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Message-ID: <CAHp75VeNs9Zr1vayO8TwVq6=B8fwvv0chOt0in6Dw+WLCezL2g@mail.gmail.com>
Date: Thu, 30 Jan 2020 18:37:30 +0200
From: Andy Shevchenko <andy.shevchenko@...il.com>
To: Eddie James <eajames@...ux.ibm.com>
Cc: linux-spi <linux-spi@...r.kernel.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Mark Brown <broonie@...nel.org>, Joel Stanley <joel@....id.au>,
Andrew Jeffery <andrew@...id.au>
Subject: Re: [PATCH] spi: Add FSI-attached SPI controller driver
On Wed, Jan 29, 2020 at 10:09 PM Eddie James <eajames@...ux.ibm.com> wrote:
>
> There exists a set of SPI controllers on some POWER processors that may
> be accessed through the FSI bus. Add a driver to traverse the FSI CFAM
> engine that can access and drive the SPI controllers. This driver would
> typically be used by a baseboard management controller (BMC).
...
> +#include <linux/bitfield.h>
> +#include <linux/bits.h>
> +#include <linux/of.h>
...
> +struct fsi_spi {
> + struct device *dev;
Isn't fsl->dev the same?
Perhaps kernel doc to explain the difference?
> + struct fsi_device *fsi;
> + u32 base;
> +};
...
> +static int fsi_spi_read_reg(struct fsi_spi *ctx, u32 offset, u64 *value)
> +{
> + int rc;
> + __be32 cmd_be;
> + __be32 data_be;
> + *value = 0ULL;
Usually the pattern is don't pollute output on error condition. Any
reason why you zeroing output beforehand?
> + cmd_be = cpu_to_be32(offset + ctx->base);
> + rc = fsi_device_write(ctx->fsi, FSI2SPI_CMD, &cmd_be, sizeof(cmd_be));
> + if (rc)
> + return rc;
> + return 0;
> +}
...
> + data_be = cpu_to_be32((value >> 32) & 0xFFFFFFFF);
Redundant & 0xff... part.
> + data_be = cpu_to_be32(value & 0xFFFFFFFF);
Ditto.
You may use upper_32_bits() / lower_32_bits() instead.
...
> +static int fsi_spi_data_in(u64 in, u8 *rx, int len)
> +{
> + int i;
> + int num_bytes = len > 8 ? 8 : len;
min(len, 8);
> + for (i = 0; i < num_bytes; ++i)
> + rx[i] = (u8)((in >> (8 * ((num_bytes - 1) - i))) & 0xffULL);
Redundant & 0xffULL part.
Isn't it NIH of get_unalinged_be64 / le64 or something similar?
> + return num_bytes;
> +}
> +static int fsi_spi_data_out(u64 *out, const u8 *tx, int len)
> +{
Ditto as for above function. (put_unaligned ...)
> +}
...
> + dev_info(ctx->dev, "Resetting SPI controller.\n");
info?! Why?
> + rc = fsi_spi_write_reg(ctx, SPI_FSI_CLOCK_CFG,
> + SPI_FSI_CLOCK_CFG_RESET2);
> + return rc;
return fsi_spi_write_reg();
...
> + return ((64 - seq->bit) / 8) - 2;
Too many parentheses.
...
> +static int fsi_spi_sequence_transfer(struct fsi_spi *ctx,
> + struct fsi_spi_sequence *seq,
> + struct spi_transfer *transfer)
> +{
> + int loops = 1;
> + int idx = 0;
> + int rc;
> + u8 len;
> + u8 rem = 0;
> + if (transfer->len > 8) {
> + loops = transfer->len / 8;
> + rem = transfer->len - (loops * 8);
> + len = 8;
> + } else {
> + len = transfer->len;
> + }
len = min(transfer->len, 8);
loops = transfer->len / len;
rem = transfer->len % len;
(I think compiler is clever enough to find out that the division can be avoided)
...and drop assignments in definition block.
I didn't look carefully in the implementation, but I believe there is
still room for improvement / optimization.
> + if (loops > 1) {
> + rc = fsi_spi_write_reg(ctx, SPI_FSI_COUNTER_CFG,
> + SPI_FSI_COUNTER_CFG_LOOPS(loops - 1));
> + if (rc) {
> + /* Ensure error returns < 0 in this case. */
I didn't get why this case is special? Why not to be consistent with
return value?
> + if (rc > 0)
> + rc = -rc;
> +
> + return rc;
> + }
> + return loops;
If we return here the amount of loops...
> + }
> +
> + return 0;
...why here is 0?
I think more consistency is required.
> +}
...
> +static int fsi_spi_transfer_data(struct fsi_spi *ctx,
> + struct spi_transfer *transfer)
> +{
Can you refactor to tx and rx parts?
> + return 0;
> +}
...
> + do {
> + rc = fsi_spi_read_reg(ctx, SPI_FSI_STATUS, &status);
> + if (rc)
> + return rc;
> +
> + if (status & (SPI_FSI_STATUS_ANY_ERROR |
> + SPI_FSI_STATUS_TDR_FULL |
> + SPI_FSI_STATUS_RDR_FULL)) {
> + rc = fsi_spi_reset(ctx);
> + if (rc)
> + return rc;
> +
> + continue;
I forgot if this to be infinite loop or if it's going to check
previous seq_state value. In any case this code is a bit fishy. Needs
comments / refactoring.
> + }
> +
> + seq_state = status & SPI_FSI_STATUS_SEQ_STATE;
> + } while (seq_state && (seq_state != SPI_FSI_STATUS_SEQ_STATE_IDLE));
...
> + if ((clock_cfg & (SPI_FSI_CLOCK_CFG_MM_ENABLE |
> + SPI_FSI_CLOCK_CFG_ECC_DISABLE |
> + SPI_FSI_CLOCK_CFG_MODE |
> + SPI_FSI_CLOCK_CFG_SCK_RECV_DEL |
> + SPI_FSI_CLOCK_CFG_SCK_DIV)) != wanted_clock_cfg)
> + rc = fsi_spi_write_reg(ctx, SPI_FSI_CLOCK_CFG,
> + wanted_clock_cfg);
Missed {} ?
> +
> + return rc;
> +}
...
> + rc = fsi_slave_read(fsi->slave, 0x2860, &root_ctrl_8,
What is this magic for?
> + sizeof(root_ctrl_8));
> + if (rc)
> + return rc;
...
> +static int fsi_spi_remove(struct device *dev)
> +{
> + return 0;
> +}
Why do you need this?
...
> +static struct fsi_driver fsi_spi_driver = {
> + .id_table = fsi_spi_ids,
> + .drv = {
> + .name = "spi-fsi",
> + .bus = &fsi_bus_type,
Why is it not in the module_fsi_driver() macro?
> + .probe = fsi_spi_probe,
> + .remove = fsi_spi_remove,
> + },
> +};
> +
> +module_fsi_driver(fsi_spi_driver);
--
With Best Regards,
Andy Shevchenko
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