linux-kernel - [PATCH 1/4] clk: at91: usb: continue if clk_hw_round

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Message-ID: <1579261009-4573-2-git-send-email-claudiu.beznea@microchip.com>
Date:   Fri, 17 Jan 2020 13:36:46 +0200
From:   Claudiu Beznea <claudiu.beznea@...rochip.com>
To:     <mturquette@...libre.com>, <sboyd@...nel.org>,
        <nicolas.ferre@...rochip.com>, <alexandre.belloni@...tlin.com>,
        <ludovic.desroches@...rochip.com>
CC:     <linux-clk@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>,
        Claudiu Beznea <claudiu.beznea@...rochip.com>
Subject: [PATCH 1/4] clk: at91: usb: continue if clk_hw_round_rate() return zero

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@...rochip.com>
---
 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 22aede42a336..3c0bd7e51b09 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;
-- 
2.7.4