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

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Message-ID: <158155032378.184098.13418432475305981955@swboyd.mtv.corp.google.com>
Date:   Wed, 12 Feb 2020 15:32:03 -0800
From:   Stephen Boyd <sboyd@...nel.org>
To:     Claudiu Beznea <claudiu.beznea@...rochip.com>,
        alexandre.belloni@...tlin.com, ludovic.desroches@...rochip.com,
        mturquette@...libre.com, nicolas.ferre@...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: Re: [PATCH 1/4] clk: at91: usb: continue if clk_hw_round_rate() return zero

Quoting Claudiu Beznea (2020-01-17 03:36:46)
> 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>
> ---

Applied to clk-next