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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no 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 B5748C2BA12 for ; Thu, 2 Apr 2020 14:15:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 97329206E9 for ; Thu, 2 Apr 2020 14:15:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1733133AbgDBOPL convert rfc822-to-8bit (ORCPT ); Thu, 2 Apr 2020 10:15:11 -0400 Received: from gloria.sntech.de ([185.11.138.130]:46592 "EHLO gloria.sntech.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729033AbgDBOPK (ORCPT ); Thu, 2 Apr 2020 10:15:10 -0400 Received: from ip5f5aa64a.dynamic.kabel-deutschland.de ([95.90.166.74] helo=diego.localnet) by gloria.sntech.de with esmtpsa (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.89) (envelope-from ) id 1jK0cU-000843-Rk; Thu, 02 Apr 2020 16:14:58 +0200 From: Heiko =?ISO-8859-1?Q?St=FCbner?= To: Robin Murphy Cc: =?ISO-8859-1?Q?Myl=E8ne?= Josserand , sboyd@kernel.org, mturquette@baylibre.com, linux-kernel@vger.kernel.org, kever.yang@rock-chips.com, linux-rockchip@lists.infradead.org, geert@linux-m68k.org, kernel@collabora.com, linux-clk@vger.kernel.org, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH v2 1/2] soc: rockchip: Register a soc_device to retrieve revision Date: Thu, 02 Apr 2020 16:14:58 +0200 Message-ID: <4543799.QtudHIFNrS@diego> In-Reply-To: <4844d3ba-87fa-51f4-0a56-3131e390589a@arm.com> References: <20200401153513.423683-1-mylene.josserand@collabora.com> <5143930.cPWVAAQKI9@diego> <4844d3ba-87fa-51f4-0a56-3131e390589a@arm.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8BIT Content-Type: text/plain; charset="iso-8859-1" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Am Donnerstag, 2. April 2020, 13:45:34 CEST schrieb Robin Murphy: > On 2020-04-01 5:34 pm, Heiko Stübner wrote: > [...] > > The possible problem I see here is clocking and power-domain of the hdmi > > controller in corner-cases. In the past we already had a lot of fun with > > kexec, which also indicates that people actually use kexec productively. > > > > So while all clocks are ungated and all power-domains are powered on first > > boot, on a system without graphics the pclk+power-domain could be off when > > doing a kexec into a second kernel, which then would probably hang here. > > Just to be that guy, how about kdump, where entry to the second kernel > is predicated on there *not* being a nice clean shutdown? ;) > > IMO relying on any particular bootloader behaviour in the kernel is > fairly fragile - U-Boot has a lot more latitude in assuming it's running > straight out of reset than Linux does. You'll have to take into account that there are more boot options than uboot ;-) ... especially the rk3288 also needs to support some ancient version of coreboot - that definitly won't see any updates anymore and isn't really user upgradeable. > If we're not going to trust the > DT to correctly describe the SoC variant in the first place, I'm still all for "just put a rk3288w" into the devicetree compatible, but so far other participants seem to prefer a software solution ;-) . > then it's > somewhat questionable whether we should trust it for indirectly > identifying the SoC variant either - it would seem a lot more robust to > just map the known physical addresses to run a canned sequence of > register writes that puts things in a known-good state (on the basis > that this has to run before the 'real' drivers for those things are up, > and thus can't interfere with them). The problem is, the "known physical address" is part of the dw-hdmi controller ip block, so we'll also need to take into account clocks and power-domains. So that would mean the soc-"driver" would need to - ioremap hdmi, cru and pmu - ungate all clocks (on reboot we don't know the hirarchy) - enable at least the pd_vio power-domain via direct register writes. Doable but definitly very ugly and I also don't really know what more people farther upstream would say to that. Anybody interested in just adding that new dt-compatible? Heiko > > Of course with the hdmi-pclk being sourced from hclk_vio we run into a > > chicken-egg-problem, as we need pclk_hdmi_ctrl to register hclk_vio at all. > > > > So I guess one way out of this could be to > > - amend rk3288_clk_shutdown() to also ungate the hdmi-pclk on shutdown > > - add a shutdown mechanism to the power-domain driver so that it can > > enable PD_VIO on shutdown > > > >> + > >> + if (readl_relaxed(hdmi_base + RK3288_HDMI_REV_REG) > >> + == RK3288W_HDMI_REV) > > > > nit: a nicer look would be something like > > val = readl_relaxed(hdmi_base + RK3288_HDMI_REV_REG); > > if (val == RK3288W_HDMI_REV) > > > >> + revision = RK3288_SOC_REV_RK3288W; > >> + else > >> + revision = RK3288_SOC_REV_RK3288; > >> + > >> + iounmap(hdmi_base); > >> + > >> + return revision; > >> +} > >> + > >> +static const char *rk3288_socinfo_revision(u32 rev) > >> +{ > >> + const char *soc_rev; > >> + > >> + switch (rev) { > >> + case RK3288_SOC_REV_RK3288: > >> + soc_rev = "RK3288"; > >> + break; > >> + > >> + case RK3288_SOC_REV_RK3288W: > >> + soc_rev = "RK3288w"; > > > > can we maybe use lower-case letters for all here? > > > >> + break; > >> + > >> + case RK3288_SOC_REV_NOT_DETECT: > >> + soc_rev = ""; > >> + break; > >> + > >> + default: > >> + soc_rev = "unknown"; > >> + break; > >> + } > >> + > >> + return kstrdup_const(soc_rev, GFP_KERNEL); > >> +} > >> + > >> +static const struct of_device_id rk3288_soc_match[] = { > >> + { .compatible = "rockchip,rk3288", }, > >> + { } > >> +}; > >> + > >> +static int __init rk3288_soc_init(void) > > > > as noted at the top, I'd really like to see this more generalized so that > > other socs can just hook in there with a revision callback in a > > rockchip_soc_data struct. > > > > > >> +{ > >> + struct soc_device_attribute *soc_dev_attr; > >> + struct soc_device *soc_dev; > >> + struct device_node *np; > >> + > >> + np = of_find_matching_node(NULL, rk3288_soc_match); > >> + if (!np) > >> + return -ENODEV; > >> + > >> + soc_dev_attr = kzalloc(sizeof(*soc_dev_attr), GFP_KERNEL); > >> + if (!soc_dev_attr) > >> + return -ENOMEM; > >> + > >> + soc_dev_attr->family = "Rockchip"; > >> + soc_dev_attr->soc_id = "RK32xx"; > > > > nit: rk3288 instead of "32xx" please > > > >> + > >> + np = of_find_node_by_path("/"); > >> + of_property_read_string(np, "model", &soc_dev_attr->machine); > >> + of_node_put(np); > >> + > >> + soc_dev_attr->revision = rk3288_socinfo_revision(rk3288_revision()); > >> + > >> + soc_dev = soc_device_register(soc_dev_attr); > >> + if (IS_ERR(soc_dev)) { > >> + kfree_const(soc_dev_attr->revision); > >> + kfree_const(soc_dev_attr->soc_id); > >> + kfree(soc_dev_attr); > >> + return PTR_ERR(soc_dev); > >> + } > >> + > >> + dev_info(soc_device_to_device(soc_dev), "Rockchip %s %s detected\n", > >> + soc_dev_attr->soc_id, soc_dev_attr->revision); > > > > nit: dev_dbg should be enough, that information doesn't really matter for > > most people, as it's only relevant to clock internals. > > > > > > Heiko > > > > > > > > _______________________________________________ > > Linux-rockchip mailing list > > Linux-rockchip@lists.infradead.org > > http://lists.infradead.org/mailman/listinfo/linux-rockchip > > >