linux-kernel - Re: [PATCH v14 8/8] soc: amd: Add support for AMD Pensando SoC Controller

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Date:   Tue, 16 May 2023 00:05:32 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Brad Larson <blarson@....com>
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-mmc@...r.kernel.org, linux-spi@...r.kernel.org,
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Subject: Re: [PATCH v14 8/8] soc: amd: Add support for AMD Pensando SoC Controller

On Mon, May 15, 2023 at 9:18 PM Brad Larson <blarson@....com> wrote:
>
> The Pensando SoC controller is a SPI connected companion device
> that is present in all Pensando SoC board designs.  The essential
> board management registers are accessed on chip select 0 with
> board mgmt IO support accessed using additional chip selects.

...

> +#include <linux/cdev.h>
> +#include <linux/device.h>
> +#include <linux/err.h>
> +#include <linux/init.h>
> +#include <linux/mod_devicetable.h>
> +#include <linux/module.h>
> +#include <linux/mutex.h>

> +#include <linux/of.h>

Unneeded inclusion.

> +#include <linux/reset-controller.h>
> +#include <linux/spi/spi.h>

...


> +       u8 tx_buf[PENCTRL_MAX_MSG_LEN];
> +       u8 rx_buf[PENCTRL_MAX_MSG_LEN];

Does it need to be DMA-capable?

...

> +       spi->chip_select = current_cs;
> +       spi->cs_gpiod = spi->controller->cs_gpiods[current_cs];

Nowadays these require API calls instead of direct assignments.

...

> +static int penctrl_release(struct inode *inode, struct file *filp)
> +{
> +       filp->private_data = NULL;
> +       return 0;
> +}

Is it possible to unload the module without releasing the device node?

...

> +       u8 txbuf[3];
> +       u8 rxbuf[1];

Same question about DMA.

...

> +       ret = spi_sync(spi, &m);

> +       if (ret == 0)
> +               *val = rxbuf[0];
> +
> +       return ret;

Can also be written in more usual way:

  if (ret)
    return ret;
  ...
  return 0;

...

> +       u8 txbuf[4];

DMA?

...

> +       spi->chip_select = 0;
> +       spi->cs_gpiod = spi->controller->cs_gpiods[0];

Setter APIs.

...

> +       spi->chip_select = 0;
> +       spi->cs_gpiod = spi->controller->cs_gpiods[0];

Ditto.


> +       ret = device_property_read_u32(spi->dev.parent, "num-cs", &num_cs);
> +       if (ret)
> +               return dev_err_probe(&spi->dev, ret,
> +                                    "number of chip-selects not defined\n");

Hmm... Shouldn't SPI core take care of this in a generic way? Yes, I
understand that you need the number for the allocation, but I would
expect something like spi_fw_get_num_cs() to exist (seems not?).

...

> +       penctrl->rcdev.of_node = spi->dev.of_node;

Use device_set_node(). It helps to modify the data types beneath.

--
With Best Regards,
Andy Shevchenko