linux-kernel - Re: [PATCH v2 2/5] spi: spi-ti-qspi: add mmap mode read support

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <563AF429.1000406@ti.com>
Date:	Thu, 5 Nov 2015 11:46:09 +0530
From:	Vignesh R <vigneshr@...com>
To:	Mark Brown <broonie@...nel.org>
CC:	Tony Lindgren <tony@...mide.com>,
	Michal Suchanek <hramrach@...il.com>,
	Russell King <linux@....linux.org.uk>,
	<devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<linux-omap@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>,
	<linux-mtd@...ts.infradead.org>, <linux-spi@...r.kernel.org>
Subject: Re: [PATCH v2 2/5] spi: spi-ti-qspi: add mmap mode read support



On 11/04/2015 08:11 PM, Mark Brown wrote:
> On Tue, Nov 03, 2015 at 03:36:11PM +0530, Vignesh R wrote:
> 
>> +	ti_qspi_enable_memory_map(spi);
>> +	ti_qspi_setup_mmap_read(spi, read_opcode, addr_width,
>> +				dummy_bytes);
>> +	memcpy_fromio(buf, qspi->mmap_base + from, len);
>> +	*retlen = len;
>> +	ti_qspi_disable_memory_map(spi);
> 
> We'll be constantly enabling and disabling memory mapping with this.
> I'm not sure that's a meaningful cost given that it doesn't actually
> remap anything but rather just switches hardware modes, we can always
> optimise it later if it is.
> 

Hmm, I will move the ti_qspi_disable_memory_map() call to
ti_qspi_start_transfer_one(), so that mmap mode is disabled only when
normal SPI bus transfer is requested. Further, "mmap_enabled" status
flag can be used to determine whether mode switch is required or not.
This should help to overcome enabling and disabling memory mapping
between successive mmap read requests.

-- 
Regards
Vignesh
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/