From mboxrd@z Thu Jan 1 00:00:00 1970 From: robert.jarzmik@free.fr (Robert Jarzmik) Date: Tue, 23 Feb 2016 23:23:42 +0100 Subject: [RFC PATCH 1/2] memremap: add arch specific hook for MEMREMAP_WB mappings In-Reply-To: (Dan Williams's message of "Tue, 23 Feb 2016 09:21:44 -0800") References: <1456149728-16706-1-git-send-email-ard.biesheuvel@linaro.org> <1456149728-16706-2-git-send-email-ard.biesheuvel@linaro.org> <20160222200227.GF19428@n2100.arm.linux.org.uk> <20160223115835.GI19428@n2100.arm.linux.org.uk> Message-ID: <87twkzukup.fsf@belgarion.home> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Dan Williams writes: > On Tue, Feb 23, 2016 at 4:26 AM, Ard Biesheuvel > wrote: >> On 23 February 2016 at 13:03, Ard Biesheuvel wrote: >>> On 23 February 2016 at 12:58, Russell King - ARM Linux >>> wrote: >>>> On Mon, Feb 22, 2016 at 09:35:24PM +0100, Ard Biesheuvel wrote: >> OK, I see what you mean. I find it unfortunate that ioremap_cache() >> instances are blindly being replaced with memremap(), and I wonder if >> this wasted test by and/or cc'ed to people who can actually test this >> driver. Dan? Actually I have the hardware to test it. And I also know what is behind : - it's a CFI NOR based memory - these are Intel StrataFlash 28F128J3A chips - as a CFI memory it is mapped on the system bus - from a read perspective, it behaves like a normal memory - but once the first write reaches the CFI, everything changes (the address space layout doesn't have the same meaning, be that becoming a status code or something else). In these conditions reordering of writes versus reads, merging reads after a write or coalescing writes is a recipe for disaster. All of this to say I can make a small discrete number of tests (less than 10 write or erase ones to preserve the precious NOR). Cheers. -- Robert