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[73.183.53.213]) by smtp.gmail.com with ESMTPSA id 00721157ae682-823f75c1c17sm60279477b3.47.2026.08.10.10.18.01 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 10 Aug 2026 10:18:02 -0700 (PDT) Date: Mon, 10 Aug 2026 13:17:59 -0400 From: Brian Masney To: Luo Jie Cc: Bjorn Andersson , Michael Turquette , Stephen Boyd , Rob Herring , Krzysztof Kozlowski , Conor Dooley , Konrad Dybcio , linux-arm-msm@vger.kernel.org, linux-clk@vger.kernel.org, linux-kernel@vger.kernel.org, devicetree@vger.kernel.org, quic_kkumarcs@quicinc.com, quic_linchen@quicinc.com, quic_leiwei@quicinc.com, quic_suruchia@quicinc.com Subject: Re: [PATCH v2 03/12] clk: divider: Introduce CLK_DIVIDER_EVEN_INTEGERS_NO_OFFSET flag Message-ID: References: <20260806-qcom_ipq5210_cmnpll-v2-0-cce718b8ec17@oss.qualcomm.com> <20260806-qcom_ipq5210_cmnpll-v2-3-cce718b8ec17@oss.qualcomm.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260806-qcom_ipq5210_cmnpll-v2-3-cce718b8ec17@oss.qualcomm.com> User-Agent: Mutt/2.4.0 (2026-06-19) Hi Luo, On Thu, Aug 06, 2026 at 11:53:07PM -0700, Luo Jie wrote: > Some hardware dividers derive an even divisor directly from the raw > register value, i.e. divisor = 2 * val, with no +1 offset. This differs > from CLK_DIVIDER_EVEN_INTEGERS, which is one-based (divisor = 2 * > (val + 1)). > > Add CLK_DIVIDER_EVEN_INTEGERS_NO_OFFSET for this variant, updating > _get_maxdiv()/_get_div()/_get_val() accordingly. _is_valid_div() is > extended to also reject odd divisors, since _get_val()'s `div >> 1` > would otherwise silently decode them to the wrong even value (e.g. 3 > -> 1 -> 2). > > To avoid regressing rate requests that previously computed an odd > divisor (which used to succeed with a silently wrong rate), round to > the nearest even divisor in _div_round_up(), _div_round_closest(), and > _next_div(), mirroring how CLK_DIVIDER_POWER_OF_TWO already rounds to > the nearest power of two. > > Also guard divider_ro_determine_rate() against a zero divisor, which > can occur from an unprogrammed/reset register, the same way > divider_recalc_rate() already does: WARN unless CLK_DIVIDER_ALLOW_ZERO > is set, and return -EINVAL. > > Signed-off-by: Luo Jie One of the other patches in your series says: The NSS (network subsystem) clock is derived from the CMN PLL output divided by 2 and then further divided by a configurable 6-bit divider. Can you register a fixed-factor-clock parent with /2, then use CLK_DIVIDER_ONE_BASED? That should yield the same results and it may more accurately represent the hardware as well. Brian