From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail.bootlin.com ([62.4.15.54]) by bombadil.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1fIvlE-0000UY-Nv for linux-mtd@lists.infradead.org; Wed, 16 May 2018 12:42:31 +0000 Date: Wed, 16 May 2018 14:42:04 +0200 From: Boris Brezillon To: Xiangsheng Hou Cc: , , , , , Subject: Re: Some questions about the spi mem framework Message-ID: <20180516144204.65bb20c5@bbrezillon> In-Reply-To: <1526472699.31853.80.camel@mhfsdcap03> References: <1526355800.31853.45.camel@mhfsdcap03> <20180515172551.1adcf276@bbrezillon> <1526472699.31853.80.camel@mhfsdcap03> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Wed, 16 May 2018 20:11:39 +0800 Xiangsheng Hou wrote: > Hi Boris, > > On Tue, 2018-05-15 at 17:25 +0200, Boris Brezillon wrote: > > Hi, > > > > On Tue, 15 May 2018 11:43:20 +0800 > > Xiangsheng Hou wrote: > > > > > Hello Boris, > > > > > > I have seen you are working on extend the framework to generically > > > support spi memory devices. > > > And, I am working on upstream SPI Nand driver of Mediatek SPI NAND > > > controller based on your branch[1]. > > > > Great! > > > > > I have some questions need your comment. > > > > > > 1) There is a difference between different SPI NAND Flash when using the > > > Quad SPI command,for example Macronix,Etron and GigaDevice, > > > Quad SPI commands require the Quad Enable bit in Status Register(B0H) to > > > be set. > > > However, current spi-mem framework does not have this operation, > > > do you have a plan to support it? > > > > I added support for the QE bit in the v7 I sent just a few minutes ago > > [1]. > > Ok,I have studied v7. > > > > > > > > > 2) I see that current spi-mem framework doesn't support ECC, > > > But we need ECC, and we use Mediatek controller's HW ECC > > > instead of spi nand on-chip ECC, > > > maybe other companies also have this behavior, > > > So the ECC part must be implemented in controller's driver. > > > Will you abstract ECC interface in future? > > > > Well, I added support for on-die ECC in my v7 since all chips seem to > > provide this feature. I was initially planning on abstracting ECC > > engines, but I decided to go for a simpler approach and only support > > on-die ECC. That does not mean we shouldn't work on this "ECC engine > > abstraction", just that I wanted to get something out and didn't have > > time to spend on this topic. > > > > I'd be happy if someone else could work on that aspect though. BTW, do > > you plan to use this engine [2], or is this yet another ECC engine? > > Yes,I plan to use this ecc engine[2]. Cool. That probably means we'll have to move the driver one level up (in drivers/mtd/nand) and work on this ECC engine interface I was talking about. > > > > > > > > > 3) You know, some nand controller need configure their registers when > > > getting some information(page size, spare size) of nand flash, > > > But the spi-mem framework doesn't has an interface for scanning NAND > > > flash, when controller driver initialization. > > > > You seem to mix 2 different things: > > - spi-mem: this is generic interface provided by the SPI framework to > > send spi_mem_op. There's nothing NOR or NAND specific in there, and > > I'd like it to stay like that as much as possible > > - spinand: this the spi-mem driver that is dealing with SPI NAND > > devices, and this is where all the code related to SPI NAND support > > should end up. > > > > Can you tell me exactly why your SPI controller needs such a detailed > > description? Is it able to program/read pages or erase blocks on its > > own? Do you have a spec of this controller publicly available? > > For Mediatek SPI Nand controller,I have to configure registers for ECC > engine,page format and spare format according to nand information just > like[3] in mtk_nfc_hw_runtime_config() function. So it's all related to the NAND controller, nothing specific to the SPI controller, right? > > > > > > Now we have to do the setting in spi_controller_mem_ops->exec_op for > > > every operation. > > > > Yes, you do, at least for now. > > Yes,I do it for now.BTW,I have to disable on-die ECC in there, because > we use Mediatek controller's HW ECC. Why don't you start by supporting things without the HW ECC engine (using on-die ECC), and then, once the SPI controller driver is working properly, work on the ECC engine abstraction I was talking about? In my experience, it's better to do things iteratively rather than trying to support everything in the first version. > > > > > > Maybe it not an efficient practice. > > > Could we supply an interface for controller to scanning NAND Flash when > > > in module probe process? > > > > I'm thinking about a direct mapping API that could be used by spi-mem > > drivers to directly map portions of the SPI-mem in the CPU address > > space, but I don't have code yet. Having a datasheet of your controller > > would probably help understanding what your needs are exactly and how > > we can expose that through the spi-mem API. > > Ok,I will apply to the company for public spec of Mediatek SPI Nand > controller. Thanks, Boris