From: Mike Dunn <miked...@newsguy.com> This patch adds support for the length argument to the xscale implementation of the wp command. Per discussion with David, the length argument specifies the range of addresses over which a memory access should generate a debug exception. This patch utilizes the "mask" feature of the xscale debug hardware to implement the correct functionality of the length argument. Some limitations imposed by the hardware are:
- The length must be a power of two, with a minumum of 4. - Two data breakpoint registers are available, allowing for two watchpoints. However, if the length of a watchpoint is greater than four, both registers are used (the second for a mask value), limiting the number of watchpoints to one. This patch also removes a useless call to xscale_get_reg(dbcon) in xscale_set_watchpoint() (value had already been read from the register cache, and the same previously read value is then modified and written back). I have been using and testing this patch for a couple days. Questions, corrections, criticisms of course gratefully received. --- src/target/xscale.c | 59 ++++++++++++++++++++++++++++++++++++++++++++------- 1 files changed, 51 insertions(+), 8 deletions(-) diff --git a/src/target/xscale.c b/src/target/xscale.c index ddc73d2..ed0eef3 100644 --- a/src/target/xscale.c +++ b/src/target/xscale.c @@ -2266,7 +2266,7 @@ static int xscale_set_watchpoint(struct target *target, struct watchpoint *watchpoint) { struct xscale_common *xscale = target_to_xscale(target); - uint8_t enable = 0; + uint32_t enable = 0; struct reg *dbcon = &xscale->reg_cache->reg_list[XSCALE_DBCON]; uint32_t dbcon_value = buf_get_u32(dbcon->value, 0, 32); @@ -2276,8 +2276,6 @@ static int xscale_set_watchpoint(struct target *target, return ERROR_TARGET_NOT_HALTED; } - xscale_get_reg(dbcon); - switch (watchpoint->rw) { case WPT_READ: @@ -2293,6 +2291,24 @@ static int xscale_set_watchpoint(struct target *target, LOG_ERROR("BUG: watchpoint->rw neither read, write nor access"); } + /* For watchpoint across more than one word, both DBR registers must + be enlisted, with the second used as a mask. */ + if (watchpoint->length > 4) + { + if (xscale->dbr0_used || xscale->dbr1_used) + { + LOG_ERROR("BUG: sufficient hardware comparators unavailable"); + return ERROR_TARGET_RESOURCE_NOT_AVAILABLE; + } + + /* Write mask value to DBR1, based on the length argument. + * Address bits ignored by the comparator are those set in mask. */ + xscale_set_reg_u32(&xscale->reg_cache->reg_list[XSCALE_DBR1], + watchpoint->length - 1); + xscale->dbr1_used = 1; + enable |= 0x100; /* DBCON[M] */ + } + if (!xscale->dbr0_used) { xscale_set_reg_u32(&xscale->reg_cache->reg_list[XSCALE_DBR0], watchpoint->address); @@ -2312,7 +2328,7 @@ static int xscale_set_watchpoint(struct target *target, else { LOG_ERROR("BUG: no hardware comparator available"); - return ERROR_OK; + return ERROR_TARGET_RESOURCE_NOT_AVAILABLE; } return ERROR_OK; @@ -2328,13 +2344,30 @@ static int xscale_add_watchpoint(struct target *target, return ERROR_TARGET_RESOURCE_NOT_AVAILABLE; } - if ((watchpoint->length != 1) && (watchpoint->length != 2) && (watchpoint->length != 4)) + if (watchpoint->value) + LOG_WARNING("xscale does not support value, mask arguments; ignoring"); + + /* check that length is a power of two */ + for (uint32_t len = watchpoint->length; len != 1; len /= 2) { - return ERROR_TARGET_RESOURCE_NOT_AVAILABLE; + if (len % 2) + { + LOG_ERROR("xscale requires that watchpoint length is a power of two"); + return ERROR_COMMAND_ARGUMENT_INVALID; + } } - xscale->dbr_available--; + if (watchpoint->length == 4) /* single word watchpoint */ + { + xscale->dbr_available--; /* one DBR reg used */ + return ERROR_OK; + } + /* watchpoints across multiple words require both DBR registers */ + if (xscale->dbr_available < 2) + return ERROR_TARGET_RESOURCE_NOT_AVAILABLE; + + xscale->dbr_available = 0; return ERROR_OK; } @@ -2359,7 +2392,14 @@ static int xscale_unset_watchpoint(struct target *target, if (watchpoint->set == 1) { - dbcon_value &= ~0x3; + if (watchpoint->length > 4) + { + dbcon_value &= ~0x103; /* clear DBCON[M] as well */ + xscale->dbr1_used = 0; /* DBR1 was used for mask */ + } + else + dbcon_value &= ~0x3; + xscale_set_reg_u32(dbcon, dbcon_value); xscale->dbr0_used = 0; } @@ -2389,6 +2429,9 @@ static int xscale_remove_watchpoint(struct target *target, struct watchpoint *wa xscale_unset_watchpoint(target, watchpoint); } + if (watchpoint->length > 4) + xscale->dbr_available++; /* both DBR regs now available */ + xscale->dbr_available++; return ERROR_OK; -- 1.6.4.4 _______________________________________________ Openocd-development mailing list Openocd-development@lists.berlios.de https://lists.berlios.de/mailman/listinfo/openocd-development