linux-kernel - Re: [PATCH v2 2/5] MIPS: ralink: implement 'pcibios_root_bridge

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Date:   Thu, 2 Dec 2021 07:06:00 -0800
From:   Guenter Roeck <linux@...ck-us.net>
To:     Sergio Paracuellos <sergio.paracuellos@...il.com>
Cc:     linux-pci <linux-pci@...r.kernel.org>,
        "open list:MIPS" <linux-mips@...r.kernel.org>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Arnd Bergmann <arnd@...db.de>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 2/5] MIPS: ralink: implement
 'pcibios_root_bridge_prepare()'

On 12/2/21 12:29 AM, Sergio Paracuellos wrote:
> Hi Guenter,
> 
> On Wed, Dec 1, 2021 at 11:17 PM Guenter Roeck <linux@...ck-us.net> wrote:
>>
>> On 12/1/21 1:51 PM, Sergio Paracuellos wrote:
>>> PCI core code call 'pcibios_root_bridge_prepare()' function inside function
>>> 'pci_register_host_bridge()'. This point is very good way to properly enter
>>> into this MIPS ralink specific code to properly setup I/O coherency units
>>> with PCI memory addresses.
>>>
>>> Signed-off-by: Sergio Paracuellos <sergio.paracuellos@...il.com>
>>> ---
>>>    arch/mips/ralink/mt7621.c | 30 ++++++++++++++++++++++++++++++
>>>    1 file changed, 30 insertions(+)
>>>
>>> diff --git a/arch/mips/ralink/mt7621.c b/arch/mips/ralink/mt7621.c
>>> index bd71f5b14238..7649416c1cd7 100644
>>> --- a/arch/mips/ralink/mt7621.c
>>> +++ b/arch/mips/ralink/mt7621.c
>>> @@ -10,6 +10,7 @@
>>>    #include <linux/slab.h>
>>>    #include <linux/sys_soc.h>
>>>    #include <linux/memblock.h>
>>> +#include <linux/pci.h>
>>>
>>>    #include <asm/bootinfo.h>
>>>    #include <asm/mipsregs.h>
>>> @@ -22,6 +23,35 @@
>>>
>>>    static void *detect_magic __initdata = detect_memory_region;
>>>
>>> +int pcibios_root_bridge_prepare(struct pci_host_bridge *bridge)
>>> +{
>>> +     struct resource_entry *entry;
>>> +     resource_size_t mask;
>>> +
>>> +     entry = resource_list_first_type(&bridge->windows, IORESOURCE_MEM);
>>> +     if (!entry) {
>>> +             pr_err("Cannot get memory resource\n");
>>> +             return -EINVAL;
>>> +     }
>>> +
>>> +     if (mips_cps_numiocu(0)) {
>>> +             /*
>>> +              * FIXME: hardware doesn't accept mask values with 1s after
>>> +              * 0s (e.g. 0xffef), so it would be great to warn if that's
>>> +              * about to happen
>>> +              */ > +         mask = ~(entry->res->end - entry->res->start);
>>> +
>>
>> Try something like this:
>>                  WARN_ON((mask != ~0UL && BIT(ffz(mask)) - 1 != mask);
> 
> Thanks for the tip. The following works for me:
> 
>                    WARN_ON(mask != ~0UL && ~(BIT(__ffs(mask)) - 1) != mask);

Are you sure ? __ffs() returns the first bit set, which isn't useful
for this test.

Guenter

> 
> I will send this as a different patch, though.
> 
> Best regards,
>      Sergio Paracuellos
> 
>>
>>> +             write_gcr_reg1_base(entry->res->start);
>>> +             write_gcr_reg1_mask(mask | CM_GCR_REGn_MASK_CMTGT_IOCU0);
>>> +             pr_info("PCI coherence region base: 0x%08llx, mask/settings: 0x%08llx\n",
>>> +                     (unsigned long long)read_gcr_reg1_base(),
>>> +                     (unsigned long long)read_gcr_reg1_mask());
>>> +     }
>>> +
>>> +     return 0;
>>> +}
>>> +
>>>    phys_addr_t mips_cpc_default_phys_base(void)
>>>    {
>>>        panic("Cannot detect cpc address");
>>>
>>