linux-kernel - Re: [PATCH 1/1] spi: altera: Change to dynamic allocation of spi id

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Date:   Mon, 18 Oct 2021 17:27:38 -0700
From:   Russ Weight <russell.h.weight@...el.com>
To:     <broonie@...nel.org>, <linux-spi@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
CC:     <trix@...hat.com>, <lgoncalv@...hat.com>, <yilun.xu@...el.com>,
        <hao.wu@...el.com>, <matthew.gerlach@...el.com>
Subject: Re: [PATCH 1/1] spi: altera: Change to dynamic allocation of spi id

If there are no concerns with this patch, it will need to have the "cc stable"
tag added for earlier kernels.

I don't think it needs a "Fixes" tag, as the problem has been there since the
driver was introduced.

Thanks,
- Russ

On 10/18/21 5:24 PM, Russ Weight wrote:
> The spi-altera driver has two flavors: platform and dfl. I'm seeing
> a case where I have both device types in the same machine, and they
> are conflicting on the SPI ID:
>
> ... kernel: couldn't get idr
> ... kernel: WARNING: CPU: 28 PID: 912 at drivers/spi/spi.c:2920 spi_register_controller.cold+0x84/0xc0a
>
> Both the platform and dfl drivers use the parent's driver ID as the SPI
> ID. In the error case, the parent devices are dfl_dev.4 and
> subdev_spi_altera.4.auto. When the second spi-master is created, the
> failure occurs because the SPI ID of 4 has already been allocated.
>
> Change the ID allocation to dynamic (by initializing bus_num to -1) to
> avoid duplicate SPI IDs.
>
> Signed-off-by: Russ Weight <russell.h.weight@...el.com>
> ---
>  drivers/spi/spi-altera-dfl.c      | 2 +-
>  drivers/spi/spi-altera-platform.c | 2 +-
>  2 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/spi/spi-altera-dfl.c b/drivers/spi/spi-altera-dfl.c
> index 44fc9ee13fc7..ca40923258af 100644
> --- a/drivers/spi/spi-altera-dfl.c
> +++ b/drivers/spi/spi-altera-dfl.c
> @@ -134,7 +134,7 @@ static int dfl_spi_altera_probe(struct dfl_device *dfl_dev)
>  	if (!master)
>  		return -ENOMEM;
>  
> -	master->bus_num = dfl_dev->id;
> +	master->bus_num = -1;
>  
>  	hw = spi_master_get_devdata(master);
>  
> diff --git a/drivers/spi/spi-altera-platform.c b/drivers/spi/spi-altera-platform.c
> index f7a7c14e3679..65147aae82a1 100644
> --- a/drivers/spi/spi-altera-platform.c
> +++ b/drivers/spi/spi-altera-platform.c
> @@ -48,7 +48,7 @@ static int altera_spi_probe(struct platform_device *pdev)
>  		return err;
>  
>  	/* setup the master state. */
> -	master->bus_num = pdev->id;
> +	master->bus_num = -1;
>  
>  	if (pdata) {
>  		if (pdata->num_chipselect > ALTERA_SPI_MAX_CS) {