From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0229EC4332F for ; Wed, 13 Apr 2022 14:23:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234529AbiDMO0Q (ORCPT ); Wed, 13 Apr 2022 10:26:16 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43630 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233908AbiDMO0O (ORCPT ); Wed, 13 Apr 2022 10:26:14 -0400 Received: from mail-pf1-x433.google.com (mail-pf1-x433.google.com [IPv6:2607:f8b0:4864:20::433]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id ED8145EBF7; Wed, 13 Apr 2022 07:23:51 -0700 (PDT) Received: by mail-pf1-x433.google.com with SMTP id a21so2125616pfv.10; Wed, 13 Apr 2022 07:23:51 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=qGn5f7k2yKCgkj76DQyVMzIi7+OrsbeUPXvf0P2SY2M=; b=CnLieJzQV++9j5D60413ZX/83NOL/QRBxR+aLxN1M4jx1vHBCwvxb9tlb0hjhhsPS1 cwEoI2Yw1LeUbogR94teFmwe25lVCOX0IOlryzntsqhU+Qk4hLyhQXvhTbp7tNly/QAk 8eTcm9zkE0nZ227frEcOwiKj+C/xFPNRFXxh2BXxMYsRy94zU7YdlPmhk/Gj9bj0kaAu mYXboxjMrYl+6asLx64mnXnx287AGoXBkJDcW1QFqLym6E9IqY4/n0GW+OvkIUua9JoJ 3ctTef1GWjfb1FxPOoDPe7tHrWNPNzSlqWSw8NNBjDhww3ZJveGlpOdC1XQOL23Jffq6 lgQQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=qGn5f7k2yKCgkj76DQyVMzIi7+OrsbeUPXvf0P2SY2M=; b=JMsGHraVKgwal7I4rInNStsa7AiIjDOIKz0uCUtzsSM0jaDraVAiqC/IHe2AJ7TfJr ywmnrilR9e/JUg2j/D21y5fm5FPU7IrySUBkalFVK9oheTTD93vxwL+UskjRLm8qs8uR O8+cTVIwopzf+twtMTdZCwbHUHlnhf+ENVogEmHPAVFWNfSv0b7eEHhSeHA/FrT/xtYh DaC1Ln7LHXTpSF16DhTzV6/Y/FJJs7nc7+Qec1pC2Mo+4n8+kUEv38MN2OvAp3rJWFgR Wn7IJwi2I4BwdApNqNmX0e+KvXPYyP77Y+ZXtfkUdtX3cnJdgnHa+87BJuaIFQZl18Mj Kn4Q== X-Gm-Message-State: AOAM5322nfXyyETk7kF7+1FY0ayQidvCfm3ImLdgdNqZkq7fBwPrCt2D 3AxUAPCteAJ8wKFcXJ/kzi4= X-Google-Smtp-Source: ABdhPJzdTxqKmn32bzrzu2vfAdtQLbkM7pjzkYz7VLLkmWVupFe/a6VCGJmYQ9xX2omgC3FJcCTyfQ== X-Received: by 2002:a05:6a00:b44:b0:505:a8f3:6958 with SMTP id p4-20020a056a000b4400b00505a8f36958mr10069350pfo.22.1649859831286; Wed, 13 Apr 2022 07:23:51 -0700 (PDT) Received: from jagath-PC ([27.4.62.241]) by smtp.gmail.com with ESMTPSA id 137-20020a63078f000000b0039d9c13cd39sm5461569pgh.67.2022.04.13.07.23.49 (version=TLS1_2 cipher=ECDHE-ECDSA-CHACHA20-POLY1305 bits=256/256); Wed, 13 Apr 2022 07:23:50 -0700 (PDT) Date: Wed, 13 Apr 2022 19:53:46 +0530 From: Jagath Jog J To: Andy Shevchenko Cc: Dan Robertson , Jonathan Cameron , linux-iio , Linux Kernel Mailing List Subject: Re: [PATCH v3 4/9] iio: accel: bma400: Add triggered buffer support Message-ID: <20220413142345.GA3283@jagath-PC> References: <20220411203133.19929-1-jagathjog1996@gmail.com> <20220411203133.19929-5-jagathjog1996@gmail.com> <20220412193013.GA25279@jagath-PC> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.9.4 (2018-02-28) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Apr 13, 2022 at 12:24:54AM +0300, Andy Shevchenko wrote: > On Wednesday, April 13, 2022, Andy Shevchenko > wrote: > > > > > > > On Tuesday, April 12, 2022, Jagath Jog J wrote: > > > >> Hello Andy, > >> > >> On Tue, Apr 12, 2022 at 12:12:21PM +0300, Andy Shevchenko wrote: > >> > On Mon, Apr 11, 2022 at 11:31 PM Jagath Jog J > >> wrote: > >> > > > >> > > Added trigger buffer support to read continuous acceleration > >> > > data from device with data ready interrupt which is mapped > >> > > to INT1 pin. > >> > > >> > Can you explain the locking schema in this driver? > >> > > >> > > + /* Configure INT1 pin to open drain */ > >> > > + ret = regmap_write(data->regmap, BMA400_INT_IO_CTRL_REG, > >> 0x06); > >> > > + if (ret) > >> > > + return ret; > >> > > >> > No locking (or regmap only locking). > >> > >> This is bma400_init() function which will run when probe runs so there is > >> no > >> locking in this bma400_init(). > >> > >> > > >> > ... > >> > > >> > > +static int bma400_data_rdy_trigger_set_state(struct iio_trigger > >> *trig, > >> > > + bool state) > >> > > +{ > >> > > + struct iio_dev *indio_dev = iio_trigger_get_drvdata(trig); > >> > > + struct bma400_data *data = iio_priv(indio_dev); > >> > > + int ret; > >> > > + > >> > > + ret = regmap_update_bits(data->regmap, > >> BMA400_INT_CONFIG0_REG, > >> > > + BMA400_INT_DRDY_MSK, > >> > > + FIELD_PREP(BMA400_INT_DRDY_MSK, > >> state)); > >> > > + if (ret) > >> > > + return ret; > >> > > + > >> > > + return regmap_update_bits(data->regmap, BMA400_INT1_MAP_REG, > >> > > + BMA400_INT_DRDY_MSK, > >> > > + FIELD_PREP(BMA400_INT_DRDY_MSK, > >> state)); > >> > > +} > >> > > >> > Ditto. > >> > >> Sorry, I missed this. > >> I will add lock and unlocking in the next patch. > >> > >> > > >> > ... > >> > > >> > > + mutex_lock(&data->mutex); > >> > > + > >> > > + /* bulk read six registers, with the base being the LSB > >> register */ > >> > > + ret = regmap_bulk_read(data->regmap, BMA400_X_AXIS_LSB_REG, > >> > > + &data->buffer.buff, > >> sizeof(data->buffer.buff)); > >> > > + mutex_unlock(&data->mutex); > >> > > + if (ret) > >> > > + return IRQ_NONE; > >> > > >> > But here only above with locking... > >> > > >> > > + ret = regmap_read(data->regmap, BMA400_TEMP_DATA_REG, &temp); > >> > > + if (ret) > >> > > + return IRQ_NONE; > >> > > >> > ...followed by no locking. > >> > >> Okay I will add lock in the next patch. > >> > >> > > >> > ... > >> > > >> > > + mutex_lock(&data->mutex); > >> > > + ret = regmap_bulk_read(data->regmap, BMA400_INT_STAT0_REG, > >> &status, > >> > > + sizeof(status)); > >> > > + mutex_unlock(&data->mutex); > >> > > + if (ret) > >> > > + return IRQ_NONE; > >> > > >> > And again with locking. > >> > > >> > ... > >> > > >> > So, > >> > 1) Does regmap is configured with locking? What for? > >> > 2) What's the role of data->mutex? > >> > >> 1. > >> NO, > > > > > > Are you sure? > > > > > >> regmap is not configured with locking. > >> In the remap_config structure variable below these members are not defined > >> in the driver. > >> > >> struct regmap_config { > >> regmap_lock lock; > >> regmap_unlock unlock; > >> void *lock_arg; > >> > >> > > It means that default may be used. > > > > > >> 2. > >> data->mutex is used to protect the register read, write access from the > >> device. > >> > >> Is the regmap functions handle locking and unlocking internally if these > >> below > >> struct members are not defined? > > > > > > Yes. Look at this: https://elixir.bootlin.com/linux/latest/C/ident/ > > disable_locking Please your advise will be very helpful for this. I'm going through the same documentation. In this driver, disable_locking is not initialized. The functions which are called in the bma400_init() are not protected by mutex for regmap since bma400_init() will run when the probe runs. The functions which are called by read_raw() and write_raw() are protected by mutex for regmap access. There are some members in the device's private data structure and they are being accessed in multiple places in the driver. struct bma400_data { enum bma400_power_mode power_mode; struct bma400_sample_freq sample_freq; int oversampling_ratio; int scale; ..... I think mutex is used to protect these above struct members since they are critical resource, but in the struct bma400_data comment for mutex is "data register lock". > > > > > >> > >> regmap_lock lock; > >> regmap_unlock unlock; > >> void *lock_arg; > >> > >> > >> > > >> > -- > >> > With Best Regards, > >> > Andy Shevchenko > >> > > > >> > > You may read the kernel documentation what those fields mean: > https://elixir.bootlin.com/linux/latest/source/include/linux/regmap.h#L278 > > > > > -- > > With Best Regards, > > Andy Shevchenko > > > > > > > > -- > With Best Regards, > Andy Shevchenko Thank you, Jagath