Re: (EXT) Re: [PATCH mmc-next v2] mmc: allow setting slot index via device tree alias

[Matthias Schiffer]

On Fri, 2020-08-21 at 13:39 +0200, Ulf Hansson wrote:
> On Thu, 20 Aug 2020 at 09:59, Matthias Schiffer
> <matthias.schiffer@xxxxxxxxxxxxxxx> wrote:
> > 
> > As with GPIO, UART and others, allow specifying the device index
> > via the
> > aliases node in the device tree.
> > 
> > On embedded devices, there is often a combination of removable
> > (e.g.
> > SD card) and non-removable MMC devices (e.g. eMMC).
> > Therefore the index might change depending on
> > 
> > * host of removable device
> > * removable card present or not
> > 
> > This makes it difficult to hardcode the root device, if it is on
> > the
> > non-removable device. E.g. if SD card is present eMMC will be
> > mmcblk1,
> > if SD card is not present at boot, eMMC will be mmcblk0.
> 
> Can you please add some information why Part-UUID/labels don't work
> well to solve this problem on some embedded systems?
> 
> I think that deserves to be in the changelog, after all the long
> discussions we had in the history around this.

Makes sense. I'll wait for your review before I send a v3 with an
updated description.

Matthias


> 
> I will continue to review the code in a separate email, in a while.
> 
> Kind regards
> Uffe
> 
> > 
> > All indices defined in the aliases node will be reserved for use by
> > the
> > respective MMC device, moving the indices of devices that don't
> > have an
> > alias up into the non-reserved range. If the aliases node is not
> > found,
> > the driver will act as before.
> > 
> > This is a rebased and slightly cleaned up version of
> > https://www.spinics.net/lists/linux-mmc/msg26588.html .
> > 
> > Based-on-patch-by: Sascha Hauer <s.hauer@xxxxxxxxxxxxxx>
> > Link: https://lkml.org/lkml/2020/8/5/194
> > Signed-off-by: Matthias Schiffer <matthias.schiffer@xxxxxxxxxxxxxxx
> > >
> > ---
> > 
> > v2: fix missing symbols for modular mmcblock
> > 
> >  drivers/mmc/core/block.c | 13 +++++++++++--
> >  drivers/mmc/core/core.c  | 40
> > ++++++++++++++++++++++++++++++++++++++++
> >  drivers/mmc/core/core.h  |  3 +++
> >  drivers/mmc/core/host.c  | 15 +++++++++++++--
> >  4 files changed, 67 insertions(+), 4 deletions(-)
> > 
> > diff --git a/drivers/mmc/core/block.c b/drivers/mmc/core/block.c
> > index 7896952de1ac..4620afaf0e50 100644
> > --- a/drivers/mmc/core/block.c
> > +++ b/drivers/mmc/core/block.c
> > @@ -38,6 +38,7 @@
> >  #include <linux/pm_runtime.h>
> >  #include <linux/idr.h>
> >  #include <linux/debugfs.h>
> > +#include <linux/of.h>
> > 
> >  #include <linux/mmc/ioctl.h>
> >  #include <linux/mmc/card.h>
> > @@ -2260,9 +2261,17 @@ static struct mmc_blk_data
> > *mmc_blk_alloc_req(struct mmc_card *card,
> >                                               int area_type)
> >  {
> >         struct mmc_blk_data *md;
> > -       int devidx, ret;
> > +       int rsvidx, devidx = -1, ret;
> > +
> > +       rsvidx = mmc_get_reserved_index(card->host);
> > +       if (rsvidx >= 0)
> > +               devidx = ida_simple_get(&mmc_blk_ida, rsvidx,
> > rsvidx + 1,
> > +                                       GFP_KERNEL);
> > +       if (devidx < 0)
> > +               devidx = ida_simple_get(&mmc_blk_ida,
> > +                                       mmc_first_nonreserved_index
> > (),
> > +                                       max_devices, GFP_KERNEL);
> 
> 
> 
> > 
> > -       devidx = ida_simple_get(&mmc_blk_ida, 0, max_devices,
> > GFP_KERNEL);
> >         if (devidx < 0) {
> >                 /*
> >                  * We get -ENOSPC because there are no more any
> > available
> > diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
> > index 8ccae6452b9c..5bce281a5faa 100644
> > --- a/drivers/mmc/core/core.c
> > +++ b/drivers/mmc/core/core.c
> > @@ -2419,10 +2419,50 @@ void mmc_unregister_pm_notifier(struct
> > mmc_host *host)
> >  }
> >  #endif
> > 
> > +static int mmc_max_reserved_idx = -1;
> > +
> > +/**
> > + * mmc_first_nonreserved_index() - get the first index that is not
> > reserved
> > + */
> > +int mmc_first_nonreserved_index(void)
> > +{
> > +       return mmc_max_reserved_idx + 1;
> > +}
> > +EXPORT_SYMBOL(mmc_first_nonreserved_index);
> > +
> > +/**
> > + * mmc_get_reserved_index() - get the index reserved for this MMC
> > host
> > + *
> > + * Returns:
> > + *   The index reserved for this host on success,
> > + *   negative error if no index is reserved for this host
> > + */
> > +int mmc_get_reserved_index(struct mmc_host *host)
> > +{
> > +       return of_alias_get_id(host->parent->of_node, "mmc");
> > +}
> > +EXPORT_SYMBOL(mmc_get_reserved_index);
> > +
> > +static void __init mmc_of_reserve_idx(void)
> > +{
> > +       int max;
> > +
> > +       max = of_alias_get_highest_id("mmc");
> > +       if (max < 0)
> > +               return;
> > +
> > +       mmc_max_reserved_idx = max;
> > +
> > +       pr_debug("MMC: reserving %d slots for OF aliases\n",
> > +                mmc_max_reserved_idx + 1);
> > +}
> > +
> >  static int __init mmc_init(void)
> >  {
> >         int ret;
> > 
> > +       mmc_of_reserve_idx();
> > +
> >         ret = mmc_register_bus();
> >         if (ret)
> >                 return ret;
> > diff --git a/drivers/mmc/core/core.h b/drivers/mmc/core/core.h
> > index 575ac0257af2..6aef6cf4e90f 100644
> > --- a/drivers/mmc/core/core.h
> > +++ b/drivers/mmc/core/core.h
> > @@ -79,6 +79,9 @@ int mmc_attach_mmc(struct mmc_host *host);
> >  int mmc_attach_sd(struct mmc_host *host);
> >  int mmc_attach_sdio(struct mmc_host *host);
> > 
> > +int mmc_first_nonreserved_index(void);
> > +int mmc_get_reserved_index(struct mmc_host *host);
> > +
> >  /* Module parameters */
> >  extern bool use_spi_crc;
> > 
> > diff --git a/drivers/mmc/core/host.c b/drivers/mmc/core/host.c
> > index ce43f7573d80..386e15afde83 100644
> > --- a/drivers/mmc/core/host.c
> > +++ b/drivers/mmc/core/host.c
> > @@ -387,6 +387,7 @@ struct mmc_host *mmc_alloc_host(int extra,
> > struct device *dev)
> >  {
> >         int err;
> >         struct mmc_host *host;
> > +       int alias_id, min_idx, max_idx;
> > 
> >         host = kzalloc(sizeof(struct mmc_host) + extra,
> > GFP_KERNEL);
> >         if (!host)
> > @@ -395,7 +396,18 @@ struct mmc_host *mmc_alloc_host(int extra,
> > struct device *dev)
> >         /* scanning will be enabled when we're ready */
> >         host->rescan_disable = 1;
> > 
> > -       err = ida_simple_get(&mmc_host_ida, 0, 0, GFP_KERNEL);
> > +       host->parent = dev;
> > +
> > +       alias_id = mmc_get_reserved_index(host);
> > +       if (alias_id >= 0) {
> > +               min_idx = alias_id;
> > +               max_idx = alias_id + 1;
> > +       } else {
> > +               min_idx = mmc_first_nonreserved_index();
> > +               max_idx = 0;
> > +       }
> > +
> > +       err = ida_simple_get(&mmc_host_ida, min_idx, max_idx,
> > GFP_KERNEL);
> >         if (err < 0) {
> >                 kfree(host);
> >                 return NULL;
> > @@ -406,7 +418,6 @@ struct mmc_host *mmc_alloc_host(int extra,
> > struct device *dev)
> >         dev_set_name(&host->class_dev, "mmc%d", host->index);
> >         host->ws = wakeup_source_register(NULL, dev_name(&host-
> > >class_dev));
> > 
> > -       host->parent = dev;
> >         host->class_dev.parent = dev;
> >         host->class_dev.class = &mmc_host_class;
> >         device_initialize(&host->class_dev);
> > --
> > 2.17.1
> >