Re: [PATCH v5 01/11] hw/misc: Add NPCM7xx System Global Control Registers device model

[Philippe Mathieu-Daudé]

On 7/9/20 7:09 PM, Havard Skinnemoen wrote:
> On Thu, Jul 9, 2020 at 9:23 AM Philippe Mathieu-Daudé <f4bug@amsat.org> wrote:
>> On 7/9/20 8:43 AM, Havard Skinnemoen wrote:
>>> On Wed, Jul 8, 2020 at 11:04 PM Philippe Mathieu-Daudé <f4bug@amsat.org> 
>>> wrote:
>>>> On 7/9/20 2:35 AM, Havard Skinnemoen wrote:
>>>>> Implement a device model for the System Global Control Registers in the
>>>>> NPCM730 and NPCM750 BMC SoCs.
>>>>>
>>>>> This is primarily used to enable SMP boot (the boot ROM spins reading
>>>>> the SCRPAD register) and DDR memory initialization; other registers are
>>>>> best effort for now.
>>>>>
>>>>> The reset values of the MDLR and PWRON registers are determined by the
>>>>> SoC variant (730 vs 750) and board straps respectively.
>>>>>
>>>>> Reviewed-by: Joel Stanley <joel@jms.id.au>
>>>>> Reviewed-by: Cédric Le Goater <clg@kaod.org>
>>>>> Signed-off-by: Havard Skinnemoen <hskinnemoen@google.com>
>>>>> ---
>> [...]
>>>>> diff --git a/hw/misc/npcm7xx_gcr.c b/hw/misc/npcm7xx_gcr.c
>>>>> new file mode 100644
>>>>> index 0000000000..9934cd238d
>>>>> --- /dev/null
>>>>> +++ b/hw/misc/npcm7xx_gcr.c
>>>>> @@ -0,0 +1,226 @@
>>>>> +/*
>>>>> + * Nuvoton NPCM7xx System Global Control Registers.
>>>>> + *
>>>>> + * Copyright 2020 Google LLC
>>>>> + *
>>>>> + * This program is free software; you can redistribute it and/or modify 
>>>>> it
>>>>> + * under the terms of the GNU General Public License as published by the
>>>>> + * Free Software Foundation; either version 2 of the License, or
>>>>> + * (at your option) any later version.
>>>>> + *
>>>>> + * 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 "qemu/osdep.h"
>>>>> +
>>>>> +#include "hw/misc/npcm7xx_gcr.h"
>>>>> +#include "hw/qdev-properties.h"
>>>>> +#include "migration/vmstate.h"
>>>>> +#include "qapi/error.h"
>>>>> +#include "qemu/log.h"
>>>>> +#include "qemu/module.h"
>>>>> +#include "qemu/units.h"
>>>>> +
>>>>> +#include "trace.h"
>>>>> +
>>>>> +static const uint32_t cold_reset_values[NPCM7XX_GCR_NR_REGS] = {
>>>>> +    [NPCM7XX_GCR_PDID]          = 0x04a92750,   /* Poleg A1 */
>>>>> +    [NPCM7XX_GCR_MISCPE]        = 0x0000ffff,
>>>>> +    [NPCM7XX_GCR_SPSWC]         = 0x00000003,
>>>>> +    [NPCM7XX_GCR_INTCR]         = 0x0000035e,
>>>>> +    [NPCM7XX_GCR_HIFCR]         = 0x0000004e,
>>>>> +    [NPCM7XX_GCR_INTCR2]        = (1U << 19),   /* DDR initialized */
>>>>> +    [NPCM7XX_GCR_RESSR]         = 0x80000000,
>>>>> +    [NPCM7XX_GCR_DSCNT]         = 0x000000c0,
>>>>> +    [NPCM7XX_GCR_DAVCLVLR]      = 0x5a00f3cf,
>>>>> +    [NPCM7XX_GCR_SCRPAD]        = 0x00000008,
>>>>> +    [NPCM7XX_GCR_USB1PHYCTL]    = 0x034730e4,
>>>>> +    [NPCM7XX_GCR_USB2PHYCTL]    = 0x034730e4,
>>>>> +};
>>>>> +
>>>>> +static uint64_t npcm7xx_gcr_read(void *opaque, hwaddr offset, unsigned 
>>>>> size)
>>>>> +{
>>>>> +    uint32_t reg = offset / sizeof(uint32_t);
>>>>> +    NPCM7xxGCRState *s = opaque;
>>>>> +
>>>>> +    if (reg >= NPCM7XX_GCR_NR_REGS) {
>>>>> +        qemu_log_mask(LOG_GUEST_ERROR, "%s: offset 0x%04x out of 
>>>>> range\n",
>>>>> +                      __func__, (unsigned int)offset);
>>>>
>>>> Maybe use HWADDR_PRIx instead of casting to int?
>>>
>>> Will do, thanks!
>>
>> Glad you are not annoyed by my review comments.
>>
>> FYI your series quality is in my top-4 "adding new machine to QEMU".
>> I'd like to use it as example to follow.
>>
>> I am slowly reviewing because this is not part of my work duties,
>> so I do that in my free time before/after work, which is why I can
>> barely do more that 2 per day, as I have to learn the SoC and
>> cross check documentation (or in this case, existing firmware code
>> since there is no public doc).
> 
> Your feedback is super valuable, thanks a lot. I really appreciate it.

OK I'll continue, but might not have time until next week.
After I plan to test too.

What would be useful is an acceptance test (see examples in
tests/acceptance/), using the artefacts from the link you shared
elsewhere:
https://openpower.xyz/job/run-meta-ci/distro=ubuntu,label=builder,target=gsj/lastSuccessfulBuild/artifact/openbmc/build/tmp/deploy/images/gsj/

But these are apparently not stable links (expire after 30 days?).

>> [...]
>>>>> +static void npcm7xx_gcr_realize(DeviceState *dev, Error **errp)
>>>>> +{
>>>>> +    NPCM7xxGCRState *s = NPCM7XX_GCR(dev);
>>>>> +    uint64_t dram_size;
>>>>> +    Error *err = NULL;
>>>>> +    Object *obj;
>>>>> +
>>>>> +    obj = object_property_get_link(OBJECT(dev), "dram-mr", &err);
>>>>> +    if (!obj) {
>>>>> +        error_setg(errp, "%s: required dram-mr link not found: %s",
>>>>> +                   __func__, error_get_pretty(err));
>>>>> +        return;
>>>>> +    }
>>>>> +    dram_size = memory_region_size(MEMORY_REGION(obj));
>>>>> +
>>>>> +    /* Power-on reset value */
>>>>> +    s->reset_intcr3 = 0x00001002;
>>>>> +
>>>>> +    /*
>>>>> +     * The GMMAP (Graphics Memory Map) field is used by u-boot to detect 
>>>>> the
>>>>> +     * DRAM size, and is normally initialized by the boot block as part 
>>>>> of DRAM
>>>>> +     * training. However, since we don't have a complete emulation of the
>>>>> +     * memory controller and try to make it look like it has already been
>>>>> +     * initialized, the boot block will skip this initialization, and we 
>>>>> need
>>>>> +     * to make sure this field is set correctly up front.
>>>>> +     *
>>>>> +     * WARNING: some versions of u-boot only looks at bits 8 and 9, so 2 
>>>>> GiB or
>>>>> +     * more of DRAM will be interpreted as 128 MiB.
>>>>
>>>> I'd say u-boot is right in wrapping at 2GB, as more DRAM is
>>>> un-addressable.
>>>
>>> Ah, maybe I shouldn't have said "or more". The bug is that if you
>>> specify _exactly_ 2GiB, u-boot will see 128 MiB.
>>>
>>> But I agree more than 2GiB doesn't make sense, so I'll add a check for that.
>>>
>>> Not sure if I agree that the check should be here. > 2 GiB is an
>>> addressing limitation, and the GCR module shouldn't really know what
>>> the SoC's address space looks like. The lower limit is because the GCR
>>> module can't encode anything less than 128 MiB.
>>>
>>>>> +     *
>>>>> +     * 
>>>>> https://github.com/Nuvoton-Israel/u-boot/blob/2aef993bd2aafeb5408dbaad0f3ce099ee40c4aa/board/nuvoton/poleg/poleg.c#L244
>>>>> +     */
>>>>> +    if (dram_size >= 2 * GiB) {
>>>>
>>>> See my comment in this series on the machine patch.
>>>>
>>>>> +        s->reset_intcr3 |= 4 << 8;
>>>>> +    } else if (dram_size >= 1 * GiB) {
>>>>> +        s->reset_intcr3 |= 3 << 8;
>>>>> +    } else if (dram_size >= 512 * MiB) {
>>>>> +        s->reset_intcr3 |= 2 << 8;
>>>>> +    } else if (dram_size >= 256 * MiB) {
>>>>> +        s->reset_intcr3 |= 1 << 8;
>>>>> +    } else if (dram_size >= 128 * MiB) {
>>>>> +        s->reset_intcr3 |= 0 << 8;
>>
>> I think this can be simplified as:
>>
>>          s->reset_intcr3 = (4 - clz32(dram_size)) << 8;
>>
>> Which implicitly truncate to power of 2 (which is what this
>> block does, as you can have only 1 bank managed per this SGC).
> 
> Good idea. I find this a little easier to understand though:
> 
> #define NPCM7XX_GCR_MIN_DRAM_SIZE   (128 * MiB)
> 
>     s->reset_intcr3 |= ctz64(dram_size / NPCM7XX_GCR_MIN_DRAM_SIZE) << 8;

I like it, furthermore it will work with >4GB if this model is
ever reused on an ARMv8-A SoC.

>> But checking is_power_of_2(dram_size) and reporting an error
>> else, is probably even better.
> 
> OK, I'll add a check for this, and also explicit checks for too large
> and too small. The former is currently redundant with the DRAM size
> check I'm adding to npcm7xx_realize(), but I kind of like the idea of
> checking for encoding limitations and addressing limitations
> separately, as they may not necessarily stay the same forever.
> 
>>>>> +    } else {
>>>>> +        error_setg(errp,
>>>>> +                   "npcm7xx_gcr: DRAM size %" PRIu64
>>>>> +                   " is too small (need 128 MiB minimum)",
>>>>> +                   dram_size);
>>>>
>>>> Ah, so you could add the same error for >2GB. Easier.
>>>>
>>>> Preferably using HWADDR_PRIx, and similar error for >2GB:
>>>> Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
>