From nobody Fri Dec 26 19:35:32 2025 Received: from mail-yw1-f201.google.com (mail-yw1-f201.google.com [209.85.128.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 29C5B944B for ; Sun, 31 Dec 2023 18:29:59 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--vamshigajjela.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="arNfgIfm" Received: by mail-yw1-f201.google.com with SMTP id 00721157ae682-5e8d2c6903dso132192257b3.0 for ; Sun, 31 Dec 2023 10:29:59 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1704047398; x=1704652198; darn=vger.kernel.org; h=cc:to:from:subject:message-id:mime-version:date:from:to:cc:subject :date:message-id:reply-to; bh=uMZVz/UW8puWfXdgiZf80krGZeVv7b49r1xaHw6OLh8=; b=arNfgIfm9fkWd0ejpTGVDw0Kx0hy9DrnPCRk/+7MGupRfHCBdUxLMwCGqy7NPeK+As rFhiswAoF9Urs2tOFa2TzNGVIaDjl6fwm/FMg8T4Up4iIqQQZhmKzXvxKXWLe8OAR4fV lCYhwm4HTcJoD1ZHoM/ZKc+IEAyzoQ/jH5BVHe4c705HqUG4A8lVDRnk6wGOnilAhtB8 zEMwBUaoRUwf8vAXTizvkfNGfPbWJg8zmxzCc6gi+cWrQClHGuN15XOS+7+xryOxMJu/ GdDEY70RIZdoHuE4pjDQRwlCegDf+1pP6KMVyBM2t/Bfyc5Uyepu0l1m3P3PHlWgGF5q Tftg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1704047398; x=1704652198; h=cc:to:from:subject:message-id:mime-version:date:x-gm-message-state :from:to:cc:subject:date:message-id:reply-to; bh=uMZVz/UW8puWfXdgiZf80krGZeVv7b49r1xaHw6OLh8=; b=u5ba3SYIxvCcbE/pSlRLXKiFKpLE2hdvKzz+PJ8r2GuEoVv0LUwz6X950kVH3sNJA7 lr5a/Z76soXDxFf5f29po8EspAQGbHUoRzi2KWTt7XKOiDs8RkLJ5ANVd1rF4VKTMzr+ XrVOmEStgs/u6OXdhcp3CXXQ/xLmyG7d7pRZRuJNelHIaMyUbvI9H7vV6uYv1oQm7bue BKanl2f9yX6I94XOimZpyvh0Zi3XyLPOvCQ00s01gSrnL8FEHO3AZrPnoVc9qaAIhWDZ l0jXlC+AHRux87gwTMl8d+aagZJB0g157VEAC0JWh4j+VDynl2WMVzKpSEIRL9akhH+f s1qA== X-Gm-Message-State: AOJu0YyRMxU3QlE3GrsaqYby81oGTVIsj+JLgaHzdgew5aDOuK32Qoky QP068Bb3HNjFhl6cDBJUrcAyc1PtY/qNKhRBinZRxoywR2Y= X-Google-Smtp-Source: AGHT+IEnE32X76P7Izi1WqjwmXwc8RSLGP5pb3wwKbUQr/o9QMgvchl1KpiYQMWEwjUlPqvx/isabCmpM+96eTNAJ8GA X-Received: from vamshig51.c.googlers.com ([fda3:e722:ac3:cc00:3:22c1:c0a8:70c]) (user=vamshigajjela job=sendgmr) by 2002:a05:690c:3509:b0:5e8:bea4:4d37 with SMTP id fq9-20020a05690c350900b005e8bea44d37mr7440280ywb.7.1704047398192; Sun, 31 Dec 2023 10:29:58 -0800 (PST) Date: Sun, 31 Dec 2023 23:59:51 +0530 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 X-Mailer: git-send-email 2.43.0.472.g3155946c3a-goog Message-ID: <20231231182951.877805-1-vamshigajjela@google.com> Subject: [PATCH] serial: 8250_dw: Do not bailout on UCV read returning zero From: Vamshi Gajjela To: Greg Kroah-Hartman , Jiri Slaby , ilpo.jarvinen@linux.intel.com, Andy Shevchenko Cc: linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org, manugautam@google.com, Vamshi Gajjela Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Designware UART has optional feature FIFO_MODE to implement FIFO. Encoding FIFO capabilities through Component Parameter Register CPR is optional and it can be enabled using parameter UART_ADD_ENCODED_PARAMS. Driver can exercise fifo capabilities by decoding CPR if implemented or from cpr_val provided from the dw8250_platform_data otherwise. dw8250_setup_port() checks for CPR or cpr_val to determine FIFO size only when Component Version (UCV) is non-zero. Bailing out early on UCV read returning zero will leave fifosize as zero and !UART_CAP_FIFO, hence prevent early return and continue to process CPR or cpr_val for the driver to utilize FIFO. Non-zero UCV implies ADDITIONAL_FEATURES=3D1, preventing early return will not be an overhead here. Signed-off-by: Vamshi Gajjela --- drivers/tty/serial/8250/8250_dwlib.c | 12 +++--------- 1 file changed, 3 insertions(+), 9 deletions(-) diff --git a/drivers/tty/serial/8250/8250_dwlib.c b/drivers/tty/serial/8250= /8250_dwlib.c index 136ad093c5b6..3e33ddf7bc80 100644 --- a/drivers/tty/serial/8250/8250_dwlib.c +++ b/drivers/tty/serial/8250/8250_dwlib.c @@ -271,16 +271,10 @@ void dw8250_setup_port(struct uart_port *p) p->set_divisor =3D dw8250_set_divisor; } =20 - /* - * If the Component Version Register returns zero, we know that - * ADDITIONAL_FEATURES are not enabled. No need to go any further. - */ reg =3D dw8250_readl_ext(p, DW_UART_UCV); - if (!reg) - return; - - dev_dbg(p->dev, "Designware UART version %c.%c%c\n", - (reg >> 24) & 0xff, (reg >> 16) & 0xff, (reg >> 8) & 0xff); + if (reg) + dev_dbg(p->dev, "Designware UART version %c.%c%c\n", + (reg >> 24) & 0xff, (reg >> 16) & 0xff, (reg >> 8) & 0xff); =20 reg =3D dw8250_readl_ext(p, DW_UART_CPR); if (!reg) { --=20 2.43.0.472.g3155946c3a-goog