On Thu, Aug 20, 2015 at 12:37:29PM +0100, Jens Wiklander wrote: > On Wed, Aug 19, 2015 at 05:50:09PM +0100, Will Deacon wrote: > > On Wed, Aug 19, 2015 at 09:40:25AM +0100, Jens Wiklander wrote: > > > Adds helpers to do SMC based on ARM SMC Calling Convention. > > > CONFIG_HAVE_SMCCC is enabled for architectures that may support > > > the SMC instruction. It's the responsibility of the caller to > > > know if the SMC instruction is supported by the platform. > > > > [...] > > > diff --git a/arch/arm64/kernel/smccc-call.S b/arch/arm64/kernel/smccc-call.S > > > new file mode 100644 > > > index 0000000..3ce7fe8 > > > --- /dev/null > > > +++ b/arch/arm64/kernel/smccc-call.S > > > @@ -0,0 +1,34 @@ > > > +/* > > > + * Copyright (c) 2015, Linaro Limited > > > + * > > > + * This program is free software; you can redistribute it and/or modify > > > + * it under the terms of the GNU General Public License Version 2 as > > > + * published by the Free Software Foundation. > > > + * > > > + * This program is distributed in the hope that it will be useful, > > > + * but WITHOUT ANY WARRANTY; without even the implied warranty of > > > + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the > > > + * GNU General Public License for more details. > > > + * > > > + */ > > > +#include <linux/linkage.h> > > > + > > > +#define SMC_PARAM_W0_OFFS 0 > > > +#define SMC_PARAM_W2_OFFS 8 > > > +#define SMC_PARAM_W4_OFFS 16 > > > +#define SMC_PARAM_W6_OFFS 24 > > > + > > > +/* void smccc_call32(struct smccc_param32 *param) */ > > > +ENTRY(smccc_call32) > > > + stp x28, x30, [sp, #-16]! > > > > Why are you saving lr? > > Agree, no point in saving lr, but I still need to decrease sp with 16 to > maintain correct alignment. I'll do it with an str instruction instead. That or pad out with xzr > > > > > + mov x28, x0 > > > + ldp w0, w1, [x28, #SMC_PARAM_W0_OFFS] > > > + ldp w2, w3, [x28, #SMC_PARAM_W2_OFFS] > > > + ldp w4, w5, [x28, #SMC_PARAM_W4_OFFS] > > > + ldp w6, w7, [x28, #SMC_PARAM_W6_OFFS] > > > + smc #0 > > > + stp w0, w1, [x28, #SMC_PARAM_W0_OFFS] > > > + stp w2, w3, [x28, #SMC_PARAM_W2_OFFS] > > > + ldp x28, x30, [sp], #16 > > > + ret > > > +ENDPROC(smccc_call32) > > > > Could we deal with this like we do for PSCI instead? (see > > __invoke_psci_fn_smc). We could also then rename psci-call.S to fw-call.S > > and stick this in there too. > > I assume you're referring to when to use "hvc" and "smc". No, I mean use a C prototype to avoid marshalling the parameters in assembly like this. As Rutland pointed out, the return value is a bit messy, but the arguments align nicely with the PCS afaict. Will -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
