From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eddie James Subject: Re: [PATCH] spi: Add FSI-attached SPI controller driver Date: Mon, 3 Feb 2020 14:33:11 -0600 Message-ID: <29f6cc86-69ca-bc88-b6ae-2b1a24c0dae3@linux.vnet.ibm.com> References: <1580328504-436-1-git-send-email-eajames@linux.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Cc: linux-spi , Linux Kernel Mailing List , Mark Brown , Joel Stanley , Andrew Jeffery To: Andy Shevchenko , Eddie James Return-path: In-Reply-To: Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-spi.vger.kernel.org On 1/30/20 10:37 AM, Andy Shevchenko wrote: > On Wed, Jan 29, 2020 at 10:09 PM Eddie James 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 >> +#include >> +#include > ... > >> +struct fsi_spi { >> + struct device *dev; > Isn't fsl->dev the same? > Perhaps kernel doc to explain the difference? No, it's not the same, as dev here is the SPI controller. I'll add a comment. > >> + 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? Well otherwise I have to store another 64 bit int and do another assignment at the end. This is an internal function and all the users below know what's happening. > >> + 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. OK, thanks. > > ... > >> +static int fsi_spi_data_in(u64 in, u8 *rx, int len) >> +{ >> + int i; >> + int num_bytes = len > 8 ? 8 : len; > min(len, 8); Sure. > >> + 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? No, these are shift in/out operations. The read register will also have previous operations data in them and must be extracted with only the correct number of bytes. > >> + 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. I prefer using 2 extra characters to make it much clearer at a glance. > > ... > >> +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; Sure. > > (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? Sure, will fix, this was leftover from some testing. > >> + 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. Will refactor. > >> +} > ... > >> +static int fsi_spi_transfer_data(struct fsi_spi *ctx, >> + struct spi_transfer *transfer) >> +{ > Can you refactor to tx and rx parts? Why? > >> + 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. I'll add a timeout. > >> + } >> + >> + 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 {} ? No? It's one line under the if. > >> + >> + return rc; >> +} > ... > >> + rc = fsi_slave_read(fsi->slave, 0x2860, &root_ctrl_8, > What is this magic for? Added comment. > >> + sizeof(root_ctrl_8)); >> + if (rc) >> + return rc; > ... > >> +static int fsi_spi_remove(struct device *dev) >> +{ >> + return 0; >> +} > Why do you need this? Will drop it. Thanks for the review! Eddie > > ... > >> +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);