Date: Mon, 24 Apr 2017 10:25:27 -0700
From: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
To: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>, michael.neuling@au1.ibm.com,
        stewart@linux.vnet.ibm.com, apopple@au1.ibm.com, hbabu@us.ibm.com,
        oohall@gmail.com, bsingharora@gmail.com, linuxppc-dev@ozlabs.org,
        linux-kernel@vger.kernel.org, aneesh.kumar@linux.vnet.ibm.com
Subject: Re: [PATCH v4 05/11] VAS: Define helpers for access MMIO regions
References: <1490937224-29149-1-git-send-email-sukadev@linux.vnet.ibm.com>
 <1490937224-29149-6-git-send-email-sukadev@linux.vnet.ibm.com>
 <1493015287.25766.213.camel@kernel.crashing.org>
MIME-Version: 1.0
Content-Type: text/plain; charset=iso-8859-1
Content-Disposition: inline
Content-Transfer-Encoding: 8BIT
In-Reply-To: <1493015287.25766.213.camel@kernel.crashing.org>
User-Agent: Mutt/1.7.1 (2016-10-04)
Message-Id: <20170424172527.GA15532@us.ibm.com>
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1473
Lines: 52

Benjamin Herrenschmidt [benh@kernel.crashing.org] wrote:
> On Thu, 2017-03-30 at 22:13 -0700, Sukadev Bhattiprolu wrote:
> > +static void *map_mmio_region(char *name, uint64_t start, int len)
> > +{
> > +???????void *map;
> > +
> > +???????if (!request_mem_region(start, len, name)) {
> > +???????????????pr_devel("%s(): request_mem_region(0x%llx, %d) failed\n",
> > +???????????????????????????????__func__, start, len);
> > +???????????????return NULL;
> > +???????}
> > +
> > +???????map = __ioremap(start, len, pgprot_val(pgprot_cached(__pgprot(0))));
> > +???????if (!map) {
> > +???????????????pr_devel("%s(): ioremap(0x%llx, %d) failed\n", __func__, start,
> > +???????????????????????????????len);
> > +???????????????return NULL;
> > +???????}
> > +
> > +???????return map;
> > +}
> 
> That's very wrong. I assume this never worked right ?

Untl recently, only tested on simics and has been working there. On the
hardware, hitting a crash on the first mmio write...
> 
> MMIO regions must be mapped non-cachable. Only the paste region

which maybe due to this :-) Should I change to pgprot_noncached() for the
MMIO writes?

> requires being mapped cachable. Ask Aneesh for a cleaner way of
> doing it too while at it.

Ok.

> 
> > +/*
> > + * Unmap the MMIO regions for a window.
> > + */
> > +static void unmap_wc_paste_kaddr(struct vas_window *window)
> > +{
> > +???????int len;
> 
> Don't use "wc"... that usually means "write combine".

Ok.

Thanks,

Sukadev