linux-kernel - Re: [PATCH v3 1/2] iio: dac: adi-axi-dac: fix bus read

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Message-ID: <20250525144725.4bc9b8ad@jic23-huawei>
Date: Sun, 25 May 2025 14:47:25 +0100
From: Jonathan Cameron <jic23@...nel.org>
To: Angelo Dureghello <adureghello@...libre.com>
Cc: Lars-Peter Clausen <lars@...afoo.de>, Michael Hennerich
 <Michael.Hennerich@...log.com>, Nuno Sa <nuno.sa@...log.com>, David Lechner
 <dlechner@...libre.com>, Andy Shevchenko <andy@...nel.org>, Jonathan
 Cameron <Jonathan.Cameron@...wei.com>, linux-iio@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 1/2] iio: dac: adi-axi-dac: fix bus read

On Fri, 23 May 2025 11:00:51 +0200
Angelo Dureghello <adureghello@...libre.com> wrote:

> From: Angelo Dureghello <adureghello@...libre.com>
> 
> Fix bus read function.
> 
> Testing the driver, on a random basis, wrong reads was detected, mainly
> by a wrong DAC chip ID read at first boot.
> Before reading the expected value from the AXI regmap, need always to
> wait for busy flag to be cleared.
> 
> Fixes: e61d7178429a ("iio: dac: adi-axi-dac: extend features")
> Signed-off-by: Angelo Dureghello <adureghello@...libre.com>
Huh. Seems I never replied to original thread, but I took this a while
back.  Looks unchanged at a quick glance so no problem.

Jonathan


> ---
>  drivers/iio/dac/adi-axi-dac.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/drivers/iio/dac/adi-axi-dac.c b/drivers/iio/dac/adi-axi-dac.c
> index 8ed5ad1fa24cef649056bc5f4ca80abbf28b9323..5ee077c58d7f9730aec8a9c9dff5b84108b3a47e 100644
> --- a/drivers/iio/dac/adi-axi-dac.c
> +++ b/drivers/iio/dac/adi-axi-dac.c
> @@ -760,6 +760,7 @@ static int axi_dac_bus_reg_read(struct iio_backend *back, u32 reg, u32 *val,
>  {
>  	struct axi_dac_state *st = iio_backend_get_priv(back);
>  	int ret;
> +	u32 ival;
>  
>  	guard(mutex)(&st->lock);
>  
> @@ -772,6 +773,13 @@ static int axi_dac_bus_reg_read(struct iio_backend *back, u32 reg, u32 *val,
>  	if (ret)
>  		return ret;
>  
> +	ret = regmap_read_poll_timeout(st->regmap,
> +				AXI_DAC_UI_STATUS_REG, ival,
> +				FIELD_GET(AXI_DAC_UI_STATUS_IF_BUSY, ival) == 0,
> +				10, 100 * KILO);
> +	if (ret)
> +		return ret;
> +
>  	return regmap_read(st->regmap, AXI_DAC_CUSTOM_RD_REG, val);
>  }
>  
>