Thanks for the feedback! Some replies and follow-up comments below. On Tue, Dec 28, 2021 at 05:15:25PM +0100, Ulf Hansson wrote: > On Wed, 15 Dec 2021 at 14:09, Gabriel Somlo <gsomlo@xxxxxxxxx> wrote: > > > > LiteX (https://github.com/enjoy-digital/litex) is a SoC framework > > that targets FPGAs. LiteSDCard is a small footprint, configurable > > SDCard core commonly used in LiteX designs. > > > > The driver was first written in May 2020 and has been maintained > > cooperatively by the LiteX community. Thanks to all contributors! > > > > Co-developed-by: Kamil Rakoczy <krakoczy@xxxxxxxxxxxx> > > Signed-off-by: Kamil Rakoczy <krakoczy@xxxxxxxxxxxx> > > Co-developed-by: Maciej Dudek <mdudek@xxxxxxxxxxxxxxxxxxxxxxxx> > > Signed-off-by: Maciej Dudek <mdudek@xxxxxxxxxxxxxxxxxxxxxxxx> > > Co-developed-by: Paul Mackerras <paulus@xxxxxxxxxx> > > Signed-off-by: Paul Mackerras <paulus@xxxxxxxxxx> > > Signed-off-by: Gabriel Somlo <gsomlo@xxxxxxxxx> > > Cc: Mateusz Holenko <mholenko@xxxxxxxxxxxx> > > Cc: Karol Gugala <kgugala@xxxxxxxxxxxx> > > Cc: Joel Stanley <joel@xxxxxxxxx> > > Cc: Stafford Horne <shorne@xxxxxxxxx> > > Cc: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx> > > Cc: David Abdurachmanov <david.abdurachmanov@xxxxxxxxxx> > > Cc: Florent Kermarrec <florent@xxxxxxxxxxxxxxxx> > > Reviewed-by: Joel Stanley <joel@xxxxxxxxx> > > [...] > > > + > > +static int litex_mmc_set_bus_width(struct litex_mmc_host *host) > > +{ > > + bool app_cmd_sent; > > + int ret; > > + > > + if (host->is_bus_width_set) > > + return 0; > > + > > + /* ensure 'app_cmd' precedes 'app_set_bus_width_cmd' */ > > + app_cmd_sent = host->app_cmd; /* was preceding command app_cmd? */ > > + if (!app_cmd_sent) { > > + ret = litex_mmc_send_app_cmd(host); > > + if (ret) > > + return ret; > > + } > > + > > + /* litesdcard only supports 4-bit bus width */ > > + ret = litex_mmc_send_set_bus_w_cmd(host, MMC_BUS_WIDTH_4); > > + if (ret) > > + return ret; > > + > > + /* re-send 'app_cmd' if necessary */ > > + if (app_cmd_sent) { > > + ret = litex_mmc_send_app_cmd(host); > > + if (ret) > > + return ret; > > + } > > I understand that you are trying to address the limitation that the > controller supports 4-bit width only. In principle it looks like we > may need to violate the SD spec to be able to initialise an SD card, > right? Isn't that a concern for you? This would only be a concern for SDcard media that do not support 4-bit wide data transfer (if any such models even/still exist!). This driver simply forces 4-bit wide data mode as soon as the very first data transfer is "snooped", which is AFAICT legal w.r.t. the spec. If the card does not support 4-bit wide data transfers, then litex_mmc_set_bus_width() will fail, and the card will fail to initialize, but I don't foresee much of anything else going wrong. > > + > > + host->is_bus_width_set = true; > > + > > + return 0; > > +} > > [...] > > > + > > +static void litex_mmc_request(struct mmc_host *mmc, struct mmc_request *mrq) > > +{ > > + struct litex_mmc_host *host = mmc_priv(mmc); > > + struct device *dev = mmc_dev(mmc); > > + struct mmc_command *cmd = mrq->cmd; > > + struct mmc_command *sbc = mrq->sbc; > > + struct mmc_data *data = mrq->data; > > + struct mmc_command *stop = mrq->stop; > > + unsigned int retries = cmd->retries; > > + unsigned int len = 0; > > + bool direct = false; > > + u32 response_len = litex_mmc_response_len(cmd); > > + u8 transfer = SD_CTL_DATA_XFER_NONE; > > + > > + /* First check that the card is still there */ > > + if (!litex_mmc_get_cd(mmc)) { > > + cmd->error = -ENOMEDIUM; > > + mmc_request_done(mmc, mrq); > > + return; > > + } > > + > > + /* Send set-block-count command if needed */ > > + if (sbc) { > > + sbc->error = litex_mmc_send_cmd(host, sbc->opcode, sbc->arg, > > + litex_mmc_response_len(sbc), > > + SD_CTL_DATA_XFER_NONE); > > + if (sbc->error) { > > + host->is_bus_width_set = false; > > + mmc_request_done(mmc, mrq); > > + return; > > + } > > + } > > + > > + if (data) { > > + /* LiteSDCard only supports 4-bit bus width; therefore, we MUST > > + * inject a SET_BUS_WIDTH (acmd6) before the very first data > > + * transfer, earlier than when the mmc subsystem would normally > > + * get around to it! > > This means that you may end up trying to switch bus-width, to a width > that isn't supported by the card, for example. > > As also stated above, I wonder how this conforms to the SD spec from > the initialization sequence point of view. Have you verified that this > isn't a problem? During litex_mmc_probe(), I have: ... ret = mmc_of_parse(mmc); if (ret) goto err; /* force 4-bit bus_width (only width supported by hardware) */ mmc->caps &= ~MMC_CAP_8_BIT_DATA; mmc->caps |= MMC_CAP_4_BIT_DATA; ... This ensures no bus-width switches to anything other than 4-bit data should ever occur. As far as I understand the SDcard spec, it's legal to both send multiple redundant bus-width-set commands, and to start doing so before the very first data transfer request is processed (regardless of the fact that linux typically does a few 1-bit-wide data transfers during card initialization before switching to a wider mode, if available). This driver simply ensures that any time we ever have a data transfer, the bus width is set to 4 *before* said transfer is acted upon. As I mentioned earlier, if we get a "weird" SDcard that can't support 4-bit data transfers, its initialization should fail shortly after detection, and that's all there is to it, as far as I can tell. > > + */ > > + cmd->error = litex_mmc_set_bus_width(host); > > + if (cmd->error) { > > + dev_err(dev, "Can't set bus width!\n"); > > + mmc_request_done(mmc, mrq); > > + return; > > + } > > + > > + litex_mmc_do_dma(host, data, &len, &direct, &transfer); > > + } > > + > > + do { > > + cmd->error = litex_mmc_send_cmd(host, cmd->opcode, cmd->arg, > > + response_len, transfer); > > + } while (cmd->error && retries-- > 0); > > + > > + if (cmd->error) { > > + /* card may be gone; don't assume bus width is still set */ > > + host->is_bus_width_set = false; > > + } > > + > > + if (response_len == SD_CTL_RESP_SHORT) { > > + /* pull short response fields from appropriate host registers */ > > + cmd->resp[0] = host->resp[3]; > > + cmd->resp[1] = host->resp[2] & 0xFF; > > + } else if (response_len == SD_CTL_RESP_LONG) { > > + cmd->resp[0] = host->resp[0]; > > + cmd->resp[1] = host->resp[1]; > > + cmd->resp[2] = host->resp[2]; > > + cmd->resp[3] = host->resp[3]; > > + } > > + > > + /* Send stop-transmission command if required */ > > + if (stop && (cmd->error || !sbc)) { > > + stop->error = litex_mmc_send_cmd(host, stop->opcode, stop->arg, > > + litex_mmc_response_len(stop), > > + SD_CTL_DATA_XFER_NONE); > > + if (stop->error) > > + host->is_bus_width_set = false; > > + } > > + > > + if (data) { > > + dma_unmap_sg(dev, data->sg, data->sg_len, > > + mmc_get_dma_dir(data)); > > + } > > + > > + if (!cmd->error && transfer != SD_CTL_DATA_XFER_NONE) { > > + data->bytes_xfered = min(len, mmc->max_req_size); > > + if (transfer == SD_CTL_DATA_XFER_READ && !direct) { > > + sg_copy_from_buffer(data->sg, sg_nents(data->sg), > > + host->buffer, data->bytes_xfered); > > + } > > + } > > + > > + mmc_request_done(mmc, mrq); > > +} > > + > > [...] > > > + > > + mmc->ocr_avail = MMC_VDD_32_33 | MMC_VDD_33_34; > > I noticed that you use these hard coded values and don't really care > to manage voltage changes via ->set_ios(). > > Rather than doing it like this, I would prefer if you can hook up a > fixed vmmc regulator in the DTS. Then call mmc_regulator_get_supply() > to fetch it from here, which will let the mmc core create the > mmc->ocr_avail mask, based upon the voltage level the regulator > supports. > > This becomes more generic and allows more flexibility for the platform > configuration. The LiteSDCard "hardware" (i.e., *gateware*) does not allow modification or selection of voltage from the software side. When a CMD8 is issued, the "voltage supplied" bit pattern is expected to be '0001b', which per the spec means "2.7-3.6V". I tried adding this to the overall DTS: vreg_mmc: vreg_mmc_3v { compatible = "regulator-fixed"; regulator-min-microvolt = <3300000>; regulator-max-microvolt = <3300000>; }; and then added a reference to it to the LiteSDCard "mmc0" node in DTS, like so: mmc0: mmc@12005000 { compatible = "litex,mmc"; reg = <0x12005000 0x100>, <0x12003800 0x100>, <0x12003000 0x100>, <0x12004800 0x100>, <0x12004000 0x100>; reg-names = "phy", "core", "reader", "writer", "irq"; clocks = <&sys_clk>; vmmc-supply = <&vreg_mmc>; /* <-------- HERE !!! */ interrupt-parent = <&L1>; interrupts = <4>; }; Finally, I replaced the hardcoded setting of `mmc->ocr_avail` with a call to `mmc_regulator_get_supply(mmc)`. Now, I get a bunch of timeouts during attempts to send e.g., CMD8 and CMD55. (going for 3200000 and 3400000 for min- and max-microvolt, respectively, -- or anything else in the allowed 2.7-3.6 range -- doesn't help either). I might be doing something subtly wrong in the way I set things up above, but it feels a bit overengineered, and IMHO fragile. OTOH, going all out and setting: /* allow for generic 2.7-3.6V range, no software tuning available */ mmc->ocr_avail = MMC_VDD_27_28 | MMC_VDD_28_29 | MMC_VDD_29_30 | MMC_VDD_30_31 | MMC_VDD_31_32 | MMC_VDD_32_33 | MMC_VDD_33_34 | MMC_VDD_34_35 | MMC_VDD_35_36; seems to work just fine... :) Please do let me know what you think! > > + mmc->ops = &litex_mmc_ops; > > + > > + /* set default sd_clk frequency range based on empirical observations > > + * of LiteSDCard gateware behavior on typical SDCard media > > + */ > > + mmc->f_min = 12.5e6; > > + mmc->f_max = 50e6; > > + > > + ret = mmc_of_parse(mmc); > > + if (ret) > > + goto err; > > + > > + /* force 4-bit bus_width (only width supported by hardware) */ > > + mmc->caps &= ~MMC_CAP_8_BIT_DATA; > > + mmc->caps |= MMC_CAP_4_BIT_DATA; > > + > > + /* set default capabilities */ > > + mmc->caps |= MMC_CAP_WAIT_WHILE_BUSY | > > + MMC_CAP_DRIVER_TYPE_D | > > + MMC_CAP_CMD23; > > + mmc->caps2 |= MMC_CAP2_NO_WRITE_PROTECT | > > + MMC_CAP2_FULL_PWR_CYCLE | > > A full power cycle requires you to be able to power on/off the vmmc > regulator (unless this is internally managed by the controller). Can > you really do that? Nope, I cannot -- so I removed MMC_CAP2_FULL_PWR_CYCLE from the list, should be there in v6 of the series. Thanks for pointing that out! > > + MMC_CAP2_NO_SDIO; > > We should add MMC_CAP2_NO_MMC here as well, as it looks like it can't > be supported. Right? Right, and done -- lined up for v6. > > + > > + platform_set_drvdata(pdev, host); > > + > > + ret = mmc_add_host(mmc); > > + if (ret < 0) > > + goto err; > > + > > + return 0; > > + > > +err: > > + mmc_free_host(mmc); > > + return ret; > > +} > > + > > +static int litex_mmc_remove(struct platform_device *pdev) > > +{ > > + struct litex_mmc_host *host = dev_get_drvdata(&pdev->dev); > > + > > + if (host->irq > 0) > > + free_irq(host->irq, host->mmc); > > + mmc_remove_host(host->mmc); > > + mmc_free_host(host->mmc); > > + > > + return 0; > > +} > > + > > +static const struct of_device_id litex_match[] = { > > + { .compatible = "litex,mmc" }, > > + { } > > +}; > > +MODULE_DEVICE_TABLE(of, litex_match); > > + > > +static struct platform_driver litex_mmc_driver = { > > + .probe = litex_mmc_probe, > > + .remove = litex_mmc_remove, > > + .driver = { > > + .name = "litex-mmc", > > + .of_match_table = of_match_ptr(litex_match), > > + }, > > +}; > > +module_platform_driver(litex_mmc_driver); > > + > > +MODULE_DESCRIPTION("LiteX SDCard driver"); > > +MODULE_AUTHOR("Antmicro <contact@xxxxxxxxxxxx>"); > > +MODULE_AUTHOR("Kamil Rakoczy <krakoczy@xxxxxxxxxxxx>"); > > +MODULE_AUTHOR("Maciej Dudek <mdudek@xxxxxxxxxxxxxxxxxxxxxxxx>"); > > +MODULE_AUTHOR("Paul Mackerras <paulus@xxxxxxxxxx>"); > > +MODULE_AUTHOR("Gabriel Somlo <gsomlo@xxxxxxxxx>"); > > +MODULE_LICENSE("GPL v2"); > > -- > > Other than the comments above, the code looks nice and was easy to > review, thanks! Thanks again for the review, and please LMK about the voltage regulator question. Happy New Year, --Gabriel
