From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-19.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9505CC433EF for ; Thu, 9 Sep 2021 13:20:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7AC0060E94 for ; Thu, 9 Sep 2021 13:20:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1354717AbhIINVe (ORCPT ); Thu, 9 Sep 2021 09:21:34 -0400 Received: from mail.kernel.org ([198.145.29.99]:36126 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1358965AbhIINLk (ORCPT ); Thu, 9 Sep 2021 09:11:40 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 7CA3D60F93; Thu, 9 Sep 2021 12:01:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1631188898; bh=lIy+05ziBAwE/jn8HtkwCLYTq8qkrvmDc5Ss5MhF1/A=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=SohDMWy+lk+jqy8TneIxwGW3oj6THw1LxFCVwf4ztG0KeB/IwL0vi36/C5OhaAlXa ZlK2Oo3pduP8yiTa7+FHbnxvegAslZSt5PFJoW/3KK8KChV/aJAFAQswKtPt9qB3bP NOLdR9flv1Eht0CyAcTNEuj0bAhk8/C/wnG0p0RdEz60/Qie+SmNLEqw+LDnk4XS50 pOlEtfXqZfX1oRnltu7MKucmbpaaJ67XsfdbQmPOcfmx95C+AINlqB+ESuc2AlAJSt EEIx2MoIDng28htICsTCNMrEzxNZMPcRBTY0I2F2Gq2aDyQWhIoD9a73o2SHku6Rvu 6hiFcQm6TQtEg== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: "Maciej W. Rozycki" , Greg Kroah-Hartman , Sasha Levin , linux-serial@vger.kernel.org Subject: [PATCH AUTOSEL 4.4 17/35] serial: 8250: Define RX trigger levels for OxSemi 950 devices Date: Thu, 9 Sep 2021 08:00:58 -0400 Message-Id: <20210909120116.150912-17-sashal@kernel.org> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20210909120116.150912-1-sashal@kernel.org> References: <20210909120116.150912-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-serial@vger.kernel.org From: "Maciej W. Rozycki" [ Upstream commit d7aff291d069c4418285f3c8ee27b0ff67ce5998 ] Oxford Semiconductor 950 serial port devices have a 128-byte FIFO and in the enhanced (650) mode, which we select in `autoconfig_has_efr' with the ECB bit set in the EFR register, they support the receive interrupt trigger level selectable with FCR bits 7:6 from the set of 16, 32, 112, 120. This applies to the original OX16C950 discrete UART[1] as well as 950 cores embedded into more complex devices. For these devices we set the default to 112, which sets an excessively high level of 112 or 7/8 of the FIFO capacity, unlike with other port types where we choose at most 1/2 of their respective FIFO capacities. Additionally we don't make the trigger level configurable. Consequently frequent input overruns happen with high bit rates where hardware flow control cannot be used (e.g. terminal applications) even with otherwise highly-performant systems. Lower the default receive interrupt trigger level to 32 then, and make it configurable. Document the trigger levels along with other port types, including the set of 16, 32, 64, 112 for the transmit interrupt as well[2]. References: [1] "OX16C950 rev B High Performance UART with 128 byte FIFOs", Oxford Semiconductor, Inc., DS-0031, Sep 05, Table 10: "Receiver Trigger Levels", p. 22 [2] same, Table 9: "Transmit Interrupt Trigger Levels", p. 22 Signed-off-by: Maciej W. Rozycki Link: https://lore.kernel.org/r/alpine.DEB.2.21.2106260608480.37803@angie.orcam.me.uk Signed-off-by: Greg Kroah-Hartman Signed-off-by: Sasha Levin --- drivers/tty/serial/8250/8250_port.c | 3 ++- include/uapi/linux/serial_reg.h | 1 + 2 files changed, 3 insertions(+), 1 deletion(-) diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c index 041bfe1d4191..d0d90752f9f3 100644 --- a/drivers/tty/serial/8250/8250_port.c +++ b/drivers/tty/serial/8250/8250_port.c @@ -124,7 +124,8 @@ static const struct serial8250_config uart_config[] = { .name = "16C950/954", .fifo_size = 128, .tx_loadsz = 128, - .fcr = UART_FCR_ENABLE_FIFO | UART_FCR_R_TRIG_10, + .fcr = UART_FCR_ENABLE_FIFO | UART_FCR_R_TRIG_01, + .rxtrig_bytes = {16, 32, 112, 120}, /* UART_CAP_EFR breaks billionon CF bluetooth card. */ .flags = UART_CAP_FIFO | UART_CAP_SLEEP, }, diff --git a/include/uapi/linux/serial_reg.h b/include/uapi/linux/serial_reg.h index 1e5ac4e776da..5bcc637cee46 100644 --- a/include/uapi/linux/serial_reg.h +++ b/include/uapi/linux/serial_reg.h @@ -61,6 +61,7 @@ * ST16C654: 8 16 56 60 8 16 32 56 PORT_16654 * TI16C750: 1 16 32 56 xx xx xx xx PORT_16750 * TI16C752: 8 16 56 60 8 16 32 56 + * OX16C950: 16 32 112 120 16 32 64 112 PORT_16C950 * Tegra: 1 4 8 14 16 8 4 1 PORT_TEGRA */ #define UART_FCR_R_TRIG_00 0x00 -- 2.30.2