Re: [Qemu-devel] [PATCH v3 2/2] Add AT24Cxx I2C EEPROM device model

[Jan Kiszka]

On 2013-04-26 14:16, Peter Crosthwaite wrote:
> Hi Jan,
> 
> On Fri, Apr 26, 2013 at 7:19 PM, Jan Kiszka <address@hidden> wrote:
>> This implements I2C EEPROMs of the AT24Cxx series. Sizes from 1Kbit to
>> 1024Kbit are supported. Each EEPROM is backed by a block device. Its
>> size can be explicitly specified by the "size" property (required for
>> sizes < 512, the blockdev sector size) or is derived from the size of
>> the backing block device. Device addresses are built from the device
>> number property. Write protection can be configured by declaring the
>> block device read-only.
>>
>> Signed-off-by: Jan Kiszka <address@hidden>
>> ---
>>  hw/nvram/Makefile.objs |    2 +-
>>  hw/nvram/at24.c        |  347 
>> ++++++++++++++++++++++++++++++++++++++++++++++++
>>  2 files changed, 348 insertions(+), 1 deletions(-)
>>  create mode 100644 hw/nvram/at24.c
>>
>> diff --git a/hw/nvram/Makefile.objs b/hw/nvram/Makefile.objs
>> index e9a6694..8271cd6 100644
>> --- a/hw/nvram/Makefile.objs
>> +++ b/hw/nvram/Makefile.objs
>> @@ -1,5 +1,5 @@
>>  common-obj-$(CONFIG_DS1225Y) += ds1225y.o
>> -common-obj-y += eeprom93xx.o
>> +common-obj-y += eeprom93xx.o at24.o
>>  common-obj-y += fw_cfg.o
>>  common-obj-$(CONFIG_MAC_NVRAM) += mac_nvram.o
>>  obj-$(CONFIG_PSERIES) += spapr_nvram.o
>> diff --git a/hw/nvram/at24.c b/hw/nvram/at24.c
>> new file mode 100644
>> index 0000000..91e58e0
>> --- /dev/null
>> +++ b/hw/nvram/at24.c
>> @@ -0,0 +1,347 @@
>> +/*
>> + * AT24Cxx EEPROM emulation
>> + *
>> + * Copyright (c) Siemens AG, 2012, 2013
>> + * Author: Jan Kiszka
>> + *
>> + * Permission is hereby granted, free of charge, to any person obtaining a 
>> copy
>> + * of this software and associated documentation files (the "Software"), to 
>> deal
>> + * in the Software without restriction, including without limitation the 
>> rights
>> + * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
>> + * copies of the Software, and to permit persons to whom the Software is
>> + * furnished to do so, subject to the following conditions:
>> + *
>> + * The above copyright notice and this permission notice shall be included 
>> in
>> + * all copies or substantial portions of the Software.
>> + *
>> + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS 
>> OR
>> + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
>> + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
>> + * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR 
>> OTHER
>> + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING 
>> FROM,
>> + * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
>> + * THE SOFTWARE.
>> + */
>> +
>> +#include "hw/hw.h"
>> +#include "hw/i2c/i2c.h"
>> +#include "hw/block/block.h"
>> +#include "sysemu/blockdev.h"
>> +
>> +#define TYPE_AT24 "at24"
>> +#define AT24(obj) OBJECT_CHECK(AT24State, (obj), TYPE_AT24)
>> +
>> +#define AT24_BASE_ADDRESS   0x50
>> +#define AT24_MAX_PAGE_LEN   256
>> +
>> +typedef struct AT24Parameters {
>> +    unsigned int size;
>> +    unsigned int page_size;
>> +    unsigned int device_bits;
>> +    unsigned int hi_addr_bits;
>> +    bool addr16;
>> +} AT24Parameters;
>> +
>> +typedef enum AT24TransferState {
>> +    AT24_IDLE,
>> +    AT24_RD_ADDR,
>> +    AT24_WR_ADDR_HI,
>> +    AT24_WR_ADDR_LO,
>> +    AT24_RW_DATA0,
>> +    AT24_RD_DATA,
>> +    AT24_WR_DATA,
>> +} AT24TransferState;
>> +
>> +typedef struct AT24State {
>> +    I2CSlave parent_obj;
>> +
>> +    BlockConf block_conf;
>> +    BlockDriverState *bs;
>> +    uint32_t size;
>> +    bool wp;
>> +    unsigned int addr_mask;
>> +    unsigned int page_mask;
>> +    bool addr16;
>> +    unsigned int hi_addr_mask;
>> +    uint8_t device;
>> +    AT24TransferState transfer_state;
>> +    uint8_t sector_buffer[BDRV_SECTOR_SIZE];
>> +    int cached_sector;
>> +    bool cache_dirty;
>> +    uint32_t transfer_addr;
>> +} AT24State;
>> +
>> +static void at24_flush_transfer_buffer(AT24State *s)
>> +{
>> +    if (s->cached_sector < 0 || !s->cache_dirty) {
>> +        return;
>> +    }
>> +    bdrv_write(s->bs, s->cached_sector, s->sector_buffer, 1);
>> +    s->cache_dirty = false;
>> +}
>> +
>> +static void at24_event(I2CSlave *i2c, enum i2c_event event, uint8_t param)
>> +{
>> +    AT24State *s = AT24(i2c);
>> +
>> +    switch (event) {
>> +    case I2C_START_SEND:
>> +        switch (s->transfer_state) {
>> +        case AT24_IDLE:
>> +            if (s->addr16) {
>> +                s->transfer_addr = (param & s->hi_addr_mask) << 16;
>> +                s->transfer_state = AT24_WR_ADDR_HI;
>> +            } else {
>> +                s->transfer_addr = (param & s->hi_addr_mask) << 8;
>> +                s->transfer_state = AT24_WR_ADDR_LO;
>> +            }
>> +            break;
>> +        default:
>> +            s->transfer_state = AT24_IDLE;
>> +            break;
>> +        }
>> +        break;
>> +    case I2C_START_RECV:
>> +        switch (s->transfer_state) {
>> +        case AT24_IDLE:
>> +            s->transfer_state = AT24_RD_ADDR;
>> +            break;
>> +        case AT24_RW_DATA0:
>> +            s->transfer_state = AT24_RD_DATA;
>> +            break;
>> +        default:
>> +            s->transfer_state = AT24_IDLE;
>> +            break;
>> +        }
>> +        break;
>> +    case I2C_FINISH:
>> +        switch (s->transfer_state) {
>> +        case AT24_WR_DATA:
>> +            at24_flush_transfer_buffer(s);
>> +            /* fall through */
>> +        default:
>> +            s->transfer_state = AT24_IDLE;
>> +            break;
>> +        }
>> +        break;
>> +    default:
>> +        s->transfer_state = AT24_IDLE;
>> +        break;
>> +    }
>> +}
>> +
>> +static int at24_cache_sector(AT24State *s, int sector)
>> +{
>> +    int ret;
>> +
>> +    if (s->cached_sector == sector) {
>> +        return 0;
>> +    }
>> +    ret = bdrv_read(s->bs, sector, s->sector_buffer, 1);
>> +    if (ret < 0) {
>> +        s->cached_sector = -1;
>> +        return ret;
>> +    }
>> +    s->cached_sector = sector;
>> +    s->cache_dirty = false;
>> +    return 0;
>> +}
>> +
>> +static int at24_tx(I2CSlave *i2c, uint8_t data)
>> +{
>> +    AT24State *s = AT24(i2c);
>> +
>> +    switch (s->transfer_state) {
>> +    case AT24_WR_ADDR_HI:
>> +        s->transfer_addr |= (data << 8) & s->addr_mask;
>> +        s->transfer_state = AT24_WR_ADDR_LO;
>> +        break;
>> +    case AT24_WR_ADDR_LO:
>> +        s->transfer_addr |= data & s->addr_mask;
>> +        s->transfer_state = AT24_RW_DATA0;
>> +        break;
>> +    case AT24_RW_DATA0:
>> +        s->transfer_state = AT24_WR_DATA;
>> +        if (at24_cache_sector(s, s->transfer_addr >> BDRV_SECTOR_BITS) < 0) 
>> {
>> +            s->transfer_state = AT24_IDLE;
>> +            return -1;
>> +        }
>> +        /* fall through */
>> +    case AT24_WR_DATA:
>> +        if (!s->wp) {
>> +            s->sector_buffer[s->transfer_addr & ~BDRV_SECTOR_MASK] = data;
>> +            s->cache_dirty = true;
>> +        }
>> +        s->transfer_addr = (s->transfer_addr & s->page_mask) |
>> +            ((s->transfer_addr + 1) & ~s->page_mask);
>> +        break;
>> +    default:
>> +        s->transfer_state = AT24_IDLE;
>> +        return -1;
>> +    }
>> +    return 0;
>> +}
>> +
>> +static int at24_rx(I2CSlave *i2c)
>> +{
>> +    AT24State *s = AT24(i2c);
>> +    unsigned int sector, offset;
>> +    int result;
>> +
>> +    switch (s->transfer_state) {
>> +    case AT24_RD_ADDR:
>> +        s->transfer_state = AT24_IDLE;
>> +        result = s->transfer_addr;
>> +        break;
>> +    case AT24_RD_DATA:
>> +        sector = s->transfer_addr >> BDRV_SECTOR_BITS;
>> +        offset = s->transfer_addr & ~BDRV_SECTOR_MASK;
>> +        s->transfer_addr = (s->transfer_addr + 1) & s->addr_mask;
>> +        if (at24_cache_sector(s, sector) < 0) {
>> +            result = 0;
>> +            break;
>> +        }
>> +        result = s->sector_buffer[offset];
>> +        break;
>> +    default:
>> +        s->transfer_state = AT24_IDLE;
>> +        result = 0;
>> +        break;
>> +    }
>> +    return result;
>> +}
>> +
>> +static void at24_reset(DeviceState *d)
>> +{
>> +    AT24State *s = AT24(d);
>> +
>> +    s->transfer_state = AT24_IDLE;
>> +    s->cached_sector = -1;
>> +}
>> +
>> +static const AT24Parameters at24_parameters[] = {
>> +    {    1*1024,   8, 3, 0, false },
>> +    {    2*1024,   8, 3, 0, false },
>> +    {    4*1024,  16, 2, 1, false },
>> +    {    8*1024,  16, 1, 2, false },
>> +    {   16*1024,  16, 0, 3, false },
>> +    {   32*1024,  32, 3, 0, true },
>> +    {   64*1024,  32, 3, 0, true },
>> +    {  128*1024,  64, 2, 0, true },
>> +    {  256*1024,  64, 2, 0, true },
>> +    {  512*1024, 128, 2, 0, true },
>> +    { 1024*1024, 256, 1, 1, true },
>> +    { },
> 
> You could potentially add a string field to this array for the part
> name. "at24c08" etc.
> Then in the register types function you can iterate through the array
> and instantiate a
> type for each different part. This would allow you to go
> 
> qemu-system-foo -device at24c08
> 
> rather than
> 
> qemu-system-foo -device at24cXX,size=4096

You only need the size property if your EEPROM image is larger than the
target type. But I could add explicit types, too.

> 
> etc.
> 
> See block/m25p80.c for a similar situation.
> 
>> +};
>> +
>> +static void at24_realize(DeviceState *d, Error **errp)
>> +{
>> +    I2CSlave *i2c = I2C_SLAVE(d);
>> +    AT24State *s = AT24(d);
>> +    const AT24Parameters *params;
>> +    int64_t image_size;
>> +    int dev_no;
>> +
>> +    s->bs = s->block_conf.bs;
>> +    if (!s->bs) {
>> +        error_setg(errp, "drive property not set");
>> +        return;
>> +    }
>> +
>> +    s->wp = bdrv_is_read_only(s->bs);
>> +
>> +    image_size = bdrv_getlength(s->bs);
>> +    if (s->size == 0) {
>> +        s->size = image_size;
>> +    } else if (image_size < s->size) {
>> +        error_setg(errp, "image file smaller than specified EEPROM size");
>> +        return;
>> +    }
>> +
>> +    for (params = at24_parameters; params->size != 0; params++) {
>> +        if (s->size * 8 == params->size) {
>> +            break;
>> +        }
>> +    }
>> +    if (params->size == 0) {
>> +        error_setg(errp, "invalid EEPROM size, must be 2^(10..17)");
>> +        return;
>> +    }
>> +    s->addr_mask = s->size - 1;
>> +    s->page_mask = ~(params->page_size - 1);
>> +    s->hi_addr_mask = (1 << params->hi_addr_bits) - 1;
>> +    s->addr16 = params->addr16;
>> +
>> +    dev_no = (s->device & ((1 << params->device_bits) - 1)) <<
>> +        params->hi_addr_bits;
> 
> I still think this device bits has a place in the I2C layer itself.
> But i'm happy to send
> cleanup patches myself after a merge. I need this for another I2C
> device and rather
> not copy paste.

Perfect, thanks.

Jan

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