From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pl1-f177.google.com (mail-pl1-f177.google.com [209.85.214.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E2D572C11CA for ; Sat, 2 May 2026 02:09:03 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.214.177 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777687745; cv=none; b=r2s3zX5q2pozatd74U17fkRZkL2pijM6GYLMwPDCMo3t+dJX69EkbDE/Ros1oB+cvyzy7bcFBMAQZZgJzijzuSUc5A1QxQFB4bJ4QZMu7HK3NH1x52L4dzYFFF+tOD5mb3M3RxdyE0KjRoaRtdFCofS477fV99HAz+gzN+faZMI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777687745; c=relaxed/simple; bh=0h5BEMG7ZbzlYE1qYJc8sPYWwfEyMLY79w8gc6hehOg=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=QVnYfbh/M0AdlXY+r5NeoH1KTRFt0AiWlW/Hum89hfXbloQBNAH0rTj4VnEtYfj0Neowl8+O0/buVPrbHgnp/4T5Nu4XlSvf/F5EbtNm5pAfuysTvad8CSVHemHID1dOJjXVW4PJSl0tSmqZ8B3QggP9KYwKqSRL4ZuM98u30cU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=Y4EKpbFZ; arc=none smtp.client-ip=209.85.214.177 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="Y4EKpbFZ" Received: by mail-pl1-f177.google.com with SMTP id d9443c01a7336-2b23fcf90b2so21917895ad.3 for ; Fri, 01 May 2026 19:09:03 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1777687743; x=1778292543; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=fv+LaawXWM5Be8S4ugblbJPLa3ayLH0tuydTTKYUZtA=; b=Y4EKpbFZuiIRAzAdG+Vq8xHc7oo4RBjvdp+yMxrn2FZ27dU9t4ZZvgqVxiNBbc7vOj 7Nf9lcRIHiq+XYZ7RBh7gBlo/+N0lbRSVtG6Dw5uBB1Nsuv4T6E/iD/fQMFOAlkqBQAs MunNPP7Ums1DYhEfmRz1bhivCFZPP+8Xrpo84FIVAjPOW851MQQM23iWAnLBjR4VH/5V ZUuXpeyvDYvRAnKbFGTCl2Rs4wN9fFLcCRYIi8SaqbMmFTGmK1y8OiWCvv+AG9EawIvV 2dmVaEJfGw/DIZkDrx5nz4FzGpys2h4KogoOXxLZwKIRbR7Gl0OLZdfW+4niIFEGqU7a 9ZOg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1777687743; x=1778292543; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-gg:x-gm-message-state:from :to:cc:subject:date:message-id:reply-to; bh=fv+LaawXWM5Be8S4ugblbJPLa3ayLH0tuydTTKYUZtA=; b=dcZE9af3nF6+ZdMNgxPh3vJX42qyWq2GjgjV7EKTodOZ5bO6nwncrkzptjqv2BLdlK lR76cxwHpU52mnYRotH9Gq4HIxDHbeDOzBQDqaxDTZJoa0EsF9rC8fx8AasAqxPNkZTI 2XBw9dUE9zYwZ3z0oJMjhbud2Qu1jUG5t1kgKfwEyEd8eI336+O34OQgEux5EYGErNdl S3u7+tJU1QfAAaFRiind3QrLXLz9v/90Nj21TRj4hUdSn2DdMP4vljU7v87VMgtXP4k7 1D8keaZS2DYSUie1aFU5WYqqzt6USUsuCmyi/KHY9EpbGWrA7xrVbPgOJAmDIcaYNQ4n E2Dg== X-Gm-Message-State: AOJu0YxOGqsZyr/498sVWPxBzYinnqCPebun8TkyhmmKWHUWXo1gK7Xq b/HTNTNJTFCbuf7/UWO+4Z4SgEnipBKWuahQ0baz3BBsqyohOTwsHzXQ/+H6qQ== X-Gm-Gg: AeBDievxG0FunnsPI2wgMEDhZ2ByGQkw7OkB8FxKKFGmqQ54MQ/KmQODGCxVf+uKXoD gBJ3JQsDuwh1Si2TWhwSz5U0M0N1y9eE9JG/pj+OIIkBI/hEQgCYxniCBOslsVn/wKffcwjY/m8 jbXdriGBKj14/l7HSZ04VGwuqmolWef9e5SM6QL6IUhD9wZ4HV+GroxokA5I4uULWwykZt1dPB8 BAdDXYSIi26utXC/bu2AZJdQ7nPxGyYISEYdU0kUyVzo+iBuXk2Jptmtp5zGHhKc+j6rWOM+dR/ h/cienab5xJHHt65Kh4I4zxEPwY0Yqx1eQAzK8/JZvM8x9fR7zFhDaf6nc7QJ8Mh7x2h5Ob9UYG dGEQvP5B0FM1fFLFyfE89CP32UaRXly3H/awNJ7hf75G4aHusR7tNUQDn7ewd73IOrmzQhHQ6w8 aes2oBtvHjVR647Q5D0sGS0ooK4+h8J+4GwCSNCpjamZLwDvExb9p3HsN4B89MnyhCqaGkRIgy+ qYLqw== X-Received: by 2002:a17:903:1984:b0:2b2:ec46:dfd4 with SMTP id d9443c01a7336-2b9f25df2fcmr14482125ad.22.1777687742996; Fri, 01 May 2026 19:09:02 -0700 (PDT) Received: from tabrez-VivoBook-ASUSLaptop-X513UA-KM513UA.. ([116.72.73.183]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2b9cae39e91sm34519135ad.56.2026.05.01.19.09.00 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 01 May 2026 19:09:02 -0700 (PDT) From: Tabrez Ahmed To: linux-hwmon@vger.kernel.org, linux-kernel@vger.kernel.org Cc: linux@roeck-us.net, david.laight.linux@gmail.com, me@brighamcampbell.com, shuah@kernel.org, Tabrez Ahmed Subject: [PATCH v6 3/3] hwmon: (ads7871) Use DMA-safe buffer for SPI writes Date: Sat, 2 May 2026 07:38:44 +0530 Message-ID: <20260502020844.110038-4-tabreztalks@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260502020844.110038-1-tabreztalks@gmail.com> References: <20260502020844.110038-1-tabreztalks@gmail.com> Precedence: bulk X-Mailing-List: linux-hwmon@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit The driver currently passes a stack-allocated buffer to spi_write(), which is incompatible with DMA on systems with CONFIG_VMAP_STACK enabled. Move the transfer buffer into the driver's private data structure to ensure it is DMA-safe. Since this shared buffer now requires serialization, this change depends on the previous commit which migrated the driver to the hwmon 'with_info' API. While moving the logic, also: - Corrected the sign extension for 14-bit data by casting to s16. - Scaled the output to millivolts (2500mV full scale ) to comply with the hwmon ABI. Signed-off-by: Tabrez Ahmed --- drivers/hwmon/ads7871.c | 35 +++++++++++++++++++++-------------- 1 file changed, 21 insertions(+), 14 deletions(-) diff --git a/drivers/hwmon/ads7871.c b/drivers/hwmon/ads7871.c index 8ffcc4c823a60..83ea09a935bc4 100644 --- a/drivers/hwmon/ads7871.c +++ b/drivers/hwmon/ads7871.c @@ -62,6 +62,7 @@ #define DEVICE_NAME "ads7871" struct ads7871_data { struct spi_device *spi; + u8 tx_buf[2] ____cacheline_aligned; }; static umode_t ads7871_is_visible(const void *data, @@ -94,11 +95,12 @@ static int ads7871_read_reg16(struct spi_device *spi, int reg) return le16_to_cpu((__force __le16)ret); } -static int ads7871_write_reg8(struct spi_device *spi, int reg, u8 val) +static int ads7871_write_reg8(struct ads7871_data *pdata, int reg, u8 val) { - u8 tmp[2] = {reg, val}; + pdata->tx_buf[0] = reg; + pdata->tx_buf[1] = val; - return spi_write(spi, tmp, sizeof(tmp)); + return spi_write(pdata->spi, pdata->tx_buf, 2); } static int ads7871_read(struct device *dev, enum hwmon_sensor_types type, @@ -117,7 +119,7 @@ static int ads7871_read(struct device *dev, enum hwmon_sensor_types type, */ /*MUX_M3_BM forces single ended*/ /*This is also where the gain of the PGA would be set*/ - ret = ads7871_write_reg8(spi, REG_GAIN_MUX, + ret = ads7871_write_reg8(pdata, REG_GAIN_MUX, (MUX_CNV_BM | MUX_M3_BM | channel)); if (ret < 0) return ret; @@ -125,6 +127,7 @@ static int ads7871_read(struct device *dev, enum hwmon_sensor_types type, ret = ads7871_read_reg8(spi, REG_GAIN_MUX); if (ret < 0) return ret; + mux_cnv = ((ret & MUX_CNV_BM) >> MUX_CNV_BV); /* * on 400MHz arm9 platform the conversion @@ -144,8 +147,11 @@ static int ads7871_read(struct device *dev, enum hwmon_sensor_types type, if (raw_val < 0) return raw_val; - /*result in volts*10000 = (val/8192)*2.5*10000*/ - *val = ((raw_val >> 2) * 25000) / 8192; + /* + * Use (s16) to ensure the sign bit is preserved during the shift. + * Report millivolts (2.5V = 2500mV). + */ + *val = ((s16)raw_val >> 2) * 2500 / 8192; return 0; } @@ -182,11 +188,17 @@ static int ads7871_probe(struct spi_device *spi) spi->bits_per_word = 8; spi_setup(spi); - ads7871_write_reg8(spi, REG_SER_CONTROL, 0); - ads7871_write_reg8(spi, REG_AD_CONTROL, 0); + pdata = devm_kzalloc(dev, sizeof(*pdata), GFP_KERNEL); + if (!pdata) + return -ENOMEM; + + pdata->spi = spi; + + ads7871_write_reg8(pdata, REG_SER_CONTROL, 0); + ads7871_write_reg8(pdata, REG_AD_CONTROL, 0); val = (OSC_OSCR_BM | OSC_OSCE_BM | OSC_REFE_BM | OSC_BUFE_BM); - ads7871_write_reg8(spi, REG_OSC_CONTROL, val); + ads7871_write_reg8(pdata, REG_OSC_CONTROL, val); ret = ads7871_read_reg8(spi, REG_OSC_CONTROL); dev_dbg(dev, "REG_OSC_CONTROL write:%x, read:%x\n", val, ret); @@ -197,11 +209,6 @@ static int ads7871_probe(struct spi_device *spi) if (val != ret) return -ENODEV; - pdata = devm_kzalloc(dev, sizeof(struct ads7871_data), GFP_KERNEL); - if (!pdata) - return -ENOMEM; - - pdata->spi = spi; hwmon_dev = devm_hwmon_device_register_with_info(dev, spi->modalias, pdata, &ads7871_chip_info, -- 2.43.0