linux-kernel - Re: [PATCH] mmc: omap_hsmmc: fix initialization order of mmc block devices

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Message-ID: <561D0E38.6030006@gmail.com>
Date:	Tue, 13 Oct 2015 15:59:20 +0200
From:	Dirk Behme <dirk.behme@...il.com>
To:	Heiko Schocher <hs@...x.de>, linux-kernel@...r.kernel.org
Cc:	Arnd Bergmann <arnd@...db.de>, linux-mmc@...r.kernel.org,
	Dirk Behme <dirk.behme@...ch.com>, Georg.Soffel@...ch-si.com,
	linux-omap@...r.kernel.org, Ulf Hansson <ulf.hansson@...aro.org>
Subject: Re: [PATCH] mmc: omap_hsmmc: fix initialization order of mmc block
 devices

On 13.10.2015 07:29, Heiko Schocher wrote:
> On embedded devices, often there is a combination of
> removable mmc devices (e.g. MMC/SD cards) and hard
> wired ones (e.g. eMMC). Depending on the hardware
> configuration, the 'mmcblkN' node might change if
> the removable device is available or not at boot time.
>
> E.g. if the removable device is attached at boot time,
> it might become mmxblk0. And the hard wired one mmcblk1.
> But if the removable device isn't there at boot time,
> the hard wired one will become mmcblk0. This makes it
> somehow difficult to hard code the root device to the
> non-removable device and boot fast.
>
> Signed-off-by: Heiko Schocher <hs@...x.de>
> ---
> Dirk Behme tried to bring this in, last mail I found:
> http://lists.infradead.org/pipermail/linux-arm-kernel/2012-July/111022.html
> where Dirk worked in Arnds suggestion to use the
> "/aliases" device node"


The last attempt I remember is from last year


http://www.spinics.net/lists/linux-mmc/msg26586.html

http://www.spinics.net/lists/linux-mmc/msg26588.html


I can't remember why this wasn't accepted, too. But maybe searching 
the archives will help answering that.


Best regards

Dirk


> I adapt this to the omap_hsmmc driver.
>
> Is there another solution for this problem?
> Or why was this patch not accepted to mainline?
>
>   drivers/mmc/card/block.c      | 6 ++++--
>   drivers/mmc/host/omap_hsmmc.c | 6 ++++++
>   include/linux/mmc/host.h      | 3 +++
>   3 files changed, 13 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/mmc/card/block.c b/drivers/mmc/card/block.c
> index c742cfd..62250d8 100644
> --- a/drivers/mmc/card/block.c
> +++ b/drivers/mmc/card/block.c
> @@ -2106,7 +2106,8 @@ static struct mmc_blk_data *mmc_blk_alloc_req(struct mmc_card *card,
>   	struct mmc_blk_data *md;
>   	int devidx, ret;
>
> -	devidx = find_first_zero_bit(dev_use, max_devices);
> +	devidx = find_next_zero_bit(dev_use, max_devices,
> +				    card->host->devidx);
>   	if (devidx >= max_devices)
>   		return ERR_PTR(-ENOSPC);
>   	__set_bit(devidx, dev_use);
> @@ -2124,7 +2125,8 @@ static struct mmc_blk_data *mmc_blk_alloc_req(struct mmc_card *card,
>   	 * index anymore so we keep track of a name index.
>   	 */
>   	if (!subname) {
> -		md->name_idx = find_first_zero_bit(name_use, max_devices);
> +		md->name_idx = find_next_zero_bit(name_use, max_devices,
> +						  card->host->devidx);
>   		__set_bit(md->name_idx, name_use);
>   	} else
>   		md->name_idx = ((struct mmc_blk_data *)
> diff --git a/drivers/mmc/host/omap_hsmmc.c b/drivers/mmc/host/omap_hsmmc.c
> index 7fb0753..0b45b48 100644
> --- a/drivers/mmc/host/omap_hsmmc.c
> +++ b/drivers/mmc/host/omap_hsmmc.c
> @@ -2059,6 +2059,12 @@ static int omap_hsmmc_probe(struct platform_device *pdev)
>   	host->pbias_enabled = 0;
>   	host->vqmmc_enabled = 0;
>
> +	if (pdev->dev.of_node) {
> +		ret = of_alias_get_id(pdev->dev.of_node, "mmcblk");
> +		if (ret >= 0)
> +			host->mmc->devidx = ret;
> +	}
> +
>   	ret = omap_hsmmc_gpio_init(mmc, host, pdata);
>   	if (ret)
>   		goto err_gpio;
> diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h
> index 83b81fd..4f071681 100644
> --- a/include/linux/mmc/host.h
> +++ b/include/linux/mmc/host.h
> @@ -382,6 +382,9 @@ struct mmc_host {
>   	int			dsr_req;	/* DSR value is valid */
>   	u32			dsr;	/* optional driver stage (DSR) value */
>
> +	/* preferred mmc block device index (mmcblkX) */
> +	unsigned int		devidx;
> +
>   	unsigned long		private[0] ____cacheline_aligned;
>   };
>
>

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