[PATCH] ARM: realview: basic device tree implementation
Linus Walleij
linus.walleij at linaro.org
Thu May 8 01:37:59 PDT 2014
On Wed, Mar 26, 2014 at 3:56 AM, Arnd Bergmann <arnd at arndb.de> wrote:
>> + timer01: timer at 10104000 {
>> + compatible = "arm,sp804", "arm,primecell";
>> + reg = <0x10104000 0x1000>;
>> + interrupt-parent = <&intc_dc1176>;
>> + interrupts = <0 8 IRQ_TYPE_LEVEL_HIGH>, <0 9 IRQ_TYPE_LEVEL_HIGH>;
>> + clocks = <&timclk>, <&timclk>, <&pclk>;
>> + clock-names = "timclk1", "timclk2", "apb_pclk";
>> + };
>
> In the binding, the clock names are "timer1", "timer2", "apb_pclk".
> What is going on here?
What is going on is actually pretty confusing. The code just
looks for clocks at index 0 and 1:
clk1 = of_clk_get(np, 0);
clk2 = of_clk_get(np, 1);
The binding says two things:
" 3 clocks, the order is timer0 clock, timer1 clock, apb_pclk"
Then the example is:
clock-names = "timer1", "timer2", "apb_pclk";
One is indexed from zero, the other from 1.
Then the precursive examples in arch/arm/boot/dts:
vexpress-v2m.dtsi:
clock-names = "timclken1", "timclken2", "apb_pclk";
hi3620.dtsi:
clocks = <&clock HI3620_TIMER2_MUX>, <&clock HI3620_TIMER3_MUX>;
clock-names = "apb_pclk";
(This latter thing is especially weird, it's probably one gate for each
timer, but the apb_pclk is jammed together with the first of them
for unclear reasons.)
I don't really know what to do here. I have followed the example
binding and use timer1, timer2 for v2.
>> +
>> + pb1176_serial3: uart at 1010f000 {
>> + compatible = "arm,pl011", "arm,primecell";
>> + reg = <0x1010f000 0x1000>;
>> + interrupt-parent = <&intc_dc1176>;
>> + interrupts = <0 21 IRQ_TYPE_LEVEL_HIGH>;
>> + clocks = <&uartclk>, <&pclk>;
>> + clock-names = "uartclk", "apb_pclk";
>> + };
>
> Here, the binding says:
>
> - clocks: When present, must refer to exactly one clock named
> "apb_pclk"
That is a flat out lie, as can be seen from the implementation
and all device trees. I'll send a patch fixing up the binding doc.
I sent a separate patch to fix up this mess.
>> +static void __init realview_dt_init_machine(void)
>> +{
>> + struct device_node *root;
>> + struct device_node *syscon;
>> + struct soc_device *soc_dev;
>> + struct soc_device_attribute *soc_dev_attr;
>> + struct device *parent;
>> + u32 coreid;
>> + int ret;
>> +
>> +#ifdef CONFIG_CACHE_L2X0
>> + if (of_machine_is_compatible("arm,realview-eb"))
>> + /*
>> + * 1MB (128KB/way), 8-way associativity,
>> + * evmon/parity/share enabled
>> + * Bits: .... ...0 0111 1001 0000 .... .... ....
>> + */
>> + l2x0_of_init(0x00790000, 0xfe000fff);
>> + else if (of_machine_is_compatible("arm,realview-pb1176"))
>> + /*
>> + * 128Kb (16Kb/way) 8-way associativity.
>> + * evmon/parity/share enabled.
>> + */
>> + l2x0_of_init(0x00730000, 0xfe000fff);
>> + else if (of_machine_is_compatible("arm,realview-pb11mp"))
>> + /*
>> + * 1MB (128KB/way), 8-way associativity,
>> + * evmon/parity/share enabled
>> + * Bits: .... ...0 0111 1001 0000 .... .... ....
>> + */
>> + l2x0_of_init(0x00730000, 0xfe000fff);
>> + else if (of_machine_is_compatible("arm,realview-pbx"))
>> + /*
>> + * 16KB way size, 8-way associativity, parity disabled
>> + * Bits: .. 0 0 0 0 1 00 1 0 1 001 0 000 0 .... .... ....
>> + */
>> + l2x0_of_init(0x02520000, 0xc0000fff);
>> +#endif
>
> Russell just posted a long series of l2x0 cleanup patches. One
> of the things coming out of that was that we should never need to
> pass values like this here.
Yeah I knew this would be an area of contention...
> The registers are typically initialized
> to a hardwired default that should be ok, and if not, the boot loader
> should set them up correctly. Can you print out the boot-time values
> to see if realview gets this wrong?
I can do that for the PB1176, but I have no access to the other
physical platforms :-/
This was just copied from the present mach code as it stands.
>> + /* Here we create an SoC device for the root node */
>> + root = of_find_node_by_path("/");
>> + if (!root)
>> + return;
>> + syscon = of_find_matching_node(root, realview_syscon_match);
>> + if (!syscon)
>> + return;
>> +
>> + soc_dev_attr = kzalloc(sizeof(*soc_dev_attr), GFP_KERNEL);
>> + if (!soc_dev_attr)
>> + return;
>> + ret = of_property_read_string(root, "compatible",
>> + &soc_dev_attr->soc_id);
>> + if (ret)
>> + return;
>> + ret = of_property_read_string(root, "model", &soc_dev_attr->machine);
>> + if (ret)
>> + return;
>> + soc_dev_attr->family = "RealView";
>> + soc_dev = soc_device_register(soc_dev_attr);
>> + if (IS_ERR(soc_dev)) {
>> + kfree(soc_dev_attr);
>> + return;
>> + }
>> + parent = soc_device_to_device(soc_dev);
>> + ret = of_platform_populate(root, of_default_bus_match_table,
>> + NULL, parent);
>> + if (ret) {
>> + pr_crit("could not populate device tree\n");
>> + return;
>> + }
>> +
>> + syscon_regmap = syscon_node_to_regmap(syscon);
>> + if (IS_ERR(syscon_regmap)) {
>> + pr_crit("could not locate syscon regmap\n");
>> + return;
>> + }
>> + ret = regmap_read(syscon_regmap, REALVIEW_SYS_ID_OFFSET, &coreid);
>> + if (ret)
>> + return;
>> + pr_info("RealView Syscon Core ID: 0x%08x\n", coreid);
>> + /* FIXME: add attributes for SoC to sysfs */
>> +}
>
>
> I would not register a "soc" device for the root node, but rather
> reorganize the DT to put all soc specific nodes under a combined
> soc node. I suppose that could actually be the syscon node itself.
I'm not following this comment. The device tree is already organized
around a soc {} top-level node. The SoC device is a bus, the idea
is to group the devices underneath this bus as discussed between
Greg and Lee in the past, and thus make it a natural point to tie in
the sysfs entries for SoC information as is done for example in
arch/arm/mach-integrator/core.c
(Paul Walmsley recently brought up the question whether such
"drivers" should live under drivers/soc but that is still an open
question.)
>> +static void realview_dt_fixup(struct tag *tags, char **from,
>> + struct meminfo *meminfo)
>> +{
>> + /*
>> + * RealView PB1176 only has 128MB of RAM mapped at 0.
>> + */
>> + if (of_machine_is_compatible("arm,realview-pb1176")) {
>> + meminfo->bank[0].start = 0;
>> + meminfo->bank[0].size = SZ_128M;
>> + meminfo->nr_banks = 1;
>> + }
>
> This one should come right from DT I think.
OK this seems to work.
>> +#ifdef CONFIG_SPARSEMEM
>> + /*
>> + * Memory configuration with SPARSEMEM enabled on RealView PBX (see
>> + * asm/mach/memory.h for more information).
>> + */
>> + else if (of_machine_is_compatible("arm,realview-pbx")) {
>> + meminfo->bank[0].start = 0;
>> + meminfo->bank[0].size = SZ_256M;
>> + meminfo->bank[1].start = 0x20000000;
>> + meminfo->bank[1].size = SZ_512M;
>> + meminfo->bank[2].start = 0x80000000;
>> + meminfo->bank[2].size = SZ_256M;
>> + meminfo->nr_banks = 3;
>> + }
>> +#endif
>
> This one too, but I'm not completely sure about it. Do you see a reason
> for the kernel to override the memory location on PBX?
No other reason than that it is sparse. Removed this too in favor
of using device tree memory specs.
>> + /*
>> + * Generic RealView fixup
>> + * Most RealView platforms have 512MB contiguous RAM at 0x70000000.
>> + * Half of this is mirrored at 0.
>> + */
>> + else {
>> +#ifdef CONFIG_REALVIEW_HIGH_PHYS_OFFSET
>> + meminfo->bank[0].start = 0x70000000;
>> + meminfo->bank[0].size = SZ_512M;
>> + meminfo->nr_banks = 1;
>> +#else
>> + meminfo->bank[0].start = 0;
>> + meminfo->bank[0].size = SZ_256M;
>> + meminfo->nr_banks = 1;
>> +#endif
>> + }
>> +}
>
> And this one is where it gets tricky. We don't have a good way
> to describe memory aliases in DT, but we need the start of memory
> to match PHYS_OFFSET if CONFIG_SPARSEMEM is set (which implies
> !CONFIG_REALVIEW_HIGH_PHYS_OFFSET), or if we are running a no-MMU
> kernel. I have to think about this some more.
Yeah I'm completely clueless here actually. :-/
This is the point of contention we've identified earlier, the patch
only take it to the front forcing us to think about what to do with
this.
I'll look at your patch and see if I can get to test it on QEMU.
>> +static void realview_dt_restart(enum reboot_mode mode, const char *cmd)
>> +{
>> + if (IS_ERR(syscon_regmap))
>> + return;
>> +
>> + /* Unlock the reset register */
>> + regmap_write(syscon_regmap, REALVIEW_SYS_LOCK_OFFSET,
>> + REALVIEW_SYS_LOCK_VAL);
>> + /* Then hit reset on the different machines */
>> + if (of_machine_is_compatible("arm,realview-eb")) {
>> + regmap_write(syscon_regmap,
>> + REALVIEW_SYS_RESETCTL_OFFSET, 0x0008);
>> + } else if (of_machine_is_compatible("arm,realview-pb1176")) {
>> + regmap_write(syscon_regmap,
>> + REALVIEW_SYS_RESETCTL_OFFSET, 0x0100);
>> + } else if (of_machine_is_compatible("arm,realview-pb11mp") ||
>> + of_machine_is_compatible("arm,realview-pba8")) {
>> + regmap_write(syscon_regmap, REALVIEW_SYS_RESETCTL_OFFSET,
>> + 0x0000);
>> + regmap_write(syscon_regmap, REALVIEW_SYS_RESETCTL_OFFSET,
>> + 0x0004);
>> + } else if (of_machine_is_compatible("arm,realview-pbx")) {
>> + regmap_write(syscon_regmap, REALVIEW_SYS_RESETCTL_OFFSET,
>> + 0x00f0);
>> + regmap_write(syscon_regmap, REALVIEW_SYS_RESETCTL_OFFSET,
>> + 0x00f4);
>> + }
>> + dsb();
>> +}
>
> I'd be much happier if we had a separate device node to match against,
> rather than using of_machine_is_compatible(). That would allow us to
> later move this code out into a separate driver. Note that I'd still
> hope to one day have an empty directory for all the ARM reference
> platforms.
Another case for drivers/soc I think.
The thing is that all these registers are in the pretty opaque "syscon"
which has different behaviour depending on which machine's syscon it
is.
I will experiment with adding individual compatible strings for each
syscon variant, that is essentially just duplicating the same
information as the board variant, but I don't mind...
>> +DT_MACHINE_START(REALVIEW_DT, "ARM RealView Machine (Device Tree Support)")
>> + .fixup = realview_dt_fixup,
>> + .map_io = realview_dt_map_io,
>> + .init_machine = realview_dt_init_machine,
>> +#ifdef CONFIG_ZONE_DMA
>> + .dma_zone_size = SZ_256M,
>> +#endif
>> + .dt_compat = realview_dt_platform_compat,
>> + .restart = realview_dt_restart,
>
> This isn't specific to the DT version of realview, but what happens if
> CONFIG_ZONE_DMA is disabled?
I am uncertain actually, I think DMA is only used with the PCI bus
found on some RealViews.
Yours,
Linus Walleij
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