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 60939C433FE for ; Tue, 5 Apr 2022 07:41:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232017AbiDEHnN (ORCPT ); Tue, 5 Apr 2022 03:43:13 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54904 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231818AbiDEHmA (ORCPT ); Tue, 5 Apr 2022 03:42:00 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 082A290FDC; Tue, 5 Apr 2022 00:39:59 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 9CC2161668; Tue, 5 Apr 2022 07:39:58 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id A86D4C340EE; Tue, 5 Apr 2022 07:39:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1649144398; bh=y4HzoPUx0g/Wg4u5UKwImFP7XoKjSKux0f3xg0dQGf0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=v7XlfogBc6W+7QymHx9o7sPty9VR62+r6I9U2kno1RFlkbXNdlxDnzbk0HvQcSHYF a1lfvColACtCHddoVcXOiKUMQNH5n2bAibGFU2T2OV4lI+IKbJQjQESqjEjYEKTcg1 tp/F2cdbjdtf4HoHZz9YGzjaZ5dSkcF6GQh0EWOk= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Konstantin Klubnichkin , Billy Tsai , Joel Stanley , Stable@vger.kernel.org, Jonathan Cameron Subject: [PATCH 5.17 0031/1126] iio: adc: aspeed: Add divider flag to fix incorrect voltage reading. Date: Tue, 5 Apr 2022 09:12:58 +0200 Message-Id: <20220405070408.467175161@linuxfoundation.org> X-Mailer: git-send-email 2.35.1 In-Reply-To: <20220405070407.513532867@linuxfoundation.org> References: <20220405070407.513532867@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Billy Tsai commit 571426631acf46e2999c7ecd1e9d048172969a43 upstream. The formula for the ADC sampling period in ast2400/ast2500 is: ADC clock period = PCLK * 2 * (ADC0C[31:17] + 1) * (ADC0C[9:0]) When ADC0C[9:0] is set to 0 the sampling voltage will be lower than expected, because the hardware may not have enough time to charge/discharge to a stable voltage. This patch use the flag CLK_DIVIDER_ONE_BASED which will use the raw value read from the register, with the value of zero considered invalid to conform to the corrected formula. Fixes: 573803234e72 ("iio: Aspeed ADC") Reported-by: Konstantin Klubnichkin Signed-off-by: Billy Tsai Reviewed-by: Joel Stanley Link: https://lore.kernel.org/r/20220221012705.22008-1-billy_tsai@aspeedtech.com Cc: Signed-off-by: Jonathan Cameron Signed-off-by: Greg Kroah-Hartman --- drivers/iio/adc/aspeed_adc.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) --- a/drivers/iio/adc/aspeed_adc.c +++ b/drivers/iio/adc/aspeed_adc.c @@ -539,7 +539,9 @@ static int aspeed_adc_probe(struct platf data->clk_scaler = devm_clk_hw_register_divider( &pdev->dev, clk_name, clk_parent_name, scaler_flags, data->base + ASPEED_REG_CLOCK_CONTROL, 0, - data->model_data->scaler_bit_width, 0, &data->clk_lock); + data->model_data->scaler_bit_width, + data->model_data->need_prescaler ? CLK_DIVIDER_ONE_BASED : 0, + &data->clk_lock); if (IS_ERR(data->clk_scaler)) return PTR_ERR(data->clk_scaler);