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([179.179.238.247]) by smtp.gmail.com with ESMTPSA id 71dfb90a1353d-5eae9697814sm4054490e0c.1.2026.10.21.11.07.20 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 21 Oct 2026 11:07:25 -0700 (PDT) From: Vinicius Pedrosa To: Andy Shevchenko Cc: linux-serial@vger.kernel.org, gregkh@linuxfoundation.org, jirislaby@kernel.org, robh@kernel.org, krzk+dt@kernel.org, conor+dt@kernel.org, ilpo.jarvinen@linux.intel.com, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-sunxi@lists.linux.dev, Andre Przywara , Chen-Yu Tsai , Jernej Skrabec , Samuel Holland , Enzo Adriano , stable@vger.kernel.org Subject: Re: [PATCH v2 1/4] serial: 8250_dw: Keep the BUSY-safe divisor hook when DLF is present Date: Wed, 21 Oct 2026 15:07:14 -0300 Message-ID: <20261021180714.473749-1-vinicius.eduardo.pedrosa@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: References: <20261020104753.28703-1-vinicius.eduardo.pedrosa@gmail.com> <20261021100049.16504-1-vinicius.eduardo.pedrosa@gmail.com> <20261021153732.1978410-1-vinicius.eduardo.pedrosa@gmail.com> <20261021170403.2052449-1-vinicius.eduardo.pedrosa@gmail.com> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Hi Andy, On Wed, 21 Oct 2026, Andy Shevchenko wrote: > Yes. but is it only a single device/platform affected or a big class of the > devices? I assume only narrow part of them which unfortunately use DFL register > offset for something else in their RTL. The A733 is the only case I've seen, and the false DLF is what exposed it. But I don't think the BUSY problem depends on the DLF offset being reused: with a real DLF on a UART that isn't 16550-compatible, dw8250_setup_port() also replaces the BUSY-safe setter with the dwlib one, so the same path exists. I haven't confirmed that on hardware. With patch 2 the A733 no longer takes that path. > It all depends on the outcome of the above discussion. Maybe others can share > their opinions, but I lean towards a series-as-a-fix rather than a bit ugly fix > + proper refactoring on top. I'm fine with a series-as-a-fix, and with deferring the deduplication patch. Thanks, Vinicius