From patchwork Fri Jun 7 14:53:14 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: 13690298 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 ABFB319FA70; Fri, 7 Jun 2024 14:53:09 +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=1717771989; cv=none; b=pwtAMQxEHpZgQ1YLFLEhSxNqkb4KxDC39pD2Dj2j1AoF9L4Q+aYTgyTK2GqZ3dgPIPa3pNiDMlBV0heVeGAUdFHb9RC/DzZptBfAA4LACBmguzm7hL1tTJiVlgnk1/udBe/XLcsT9SCGVXQkGAw9ZxduUuVV7+plUBHXp/DaBAg= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1717771989; c=relaxed/simple; bh=hp9z0Ybu/B/EafMmtw/DvgPAfybd4iKKakb+IfmiaR4=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=ex3NPsRX4JE1zMCB1mJMEVlGGmtjqXzDFS+uLEYPkxQOkRyGtjY9hMRz+lWQx8jP5KlmjuploLTlhgi5JMTU1plKNcGv9iHwWMx0GDcposlGDcVqA4QWCW0frF10oottsDJCmMz5/8P1DJ6NIMqHvlSNt/kO5E8b6/TYCuql7+U= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Xmh3mKDT; 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="Xmh3mKDT" Received: by smtp.kernel.org (Postfix) with ESMTPS id 88D96C4AF48; Fri, 7 Jun 2024 14:53:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1717771989; bh=hp9z0Ybu/B/EafMmtw/DvgPAfybd4iKKakb+IfmiaR4=; h=From:Date:Subject:References:In-Reply-To:To:Cc:Reply-To:From; b=Xmh3mKDT0G+X19km+rkCG90/RDqvOnUunHeC5kto3FKUfAtVqG6qWnponZL3H8JiZ ceCpt75fsi03lFKJ0eWlinW1Njmvm3so5oUSJXbnHQtzFdA6jH/lqq9llEufG6oqRM ux2aEw+RrqEnH35Uji7+No4F5cF2GWkPaf+Zc5pIwVQiwsGlvjRVT9fj+NSsFcWZDS LrQ9GP/lohambEvKby022DO2G5CYi53B5m9+xuCuBiCOzDyTBTtWroiugYe7JkiYfK 857CXCR/AJKZngjXdHgD+RKS49cCKcFDVvDCLcTNtyN6CjDB95O/CjPkSPTpxrsZUQ bCpqc588lbKeg== 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 7BE06C27C6E; Fri, 7 Jun 2024 14:53:09 +0000 (UTC) From: Dumitru Ceclan via B4 Relay Date: Fri, 07 Jun 2024 17:53:14 +0300 Subject: [PATCH v7 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: <20240607-ad4111-v7-8-97e3855900a0@analog.com> References: <20240607-ad4111-v7-0-97e3855900a0@analog.com> In-Reply-To: <20240607-ad4111-v7-0-97e3855900a0@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 , Nuno Sa X-Mailer: b4 0.13.0 X-Developer-Signature: v=1; a=ed25519-sha256; t=1717771987; l=1661; i=dumitru.ceclan@analog.com; s=20240313; h=from:subject:message-id; bh=mdKO2dnGlcZH90ri/TM/oMJLgoJ91RNSOsEvtEgKDAE=; b=ssITTpfL4Seggrz3KWXnnpHuG9ukbS4R2iLyMYPBuup1yGCnywGRhUXkj/E6iFDtX5Kj6l+gM kol/veezwmSDnCgal8fTjSB7b95rqbYhId/OvQiL7fgoiHv3wejYv9B 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. Reviewed-by: Nuno Sa 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 6ed5b8fed8c0..22dcf89ef3ef 100644 --- a/drivers/iio/adc/ad7173.c +++ b/drivers/iio/adc/ad7173.c @@ -732,6 +732,21 @@ 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++)