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[98.183.112.25]) by smtp.gmail.com with ESMTPSA id mo9-20020a056871320900b001dd0ff401edsm545072oac.51.2023.10.05.17.51.05 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 05 Oct 2023 17:51:05 -0700 (PDT) From: David Lechner To: linux-iio@vger.kernel.org, linux-staging@lists.linux.dev Cc: David Lechner , Jonathan Cameron , Michael Hennerich , =?utf-8?q?Nuno_S=C3=A1?= , Axel Haslam , Philip Molloy , linux-kernel@vger.kernel.org Subject: [PATCH v4 01/17] staging: iio: resolver: ad2s1210: do not use fault register for dummy read Date: Thu, 5 Oct 2023 19:50:18 -0500 Message-ID: <20231005-ad2s1210-mainline-v4-1-ec00746840fc@baylibre.com> X-Mailer: git-send-email 2.42.0 In-Reply-To: <20231005-ad2s1210-mainline-v4-0-ec00746840fc@baylibre.com> References: <20231005-ad2s1210-mainline-v4-0-ec00746840fc@baylibre.com> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" X-Mailer: b4 0.12.3 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org When reading registers on the AD2S1210 chip, we have to supply a "dummy" address for the second SPI tx byte so that we don't accidentally write to a register. This register will be read and the value discarded on the next regmap read or write call. Reading the fault register has a side-effect of clearing the faults so we should not use this register for the dummy read. Signed-off-by: David Lechner --- v4 changes: New patch (this probably should have been done before "staging: iio: resolver: ad2s1210: use regmap for config registers" but was overlooked until now) drivers/staging/iio/resolver/ad2s1210.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/drivers/staging/iio/resolver/ad2s1210.c b/drivers/staging/iio/= resolver/ad2s1210.c index 67d8af0dd7ae..8fbde9517fe9 100644 --- a/drivers/staging/iio/resolver/ad2s1210.c +++ b/drivers/staging/iio/resolver/ad2s1210.c @@ -166,9 +166,10 @@ static int ad2s1210_regmap_reg_read(void *context, uns= igned int reg, st->tx[0] =3D reg; /* * Must be valid register address here otherwise this could write data. - * It doesn't matter which one. + * It doesn't matter which one as long as reading doesn't have side- + * effects. */ - st->tx[1] =3D AD2S1210_REG_FAULT; + st->tx[1] =3D AD2S1210_REG_CONTROL; =20 ret =3D spi_sync_transfer(st->sdev, xfers, ARRAY_SIZE(xfers)); if (ret < 0) --=20 2.42.0