Re: [PATCH v2 2/2] spi: add SPI controller driver for UniPhier SoC

[Radu Pirea]

On 07/26/2018 12:38 PM, Keiji Hayashibara wrote:
> Hello Andy,
>
> Thank you for your check!
>
>
> > From: Andy Shevchenko [mailto:andy.shevchenko@xxxxxxxxx]
> > Sent: Thursday, July 26, 2018 5:46 PM
> > To: Hayashibara, Keiji/æå åä <hayashibara.keiji@xxxxxxxxxxxxx>
> > Subject: Re: [PATCH v2 2/2] spi: add SPI controller driver for UniPhier SoC
> >
> > On Thu, Jul 26, 2018 at 10:09 AM, Keiji Hayashibara <hayashibara.keiji@xxxxxxxxxxxxx> wrote:
> > > Add SPI controller driver implemented in Socionext UniPhier SoCs.
> > >
> > > UniPhier SoCs have two types SPI controllers; SCSSI supports a single
> > > channel, and MCSSI supports multiple channels.
> > > This driver supports SCSSI only.
> > >
> > > This controller has 32bit TX/RX FIFO with depth of eight entry, and
> > > supports the SPI master mode only.
> > >
> > > This commit is implemented in PIO transfer mode, not DMA transfer.
> >
> > Few style realted comments.
> >
> > > +#include <asm/unaligned.h>
> > > +#include <linux/kernel.h>
> > > +#include <linux/bitfield.h>
> > > +#include <linux/bitops.h>
> > > +#include <linux/clk.h>
> > > +#include <linux/interrupt.h>
> > > +#include <linux/io.h>
> > > +#include <linux/module.h>
> > > +#include <linux/of.h>
> > > +#include <linux/of_platform.h>
> > > +#include <linux/platform_device.h>
> > > +#include <linux/spi/spi.h>
> >
> > Slightly better to keep them in order and put asm/* at the last.
>
> I see. I will modify this.
>
>
> > > +#define SSI_TIMEOUT            2000    /* ms */
> >
> > SSI_TIMEOUT_MS ?
> >
> > > +#define SSI_CTL                        0x0
> >
> > Slightly better to keep same width for the addresses, like 0x00 here.
> >
> > > +#define SSI_CKS                        0x4
> >
> > > +#define SSI_TXWDS              0x8
> >
> > > +#define SSI_RXWDS              0xc
> >
> > Ditto.
>
> I will modify about above.
>
> > > +static int uniphier_spi_set_baudrate(struct spi_device *spi, unsigned
> > > +int speed) {
> > > +       struct uniphier_spi_priv *priv = spi_master_get_devdata(spi->master);
> > > +       u32 val, ckrat;
> > > +
> > > +       /*
> > > +        * the supported rates are even numbers from 4 to 254. (4,6,8...254)
> > > +        * round up as we look for equal or less speed
> > > +        */
> > > +       ckrat = DIV_ROUND_UP(clk_get_rate(priv->clk), speed);
> >
> > > +       ckrat = roundup(ckrat, 2);
> >
> > ckrat += ckrat & 1;
> >
> > ?
>
> It's simple. I will modify.
>
>
> > > +       /* check if requested speed is too small */
> > > +       if (ckrat > SSI_MAX_CLK_DIVIDER)
> >
> > > +               return -EINVAL;
> >
> > So, does this critical?
>
> If set the value to SSI_MAX_CLK_DIVIDER, the clock frequency will be set high.
> I don't change it to high frequency, and it is daringly an error.
> On the other hand, when changing to low frequency, I will change it automatically.
>
> > > +
> > > +       if (ckrat < SSI_MIN_CLK_DIVIDER)
> > > +               ckrat = SSI_MIN_CLK_DIVIDER;

In fact you don't need this checks. You already set in probe function this.
master->max_speed_hz = DIV_ROUND_UP(clksrc, SSI_MIN_CLK_DIVIDER);
master->min_speed_hz = DIV_ROUND_UP(clksrc, SSI_MAX_CLK_DIVIDER);

The SPI core will check if transfer speed is higher than controller 
speed and if is, will set the transfer speed to master->max_speed_hz. In 
case of master->min_speed_hz, if transfer speed is lower than 
master->min_speed_hz __spi_validate(drivers/spi/spi.c) will return -EINVAL.

> > clamp_val()  / max() ?
>
> I will modify it to use max().
>
> > > +       val = readl(priv->base + SSI_CKS);
> > > +       val &= ~SSI_CKS_CKRAT_MASK;
> > > +       val |= ckrat & SSI_CKS_CKRAT_MASK;
> > > +       writel(val, priv->base + SSI_CKS);
> > > +
> > > +       return 0;
> > > +}
> >
> > > +       priv->irq = platform_get_irq(pdev, 0);
> > > +       if (priv->irq < 0) {
> > > +               dev_err(&pdev->dev, "failed to get IRQ\n");
> >
> > > +               ret = -ENXIO;
> >
> > What's wrong with
> >
> > ret = priv->irq;
> >
> > ?
>
> I will modify it.
>
> > > +               goto out_disable_clk;
> > > +       }
> >
> > > +static const struct of_device_id uniphier_spi_match[] = {
> > > +       { .compatible = "socionext,uniphier-scssi", },
> >
> > > +       { /* sentinel */ },
> >
> > Slightly better without comma.
>
> OK. I will modify this.
>
> -----------------
> Best Regards,
> Keiji Hayashibara
>
>
>
> > > +};
> > > +MODULE_DEVICE_TABLE(of, uniphier_spi_match);
> >
> > --
> > With Best Regards,
> > Andy Shevchenko
>
>
> --
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