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    Subject[PATCH v3 08/36] thunderbolt: Add dummy read after port capability list walk on Light Ridge
    Date
    Light Ridge has an issue where reading the next capability pointer
    location in port config space the read data is not cleared. It is fine
    to read capabilities each after another so only thing we need to do is
    to make sure we issue dummy read after tb_port_find_cap() is finished to
    avoid the issue in next read.

    Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
    ---
    drivers/thunderbolt/cap.c | 16 ++++++++++++++++
    1 file changed, 16 insertions(+)

    diff --git a/drivers/thunderbolt/cap.c b/drivers/thunderbolt/cap.c
    index a58585b4e6d9..8bf8e031f0bc 100644
    --- a/drivers/thunderbolt/cap.c
    +++ b/drivers/thunderbolt/cap.c
    @@ -52,6 +52,21 @@ static int tb_port_enable_tmu(struct tb_port *port, bool enable)
    return tb_sw_write(sw, &value, TB_CFG_SWITCH, offset, 1);
    }

    +static void tb_port_dummy_read(struct tb_port *port)
    +{
    + /*
    + * When reading from next capability pointer location in port
    + * config space the read data is not cleared on LR. To avoid
    + * reading stale data on next read perform one dummy read after
    + * port capabilities are walked.
    + */
    + if (tb_switch_is_lr(port->sw)) {
    + u32 dummy;
    +
    + tb_port_read(port, &dummy, TB_CFG_PORT, 0, 1);
    + }
    +}
    +
    static int __tb_port_find_cap(struct tb_port *port, enum tb_port_cap cap)
    {
    u32 offset = 1;
    @@ -92,6 +107,7 @@ int tb_port_find_cap(struct tb_port *port, enum tb_port_cap cap)

    ret = __tb_port_find_cap(port, cap);

    + tb_port_dummy_read(port);
    tb_port_enable_tmu(port, false);

    return ret;
    --
    2.20.1
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