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References: <20230901070041.13463-1-quic_devipriy@quicinc.com> <3fe1655e30d62493a24e1f97ab7bf710.sboyd@kernel.org> <f139041f-452a-46d9-b5af-a5ddef29c705@linaro.org>
Subject: Re: [PATCH V2] clk: qcom: clk-alpha-pll: Use determine_rate instead of round_rate
From:   Stephen Boyd <sboyd@kernel.org>
Cc:     quic_saahtoma@quicinc.com
To:     Devi Priya <quic_devipriy@quicinc.com>,
        Konrad Dybcio <konrad.dybcio@linaro.org>, agross@kernel.org,
        andersson@kernel.org, linux-arm-msm@vger.kernel.org,
        linux-clk@vger.kernel.org, linux-kernel@vger.kernel.org,
        mturquette@baylibre.com
Date:   Wed, 06 Sep 2023 14:14:16 -0700
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Quoting Konrad Dybcio (2023-09-06 00:33:38)
> On 5.09.2023 22:40, Stephen Boyd wrote:
> > Quoting Devi Priya (2023-09-01 00:00:41)
> >> The round_rate() API returns a long value as the errors are reported u=
sing
> >> negative error codes. This leads to long overflow when the clock rate
> >> exceeds 2GHz.As the clock controller treats the clock rate above signed
> >> long max as an error, use determine_rate in place of round_rate as the
> >> determine_rate API does not possess such limitations.
> >=20
> > Does this fix something, or is it preparing for PLLs that run faster
> > than 2GHz?
> I did some grepping and we already have multiple of these.
>=20
> E.g. SM8250 CAMCC PLL2 (zonda) goes (or well, should go) up to 3.6 GHz.
>=20
> Today, only stromer PLL uses determine rate, but perhaps all of them
> should.
>=20
> I would not at all be surprised if many otherwise inexplicable bugs
> went away with that change.

Are any of those arm32 systems? It would only matter on arm32 systems
because sizeof(long) is limited to 32-bits and we don't have negative
frequencies.