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    Subject[PATCH AUTOSEL 5.4 03/84] clk: at91: usb: continue if clk_hw_round_rate() return zero
    Date
    From: Claudiu Beznea <claudiu.beznea@microchip.com>

    [ Upstream commit b0ecf1c6c6e82da4847900fad0272abfd014666d ]

    clk_hw_round_rate() may call round rate function of its parents. In case
    of SAM9X60 two of USB parrents are PLLA and UPLL. These clocks are
    controlled by clk-sam9x60-pll.c driver. The round rate function for this
    driver is sam9x60_pll_round_rate() which call in turn
    sam9x60_pll_get_best_div_mul(). In case the requested rate is not in the
    proper range (rate < characteristics->output[0].min &&
    rate > characteristics->output[0].max) the sam9x60_pll_round_rate() will
    return a negative number to its caller (called by
    clk_core_round_rate_nolock()). clk_hw_round_rate() will return zero in
    case a negative number is returned by clk_core_round_rate_nolock(). With
    this, the USB clock will continue its rate computation even caller of
    clk_hw_round_rate() returned an error. With this, the USB clock on SAM9X60
    may not chose the best parent. I detected this after a suspend/resume
    cycle on SAM9X60.

    Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
    Link: https://lkml.kernel.org/r/1579261009-4573-2-git-send-email-claudiu.beznea@microchip.com
    Signed-off-by: Stephen Boyd <sboyd@kernel.org>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    drivers/clk/at91/clk-usb.c | 3 +++
    1 file changed, 3 insertions(+)

    diff --git a/drivers/clk/at91/clk-usb.c b/drivers/clk/at91/clk-usb.c
    index 22aede42a3362..3c0bd7e51b09d 100644
    --- a/drivers/clk/at91/clk-usb.c
    +++ b/drivers/clk/at91/clk-usb.c
    @@ -75,6 +75,9 @@ static int at91sam9x5_clk_usb_determine_rate(struct clk_hw *hw,
    tmp_parent_rate = req->rate * div;
    tmp_parent_rate = clk_hw_round_rate(parent,
    tmp_parent_rate);
    + if (!tmp_parent_rate)
    + continue;
    +
    tmp_rate = DIV_ROUND_CLOSEST(tmp_parent_rate, div);
    if (tmp_rate < req->rate)
    tmp_diff = req->rate - tmp_rate;
    --
    2.20.1
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