From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pl1-f181.google.com (mail-pl1-f181.google.com [209.85.214.181]) (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 29E442BEFEB for ; Fri, 1 May 2026 02:35:49 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.214.181 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777602950; cv=none; b=MlbjP8Y6eFE8ITeaxj8JnHNmTUm2qeo2lbqZMZcWn3EhltWqX05mw4VMWGvWh6qsUY5XpjXhzPjdGpbF5nzmWq4h24z30ia0UvXtVSrvYymYYTT2LU3LKibkxPT09Z9kdNK1/Lnhdmhlbd/7XK1BSoU5BiQWM3jx5nTrkZsMVVY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777602950; c=relaxed/simple; bh=nI7jEuFl5Wx1BRcYnNc+rTGFK7F6A8M4xO6oyFoLWrk=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=LQyweRdbolMtCyBeeNw9S/O+qOi2sSD4OUQOw8btzk1PR8uMMSpPAMhzJN3IAGqY8t15iFjzPy53leAjo7DrIe+Pk/pj2LQnvVSnhFp8olrnBsf1zHy8JI2vRYPb4SRgoLpC9otwjAev5puHZXZtJurr9BjkxWbWTvKLIYIcMp0= 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=Kf9ClMGu; arc=none smtp.client-ip=209.85.214.181 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="Kf9ClMGu" Received: by mail-pl1-f181.google.com with SMTP id d9443c01a7336-2ad9516a653so7926425ad.0 for ; Thu, 30 Apr 2026 19:35:49 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1777602948; x=1778207748; 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=kSnHTefyeA+2hwX9yr/+mpxR4GkNtCtvVO+4GeW9P5U=; b=Kf9ClMGuYeuHvyKoEwrVB2k92lRLV1k31k1WmBJWnLobS56JvKzlHmy2CQ8j5E3ElT L/arynh51/Fhcs/pOA6HgMl2P2wUjTE2o/Pnz4RL+vpPGCKjvhAMN/4ePvMpiHw0WWfG gjHva2//BQrIXi7s4PCEJ5n+boDcQw8RiJzapYWqWi1hyDsf01BmOhM1O1ad8FSXYWKc PkKT/vQwRJDUsbR3IJFaYuzv4aFqEblejo8Ax8aTqxbc1XZ+y6R8kFCAmJO48sw8LpS/ QvFxNcgODDtpICYGWlrRgg9ppqAFDDNWH3sDCYAghrHY6c/9ooGZIdtHiKAtVxO3t+F9 zPOQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1777602948; x=1778207748; 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=kSnHTefyeA+2hwX9yr/+mpxR4GkNtCtvVO+4GeW9P5U=; b=IOCTvTZVY6vLNZSBaeoxeyX9QfD/Zd0wobxfn590ETbY5YVJhie6gCksdOtm48zvex hcW/oZGrAsmVme08Nz1ViF/fpgNqiHsEgYNTeUuFyIndXXM/O8qIxK38eq/BK05iT0RX s9hfQdaShe6pcKBAUKDUjZc7QreVM3dIhXdv+MfV+kTAhpcqX5q/Adyy9sftc7kWXHmJ Wq3uY8xLEZTnaA3yN2obiKTr7u04YmvOvpWw2UjXsLNCtnk9wuYSqf4jE3dRhxJNgR9b o0Ej05zPhAsASoxI1KdKCKgvKzCn/9Dke9mXALlR/x5f8Ygzd9DDxPcx1D5s4grqXsu2 5U9g== X-Gm-Message-State: AOJu0YyfOyNWh0bjwsCloQM/r5ynQjwXD9b8O5gzGceA1mo+PqaLbL5D zXCAd1ofrXcRo4MYRPdDxo/iEtxuzboxNr1VlHieVoaoFNE1coNBCZS/ X-Gm-Gg: AeBDiev6pSRYuVINCzKizUp5Wq0UTXYImYDNSBwzTBsFFQEx6jJLpeJG0w/gyTFoLFv LU2uf3SWm8Rctw4GpqOXsO27wya7FH/NmNR/3Q7PljwpdvOJEtCXgt7URIug23fmvXTcFCMt4Vh HUuYHqcJTr+C6EN2R3msFHgskTyXMzMeeZrBtvt5HIqH7twCOzfe0nkShYL048K8wQZ/VHIXdZm W/z1B76v3uVpwa5b9kI+D1vf6YAVexgDGoz+3koqPAPyZmX6F4B0wXFM8sm2TyiFOoH4BGsNiJd fVF4mc0o/sTGPJTYC9388xe3xRVag/t0Kbdndt+bC3oV5x6ub+ZSRH0O/sn5naFEIoMFF9WbKKt qoiwuS7sFkrBjl1WxEqWhvkt1Tb8kHBbfVlaqRqNgFOjCGFEwRt2YKcvRjAFJCrqmzryMGcW1rh v7h8VGgTC+5/GmM2R0xXRKspzkQANcwL065nGD3Zv4jhdcU42qSYJV0Ol6g2aTwuNoIhWlEYZxG oZSyjV4Vu/80e2+ X-Received: by 2002:a17:902:b186:b0:2b2:4fe3:7b89 with SMTP id d9443c01a7336-2b9a2546e2dmr41331905ad.38.1777602948495; Thu, 30 Apr 2026 19:35:48 -0700 (PDT) Received: from tabrez-VivoBook-ASUSLaptop-X513UA-KM513UA.. ([116.72.73.183]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2b9caa7e791sm9341385ad.7.2026.04.30.19.35.46 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 30 Apr 2026 19:35:48 -0700 (PDT) From: Tabrez Ahmed To: Guenter Roeck Cc: linux-hwmon@vger.kernel.org, linux-kernel@vger.kernel.org, shuah@kernel.org, me@brighamcampbell.com, Tabrez Ahmed Subject: [PATCH v5 3/3] hwmon: (ads7871) Use DMA-safe buffer for SPI writes Date: Fri, 1 May 2026 08:05:30 +0530 Message-ID: <20260501023530.31160-4-tabreztalks@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260501023530.31160-1-tabreztalks@gmail.com> References: <20260501023530.31160-1-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 75485a2c16b0b..cbb9a88229c50 100644 --- a/drivers/hwmon/ads7871.c +++ b/drivers/hwmon/ads7871.c @@ -63,6 +63,7 @@ #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, @@ -99,11 +100,12 @@ static int ads7871_read_reg16(struct spi_device *spi, int reg) return get_unaligned_le16(rx_buf); } -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, @@ -122,7 +124,7 @@ 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; @@ -130,6 +132,7 @@ 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 @@ -149,8 +152,11 @@ 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; } @@ -187,11 +193,17 @@ 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); @@ -202,11 +214,6 @@ 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