Re: [PATCH v11 3/3] mmc: Add driver for LiteX's LiteSDCard interface

Gabriel L. Somlo
2022-01-10T22:15:33Z

On Tue, Jan 11, 2022 at 07:07:47AM +0900, Stafford Horne wrote:
> On Sun, Jan 09, 2022 at 06:20:03PM -0500, Gabriel Somlo 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@antmicro.com>
> > Signed-off-by: Kamil Rakoczy <krakoczy@antmicro.com>
> > Co-developed-by: Maciej Dudek <mdudek@internships.antmicro.com>
> > Signed-off-by: Maciej Dudek <mdudek@internships.antmicro.com>
> > Co-developed-by: Paul Mackerras <paulus@ozlabs.org>
> > Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
> > Signed-off-by: Gabriel Somlo <gsomlo@gmail.com>
> > Reviewed-by: Joel Stanley <joel@jms.id.au>
> > Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
> > ---
> >
> > New in v11:
> > - picked up r/b from Andy
> > drivers/mmc/host/litex_mmc.c:
> > - defensive coding of litex_mmc_interrupt() return logic
> > - remove `dev` member of `struct litex_mmc_host`, only used during probe
> >
> > >New in v10:
> > >drivers/mmc/host/litex_mmc.c:
> > > - group `linux/mmc/*` includes by themselves
> > > - clean-up of `return` style (multiple locations throughout source)
> > > - create `mmc_free_host()` wrapper for use with
> > > `devm_add_action_or_reset()`
> > > - use GFP_KERNEL with `dmam_alloc_coherent()`
> > >
> > >>New in v9:
> > >>drivers/mmc/host/Kconfig:
> > >> - fix OF dependency
> > >>drivers/mmc/host/litex_mmc.c:
> > >> - remove `linux/of.h` include, no longer needed since dropping
> > >> `of_match_ptr()`
> > >> - add `linux/mod_devicetable.h` include
> > >> - use devm_action_or_reset() to devm-ify mmc_alloc_host(), and obviate
> > >> the need to call mmc_free_host() explicitly during either probe()
> > >> error path or during remove()
> > >>
> > >>>New in v8:
> > >>> - remove `Cc:` lines from commit blurb
> > >>>drivers/mmc/host/litex_mmc.c:
> > >>> - fix file header comment (for real, this time)
> > >>> - add explicit `bits.h` include
> > >>> - remove `of_match_ptr()` wrapper from around .of_match_table argument
> > >>> - fix devm ordering issues: use `devm_request_irq()`, which precludes
> > >>> the need to call `free_irq()` on `probe()` error path or from `remove()`
> > >>>
> > >>>>New in v7:
> > >>>>drivers/mmc/host/Kconfig:
> > >>>> - added module name in LiteSDCard Kconfig entry
> > >>>>drivers/mmc/host/litex_mmc.c:
> > >>>> - fixed comment formatting, ordering, and capitalization throughout
> > >>>> the entire file
> > >>>> - sorted header #include statements
> > >>>> - removed redundant parantheses in readx_poll_timeout() condition
> > >>>> - explicit handling of readx_poll_timeout() timeout scenarios
> > >>>> - dev_err() used in litex_mmc_sdcard_wait_done()
> > >>>> - use memcpy_fromio() to grab command response
> > >>>> - no need to apply 0xffff mask to a 32-bit value right-shifted by 16
> > >>>> (host->resp[3])
> > >>>> - use clamp() instead of min(max(...)...)
> > >>>> - reworked platform_get_irq_optional() error handling logic
> > >>>> - no need to explicitly zero host->irq, kzalloc() does that already
> > >>>> - added missing free_irq() in litex_mmc_probe() error path
> > >>>> - reordered calls inside litex_mmc_remove() (calling mmc_free_host()
> > >>>> before free_irq()
> > >>>>
> > >>>>>New in v6:
> > >>>>> - fix handling of deferred probe vs. platform_get_irq_optional()
> > >>>>> - don't #ifdef dma_set_mask_and_coherent(), since it automatically
> > >>>>> does the right thing on both 32- and 64-bit DMA capable arches
> > >>>>> - remove MMC_CAP2_FULL_PWR_CYCLE, add MMC_CAP2_NO_MMC to list of
> > >>>>> hardcoded capabilities during litex_mmc_probe()
> > >>>>> - hardcode mmc->ocr_avail to the full 2.7-3.6V range allowed by the
> > >>>>> SDCard spec (the LiteSDCard device doesn't accept software
> > >>>>> configuration)
> > >>>>>
> > >>>>>>New in v5:
> > >>>>>> - shorter #define constant names (cosmetic, make them less unwieldy)
> > >>>>>> - picked up reviewed-by Joel
> > >>>>>>
> > >>>>>>>New in v4:
> > >>>>>>> - struct litex_mmc_host fields re-ordered so that `pahole` reports
> > >>>>>>> no holes on either 32- or 64-bit builds
> > >>>>>>> - litex_mmc_set_bus_width() now encapsulates check for
> > >>>>>>> host->is_bus_width_set
> > >>>>>>> - litex_mmc_request() - factor out dma data setup into separate
> > >>>>>>> helper function: litex_mmc_do_dma()
> > >>>>>>>
> > >>>>>>>> New in v3:
> > >>>>>>>> - fixed function signature (no line split), and naming (litex_mmc_*)
> > >>>>>>>> - more informative MODULE_AUTHOR() entries
> > >>>>>>>> - also added matching "Copyright" entries in file header
> > >>>>>>>> - fixed description and dependencies in Kconfig
> > >>>>>>>> - removed magic constants
> > >>>>>>>> - removed litex_map_status(), have sdcard_wait_done() return *real*
> > >>>>>>>> error codes directly instead.
> > >>>>>>>> - streamlined litex_mmc_reponse_len()
> > >>>>>>>> - call litex_mmc_set_bus_width() only once, and ensure it returns
> > >>>>>>>> correct error code(s)
> > >>>>>>>> - use readx_poll_timeout() -- more concise -- instead of
> > >>>>>>>> read_poll_timeout()
> > >>>>>>>> - use dev_err() in litex_mmc_send_cmd() (instead of pr_err())
> > >>>>>>>> - litex_mmc_setclk() will update host->clock before returning
> > >>>>>>>> - separate irq initialization into its own function,
> > >>>>>>>> litex_mmc_irq_init()
> > >>>>>>>> - document rationale for f_min, f_max
> > >>>>>>>> - use dmam_alloc_coherent(), which simplifies cleanup significantly
> > >>>>>>>> - bump dma_set_mask_and_coherent() to 64-bits on suitable
> > >>>>>>>> architectures
> > >>>>>>>> - clock source picked up from dedicated DT clock reference property
> > >>>>>>>> - remove gpio card-detect logic (needs testing and a dt binding
> > >>>>>>>> example before being eligible for upstream inclusion)
> > >>>>>>>> - large `if (data) { ... }` block in litex_mmc_request() left as-is,
> > >>>>>>>> there are too many variables shared with the rest of the parent
> > >>>>>>>> function body to easily separate (e.g., `len`, `transfer`, `direct`).
> > >>>>>>>> If this is indeed a blocker, I can take another shot at refactoring
> > >>>>>>>> it in a future revision!
> >
> > drivers/mmc/host/Kconfig | 9 +
> > drivers/mmc/host/Makefile | 1 +
> > drivers/mmc/host/litex_mmc.c | 657 +++++++++++++++++++++++++++++++++++
> > 3 files changed, 667 insertions(+)
> > create mode 100644 drivers/mmc/host/litex_mmc.c
> >
> > diff --git a/drivers/mmc/host/Kconfig b/drivers/mmc/host/Kconfig
> > index 5af8494c31b5..8f661f52b502 100644
> > --- a/drivers/mmc/host/Kconfig
> > +++ b/drivers/mmc/host/Kconfig
> > @@ -1093,3 +1093,12 @@ config MMC_OWL
> >
> > config MMC_SDHCI_EXTERNAL_DMA
> > bool
> > +
> > +config MMC_LITEX
> > + tristate "LiteX MMC Host Controller support"
> > + depends on ((PPC_MICROWATT || LITEX) && OF) || COMPILE_TEST
> > + help
> > + This selects support for the MMC Host Controller found in LiteX SoCs.
>
> See comment below.
>
> > + To compile this driver as a module, choose M here: the
> > + module will be called litex_mmc.
>
> Can we add this here too?
>
> If unsure, say N.

OK, lined up for v12.

> > diff --git a/drivers/mmc/host/Makefile b/drivers/mmc/host/Makefile
> > index ea36d379bd3c..4e4ceb32c4b4 100644
> > --- a/drivers/mmc/host/Makefile
> > +++ b/drivers/mmc/host/Makefile
> > @@ -101,6 +101,7 @@ obj-$(CONFIG_MMC_CQHCI) += cqhci.o
> > cqhci-y += cqhci-core.o
> > cqhci-$(CONFIG_MMC_CRYPTO) += cqhci-crypto.o
> > obj-$(CONFIG_MMC_HSQ) += mmc_hsq.o
> > +obj-$(CONFIG_MMC_LITEX) += litex_mmc.o
> >
> > ifeq ($(CONFIG_CB710_DEBUG),y)
> > CFLAGS-cb710-mmc += -DDEBUG
> > diff --git a/drivers/mmc/host/litex_mmc.c b/drivers/mmc/host/litex_mmc.c
> > new file mode 100644
> > index 000000000000..cc2848030e6b
> > --- /dev/null
> > +++ b/drivers/mmc/host/litex_mmc.c
> > @@ -0,0 +1,657 @@
> ...
> > +
> > + /* Initialize clock source */
> > + clk = devm_clk_get(dev, NULL);
> > + if (IS_ERR(clk))
> > + return dev_err_probe(dev, PTR_ERR(clk), "can't get clock\n");
> > + host->ref_clk = clk_get_rate(clk);
>
> Note, we used to have:
>
> cpu = of_get_next_cpu_node(NULL);
> ret = of_property_read_u32(cpu, "clock-frequency", &host->freq);
> of_node_put(cpu);
> if (ret) {
> dev_err(&pdev->dev, "No \"clock-frequency\" property in DT\n");
> goto err_free_host;
> }
>
> As we agree, this worked but was hacky. The new use of devm_clk_get above uses
> the COMMON_CLK framework. Which is great but OpenRISC doesn't yet support
> COMMON_CLK, so this driver no longer works on OpenRISC.
>
> I think the ideal thing is to not change the driver code and I will just add
> support for COMMON_CLK on openrisc (already done and tested). But as we
> discussed off e-mail I think we should change the config constraints to.
>
> depends on ((PPC_MICROWATT || LITEX) && OF && HAVE_CLK) || COMPILE_TEST

OK, also lined up for v12.

I'll probably send out v12 in a few hours -- thanks for the
suggestions and testing!

Best,
--Gabriel