From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [198.175.65.12]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D601028F53F for ; Wed, 7 May 2025 13:54:13 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.175.65.12 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1746626055; cv=none; b=sFyVkIVccdL8WjvnnWkTfd64p+NZcee20rps70O6DvMEi9tymi1N2WuXFfp5qUidu2ujWWjhNWKqfUBGIB+BDVxh66UBb2icERFkqyRKWZWY/hs8v976G3epLQdmTaB4qUeDf6bQ7XUfl/qGoorHKUHXpWHdWYDWhfASGl9acgY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1746626055; c=relaxed/simple; bh=vze+17XceRJoOoG/svFEL6SEfqk9yNIzPuCH+KkVmEw=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=feEBI99DvKXE3lWVugUOhP4iIdDCC2hhYPIObA9sdAt0qX2zn4mFhe6shO8prMyE091uEP0SSzmLLJi0qUCQE6GhBJJ34SZCcgu0IQV8uimqDBnYrBs463mLPnZYo18zVkxxyTOrGlgSHWYkC2nw7xPC+jgnOkJy1F6AAFA5DWs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com; spf=none smtp.mailfrom=linux.intel.com; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b=S+gt/9wC; arc=none smtp.client-ip=198.175.65.12 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b="S+gt/9wC" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1746626054; x=1778162054; h=date:from:to:cc:subject:message-id:references: mime-version:in-reply-to; bh=vze+17XceRJoOoG/svFEL6SEfqk9yNIzPuCH+KkVmEw=; b=S+gt/9wC48c2PHB4wZ0u/XYbO/42ibD/siHpSslmIrzNciPTRJIifSPF QM7zllZnQBXdYE2cQBgdRmUVX8sU0DyJ1zgH0Edb1odUYmKDrbON/lFeS nbPsfERSz4/5L++a7d78sEELdGkvO5nlJRcLRt0EqCx8RvtZzThh0DfwP OgH3sTp8mGWUmsLFVm0rGOHFSBAOQ696yKpYCHRvz/WYqIAz1h6W78hzT p1YlJpnqlU7H9giMGFcEYV0z2ms2cWrC+zRQKbu6uGq7XFTb6smyEhkNx 8tEHEKaDxzUoOOV/yaS6yOPoT6BQgFaJlgcUftDatCxHzJVwrf6zTS1W1 w==; X-CSE-ConnectionGUID: UtLgApf+TvmmsCkW+vqV7A== X-CSE-MsgGUID: y7nbrrl7Q/e9Jt6UuWL6ng== X-IronPort-AV: E=McAfee;i="6700,10204,11426"; a="59753294" X-IronPort-AV: E=Sophos;i="6.15,269,1739865600"; d="scan'208";a="59753294" Received: from orviesa003.jf.intel.com ([10.64.159.143]) by orvoesa104.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 07 May 2025 06:54:14 -0700 X-CSE-ConnectionGUID: fim/3lfsRaizCn/2Drq8kg== X-CSE-MsgGUID: 0E13cpX1SpSHJ4YXES9ypg== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.15,269,1739865600"; d="scan'208";a="140720499" Received: from smile.fi.intel.com ([10.237.72.55]) by orviesa003.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 07 May 2025 06:54:11 -0700 Received: from andy by smile.fi.intel.com with local (Exim 4.98.2) (envelope-from ) id 1uCfDr-00000003kMP-1t2w; Wed, 07 May 2025 16:54:07 +0300 Date: Wed, 7 May 2025 16:54:07 +0300 From: Andy Shevchenko To: David Woodhouse Cc: Ashish Kalra , "Kirill A. Shutemov" , linux-kernel@vger.kernel.org, Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Denis Mukhin Subject: Re: [PATCH v1 0/6] x86/boot: Enable earlyprintk on MMIO (8-bit) Message-ID: References: <20250502123145.4066635-1-andriy.shevchenko@linux.intel.com> <47a4795427d11c7c2d7713edda36d0c63c585c8d.camel@infradead.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <47a4795427d11c7c2d7713edda36d0c63c585c8d.camel@infradead.org> Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo On Tue, May 06, 2025 at 12:38:21PM -0700, David Woodhouse wrote: > On Fri, 2025-05-02 at 15:29 +0300, Andy Shevchenko wrote: > > Some of the platforms may have no legacy COM ports and only provide > > an MMIO accessible UART. Add support for such to earlyprintk for the > > boot phase of the kernel. > > Aha, I understand now... you've added this *only* for the boot code, > and haven't added the corresponding support to the in-kernel > earlyprintk, in arch/x86/kernel/early_printk.c Haven't added yet. This is part 1 only. > The latter does already support MMIO but it only supports a 32-bit > stride, not 8-bit. > > Please could you make that consistent, and ensure the earlyprintk= > arguments function the same for both phases? I'm happy to add the > kexec-debug parts on top of *that*. It's not as easy as it looks like. I had done in the past the comparison table of what we have between all early*=... for serial consoles and it all so inconsistent to begin with. A big work needs to be fulfilled in order to put this mess in order. Hence this is just the first step. > It would be really helpful if we could test this in QEMU; it shouldn't > be that hard to make it provide a 16550 on MMIO, along the lines of the > one-line hack I posted yesterday. I understand. But if no go for this series, I don't won't to spend time on the next part. In any case, thanks for looking into this. -- With Best Regards, Andy Shevchenko