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[73.183.52.120]) by smtp.gmail.com with ESMTPSA id af79cd13be357-9161a0080a7sm2137505485a.26.2026.06.18.09.55.16 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 18 Jun 2026 09:55:17 -0700 (PDT) Date: Thu, 18 Jun 2026 12:55:15 -0400 From: Brian Masney To: David Carlier Cc: Michael Turquette , Stephen Boyd , Xukai Wang , Conor Dooley , Troy Mitchell , linux-clk@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] clk: canaan: Clear rate fields before reprogramming dividers Message-ID: References: <20260618045030.12581-1-devnexen@gmail.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: <20260618045030.12581-1-devnexen@gmail.com> User-Agent: Mutt/2.3.2 (2026-04-26) On Thu, Jun 18, 2026 at 05:50:30AM +0100, David Carlier wrote: > The rate set_rate helpers perform a read-modify-write on the divider > and multiplier registers but only ever OR the new value in, without > first masking off the existing field. The first write after reset lands > on a zeroed field and looks correct, but any later reprogramming leaves > the old bits set: the field becomes the bitwise OR of the previous and > new encodings, corrupting the divider or multiplier. > > Mask off each field before writing the new value so reprogramming a > clock to a different rate produces the intended register contents. > > Fixes: a7b7c7c6c016 ("clk: canaan: Add clock driver for Canaan K230") > Signed-off-by: David Carlier Reviewed-by: Brian Masney