【xilinx】解决 I/O 时钟布局器错误：CLOCK_DEDICATED

问题描述

设备： xcvm1102-sfva784-2HP-iS
问题：尽管使用 GCIO 引脚作为时钟，但布局器返回 I/O 时钟错误

错误：

<span style="background-color:#f3f3f3"><span style="color:#333333"><code>ERROR: [Place 30-675] Sub-optimal placement for a global clock-capable IO pin and BUFG pair.If this sub optimal condition is acceptable for this design, you may use the CLOCK_DEDICATED_ROUTE constraint in the .xdc file to demote this message to a WARNING. However, the use of this override is highly discouraged. These examples can be used directly in the .xdc file to override this clock rule.
    < set_property CLOCK_DEDICATED_ROUTE FALSE [get_nets clk_in_IBUF] >
 
    Clock Rule: rule_gclkio_bufg
    Status: FAILED
    Rule Description: An IOB driving a BUFG must use a GCIO in the same clock region as the BUFG
 
    clk_in_IBUF_inst (IBUF.O) is locked to IOB_X13Y8
    bufg_in (BUFGCE.I) is provisionally placed by clockplacer on BUFGCE_X1Y23
 
    The above error could possibly be related to other connected instances. Following is a list of
    all the related clock rules and their respective instances.
 
    Clock Rule: rule_mmcm_bufg
    Status: PASS
    Rule Description: A MMCM driving a BUFG must be placed in the same clock region of the device as the
    BUFG
    MMCME5_inst (MMCME5.CLKOUT0) is provisionally placed by clockplacer on MMCM_X0Y0
    bufg_out (BUFGCE.I) is provisionally placed by clockplacer on BUFGCE_X0Y0
 
    Clock Rule: rule_bufgce_bufg_conflict
    Status: PASS
    Rule Description: Only one of the 2 available sites (BUFGCE or BUFGCE_DIV/BUFGCTRL) in a pair can be
    used at the same time
    bufg_in (BUFGCE.O) is provisionally placed by clockplacer on BUFGCE_X1Y23
 
    Clock Rule: rule_io_bufg_mmcm_1load
    Status: FAIL
    Rule Description: A BUFGCE with I/O driver driving a single MMCM must both be in the same clock region
    if CLOCK_DEDICATED_ROUTE=BACKBONE is NOT set
    bufg_in (BUFGCE.O) is provisionally placed by clockplacer on BUFGCE_X1Y23
    MMCME5_inst (MMCME5.CLKIN1) is provisionally placed by clockplacer on MMCM_X0Y0
    ERROR: The above is also an illegal clock rule
    Workaround: < set_property CLOCK_DEDICATED_ROUTE ANY_CMT_REGION [get_nets clk_in_temp] >
 
    Clock Rule: rule_bufgce_bufg_conflict
    Status: PASS
    Rule Description: Only one of the 2 available sites (BUFGCE or BUFGCE_DIV/BUFGCTRL) in a pair can be
    used at the same time
    bufg_out (BUFGCE.O) is provisionally placed by clockplacer on BUFGCE_X0Y0
 
Resolution: A dedicated routing path between the two can be used if: (a) The global clock-capable IO (GCIO) is placed on a GCIO capable site (b) The BUFG is placed in the same bank of the device as the GCIO pin. Both the above conditions must be met at the same time, else it may lead to longer and less predictable clock insertion delays.
ERROR: [Place 30-1971] Sub-optimal placement for a global clock-capable IO pin-BUFGCE-MMCM pair.
 Resolution: A dedicated routing path between the pairs can be used if: (a) The global clock-capable IO (GCIO) is placed on a GCIO capable site (b) The BUFGCE and MMCM is placed in the same clock region as the GCIO pin. If the IOB is driving BUFGCE and driving multiple MMCMs, all MMCMs must be placed in the same clock region. Both the above conditions must be met at the same time, else it may lead to longer and less predictable clock insertion delays. If this sub optimal condition is acceptable for this design, you may use the CLOCK_DEDICATED_ROUTE constraint in the .xdc file to demote this message to a WARNING. However, the use of this override is highly discouraged. These examples can be used directly in the .xdc file to override this clock rule.
    < set_property CLOCK_DEDICATED_ROUTE ANY_CMT_REGION [get_nets clk_in_temp] >
 
    Clock Rule: rule_io_bufg_mmcm_1load
    Status: FAILED
    Rule Description: A BUFGCE with I/O driver driving a single MMCM must both be in the same clock region if CLOCK_DEDICATED_ROUTE=BACKBONE is NOT set
 
    bufg_in (BUFGCE.O) is provisionally placed by clockplacer on BUFGCE_HDIO_X0Y0
    MMCME5_inst (MMCME5.CLKIN1) is provisionally placed by clockplacer on MMCM_X0Y0
 
    The above error could possibly be related to other connected instances. Following is a list of
    all the related clock rules and their respective instances.
 
    Clock Rule: rule_mmcm_bufg
    Status: PASS
    Rule Description: A MMCM driving a BUFG must be placed in the same clock region of the device as the
    BUFG
    MMCME5_inst (MMCME5.CLKOUT0) is provisionally placed by clockplacer on MMCM_X0Y0
    bufg_out (BUFGCE.I) is provisionally placed by clockplacer on BUFGCE_X0Y23
 
 
    Clock Rule: rule_bufgce_bufg_conflict
    Status: PASS
    Rule Description: Only one of the 2 available sites (BUFGCE or BUFGCE_DIV/BUFGCTRL) in a pair can be
    used at the same time
    bufg_in (BUFGCE.O) is provisionally placed by clockplacer on BUFGCE_HDIO_X0Y0
 
 
    Clock Rule: rule_bufgce_bufg_conflict
    Status: PASS
    Rule Description: Only one of the 2 available sites (BUFGCE or BUFGCE_DIV/BUFGCTRL) in a pair can be
    used at the same time
    bufg_out (BUFGCE.O) is provisionally placed by clockplacer on BUFGCE_X0Y23
 
 
    Clock Rule: rule_gclkio_bufg
    Status: PASS
    Rule Description: An IOB driving a BUFG must use a GCIO in the same clock region as the BUFG
    clk_in_IBUF_inst (IBUF.O) is locked to IOB_X13Y8
    bufg_in (BUFGCE.I) is provisionally placed by clockplacer on BUFGCE_HDIO_X0Y0</code></span></span>

在这个简单的设计示例中，我们有两个错误，提示两个 CLOCK_DEDICATED_ROUTE 解析指向两个网络。
使用错误中提到的网络名称并生成原理图，我们会看到以下时钟结构：。

输入缓冲器 → BUFG
BUFG → MMCM

输入时钟端口使用来自 HDIO 组的 Global Clock Capable Package 引脚 D11。尽管如此，布局器仍会出错，并出现上述 I/O Clock Placer 错误。让我们使用Vivado 实施 - 解决 I/O Clock Placer 错误
中概述的方法调试此问题。

这个时钟结构有两个部分

段 1 = IBUF → BUFG
段 2 = BUFG → MMCM

通过打开 post opt DCP 并运行place_ports，我们将得到这个错误。

标记输入端口、BUFG 和 MMCM 将突出显示这些单元的临时位置。

根据规则 1，布局器应将输入端口 (粉色)、BUFG (黄色) 和 MMCM (绿色) 放置在同一个时钟区域 X0Y2 中。
让我们检查设备中可用的资源。
由于涉及的组件是 BUFG 和 MMCM，我们在设备中得到了 MMCM (橙色) 和 BUFG (蓝色)。

命令：

<span style="background-color:#f3f3f3"><span style="color:#333333"><code>show_objects -name find_1 [get_sites -filter { SITE_TYPE == "MMCM" } ]
show_objects -name BUFGs [get_sites BUFG*]</code></span></span>

使用此信息，很明显，在同一个 CLOCK_REGION X0Y2 中有可用的 BUFG，但没有 MMCM。因此，在没有任何 CLOCK_DEDICATED_ROUTE 约束的情况下，布局器根据其可行性放置了段 1 和 2。
我们可以使用 CLOCK_REGION 将 BUFG 约束到 X0Y2，但是布局器仍然会在段 2 上出错，即 BUFG→MMCM

<span style="background-color:#f3f3f3"><span style="color:#333333"><code>set_property CLOCK_REGION X0Y2 [get_cells bufg_in]</code></span></span>

新错误：

<span style="background-color:#f3f3f3"><span style="color:#333333"><code>ERROR: [Place 30-1971] Sub-optimal placement for a global clock-capable IO pin-BUFGCE-MMCM pair.
 Resolution: A dedicated routing path between the pairs can be used if: (a) The global clock-capable IO (GCIO) is placed on a GCIO capable site (b) The BUFGCE and MMCM is placed in the same clock region as the GCIO pin. If the IOB is driving BUFGCE and driving multiple MMCMs, all MMCMs must be placed in the same clock region. Both the above conditions must be met at the same time, else it may lead to longer and less predictable clock insertion delays. If this sub optimal condition is acceptable for this design, you may use the CLOCK_DEDICATED_ROUTE constraint in the .xdc file to demote this message to a WARNING. However, the use of this override is highly discouraged. These examples can be used directly in the .xdc file to override this clock rule.
    < set_property CLOCK_DEDICATED_ROUTE ANY_CMT_REGION [get_nets clk_in_temp] >
 
    Clock Rule: rule_io_bufg_mmcm_1load
    Status: FAILED
    Rule Description: A BUFGCE with I/O driver driving a single MMCM must both be in the same clock region if CLOCK_DEDICATED_ROUTE=BACKBONE is NOT set
 
    bufg_in (BUFGCE.O) is provisionally placed by clockplacer on BUFGCE_HDIO_X0Y0
    MMCME5_inst (MMCME5.CLKIN1) is provisionally placed by clockplacer on MMCM_X0Y0
 
    The above error could possibly be related to other connected instances. Following is a list of
    all the related clock rules and their respective instances.
 
    Clock Rule: rule_mmcm_bufg
    Status: PASS
    Rule Description: A MMCM driving a BUFG must be placed in the same clock region of the device as the
    BUFG
    MMCME5_inst (MMCME5.CLKOUT0) is provisionally placed by clockplacer on MMCM_X0Y0
    bufg_out (BUFGCE.I) is provisionally placed by clockplacer on BUFGCE_X0Y23
 
 
    Clock Rule: rule_bufg_clockregion_prop
    Status: PASS
    Rule Description: A global clock source buffer with CLOCK_REGION property should get placed in the
    clock region specified by the property
    bufg_in (BUFGCE.O) is provisionally placed by clockplacer on BUFGCE_HDIO_X0Y0
 
 
    Clock Rule: rule_bufgce_bufg_conflict
    Status: PASS
    Rule Description: Only one of the 2 available sites (BUFGCE or BUFGCE_DIV/BUFGCTRL) in a pair can be
    used at the same time
    bufg_in (BUFGCE.O) is provisionally placed by clockplacer on BUFGCE_HDIO_X0Y0
 
 
    Clock Rule: rule_bufgce_bufg_conflict
    Status: PASS
    Rule Description: Only one of the 2 available sites (BUFGCE or BUFGCE_DIV/BUFGCTRL) in a pair can be
    used at the same time
    bufg_out (BUFGCE.O) is provisionally placed by clockplacer on BUFGCE_X0Y23
 
 
    Clock Rule: rule_gclkio_bufg
    Status: PASS
    Rule Description: An IOB driving a BUFG must use a GCIO in the same clock region as the BUFG
    clk_in_IBUF_inst (IBUF.O) is locked to IOB_X13Y8
    bufg_in (BUFGCE.I) is provisionally placed by clockplacer on BUFGCE_HDIO_X0Y0</code></span></span>

因此，除了将 CLOCK_DEDICATED_ROUTE 设置为 ANY_CMT_REGION 之外，没有其他方法可以放置此时钟结构。

这是因为 CLOCK_REGION X0Y2 中没有适用于段 2 的 MMCM。

<span style="background-color:#f3f3f3"><span style="color:#333333"><code>set_property CLOCK_DEDICATED_ROUTE ANY_CMT_REGION [get_nets clk_in_temp]</code></span></span>

在下一次运行中，我们在设计中对段 1 有 CLOCK_REGION 约束，对段 2 有 CLOCK_DEDICATED_ROUTE ANY_CMT_REGION 约束，布局器会按预期放置结构。