From patchwork Mon Jun 3 16:23:06 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Dumitru Ceclan via B4 Relay X-Patchwork-Id: 13683988 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id BEEA3136E2A; Mon, 3 Jun 2024 16:23:14 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1717431794; cv=none; b=XAztUgY2maSvZ/5FthI5AtbazHw0xZxaN1TCZh0gYzKuAquVye0b5wXI1LO700cIkEv5PyaX8SM8VaRSmzLvvXviQXw41TwXhimWDDVFWVi3/RHLWhpAPPCqUqjMguH6n7UIIgkWszM7W52CirUTcPkiEOXOjinr3KBigbz9mW4= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1717431794; c=relaxed/simple; bh=PU9CGgziLdFhXBzpFlmp5+t+whnb8pPpl3fL8FrJUo4=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=CvMUh83+P7EZZ/pu1tqxT6td2bb+7mvlw1tqfj3PJcU0m5swnrrJ0HCVlv2PJlYNJb6rSIC3uBdZ25U3PDSCg0x5ePexbo0IOAWE47tbiOq5Ngi8qPzGgVsxYegTipjKfw9loYki22xP8lDugNxNyV1brjBulasLpffN39tqEWo= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=ng1tRoRy; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="ng1tRoRy" Received: by smtp.kernel.org (Postfix) with ESMTPS id 5093DC4AF54; Mon, 3 Jun 2024 16:23:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1717431794; bh=PU9CGgziLdFhXBzpFlmp5+t+whnb8pPpl3fL8FrJUo4=; h=From:Date:Subject:References:In-Reply-To:To:Cc:Reply-To:From; b=ng1tRoRyka2FVZyNJvgc3anQzqOgKLIDFNUkdNTF36qiJ7xopmPobAcVEez0wvfpW co4Cjohy8y9f2RxLrR7WafYLdCfjUzb+THYxP+Slin/J5QFJUC7dZEJ1JGc+r49hal MP90JF1SH3eGv4SHrYTDELosLXvgFcr355H6aYLNETA1e83K2xPc1UdZxe088wFm+0 vNtN3FmKyOXLstfA+4rKH54UIqOKOTqJbK53swurpN0gWtv9rCry4NDAIkLUZNvP2s iYH94Kq4f4Md8zp0ql7hTfh0xJqpGYtK5tvbmlIo2Rk/gaXWGh9kYfLOy9VxFdj5Rl DPvOCAHn5MFuA== Received: from aws-us-west-2-korg-lkml-1.web.codeaurora.org (localhost.localdomain [127.0.0.1]) by smtp.lore.kernel.org (Postfix) with ESMTP id 44A4AC25B75; Mon, 3 Jun 2024 16:23:14 +0000 (UTC) From: Dumitru Ceclan via B4 Relay Date: Mon, 03 Jun 2024 19:23:06 +0300 Subject: [PATCH v5 8/9] iio: adc: ad7173: document sampling frequency behaviour Precedence: bulk X-Mailing-List: linux-iio@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Message-Id: <20240603-ad4111-v5-8-9a9c54d9ac78@analog.com> References: <20240603-ad4111-v5-0-9a9c54d9ac78@analog.com> In-Reply-To: <20240603-ad4111-v5-0-9a9c54d9ac78@analog.com> To: Ceclan Dumitru Cc: Lars-Peter Clausen , Michael Hennerich , Jonathan Cameron , Rob Herring , Krzysztof Kozlowski , Conor Dooley , David Lechner , linux-iio@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, Dumitru Ceclan X-Mailer: b4 0.13.0 X-Developer-Signature: v=1; a=ed25519-sha256; t=1717431792; l=1618; i=dumitru.ceclan@analog.com; s=20240313; h=from:subject:message-id; bh=2nPfloQlqJU5+9wFX+IL8WDN+iCUelg+ZAepCt2X+L0=; b=SsK8XFss3iJYziP1y5sS5l3QzebH9uY+AORf8T9s/7lhH8rpA6oEnNUH1DfBCn/Ic65KvcZWb jZ+cb59m+lmBUzYSlGSJ9TGhySH/gYyl04gwy6fYROu4F8rXClT5uUx X-Developer-Key: i=dumitru.ceclan@analog.com; a=ed25519; pk=HdqMlVyrcazwoiai7oN6ghU+Bj1pusGUFRl30jhS7Bo= X-Endpoint-Received: by B4 Relay for dumitru.ceclan@analog.com/20240313 with auth_id=140 X-Original-From: Dumitru Ceclan Reply-To: dumitru.ceclan@analog.com From: Dumitru Ceclan The ADCs supported by this driver feature a sequencer that read in a loop all the enabled chanels. When setting the individual sampling frequency for each channel and enabling multiple channels, the effective of each channel will be lower than the actual set value. Document this behaviour in a comment. Signed-off-by: Dumitru Ceclan --- drivers/iio/adc/ad7173.c | 15 +++++++++++++++ 1 file changed, 15 insertions(+) diff --git a/drivers/iio/adc/ad7173.c b/drivers/iio/adc/ad7173.c index 5ade166814d7..fb18acc83f39 100644 --- a/drivers/iio/adc/ad7173.c +++ b/drivers/iio/adc/ad7173.c @@ -742,6 +742,21 @@ static int ad7173_write_raw(struct iio_dev *indio_dev, return ret; switch (info) { + /* + * This attribute sets the sampling frequency for each channel individually. + * There are no issues for raw or buffered reads of an individual channel. + * + * When multiple channels are enabled in buffered mode, the effective + * sampling rate of a channel is lowered in correlation to the number + * of channels enabled and the sampling rate of the other channels. + * + * Example: 3 channels enabled with rates CH1:6211sps CH2,CH3:10sps + * While the reading of CH1 takes only 0.16ms, the reading of CH2 and CH3 + * will take 100ms each. + * + * This will cause the reading of CH1 to be actually done once every + * 200.16ms, an effective rate of 4.99sps. + */ case IIO_CHAN_INFO_SAMP_FREQ: freq = val * MILLI + val2 / MILLI; for (i = st->info->odr_start_value; i < st->info->num_sinc5_data_rates - 1; i++)