconds register 1 */
> -                    /* FIXME */
> -                } else if (m->cmd == 0x09) { /* seconds register 2 */
> -                    /* FIXME */
> -                } else if (m->cmd == 0x0d) { /* seconds register 3 */
> -                    /* FIXME */
> -                } else if (m->cmd == 0x31) {
> -                    /* Test Register */
> -                } else if (m->cmd == 0x35) {
> -                    /* Write Protect register */
> -                    m->wprotect = m->data_out & 1;
> -                } else if ((m->cmd & 0xf3) == 0xa1) {
> -                    /* PRAM address 0x10 -> 0x13 */
> -                    int addr = (m->cmd >> 2) & 0x03;
> -                    v1s->PRAM[addr] = m->data_out;
> -                } else if ((m->cmd & 0xf3) == 0xa1) {
> -                    /* PRAM address 0x00 -> 0x0f */
> -                    int addr = (m->cmd >> 2) & 0x0f;
> -                    v1s->PRAM[addr] = m->data_out;
> -                } else if ((m->cmd & 0xf8) == 0xb8) {
> -                    /* extended memory designator and sector number */
> -                    m->alt = m->cmd;
> -                }
> +                /* it's a read */
> +                m->data_in = v1s->PRAM[sector * 32 + addr];
> +                m->data_in_cnt = 8;
> +                trace_via1_rtc_cmd_pram_sect_read(sector, addr,
> +                                                  sector * 32 + addr,
> +                                                  m->data_in);
> +                m->cmd = REG_EMPTY;
> +            } else {
> +                /* it's a write, we need one more parameter */
> +                trace_via1_rtc_internal_set_alt(addr, sector, addr);
> +                m->alt = addr;
>              }
> +            break;
> +        default:
> +            g_assert_not_reached();
> +            break;
>          }
> -        m->data_out = 0;
> +        return;
>      }
> +
> +    /* third byte: it's the data of a REG_PRAM_SECT write */
> +    g_assert(REG_PRAM_SECT <= m->cmd && m->cmd <= REG_PRAM_SECT_LAST);
> +    sector = m->cmd - REG_PRAM_SECT;
> +    v1s->PRAM[sector * 32 + m->alt] = m->data_out;
> +    trace_via1_rtc_cmd_pram_sect_write(sector, m->alt, sector * 32 + m->alt,
> +                                       m->data_out);
> +    m->alt = REG_EMPTY;
> +    m->cmd = REG_EMPTY;
>  }
>  
>  static int adb_via_poll(MacVIAState *s, int state, uint8_t *data)
> @@ -742,6 +847,9 @@ static void mac_via_reset(DeviceState *dev)
>      v1s->next_VBL = 0;
>      timer_del(v1s->one_second_timer);
>      v1s->next_second = 0;
> +
> +    m->cmd = REG_EMPTY;
> +    m->alt = REG_EMPTY;
>  }
>  
>  static void mac_via_realize(DeviceState *dev, Error **errp)
> diff --git a/hw/misc/trace-events b/hw/misc/trace-events
> index 1deb1d08c1..2e0c820834 100644
> --- a/hw/misc/trace-events
> +++ b/hw/misc/trace-events
> @@ -149,3 +149,22 @@ bcm2835_mbox_write(unsigned int size, uint64_t addr, 
> uint64_t value) "mbox write
>  bcm2835_mbox_read(unsigned int size, uint64_t addr, uint64_t value) "mbox 
> read sz:%u addr:0x%"PRIx64" data:0x%"PRIx64
>  bcm2835_mbox_irq(unsigned level) "mbox irq:ARM level:%u"
>  bcm2835_mbox_property(uint32_t tag, uint32_t bufsize, size_t resplen) "mbox 
> property tag:0x%08x in_sz:%u out_sz:%zu"
> +
> +# mac_via.c
> +via1_rtc_update_data_out(int count, int value) "count=%d value=0x%02x"
> +via1_rtc_update_data_in(int count, int value) "count=%d value=0x%02x"
> +via1_rtc_internal_status(int cmd, int alt, int value) "cmd=0x%02x alt=0x%02x 
> value=0x%02x"
> +via1_rtc_internal_cmd(int cmd) "cmd=0x%02x"
> +via1_rtc_cmd_invalid(int value) "value=0x%02x"
> +via1_rtc_internal_time(uint32_t time) "time=0x%08x"
> +via1_rtc_internal_set_cmd(int cmd) "cmd=0x%02x"
> +via1_rtc_internal_ignore_cmd(int cmd) "cmd=0x%02x"
> +via1_rtc_internal_set_alt(int alt, int sector, int offset) "alt=0x%02x 
> sector=%u offset=%u"
> +via1_rtc_cmd_seconds_read(int reg, int value) "reg=%d value=0x%02x"
> +via1_rtc_cmd_seconds_write(int reg, int value) "reg=%d value=0x%02x"
> +via1_rtc_cmd_test_write(int value) "value=0x%02x"
> +via1_rtc_cmd_wprotect_write(int value) "value=0x%02x"
> +via1_rtc_cmd_pram_read(int addr, int value) "addr=%u value=0x%02x"
> +via1_rtc_cmd_pram_write(int addr, int value) "addr=%u value=0x%02x"
> +via1_rtc_cmd_pram_sect_read(int sector, int offset, int addr, int value) 
> "sector=%u offset=%u addr=%d value=0x%02x"
> +via1_rtc_cmd_pram_sect_write(int sector, int offset, int addr, int value) 
> "sector=%u offset=%u addr=%d value=0x%02x"

Seems like a good improvement to me.

Reviewed-by: Mark Cave-Ayland <address@hidden>


ATB,

Mark.