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

Tom Warren
2013-02-12T19:05:24Z

Simon,

On Tue, Feb 12, 2013 at 11:07 AM, Simon Glass <sjg@chromium.org> wrote:
> 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.

PTAL at the current patchset (v2) - I changed it to look for 'sdhci',
which names the node and the aliases, and seem to work fine. I also
have one function that parses all the nodes at once, so only one call
to tegra_mmc_init() is needed from the board level.

>
>>>
>>>> + /*
>>>> + * 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