From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stephen Warren Subject: Re: [PATCH v2 1/7] clk: tegra: Add support for PLLSS Date: Wed, 16 Oct 2013 11:21:12 -0600 Message-ID: <525ECB08.4020201@wwwdotorg.org> References: <1381850098-12357-1-git-send-email-pdeschrijver@nvidia.com> <1381850098-12357-2-git-send-email-pdeschrijver@nvidia.com> <525DA373.6040805@wwwdotorg.org> <20131016074829.GD5643@tbergstrom-lnx.Nvidia.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20131016074829.GD5643-Rysk9IDjsxmJz7etNGeUX8VPkgjIgRvpAL8bYrjMMd8@public.gmane.org> Sender: linux-tegra-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Peter De Schrijver Cc: Prashant Gaikwad , Mike Turquette , Thierry Reding , "linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org" , "linux-tegra-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" List-Id: linux-tegra@vger.kernel.org On 10/16/2013 01:48 AM, Peter De Schrijver wrote: > On Tue, Oct 15, 2013 at 10:20:03PM +0200, Stephen Warren wrote: >> On 10/15/2013 09:14 AM, Peter De Schrijver wrote: >>> Tegra124 introduces a new PLL type, PLLSS. Add support for it. >> >>> diff --git a/drivers/clk/tegra/clk-pll.c b/drivers/clk/tegra/clk-pll.c >> >> >>> +static int clk_pllss_set_rate(struct clk_hw *hw, unsigned long rate, >>> + unsigned long parent_rate) >> >> This function seems pretty generic. Is it possible to share a bit more >> code with any of the other pllXXX_set_rate() functions? >> >>> +struct clk *tegra_clk_register_pllss(const char *name, const char *parent_name, >>> + void __iomem *clk_base, unsigned long flags, >>> + struct tegra_clk_pll_params *pll_params, >>> + spinlock_t *lock) >> >>> + val = pll_readl_base(pll); >>> + if (val & PLLSS_REF_SRC_SEL_MASK) { >>> + WARN(1, "Unknown parent selected for %s: %d\n", name, >>> + (val & PLLSS_REF_SRC_SEL_MASK) >> >>> + PLLSS_REF_SRC_SEL_SHIFT); >>> + kfree(pll); >>> + return ERR_PTR(-EINVAL); >>> + } >> >> If there's a field in HW that muxes the clock input between n clocks, >> why does this function assume there's a single parent for this PLL, by >> taking a "const char *parent_name" parameter? >> >> What happens if the bootloader changed this field in HW; is the kernel >> simply not able to boot? >> > > This logic comes from downstream. I guess it means we're running in an > unvalidated configuration. Do you think we should expose all parents > anyway? Even if not all configurations have been validated? > (which is quite likely) If we only support one particular parent, why not force the register field to the desired value, rather than failing?