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Date:   Mon, 29 Aug 2022 16:18:27 +0800
From:   Baoquan He <bhe@redhat.com>
To:     Stafford Horne <shorne@gmail.com>
Cc:     Christoph Hellwig <hch@infradead.org>,
        linux-kernel@vger.kernel.org, linux-mm@kvack.org,
        akpm@linux-foundation.org, agordeev@linux.ibm.com,
        wangkefeng.wang@huawei.com, linux-arm-kernel@lists.infradead.org,
        Jonas Bonn <jonas@southpole.se>,
        Stefan Kristiansson <stefan.kristiansson@saunalahti.fi>,
        openrisc@lists.librecores.org
Subject: Re: [PATCH v2 07/11] openrisc: mm: Convert to GENERIC_IOREMAP
Message-ID: <Ywx2U3NpfH/Ixg6V@MiWiFi-R3L-srv>
References: <20220820003125.353570-1-bhe@redhat.com>
 <20220820003125.353570-8-bhe@redhat.com>
 <YwHYx0eXouIWnN8Z@infradead.org>
 <YwwZCO279Vh/cXGW@MiWiFi-R3L-srv>
 <YwxfxKrTUtAuejKQ@oscomms1>
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On 08/29/22 at 06:42am, Stafford Horne wrote:
> On Mon, Aug 29, 2022 at 09:40:24AM +0800, Baoquan He wrote:
> > On 08/21/22 at 12:03am, Christoph Hellwig wrote:
> > > > +	if (unlikely(!mem_init_done)) {
> > > >  		if ((fixmaps_used + (size >> PAGE_SHIFT)) > FIX_N_IOREMAPS)
> > > > +			return IOMEM_ERR_PTR(ret);
> > > >  		v = fix_to_virt(FIX_IOREMAP_BEGIN + fixmaps_used);
> > > >  		fixmaps_used += (size >> PAGE_SHIFT);
> > > >  
> > > > +		if (ioremap_page_range(v, v + size, p, __pgprot(*prot_val))) {
> > > >  			fixmaps_used -= (size >> PAGE_SHIFT);
> > > > +			return IOMEM_ERR_PTR(ret);
> > > > +		}
> > > > +
> > > > +		return (void __iomem *)(offset + (char *)v);
> > > >  	}
> > > 
> > > This code needs to go away, and all very early boot uses of ioremap
> > > need to switch to use early_ioremap insted.
> > 
> > Makes sense. On openrisc, the thing is I didn't find one place where
> > ioremap() is called in arch code. I can cut the early ioremap out and
> > wrap into a separate early_ioremap() function, however I don't know
> > where to put it. Not sure if I miss anything or openrisc doesn't really
> > need early ioremap.
> 
> Hi,
> 
> I don't know of any early_ioremap usage either in openrisc, maybe some drivers
> use it?  However, we do not initialize any early_ioremap infrastructure in
> openrisc so that may cause issues if it is used.

The variable mem_init_done indicates if mem_init() is called or not.
Driver should only initialize after mem_init(). With my understanding,
the early ioremap is only needed by arch code.
> 
> We can try to remove it all.  I tested these below additional changes and they
> work, if you want to add them we can see if kbuild robots pick anything up.

Very helpful information. Then I will remove the !mem_init_done part
code as you listed below, let's see how test robots react. Thanks a lot.

> 
> -Stafford
> 
> diff --git a/arch/openrisc/mm/ioremap.c b/arch/openrisc/mm/ioremap.c
> index bc41660e1fb0..ffe6d5e2b5fe 100644
> --- a/arch/openrisc/mm/ioremap.c
> +++ b/arch/openrisc/mm/ioremap.c
> @@ -22,14 +22,10 @@
>  
>  extern int mem_init_done;
>  
> -static unsigned int fixmaps_used __initdata;
> -
>  void __iomem *
>  arch_ioremap(phys_addr_t *paddr, size_t size, unsigned long *prot_val)
>  {
> -       phys_addr_t p;
> -       unsigned long v;
> -       unsigned long offset, last_addr, addr = *paddr;
> +       unsigned long last_addr, addr = *paddr;
>         int ret = -EINVAL;
>  
>         /* Don't allow wraparound or zero size */
> @@ -37,27 +33,6 @@ arch_ioremap(phys_addr_t *paddr, size_t size, unsigned long *prot_val)
>         if (!size || last_addr < addr)
>                 return IOMEM_ERR_PTR(ret);
>  
> -       /*
> -        * Mappings have to be page-aligned
> -        */
> -       offset = addr & ~PAGE_MASK;
> -       p = addr & PAGE_MASK;
> -       size = PAGE_ALIGN(last_addr + 1) - p;
> -
> -       if (unlikely(!mem_init_done)) {
> -               if ((fixmaps_used + (size >> PAGE_SHIFT)) > FIX_N_IOREMAPS)
> -                       return IOMEM_ERR_PTR(ret);
> -               v = fix_to_virt(FIX_IOREMAP_BEGIN + fixmaps_used);
> -               fixmaps_used += (size >> PAGE_SHIFT);
> -
> -               if (ioremap_page_range(v, v + size, p, __pgprot(*prot_val))) {
> -                       fixmaps_used -= (size >> PAGE_SHIFT);
> -                       return IOMEM_ERR_PTR(ret);
> -               }
> -
> -               return (void __iomem *)(offset + (char *)v);
> -       }
> -
>         return NULL;
>  }
>  
>