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

[Philippe Mathieu-Daudé]

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).

[...]
>>> +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).

But checking is_power_of_2(dram_size) and reporting an error
else, is probably even better.

>>> +    } 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>