From patchwork Thu Jun 16 15:24:36 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Crestez Dan Leonard X-Patchwork-Id: 9181271 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id BB47E60760 for ; Thu, 16 Jun 2016 15:25:46 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id ABA9628379 for ; Thu, 16 Jun 2016 15:25:46 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id A02BF28375; Thu, 16 Jun 2016 15:25:46 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.9 required=2.0 tests=BAYES_00,RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id EFB6F28364 for ; Thu, 16 Jun 2016 15:25:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753779AbcFPPZp (ORCPT ); Thu, 16 Jun 2016 11:25:45 -0400 Received: from mga02.intel.com ([134.134.136.20]:23965 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752339AbcFPPZo (ORCPT ); Thu, 16 Jun 2016 11:25:44 -0400 Received: from fmsmga004.fm.intel.com ([10.253.24.48]) by orsmga101.jf.intel.com with ESMTP; 16 Jun 2016 08:25:09 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.26,480,1459839600"; d="scan'208";a="123107983" Received: from cdleonard-desk.rb.intel.com ([10.237.104.169]) by fmsmga004.fm.intel.com with ESMTP; 16 Jun 2016 08:25:06 -0700 From: Crestez Dan Leonard To: Mark Brown Cc: Crestez Dan Leonard , linux-spi@vger.kernel.org, Wolfram Sang , linux-i2c@vger.kernel.org, Jonathan Cameron , linux-kernel@vger.kernel.org Subject: [RFC] regmap: Add regmap_pipe_read API Date: Thu, 16 Jun 2016 18:24:36 +0300 Message-Id: <7ca3857aa8869a1e1f4709860f57f7d92abf1c6b.1466089603.git.leonard.crestez@intel.com> X-Mailer: git-send-email 2.5.5 Sender: linux-spi-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-spi@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP The regmap API usually assumes that bulk read operations will read a range of registers but some I2C/SPI devices have certain registers for which a such a read operation will return data from an internal FIFO instead. Add an explicit API to support bulk read with pipe rather than range semantics. Some linux drivers use regmap_bulk_read or regmap_raw_read for such registers, for example mpu6050 or bmi150 from IIO. This only happens to work because when caching is disabled a single regmap read op will map to a single bus read op (as desired). This breaks if caching is enabled and reg+1 happens to be a cacheable register. Without regmap support refactoring a driver to enable regmap caching requires separate I2C and SPI paths. This is exactly what regmap is supposed to help avoid. Suggested-by: Jonathan Cameron Signed-off-by: Crestez Dan Leonard --- This works as expected for mpu6050 i2c/spi. Unfortunately looking through the regmap_bus implementations it looks that at least regmap_spmi_base_read assumes range semantics at the regmap_hw_read level. If any SPMI devices exist that have registers with this kind of pipe semantics the correct way to handle them would be reading from the same register in a loop. I'd say the correct way to handle this would be to add a regmap_hw_pipe_read bus operation which is almost always implemented identically to regmap_hw_read. If that operation is missing regmap_pipe_read should attempt to read_reg in a loop. I'm also not absolutely certain that a separate API is required. The regmap_raw_read currently doesn't work because it check for a "regmap_volatile_range" which returns true only if the entire range is volatile. It's not clear if this is intentional? drivers/base/regmap/regmap.c | 62 ++++++++++++++++++++++++++++++++++++++++++++ include/linux/regmap.h | 9 +++++++ 2 files changed, 71 insertions(+) diff --git a/drivers/base/regmap/regmap.c b/drivers/base/regmap/regmap.c index df2d2ef..342f326 100644 --- a/drivers/base/regmap/regmap.c +++ b/drivers/base/regmap/regmap.c @@ -2408,6 +2408,68 @@ int regmap_raw_read(struct regmap *map, unsigned int reg, void *val, EXPORT_SYMBOL_GPL(regmap_raw_read); /** + * regmap_pipe_read(): Read data from a register with pipe semantics + * + * @map: Register map to read from + * @reg: Register to read from + * @val: Pointer to data buffer + * @val_len: Length of output buffer in bytes. + * + * The regmap API usually assumes that bulk bus read operations will read a + * range of registers. Some devices have certain registers for which a read + * operation read will read from an internal FIFO. + * + * The target register must be volatile but registers after it can be + * completely unrelated cacheable registers. + * + * This will attempt multiple reads as required to read val_len bytes. + * + * A value of zero will be returned on success, a negative errno will be + * returned in error cases. + */ +int regmap_pipe_read(struct regmap *map, unsigned int reg, + void *val, size_t val_len) +{ + size_t read_len; + int ret; + + if (!map->bus) + return -EINVAL; + if (!map->bus->read) + return -ENOTSUPP; + if (val_len % map->format.val_bytes) + return -EINVAL; + if (!IS_ALIGNED(reg, map->reg_stride)) + return -EINVAL; + if (val_len == 0) + return -EINVAL; + + map->lock(map->lock_arg); + + if (!regmap_volatile(map, reg)) { + ret = -EINVAL; + goto out_unlock; + } + + while (val_len) { + if (map->max_raw_read && map->max_raw_read < val_len) + read_len = map->max_raw_read; + else + read_len = val_len; + ret = _regmap_raw_read(map, reg, val, read_len); + if (ret) + goto out_unlock; + val = ((u8*)val) + read_len; + val_len -= read_len; + } + +out_unlock: + map->unlock(map->lock_arg); + return ret; +} +EXPORT_SYMBOL_GPL(regmap_pipe_read); + +/** * regmap_field_read(): Read a value to a single register field * * @field: Register field to read from diff --git a/include/linux/regmap.h b/include/linux/regmap.h index 3dc08ce..18ee90e 100644 --- a/include/linux/regmap.h +++ b/include/linux/regmap.h @@ -719,6 +719,8 @@ int regmap_raw_write_async(struct regmap *map, unsigned int reg, int regmap_read(struct regmap *map, unsigned int reg, unsigned int *val); int regmap_raw_read(struct regmap *map, unsigned int reg, void *val, size_t val_len); +int regmap_pipe_read(struct regmap *map, unsigned int reg, + void *val, size_t val_len); int regmap_bulk_read(struct regmap *map, unsigned int reg, void *val, size_t val_count); int regmap_update_bits_base(struct regmap *map, unsigned int reg, @@ -955,6 +957,13 @@ static inline int regmap_raw_read(struct regmap *map, unsigned int reg, return -EINVAL; } +static inline int regmap_pipe_read(struct regmap *map, unsigned int reg, + void *val, size_t val_len) +{ + WARN_ONCE(1, "regmap API is disabled"); + return -EINVAL; +} + static inline int regmap_bulk_read(struct regmap *map, unsigned int reg, void *val, size_t val_count) {