path: root/common/usb_pd_policy.c

/* Copyright (c) 2014 The Chromium OS Authors. All rights reserved.
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */
#include "adc.h"
#include "atomic.h"
#include "charge_manager.h"
#include "common.h"
#include "console.h"
#include "flash.h"
#include "gpio.h"
#include "hooks.h"
#include "host_command.h"
#include "registers.h"
#include "rsa.h"
#include "sha256.h"
#include "system.h"
#include "task.h"
#include "timer.h"
#include "util.h"
#include "usb_api.h"
#include "usb_pd.h"
#include "usb_pd_config.h"
#include "version.h"

#ifdef CONFIG_COMMON_RUNTIME
#define CPRINTS(format, args...) cprints(CC_USBPD, format, ## args)
#define CPRINTF(format, args...) cprintf(CC_USBPD, format, ## args)
#else
#define CPRINTS(format, args...)
#define CPRINTF(format, args...)
#endif

static int rw_flash_changed = 1;

#ifdef CONFIG_USB_PD_DUAL_ROLE
/* Cap on the max voltage requested as a sink (in millivolts) */
static unsigned max_request_mv = -1; /* no cap */

/**
 * Find PDO index that offers the most amount of power and stays within
 * max_mv voltage.
 *
 * @param cnt  the number of Power Data Objects.
 * @param src_caps Power Data Objects representing the source capabilities.
 * @param max_mv maximum voltage (or -1 if no limit)
 * @return index of PDO within source cap packet
 */
static int pd_find_pdo_index(int cnt, uint32_t *src_caps, int max_mv)
{
	int i, uw, max_uw = 0, mv, ma;
	int ret = -1;

	/* max_mv of -1 represents max limit */
	if (max_mv == -1)
		max_mv = PD_MAX_VOLTAGE_MV;

	/* max voltage is always limited by this boards max request */
	max_mv = MIN(max_mv, PD_MAX_VOLTAGE_MV);

	/* Get max power that is under our max voltage input */
	for (i = 0; i < cnt; i++) {
		mv = ((src_caps[i] >> 10) & 0x3FF) * 50;
		if ((src_caps[i] & PDO_TYPE_MASK) == PDO_TYPE_BATTERY) {
			uw = 250000 * (src_caps[i] & 0x3FF);
		} else {
			ma = (src_caps[i] & 0x3FF) * 10;
			uw = ma * mv;
		}
		if ((uw > max_uw) && (mv <= max_mv)) {
			ret = i;
			max_uw = uw;
		}
	}
	return ret;
}

/**
 * Extract power information out of a Power Data Object (PDO)
 *
 * @pdo Power data object
 * @ma Current we can request from that PDO
 * @mv Voltage of the PDO
 */
static void pd_extract_pdo_power(uint32_t pdo, uint32_t *ma, uint32_t *mv)
{
	int max_ma, uw;
	*mv = ((pdo >> 10) & 0x3FF) * 50;

	if ((pdo & PDO_TYPE_MASK) == PDO_TYPE_BATTERY) {
		uw = 250000 * (pdo & 0x3FF);
		max_ma = 1000 * MIN(1000 * uw, PD_MAX_POWER_MW) / *mv;
	} else {
		max_ma = 10 * (pdo & 0x3FF);
		max_ma = MIN(max_ma, PD_MAX_CURRENT_MA);
	}

	*ma = max_ma;
}

int pd_build_request(int cnt, uint32_t *src_caps, uint32_t *rdo,
		     uint32_t *ma, uint32_t *mv, enum pd_request_type req_type)
{
	int pdo_index, flags = 0;
	int uw;

	if (req_type == PD_REQUEST_VSAFE5V)
		/* src cap 0 should be vSafe5V */
		pdo_index = 0;
	else
		/* find pdo index for max voltage we can request */
		pdo_index = pd_find_pdo_index(cnt, src_caps, max_request_mv);

	/* If could not find desired pdo_index, then return error */
	if (pdo_index == -1)
		return -EC_ERROR_UNKNOWN;

	pd_extract_pdo_power(src_caps[pdo_index], ma, mv);
	uw = *ma * *mv;
	/* Mismatch bit set if less power offered than the operating power */
	if (uw < (1000 * PD_OPERATING_POWER_MW))
		flags |= RDO_CAP_MISMATCH;

	if ((src_caps[pdo_index] & PDO_TYPE_MASK) == PDO_TYPE_BATTERY) {
		int mw = uw / 1000;
		*rdo = RDO_BATT(pdo_index + 1, mw, mw, flags);
	} else {
		*rdo = RDO_FIXED(pdo_index + 1, *ma, *ma, flags);
	}
	return EC_SUCCESS;
}

void pd_process_source_cap(int port, int cnt, uint32_t *src_caps)
{
#ifdef CONFIG_CHARGE_MANAGER
	uint32_t ma, mv;
	int pdo_index;

	/* Get max power info that we could request */
	pdo_index = pd_find_pdo_index(cnt, src_caps, -1);
	if (pdo_index < 0)
		pdo_index = 0;
	pd_extract_pdo_power(src_caps[pdo_index], &ma, &mv);

	/* Set max. limit, but apply 500mA ceiling */
	charge_manager_set_ceil(port, PD_MIN_MA);
	pd_set_input_current_limit(port, ma, mv);
#endif
}

void pd_set_max_voltage(unsigned mv)
{
	max_request_mv = mv;
}

unsigned pd_get_max_voltage(void)
{
	return max_request_mv;
}
#endif /* CONFIG_USB_PD_DUAL_ROLE */

#ifdef CONFIG_USB_PD_ALT_MODE

#ifdef CONFIG_USB_PD_ALT_MODE_DFP

static struct pd_policy pe[PD_PORT_COUNT];

void pd_dfp_pe_init(int port)
{
	memset(&pe[port], 0, sizeof(struct pd_policy));
}

static void dfp_consume_identity(int port, uint32_t *payload)
{
	int ptype = PD_IDH_PTYPE(payload[VDO_I(IDH)]);
	pd_dfp_pe_init(port);
	memcpy(&pe[port].identity, payload + 1, sizeof(pe[port].identity));
	switch (ptype) {
	case IDH_PTYPE_AMA:
		/* TODO(tbroch) do I disable VBUS here if power contract
		 * requested it
		 */
		if (!PD_VDO_AMA_VBUS_REQ(payload[VDO_I(AMA)]))
			pd_power_supply_reset(port);
		break;
		/* TODO(crosbug.com/p/30645) provide vconn support here */
	default:
		break;
	}
}

static int dfp_discover_svids(int port, uint32_t *payload)
{
	payload[0] = VDO(USB_SID_PD, 1, CMD_DISCOVER_SVID);
	return 1;
}

static void dfp_consume_svids(int port, uint32_t *payload)
{
	int i;
	uint32_t *ptr = payload + 1;
	uint16_t svid0, svid1;

	for (i = pe[port].svid_cnt; i < pe[port].svid_cnt + 12; i += 2) {
		if (i == SVID_DISCOVERY_MAX) {
			CPRINTF("ERR: too many svids discovered\n");
			break;
		}

		svid0 = PD_VDO_SVID_SVID0(*ptr);
		if (!svid0)
			break;
		pe[port].svids[i].svid = svid0;
		pe[port].svid_cnt++;

		svid1 = PD_VDO_SVID_SVID1(*ptr);
		if (!svid1)
			break;
		pe[port].svids[i + 1].svid = svid1;
		pe[port].svid_cnt++;
		ptr++;
	}
	/* TODO(tbroch) need to re-issue discover svids if > 12 */
	if (i && ((i % 12) == 0))
		CPRINTF("TODO: need to re-issue discover svids > 12\n");
}

static int dfp_discover_modes(int port, uint32_t *payload)
{
	uint16_t svid = pe[port].svids[pe[port].svid_idx].svid;
	if (pe[port].svid_idx >= pe[port].svid_cnt)
		return 0;
	payload[0] = VDO(svid, 1, CMD_DISCOVER_MODES);
	return 1;
}

static void dfp_consume_modes(int port, int cnt, uint32_t *payload)
{
	int idx = pe[port].svid_idx;
	pe[port].svids[idx].mode_cnt = cnt - 1;
	if (pe[port].svids[idx].mode_cnt < 0) {
		CPRINTF("PE ERR: no modes provided for SVID\n");
	} else {
		memcpy(pe[port].svids[pe[port].svid_idx].mode_vdo, &payload[1],
		       sizeof(uint32_t) * pe[port].svids[idx].mode_cnt);
	}

	pe[port].svid_idx++;
}

static struct svdm_amode_data *get_modep(int port)
{
	return &pe[port].amode;
}

int pd_alt_mode(int port)
{
	return get_modep(port)->opos;
}

/* Enter default mode or attempt to enter mode via svid & index arguments */
static int dfp_enter_mode(int port, uint32_t *payload, int use_payload)
{
	int i, j, done;
	struct svdm_amode_data *modep = get_modep(port);
	uint16_t svid = (use_payload) ? PD_VDO_VID(payload[0]) : 0;
	uint8_t opos = (use_payload) ? PD_VDO_OPOS(payload[0]) : 0;

	for (i = 0, done = 0; !done && (i < supported_modes_cnt); i++) {
		for (j = 0; j < pe[port].svid_cnt; j++) {
			struct svdm_svid_data *svidp = &pe[port].svids[j];
			if ((svidp->svid != supported_modes[i].svid) ||
			    (svid && (svidp->svid != svid)))
				continue;
			modep->fx = &supported_modes[i];
			modep->mode_caps = pe[port].svids[j].mode_vdo[0];
			modep->opos = (opos && (opos < 7)) ? opos : 1;
			done = 1;
			break;
		}
	}
	if (!modep->opos)
		return 0;

	if (modep->fx->enter(port, modep->mode_caps) == -1)
		return 0;

	payload[0] = VDO(modep->fx->svid, 1,
			 CMD_ENTER_MODE | VDO_OPOS(pd_alt_mode(port)));
	return 1;
}

static int validate_mode_request(struct svdm_amode_data *modep,
				 uint16_t svid, int opos)
{
	if (!modep->fx)
		return 0;

	if (svid != modep->fx->svid) {
		CPRINTF("ERR:svid r:0x%04x != c:0x%04x\n",
			svid, modep->fx->svid);
		return 0;
	}

	if (opos != modep->opos) {
		CPRINTF("ERR:opos r:%d != c:%d\n",
			opos, modep->opos);
		return 0;
	}

	return 1;
}

static void dfp_consume_attention(int port, uint32_t *payload)
{
	struct svdm_amode_data *modep = get_modep(port);
	uint16_t svid = PD_VDO_VID(payload[0]);
	int opos = PD_VDO_OPOS(payload[0]);

	if (!validate_mode_request(modep, svid, opos))
		return;

	if (modep->fx->attention)
		modep->fx->attention(port, payload);
}

uint32_t pd_dfp_exit_mode(int port)
{
	struct svdm_amode_data *modep = get_modep(port);

	if (!modep->fx)
		return 0;

	modep->fx->exit(port);

	/*
	 * TODO(crosbug.com/p/33946) : below needs revisited to allow multiple
	 * mode entry.  Additionally it should honor OPOS == 7 as DFP's request
	 * to exit all modes.
	 */
	if (pd_is_connected(port)) {
		int cur_opos = modep->opos;
		modep->opos = 0;
		return VDO(modep->fx->svid, 1, (CMD_EXIT_MODE | cur_opos));
	} else {
		pd_dfp_pe_init(port);
	}
	return 0;
}

#ifdef CONFIG_CMD_USB_PD_PE
static void dump_pe(int port)
{
	const char * const idh_ptype_names[]  = {
		"UNDEF", "Hub", "Periph", "PCable", "ACable", "AMA",
		"RSV6", "RSV7"};

	int i, j, idh_ptype;
	struct svdm_amode_data *modep;

	if (pe[port].identity[0] == 0) {
		ccprintf("No identity discovered yet.\n");
		return;
	}
	idh_ptype = PD_IDH_PTYPE(pe[port].identity[0]);
	ccprintf("IDENT:\n");
	ccprintf("\t[ID Header] %08x :: %s, VID:%04x\n", pe[port].identity[0],
		 idh_ptype_names[idh_ptype], PD_IDH_VID(pe[port].identity[0]));
	ccprintf("\t[Cert Stat] %08x\n", pe[port].identity[1]);
	for (i = 2; i < ARRAY_SIZE(pe[port].identity); i++) {
		ccprintf("\t");
		if (pe[port].identity[i])
			ccprintf("[%d] %08x ", i, pe[port].identity[i]);
	}
	ccprintf("\n");

	if (pe[port].svid_cnt < 1) {
		ccprintf("No SVIDS discovered yet.\n");
		return;
	}

	for (i = 0; i < pe[port].svid_cnt; i++) {
		ccprintf("SVID[%d]: %04x MODES:", i, pe[port].svids[i].svid);
		for (j = 0; j < pe[port].svids[j].mode_cnt; j++)
			ccprintf(" [%d] %08x", j + 1,
				 pe[port].svids[i].mode_vdo[j]);
		ccprintf("\n");
	}
	if (!modep->opos) {
		ccprintf("No mode chosen yet.\n");
		return;
	}
	modep = get_modep(port);
	ccprintf("MODE[%d]: svid:%04x caps:%08x\n", modep->opos,
		 modep->fx->svid, modep->mode_caps);
}

static int command_pe(int argc, char **argv)
{
	int port;
	char *e;
	if (argc < 3)
		return EC_ERROR_PARAM_COUNT;
	/* command: pe <port> <subcmd> <args> */
	port = strtoi(argv[1], &e, 10);
	if (*e || port >= PD_PORT_COUNT)
		return EC_ERROR_PARAM2;
	if (!strncasecmp(argv[2], "dump", 4))
		dump_pe(port);

	return EC_SUCCESS;
}

DECLARE_CONSOLE_COMMAND(pe, command_pe,
			"<port> dump",
			"USB PE",
			NULL);
#endif /* CONFIG_CMD_USB_PD_PE */

#endif /* CONFIG_USB_PD_ALT_MODE_DFP */

int pd_svdm(int port, int cnt, uint32_t *payload, uint32_t **rpayload)
{
	int cmd = PD_VDO_CMD(payload[0]);
	int cmd_type = PD_VDO_CMDT(payload[0]);
	int (*func)(int port, uint32_t *payload) = NULL;

	int rsize = 1; /* VDM header at a minimum */

	payload[0] &= ~VDO_CMDT_MASK;
	*rpayload = payload;

	if (cmd_type == CMDT_INIT) {
		switch (cmd) {
		case CMD_DISCOVER_IDENT:
			func = svdm_rsp.identity;
			break;
		case CMD_DISCOVER_SVID:
			func = svdm_rsp.svids;
			break;
		case CMD_DISCOVER_MODES:
			func = svdm_rsp.modes;
			break;
		case CMD_ENTER_MODE:
			func = svdm_rsp.enter_mode;
			break;
		case CMD_DP_STATUS:
			func = svdm_rsp.amode->status;
			break;
		case CMD_DP_CONFIG:
			func = svdm_rsp.amode->config;
			break;
		case CMD_EXIT_MODE:
			func = svdm_rsp.exit_mode;
			break;
#ifdef CONFIG_USB_PD_ALT_MODE_DFP
		case CMD_ATTENTION:
			/*
			 * attention is only SVDM with no response
			 * (just goodCRC) return zero here.
			 */
			dfp_consume_attention(port, payload);
			return 0;
#endif
		default:
			CPRINTF("PE ERR: unknown command %d\n", cmd);
			rsize = 0;
		}
		if (func)
			rsize = func(port, payload);
		else /* not supported : NACK it */
			rsize = 0;
		if (rsize >= 1)
			payload[0] |= VDO_CMDT(CMDT_RSP_ACK);
		else if (!rsize) {
			payload[0] |= VDO_CMDT(CMDT_RSP_NAK);
			rsize = 1;
		} else {
			payload[0] |= VDO_CMDT(CMDT_RSP_BUSY);
			rsize = 1;
		}
	} else if (cmd_type == CMDT_RSP_ACK) {
		switch (cmd) {
#ifdef CONFIG_USB_PD_ALT_MODE_DFP
		case CMD_DISCOVER_IDENT:
			dfp_consume_identity(port, payload);
			rsize = dfp_discover_svids(port, payload);
			break;
		case CMD_DISCOVER_SVID:
			dfp_consume_svids(port, payload);
			rsize = dfp_discover_modes(port, payload);
			break;
		case CMD_DISCOVER_MODES:
			dfp_consume_modes(port, cnt, payload);
			rsize = dfp_discover_modes(port, payload);
			if (!rsize)
				rsize = dfp_enter_mode(port, payload, 0);
			break;
		case CMD_ENTER_MODE:
			/*
			 * TODO(crosbug.com/p/33946): Fix won't allow multiple
			 * mode entry.
			 */
			if (!pe[port].amode.opos)
				dfp_enter_mode(port, payload, 1);
			if (pe[port].amode.opos) {
				rsize = pe[port].amode.fx->status(port,
								  payload);
				payload[0] |= VDO_OPOS(pd_alt_mode(port));
			}
			break;
		case CMD_DP_STATUS:
			/* DP status response & UFP's DP attention have same
			   payload */
			dfp_consume_attention(port, payload);
			if (pe[port].amode.opos)
				rsize = pe[port].amode.fx->config(port,
								  payload);
			else
				rsize = 0;
			break;
		case CMD_DP_CONFIG:
			if (pe[port].amode.opos &&
			    pe[port].amode.fx->post_config)
				pe[port].amode.fx->post_config(port);
			/* no response after DFPs ack */
			rsize = 0;
			break;
		case CMD_EXIT_MODE:
			/* no response after DFPs ack */
			rsize = 0;
			break;
#endif
		case CMD_ATTENTION:
			/* no response after DFPs ack */
			rsize = 0;
			break;
		default:
			CPRINTF("PE ERR: unknown command %d\n", cmd);
			rsize = 0;
		}

		payload[0] |= VDO_CMDT(CMDT_INIT);
#ifdef CONFIG_USB_PD_ALT_MODE_DFP
	} else if (cmd_type == CMDT_RSP_BUSY) {
		switch (cmd) {
		case CMD_DISCOVER_IDENT:
		case CMD_DISCOVER_SVID:
		case CMD_DISCOVER_MODES:
			/* resend if its discovery */
			rsize = 1;
			break;
		case CMD_ENTER_MODE:
			/* Error */
			CPRINTF("PE ERR: received BUSY for Enter mode\n");
			rsize = 0;
			break;
		case CMD_EXIT_MODE:
			rsize = 0;
			break;
		default:
			rsize = 0;
		}
	} else if (cmd_type == CMDT_RSP_NAK) {
		/* nothing to do */
		rsize = 0;
#endif /* CONFIG_USB_PD_ALT_MODE_DFP */
	} else {
		CPRINTF("PE ERR: unknown cmd type %d\n", cmd);
	}
	return rsize;
}

#else

int pd_svdm(int port, int cnt, uint32_t *payload, uint32_t **rpayload)
{
	return 0;
}

#endif /* CONFIG_USB_PD_ALT_MODE */

#ifndef CONFIG_USB_PD_CUSTOM_VDM
int pd_vdm(int port, int cnt, uint32_t *payload, uint32_t **rpayload)
{
	return 0;
}
#endif /* !CONFIG_USB_PD_CUSTOM_VDM */

void pd_usb_billboard_deferred(void)
{
#if defined(CONFIG_USB_PD_ALT_MODE) && !defined(CONFIG_USB_PD_ALT_MODE_DFP) \
	&& !defined(CONFIG_USB_PD_SIMPLE_DFP)

	/* port always zero for these UFPs */
	if (!pd_alt_mode(0))
		usb_connect();

#endif
}
DECLARE_DEFERRED(pd_usb_billboard_deferred);

#ifdef CONFIG_USB_PD_ALT_MODE_DFP
static int hc_remote_pd_discovery(struct host_cmd_handler_args *args)
{
	const uint8_t *port = args->params;
	struct ec_params_usb_pd_discovery_entry *r = args->response;

	if (*port >= PD_PORT_COUNT)
		return EC_RES_INVALID_PARAM;

	r->vid = PD_IDH_VID(pe[*port].identity[0]);
	r->ptype = PD_IDH_PTYPE(pe[*port].identity[0]);
	/* pid only included if vid is assigned */
	if (r->vid)
		r->pid = PD_PRODUCT_PID(pe[*port].identity[2]);

	args->response_size = sizeof(*r);
	return EC_RES_SUCCESS;
}
DECLARE_HOST_COMMAND(EC_CMD_USB_PD_DISCOVERY,
		     hc_remote_pd_discovery,
		     EC_VER_MASK(0));

static int hc_remote_pd_get_amode(struct host_cmd_handler_args *args)
{
	const struct ec_params_usb_pd_get_mode_request *p = args->params;
	struct ec_params_usb_pd_get_mode_response *r = args->response;

	if (p->port >= PD_PORT_COUNT)
		return EC_RES_INVALID_PARAM;

	/* no more to send */
	if (p->svid_idx >= pe[p->port].svid_cnt) {
		r->svid = 0;
		args->response_size = sizeof(r->svid);
		return EC_RES_SUCCESS;
	}

	r->svid = pe[p->port].svids[p->svid_idx].svid;
	r->active = 0;
	memcpy(r->vdo, pe[p->port].svids[p->svid_idx].mode_vdo, 24);

	if (pe[p->port].amode.opos && pe[p->port].amode.fx->svid == r->svid) {
		r->active = 1;
		r->opos = pd_alt_mode(p->port);
	}
	args->response_size = sizeof(*r);
	return EC_RES_SUCCESS;
}
DECLARE_HOST_COMMAND(EC_CMD_USB_PD_GET_AMODE,
		     hc_remote_pd_get_amode,
		     EC_VER_MASK(0));

#endif

#define FW_RW_END (CONFIG_FW_RW_OFF + CONFIG_FW_RW_SIZE)

uint8_t *flash_hash_rw(void)
{
	static struct sha256_ctx ctx;

	/* re-calculate RW hash when changed as its time consuming */
	if (rw_flash_changed) {
		rw_flash_changed = 0;
		SHA256_init(&ctx);
		SHA256_update(&ctx, (void *)CONFIG_FLASH_BASE +
			      CONFIG_FW_RW_OFF,
			      CONFIG_FW_RW_SIZE - RSANUMBYTES);
		return SHA256_final(&ctx);
	} else {
		return ctx.buf;
	}
}

void pd_get_info(uint32_t *info_data)
{
	void *rw_hash = flash_hash_rw();

	/* copy first 20 bytes of RW hash */
	memcpy(info_data, rw_hash, 5 * sizeof(uint32_t));
	/* copy other info into data msg */
#if defined(CONFIG_USB_PD_HW_DEV_ID_BOARD_MAJOR) && \
	defined(CONFIG_USB_PD_HW_DEV_ID_BOARD_MINOR)
	info_data[5] = VDO_INFO(CONFIG_USB_PD_HW_DEV_ID_BOARD_MAJOR,
				CONFIG_USB_PD_HW_DEV_ID_BOARD_MINOR,
				ver_get_numcommits(),
				(system_get_image_copy() != SYSTEM_IMAGE_RO));
#else
	info_data[5] = 0;
#endif
}

int pd_custom_flash_vdm(int port, int cnt, uint32_t *payload)
{
	static int flash_offset;
	int rsize = 1; /* default is just VDM header returned */

	switch (PD_VDO_CMD(payload[0])) {
	case VDO_CMD_VERSION:
		memcpy(payload + 1, &version_data.version, 24);
		rsize = 7;
		break;
	case VDO_CMD_REBOOT:
		/* ensure the power supply is in a safe state */
		pd_power_supply_reset(0);
		system_reset(0);
		break;
	case VDO_CMD_READ_INFO:
		/* copy info into response */
		pd_get_info(payload + 1);
		rsize = 7;
		break;
	case VDO_CMD_FLASH_ERASE:
		/* do not kill the code under our feet */
		if (system_get_image_copy() != SYSTEM_IMAGE_RO)
			break;
		pd_log_event(PD_EVENT_ACC_RW_ERASE, 0, 0, NULL);
		flash_offset = CONFIG_FW_RW_OFF;
		flash_physical_erase(CONFIG_FW_RW_OFF, CONFIG_FW_RW_SIZE);
		rw_flash_changed = 1;
		break;
	case VDO_CMD_FLASH_WRITE:
		/* do not kill the code under our feet */
		if ((system_get_image_copy() != SYSTEM_IMAGE_RO) ||
		    (flash_offset < CONFIG_FW_RW_OFF))
			break;
		flash_physical_write(flash_offset, 4*(cnt - 1),
				     (const char *)(payload+1));
		flash_offset += 4*(cnt - 1);
		rw_flash_changed = 1;
		break;
	case VDO_CMD_ERASE_SIG:
		/* this is not touching the code area */
		{
			uint32_t zero = 0;
			int offset;
			/* zeroes the area containing the RSA signature */
			for (offset = FW_RW_END - RSANUMBYTES;
			     offset < FW_RW_END; offset += 4)
				flash_physical_write(offset, 4,
						     (const char *)&zero);
		}
		break;
	default:
		/* Unknown : do not answer */
		return 0;
	}
	return rsize;
}