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Message-ID: <CAPDyKFp1uwkmFVWXbCG32bRtu2kkUq_Vog646c=evmTixW6adA@mail.gmail.com>
Date: Fri, 21 Aug 2020 13:39:51 +0200
From: Ulf Hansson <ulf.hansson@...aro.org>
To: Matthias Schiffer <matthias.schiffer@...tq-group.com>
Cc: Sascha Hauer <s.hauer@...gutronix.de>,
"linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH mmc-next v2] mmc: allow setting slot index via device tree alias
On Thu, 20 Aug 2020 at 09:59, Matthias Schiffer
<matthias.schiffer@...tq-group.com> 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.
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@...gutronix.de>
> Link: https://lkml.org/lkml/2020/8/5/194
> Signed-off-by: Matthias Schiffer <matthias.schiffer@...tq-group.com>
> ---
>
> 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
>
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