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

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Message-ID: <561CB653.5020707@denx.de>
Date:	Tue, 13 Oct 2015 09:44:19 +0200
From:	Heiko Schocher <hs@...x.de>
To:	Lokesh Vutla <a0131933@...com>
Cc:	linux-kernel@...r.kernel.org, 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>,
	"Menon, Nishanth" <nm@...com>
Subject: Re: [PATCH] mmc: omap_hsmmc: fix initialization order of mmc block
 devices

Hello Lokesh,

Am 13.10.2015 um 08:46 schrieb Lokesh Vutla:
> +Nishanth,
>
> On Tuesday 13 October 2015 10:59 AM, 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.
>
> Why not use "root=PARTUUID=${uuid}" option instead of relying on mmcblk no?
> U-Boot can easily detect your partuuid. Refer to [1] on how TI platforms
> does this in u-boot.

Good tip ... I do not know, if it is possible to update U-Boot
on this boards...

Current U-Boot says:
U-Boot 2013.01.01_heads/master-gc7900a0 (2015-05-06 - 20:37:15)

I2C:   ready
DRAM:  512 MiB
[...]
U-Boot# mmc rescan
U-Boot# mmc part

Partition Map for MMC device 0  --   Partition Type: DOS

Part    Start Sector    Num Sectors     UUID            Type
   1     63              144522          000ce343-01     0e Boot
   2     144585          659861          000ce343-02     83
U-Boot# part uuid mmc 0:2 uuid
Unknown command 'part' - try 'help'
U-Boot#

So, if this patch has no chance for mainline, please let me
know it, thanks!

bye,
Heiko
>
> [1]
> http://git.denx.de/?p=u-boot.git;a=commitdiff;h=437bc42e7ff930dc4d4bd47199d2e823cf84bf4c;hp=85d17be374678ec37fd1e55db994a942e400dc80
>
> Thanks and regards,
> Lokesh
>>
>> 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"
>>
>> 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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