> Subject: Re: [PATCH V2 2/2] mailbox: introduce ARM SMC based mailbox > > On 6/3/19 1:30 AM, peng.fan@xxxxxxx wrote: > > From: Peng Fan <peng.fan@xxxxxxx> > > > > This mailbox driver implements a mailbox which signals transmitted > > data via an ARM smc (secure monitor call) instruction. The mailbox > > receiver is implemented in firmware and can synchronously return data > > when it returns execution to the non-secure world again. > > An asynchronous receive path is not implemented. > > This allows the usage of a mailbox to trigger firmware actions on SoCs > > which either don't have a separate management processor or on which > > such a core is not available. A user of this mailbox could be the SCP > > interface. > > > > Modified from Andre Przywara's v2 patch > > https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Flore > > .kernel.org%2Fpatchwork%2Fpatch%2F812999%2F&data=02%7C01%7 > Cpeng.fa > > > n%40nxp.com%7Caa396ba11ba244111fe408d6e8411fba%7C686ea1d3bc2b4 > c6fa92cd > > > 99c5c301635%7C0%7C0%7C636951763738548621&sdata=UlNESNg7I7 > 4TM9xp%2F > > VMce4CSbMuJ95lh68cQw%2FnQMOw%3D&reserved=0 > > > > Cc: Andre Przywara <andre.przywara@xxxxxxx> > > Signed-off-by: Peng Fan <peng.fan@xxxxxxx> > > --- > > [snip] > > +#define ARM_SMC_MBOX_USB_IRQ BIT(1) > > That flag appears unused. I'll remove this in V3. > > > +static int arm_smc_mbox_probe(struct platform_device *pdev) { > > + struct device *dev = &pdev->dev; > > + struct mbox_controller *mbox; > > + struct arm_smc_chan_data *chan_data; > > + const char *method; > > + bool use_hvc = false; > > + int ret, irq_count, i; > > + u32 val; > > + > > + if (!of_property_read_u32(dev->of_node, "arm,num-chans", &val)) { > > + if (val < 1 || val > INT_MAX) { > > + dev_err(dev, "invalid arm,num-chans value %u of %pOFn\n", > val, pdev->dev.of_node); > > + return -EINVAL; > > + } > > + } > > Should not the upper bound check be done against UINT_MAX since val is an > unsigned int? Fix in V3. > > > + > > + irq_count = platform_irq_count(pdev); > > + if (irq_count == -EPROBE_DEFER) > > + return irq_count; > > + > > + if (irq_count && irq_count != val) { > > + dev_err(dev, "Interrupts not match num-chans\n"); > > Interrupts property does not match \"arm,num-chans\" would be more > correct. Fix in V3. > > > + return -EINVAL; > > + } > > + > > + if (!of_property_read_string(dev->of_node, "method", &method)) { > > + if (!strcmp("hvc", method)) { > > + use_hvc = true; > > + } else if (!strcmp("smc", method)) { > > + use_hvc = false; > > + } else { > > + dev_warn(dev, "invalid \"method\" property: %s\n", > > + method); > > + > > + return -EINVAL; > > + } > > Having at least one method specified does not seem to be checked later on in > the code, so if I omitted to specify that property, we would still register the > mailbox and default to use "smc" since the ARM_SMC_MBOX_USE_HVC flag > would not be set, would not we want to make sure that we do have in fact a > valid method specified given the binding documents that property as > mandatory? When arm_smc_send_data, it will check ARM_SMC_MBOX_USE_HVC, you mean there are other places needs this flag check? > > [snip] > > > + mbox->txdone_poll = false; > > + mbox->txdone_irq = false; > > + mbox->ops = &arm_smc_mbox_chan_ops; > > + mbox->dev = dev; > > + > > + ret = mbox_controller_register(mbox); > > + if (ret) > > + return ret; > > + > > + platform_set_drvdata(pdev, mbox); > > I would move this above mbox_controller_register() that way there is no room > for race conditions in case another part of the driver expects to have > pdev->dev.drvdata set before the mbox controller is registered. Right. > Since you use devm_* functions for everything, you may even remove that > call. You mean remove " platform_set_drvdata(pdev, mbox);" ? > > [snip] > > > +#ifndef _LINUX_ARM_SMC_MAILBOX_H_ > > +#define _LINUX_ARM_SMC_MAILBOX_H_ > > + > > +struct arm_smccc_mbox_cmd { > > + unsigned long a0, a1, a2, a3, a4, a5, a6, a7; }; > > Do you expect this to be used by other in-kernel users? If so, it might be good > to document how a0 can have a special meaning and be used as a substitute > for the function_id? This was to address comments here: https://lore.kernel.org/patchwork/patch/812999/#1010433 Thanks, Peng. > -- > Florian
