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Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1gyw0D-0007BE-8E; Wed, 27 Feb 2019 09:59:49 +0000 Received: from mail.kernel.org ([198.145.29.99]) by bombadil.infradead.org with esmtps (Exim 4.90_1 #2 (Red Hat Linux)) id 1gyw09-0007Aj-EU; Wed, 27 Feb 2019 09:59:47 +0000 Received: from localhost (91-160-177-164.subs.proxad.net [91.160.177.164]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 06022205F4; Wed, 27 Feb 2019 09:59:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1551261584; bh=SEGeeNAdiIiL1sHrk9uRoWVuV4aOBMHFvHuTGNX/sEw=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=h4lPA1IIGrroPggndXXI023fBc0MTaJSZ4YTw+5nXBFhJ8usA/nOvX/kx+bPjjFaz x64Xy9WLAK1T3jBE0zds5yb5GmM5hp3tulBRsknv3nUawdAFI4fMlxht8UlbGbSCRo GX0+8t71jwHHmyKXE5kGLfAcuQ29Ok8R0sVqIbs8= Date: Wed, 27 Feb 2019 10:59:37 +0100 From: Boris Brezillon To: Vignesh Raghavendra Subject: Re: [RFC PATCH 3/5] mtd: Add support for Hyperbus memory devices Message-ID: <20190227105937.527c6573@kernel.org> In-Reply-To: <3952b327-3aff-a32e-4280-6ab24c32cfd9@ti.com> References: <20190219063607.29949-1-vigneshr@ti.com> <20190219063607.29949-4-vigneshr@ti.com> <7e79fff7-2565-28f7-7b2b-bb3098f1a928@cogentembedded.com> <3952b327-3aff-a32e-4280-6ab24c32cfd9@ti.com> X-Mailer: Claws Mail 3.17.3 (GTK+ 2.24.32; x86_64-redhat-linux-gnu) MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190227_015945_524912_0D0FCD48 X-CRM114-Status: GOOD ( 30.27 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: "devicetree@vger.kernel.org" , Arnd Bergmann , Sergei Shtylyov , "tudor.ambarus@microchip.com" , Richard Weinberger , Miquel Raynal , "Nori, Sekhar" , "linux-kernel@vger.kernel.org" , Marek Vasut , Rob Herring , "linux-mtd@lists.infradead.org" , Greg Kroah-Hartman , Brian Norris , David Woodhouse , "linux-arm-kernel@lists.infradead.org" Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Wed, 27 Feb 2019 15:22:19 +0530 Vignesh Raghavendra wrote: > On 26/02/19 11:46 PM, Sergei Shtylyov wrote: > > On 02/19/2019 09:36 AM, Vignesh R (by way of Boris Brezillon ) wrote: > > > >> Cypress HyperBus is Low Signal Count, High Performance Double Data Rate Bus > >> interface between a host system master and one or more slave interfaces. > >> HyperBus is used to connect microprocessor, microcontroller, or ASIC > >> devices with random access NOR flash memory(called HyperFlash) or > >> self refresh DRAM(called HyperRAM). > >> > >> Its a 8-bit data bus (DQ[7:0]) with Read-Write Data Strobe (RWDS) > >> signal and either Single-ended clock(3.0V parts) or Differential clock > >> (1.8V parts). It uses ChipSelect lines to select b/w multiple slaves. > >> At bus level, it follows a separate protocol described in HyperBus > >> specification[1]. > >> > >> HyperFlash follows CFI AMD/Fujitsu Extended Command Set (0x0002) similar > >> to that of existing parallel NORs. Since Hyperbus is x8 DDR bus, > >> its equivalent to x16 parallel NOR flash wrt bits per clk. But Hyperbus > >> operates at >166MHz frequencies. > >> HyperRAM provides direct random read/write access to flash memory > >> array. > >> > >> But, Hyperbus memory controllers seem to abstract implementation details > >> and expose a simple MMIO interface to access connected flash. > >> > >> Add support for registering HyperFlash devices with MTD framework. MTD > >> maps framework along with CFI chip support framework are used to support > >> communicate with flash. > >> > >> Framework is modelled along the lines of spi-nor framework. HyperBus > >> memory controller(HBMC) drivers call hb_register_device() to register a > >> single HyperFlash device. HyperFlash core parses MMIO access > >> information from DT, sets up the map_info struct, probes CFI flash and > >> registers it with MTD framework. > >> > >> Some HBMC masters need calibration/training sequence[3] to be carried > >> out, in order for DLL inside the controller to lock, by reading a known > >> string/pattern. This is done by repeatedly reading CFI Query > >> Identification String. Calibration needs to be done before try to detect > >> flash as part of CFI flash probe. > >> > >> HyperRAM is not supported atm. > >> > >> HyperBus specification can be found at[1] > >> HyperFlash datasheet can be found at[2] > >> > >> [1] https://www.cypress.com/file/213356/download > >> [2] https://www.cypress.com/file/213346/download > >> [3] http://www.ti.com/lit/ug/spruid7b/spruid7b.pdf > >> Table 12-5741. HyperFlash Access Sequence > >> > >> Signed-off-by: Vignesh R > > [...] > >> diff --git a/include/linux/mtd/hyperbus.h b/include/linux/mtd/hyperbus.h > >> new file mode 100644 > >> index 000000000000..0aa11458c424 > >> --- /dev/null > >> +++ b/include/linux/mtd/hyperbus.h > >> @@ -0,0 +1,73 @@ > >> +/* SPDX-License-Identifier: GPL-2.0 > >> + * > >> + * Copyright (C) 2019 Texas Instruments Incorporated - http://www.ti.com/ > >> + */ > >> + > >> +#ifndef __LINUX_MTD_HYPERBUS_H__ > >> +#define __LINUX_MTD_HYPERBUS_H__ > >> + > >> +#include > >> + > >> +enum hb_memtype { > >> + HYPERFLASH, > >> + HYPERRAM, > >> +}; > >> + > >> +/** > >> + * struct hb_device - struct representing Hyperbus slave device > >> + * @map: map_info struct for accessing MMIO Hyperbus flash memory > >> + * @dev: device pointer of Hyperbus Controller > > > > I think we need a separate structure for the HyperBus controller, not just > > for the slave devices... > > > >> + * @np: pointer to Hyperbus slave device node > >> + * @mtd: pointer to MTD struct > >> + * @ops: pointer to custom Hyperbus ops > >> + * @memtype: type of memory device: Hyperflash or HyperRAM > >> + * @needs_calib: flag to indicate whether calibration sequence is needed > >> + * @registered: flag to indicate whether device is registered with MTD core > >> + */ > >> + > >> +struct hb_device { > >> + struct map_info map; > >> + struct device *dev; > >> + struct device_node *np; > >> + struct mtd_info *mtd; > >> + struct hb_ops *ops; > >> + enum hb_memtype memtype; > >> + bool needs_calib; > >> + bool registered; > >> +}; > >> + > >> +/** > >> + * struct hb_ops - struct representing custom Hyperbus operations > >> + * @read16: read 16 bit of data, usually from register/ID-CFI space > >> + * @write16: write 16 bit of data, usually to register/ID-CFI space > >> + * copy_from: copy data from flash memory > >> + * copy_to: copy data to flash_memory > >> + */ > >> + > >> +struct hb_ops { > >> + u16 (*read16)(struct hb_device *hbdev, unsigned long addr); > >> + void (*write16)(struct hb_device *hbdev, unsigned long addr, u16 val); > >> + > >> + void (*copy_from)(struct hb_device *hbdev, void *to, > >> + unsigned long from, ssize_t len); > >> + void (*copy_to)(struct hb_device *dev, unsigned long to, > >> + const void *from, ssize_t len); > > > > ... else these methods won't fly if you need to "massage" the controller > > registers inside them... > > > > If accessing controller register is the only need, wouldn't a private > data pointer within struct hb_device be sufficient to hold pointer to > controller specific struct? > > struct hb_device { > ... > void *priv; /* points to controller's private data */ > }; > > > Or do you see a need for separate structure for the HyperBus controller? Sorry to chime in. Just want to share my experience here: properly splitting the controller/device representation is always a good thing. When it's not done from the beginning and people start to add their own controller drivers as if it was a flash device driver it becomes messy pretty quickly and people add hacks to support that (look at the raw NAND framework if you need a proof). So, I'd recommend having this separation now, even if the onle controllers we support have a 1:1 relationship between HB controller and HB device. > > > >> +}; > > [...] > > > > MBR, Sergei > > > _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel