Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753545Ab3EFMVH (ORCPT ); Mon, 6 May 2013 08:21:07 -0400 Received: from mail-da0-f50.google.com ([209.85.210.50]:56503 "EHLO mail-da0-f50.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753431Ab3EFMVD (ORCPT ); Mon, 6 May 2013 08:21:03 -0400 From: Pranavkumar Sawargaonkar To: linux-arm-kernel@lists.infradead.org Cc: kvmarm@lists.cs.columbia.edu, linux-kernel@vger.kernel.org, rusty@rustcorp.com.au, linaro-kernel@lists.linaro.org, patches@linaro.org, anup.patel@linaro.org, amit.shah@redhat.com, Pranavkumar Sawargaonkar Subject: [PATCH V2 3/3] arm64: earlyprintk support for virtio-mmio console. Date: Mon, 6 May 2013 17:49:51 +0530 Message-Id: <1367842791-30285-4-git-send-email-pranavkumar@linaro.org> X-Mailer: git-send-email 1.7.9.5 In-Reply-To: <1367842791-30285-1-git-send-email-pranavkumar@linaro.org> References: <1367842791-30285-1-git-send-email-pranavkumar@linaro.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2260 Lines: 80 This patch implements earlyprintk based on virtio console using emerg_wr config register. Kernel args for using this will be: earlyprintk=virtio-console, Signed-off-by: Pranavkumar Sawargaonkar Signed-off-by: Anup Patel --- arch/arm64/kernel/early_printk.c | 35 +++++++++++++++++++++++++++++++++++ 1 file changed, 35 insertions(+) diff --git a/arch/arm64/kernel/early_printk.c b/arch/arm64/kernel/early_printk.c index ac974f4..ea3d2f5 100644 --- a/arch/arm64/kernel/early_printk.c +++ b/arch/arm64/kernel/early_printk.c @@ -25,6 +25,9 @@ #include #include +#include +#include +#include static void __iomem *early_base; static void (*printch)(char ch); @@ -53,6 +56,37 @@ static void smh_printch(char ch) } /* + * VIRTIO MMIO console single character Tx. + */ +static void virtio_console_printch(char ch) +{ + u32 tmp; + static u32 init_done; + static u32 can_write; + struct virtio_console_config *p = early_base + VIRTIO_MMIO_CONFIG; + + if (!init_done) { + tmp = readl_relaxed(early_base + VIRTIO_MMIO_DEVICE_ID); + if (tmp != VIRTIO_ID_CONSOLE) { + init_done = 1; + return; + } + + tmp = readl_relaxed(early_base + VIRTIO_MMIO_HOST_FEATURES); + if (!(tmp & (1 << VIRTIO_CONSOLE_F_EMERG_WRITE))) { + init_done = 1; + return; + } + + init_done = 1; + can_write = 1; + } + + if (can_write) + writeb_relaxed(ch, &p->emerg_wr); +} + +/* * 8250/16550 (8-bit aligned registers) single character TX. */ static void uart8250_8bit_printch(char ch) @@ -82,6 +116,7 @@ static const struct earlycon_match earlycon_match[] __initconst = { { .name = "smh", .printch = smh_printch, }, { .name = "uart8250-8bit", .printch = uart8250_8bit_printch, }, { .name = "uart8250-32bit", .printch = uart8250_32bit_printch, }, + { .name = "virtio-console", .printch = virtio_console_printch, }, {} }; -- 1.7.9.5 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/