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

Tom Warren
2013-02-05T21:02:47Z

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.
>
>> + /*
>> + * 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