[U-Boot] [PATCH 2/2] Tegra: MMC: Add DT support to MMC driver for all T20 boards

Simon Glass
2013-02-12T18:07:08Z

Hi,

On Tue, Feb 5, 2013 at 1:02 PM, Tom Warren <twarren.nvidia@gmail.com> wrote:
> Stephen,
>
> On Tue, Feb 5, 2013 at 1:03 PM, Stephen Warren <swarren@wwwdotorg.org> wrote:
>> On 02/04/2013 04:48 PM, Tom Warren wrote:
>>> tegra_mmc_init() now uses DT info for bus width, WP/CD GPIOs, etc.
>>> Tested on Seaboard, fully functional.
>>
>>> diff --git a/board/compal/paz00/paz00.c b/board/compal/paz00/paz00.c
>>> index 1447f47..5cee91a 100644
>>> --- a/board/compal/paz00/paz00.c
>>> +++ b/board/compal/paz00/paz00.c
>>> @@ -55,18 +55,18 @@ static void pin_mux_mmc(void)
>>> /* this is a weak define that we are overriding */
>>> int board_mmc_init(bd_t *bd)
>>> {
>>> - debug("board_mmc_init called\n");
>>> + debug("%s called\n", __func__);
>>>
>>> /* Enable muxes, etc. for SDMMC controllers */
>>> pin_mux_mmc();
>>>
>>> - debug("board_mmc_init: init eMMC\n");
>>> - /* init dev 0, eMMC chip, with 8-bit bus */
>>> - tegra_mmc_init(0, 8, -1, -1);
>>> + debug("%s: init eMMC\n", __func__);
>>> + /* init dev 0, eMMC chip */
>>> + tegra_mmc_init(0);
>>>
>>> - debug("board_mmc_init: init SD slot\n");
>>> - /* init dev 3, SD slot, with 4-bit bus */
>>> - tegra_mmc_init(3, 4, GPIO_PV1, GPIO_PV5);
>>> + debug("%s: init SD slot\n", __func__);
>>> + /* init dev 3, SD slot */
>>> + tegra_mmc_init(3);
>>>
>>> return 0;
>>> }
>>
>> That doesn't look right. The board code still has knowledge of which
>> SDHCI controllers are in use by the board. Instead, the board should
>> just call tegra_mmc_init() with no parameters at all, and the MMC driver
>> should scan the device tree for all present-and-enabled SDHCI nodes, and
>> instantiate a U-Boot SDHCI device. Without this, the device tree isn't
>> in control of the whole process, so there's little point doing the
>> conversion; a new board couldn't be supported /just/ by creating a new
>> device tree file.
>>
>>> diff --git a/drivers/mmc/tegra_mmc.c b/drivers/mmc/tegra_mmc.c
>>
>>> +#ifndef CONFIG_OF_CONTROL
>>> +#error "Please enable device tree support to use this driver"
>>> +#endif
>>
>> So CONFIG_OF_CONTROL must be enabled ...
>>
>>>
>>> static void tegra_get_setup(struct mmc_host *host, int dev_index)
>>> {
>>> - debug("tegra_get_setup: dev_index = %d\n", dev_index);
>>> + debug("%s: dev_index = %d\n", __func__, dev_index);
>>> +
>>> +#ifdef CONFIG_OF_CONTROL
>>
>> ... so there's no need for that ifdef
>
> I took Allen's recent SPI/SLINK driver(s) as an example, but as you
> point out, if CONFIG_OF_CONTROL isn't enabled, you get build errors
> anyway.
>
>>
>>> + int count, node = 0;
>>> + int node_list[MAX_HOSTS];
>>> +
>>> + count = fdtdec_find_aliases_for_id(gd->fdt_blob, "sdmmc",
>>> + COMPAT_NVIDIA_TEGRA20_SDMMC, node_list, MAX_HOSTS);
>>> + debug("%s: count of nodes is %d\n", __func__, count);
>>> +
>>> + if (count < dev_index) {
>>> + printf("%s: device index %d exceeds node count (%d)!\n",
>>> + __func__, dev_index, count);
>>> + return;
>>> + }
>>
>> This requires that an alias exist in order for the SDHCI node to be
>> found/processed. This isn't correct; the SDHCI nodes must be enumerated
>> themselves, and then the aliases (if any are present) provide a naming
>> hint for them, but even without aliases, the SDHCI nodes must be processed.
> Again, I used Allen's SLINK driver for as a template here. In fact, it
> looks like our I2C and SPI/SLINK drivers do this, as well as the
> Exynos SPI and S3C24x0 I2C driver all do this. Can you point out a
> U-Boot driver that does it the right way (preferably with more than 1
> node, like MMC)? I can take a look at that code to use as an example
> of what you're proposing above.

You have it correct already. Stephen please take another look and let
me know what problem you see with this approach. I'm very sorry that I
am so late to this discussion.

>>
>>> + /*
>>> + * NOTE: mmc->bus_width is determined by mmc.c dynamically.
>>> + * Should we override it with this value?
>>> + */
>>> + host->width = fdtdec_get_int(gd->fdt_blob, node, "bus-width", 0);
>>> + if (!host->width)
>>> + debug("%s: no sdmmc width found\n", __func__);
>>
>> It should be possible to inform the MMC core of the width of the bus in
>> terms of wires on the PCB. It should only probe the connected device up
>> to that width. If that feature is missing, it can be added later though,
>> outside the scope of this patch set.
>>
>> You didn't Cc the MMC maintainer; they should be Cc'd since this code is
>> in drivers/mmc/.
>
> Thanks, added Andy Fleming to CC.
>
> Tom
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Regards,
Simon