Re: [PATCH 1/3] i3c: master: Add driver for Synopsys DesignWare IP

Andy Shevchenko
2018-07-21T15:35:33Z

On Fri, Jul 20, 2018 at 11:57 PM, Vitor soares
<Vitor.Soares@synopsys.com> wrote:
> This patch add driver for Synopsys DesignWare IP on top of
> I3C subsystem patchset proposal V6

Some of comments below related to style.
But unaligned helpers I think is good to use.

> +#include <linux/bitops.h>
> +#include <linux/clk.h>
> +#include <linux/completion.h>
> +#include <linux/err.h>
> +#include <linux/errno.h>
> +#include <linux/i3c/master.h>
> +#include <linux/init.h>
> +#include <linux/interrupt.h>
> +#include <linux/io.h>
> +#include <linux/ioport.h>
> +#include <linux/iopoll.h>
> +#include <linux/module.h>
> +#include <linux/platform_device.h>
> +#include <linux/reset.h>

All of them required? Why?

> + default:

Just return false here?

> + break;
> + }
> +
> + return false;

> + for (i = 0; i < nbytes; i += 4) {
> + u32 data = 0;
> +

> + for (j = 0; j < 4 && (i + j) < nbytes; j++)
> + data |= (u32)bytes[i + j] << (j * 8);

NIH of get_unaligned_le32()

> +
> + writel(data, master->regs + RX_TX_DATA_PORT);
> + }
> +}
> +
> +static void dw_i3c_master_read_rx_fifo(struct dw_i3c_master *master,
> + u8 *bytes, int nbytes)
> +{
> + int i, j;
> +
> + for (i = 0; i < nbytes; i += 4) {
> + u32 data;
> +
> + data = readl(master->regs + RX_TX_DATA_PORT);
> +

> + for (j = 0; j < 4 && (i + j) < nbytes; j++)
> + bytes[i + j] = data >> (j * 8);

Ditto put_unaligned_le32() ?

> + }
> +}

I'm wondering what else you open coded instead of using helpers we already have.

> + writel(cmd->cmd_hi, master->regs + COMMAND_QUEUE_PORT);
> + writel(cmd->cmd_lo, master->regs + COMMAND_QUEUE_PORT);

hmm... writesl()?

> + info->pid = (u64)readl(master->regs + SLV_PID_VALUE);

Why explicit casting?

> + u32 r;
> +
> +
> + core_rate = clk_get_rate(master->core_clk);

Too many blank lines in between.

> +
> +

Ditto.

> + /* Prepare DAT before launching DAA. */
> + for (pos = 0; pos < master->maxdevs; pos++) {
> + if (olddevs & BIT(pos))
> + continue;
> +
> + ret = i3c_master_get_free_addr(m, last_addr + 1);
> + if (ret < 0)
> + return -ENOSPC;
> + master->addrs[pos] = ret;

> + p = (ret >> 6) ^ (ret >> 5) ^ (ret >> 4) ^ (ret >> 3) ^
> + (ret >> 2) ^ (ret >> 1) ^ ret ^ 1;
> + p = p & 1;

Is it parity calculus? Do we have something implemented in kernel already?

Btw, https://graphics.stanford.edu/~seander/bithacks.html#ParityNaive
offered this

v ^= v >> 4;
v &= 0xf;
v = (0x6996 >> v) & 1;

--
With Best Regards,
Andy Shevchenko