[PATCH]: 5fd1d8dd0b target/adi_v5_swd: introduce swd_check_dpidr()

[gerrit]

This is an automated email from Gerrit.

"Tomas Vanek <van...@fbl.cz>" just uploaded a new patch set to Gerrit, which 
you can find at https://review.openocd.org/c/openocd/+/8119

-- gerrit

commit 5fd1d8dd0b8551412d50aef55038c10ccb268855
Author: Tomas Vanek <van...@fbl.cz>
Date:   Fri Jan 26 11:53:49 2024 +0100

    target/adi_v5_swd: introduce swd_check_dpidr()
    
    Add two checks on DP IDR value when connecting:
    - bit 0 should read-as-one
    - DP version should comply with ADI version
    
    Signed-off-by: Tomas Vanek <van...@fbl.cz>
    Change-Id: I6fa53f28094007ae568de02e8a853f3dffced375

diff --git a/src/target/adi_v5_swd.c b/src/target/adi_v5_swd.c
index 6d6f287b05..f748e3120f 100644
--- a/src/target/adi_v5_swd.c
+++ b/src/target/adi_v5_swd.c
@@ -297,6 +297,37 @@ static int swd_multidrop_select(struct adiv5_dap *dap)
        return retval;
 }
 
+static int swd_check_dpidr(struct adiv5_dap *dap, uint32_t dpidr)
+{
+       unsigned int dp_ver = (dpidr & DP_DPIDR_VERSION_MASK) >> 
DP_DPIDR_VERSION_SHIFT;
+
+       LOG_INFO("SWD DPIDR 0x%08" PRIx32 " DPv%u", dpidr, dp_ver);
+
+       if ((dpidr & BIT(0)) == 0) {
+               /* Without this check and with SWDIO pulled down a false DP 
detection
+                * is possible on an unconnected SWD or when target does not 
respond:
+                * The gradual drop of voltage at not driven SWDIO signal 
imposed
+                * by discharging pins and wiring capacity can be misinterpreted
+                * by the adapter as a valid read result:
+                * ACK 100, RDATA 00000000000000000000000000000000, PARITY 0 */
+               LOG_ERROR("Error connecting DP: bad IDR value, bit 0 should 
read-as-one");
+               return ERROR_FAIL;
+       }
+
+       if (is_adiv6(dap)) {
+               if (dp_ver < 3) {
+                       LOG_ERROR("Error connecting DP: ADIv6 requires DPv3");
+                       return ERROR_FAIL;
+               }
+       } else {
+               if (dp_ver > 2) {
+                       LOG_ERROR("Error connecting DP: DPv3 requires dap 
create -adiv6 option");
+                       return ERROR_FAIL;
+               }
+       }
+       return ERROR_OK;
+}
+
 static int swd_connect_multidrop(struct adiv5_dap *dap)
 {
        int retval;
@@ -330,8 +361,9 @@ static int swd_connect_multidrop(struct adiv5_dap *dap)
        }
 
        swd_multidrop_in_swd_state = true;
-       LOG_INFO("SWD DPIDR 0x%08" PRIx32 ", DLPIDR 0x%08" PRIx32,
-                         dpidr, dlpidr);
+
+       retval = swd_check_dpidr(dap, dpidr);
+       LOG_INFO("multidrop DLPIDR 0x%08" PRIx32, dlpidr);
 
        return retval;
 }
@@ -387,7 +419,10 @@ static int swd_connect_single(struct adiv5_dap *dap)
                return retval;
        }
 
-       LOG_INFO("SWD DPIDR 0x%08" PRIx32, dpidr);
+       retval = swd_check_dpidr(dap, dpidr);
+       if (retval != ERROR_OK) {
+               return retval;
+       }
 
        do {
                dap->do_reconnect = false;

--