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smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=etogxosl; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 53FBD606A323; Tue, 20 Oct 2026 06:11:12 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=etogxosl Received: by smtp.kernel.org (Postfix) with ESMTPSA id A79521F000C4; Tue, 20 Oct 2026 06:11:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1792476672; bh=qURdosLx8zTZ3zVvM3xem+wSvVuHh/39HXWQNT8Qr+c=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=etogxoslE6HlpKoURqYD++MGv+S1oy/dUd3bi7iK4rFPObqwFbk6Fq1EQJqbUEhbh 648zYiZlOthgH3LfhIj+lHRuogvMCQmOVxaO05jgUXO0xhtZFU++DgY3ln9QrKUDDg nQ658iuxxpsPNwsMK8Y04xYjqBAtqBFVTpSTbms8KSWYjbQK1JVXfF1isxpJ0QEQ5G bjSBD+K6Vxq8fnGj1Ro8mEAQPew4T227Z2U7SOVZt3XBe3Mr69MUMFVBEJg3TgDSyO dGS3k/Qa4aFaee/J3hpd6L2ViRhqoqxboP+DURQAt8C1QZnbyk2cpc8yoxMIHJ5V4g fC/uEbrVXwkUQ== Message-ID: Date: Tue, 20 Oct 2026 08:11:06 +0200 X-Mailing-List: devicetree@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 2/4] serial: 8250_dw: Only accept a contiguous DLF readback To: Vinicius Pedrosa , linux-serial@vger.kernel.org Cc: gregkh@linuxfoundation.org, robh@kernel.org, krzk+dt@kernel.org, conor+dt@kernel.org, andriy.shevchenko@linux.intel.com, 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 References: Content-Language: en-US From: Jiri Slaby Autocrypt: addr=jirislaby@kernel.org; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 19. 10. 26, 22:06, Vinicius Pedrosa wrote: > --- a/drivers/tty/serial/8250/8250_dwlib.c > +++ b/drivers/tty/serial/8250/8250_dwlib.c > @@ -225,7 +225,11 @@ void dw8250_setup_port(struct uart_port *p) > reg = dw8250_readl_ext(p, DW_UART_DLF); > dw8250_writel_ext(p, DW_UART_DLF, old_dlf); > > - if (reg) { > + /* > + * DLF is a bit field starting at bit 0, so a real one reads back as > + * 2^n - 1. Any other value means this offset is something else. > + */ > + if (reg && !(reg & (reg + 1))) { Do I understand correctly, that this equivalent to: if (is_power_of_2(reg + 1)) ? thanks, -- js suse labs