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SubjectRe: [PATCH] New AT91 MCI Driver that supports both MCI slots used at the same time
Rob Emanuele wrote:
> This patch creates a new AT91 Multimedia Card Interface (MCI) driver
> that supports using both MCI slots at the same time. I'm looking for
> others to test this patch on other boards within the same family of
> chips.
>
> This driver is a port the Atmel AVR32 MCI driver which uses similar silicon.
>
I made all necessary adjustments to test this on my at91sam9261.
Unfortunately it didn't want to initialize my card so I wasn't able to
try some of the failures that I experience with the existing driver. I
sent you a private email with the logs.

> +config MMC_AT91GEN2
> + tristate "Atmel AT91 Multimedia Card Interface support 2nd gen"
> + depends on ARCH_AT91
> + help
>
On linux-arm-kernel I've detailed a lot of problems involving
WRITE_MULTIPLE_BLOCK using the at91 mmc/sd controller. In the end you
might need to exclude certain processors or else have a gigantic
warning. You can talk to me offline for details on my testing.

> +struct at91_mmc_slot_pdata {
> + unsigned int bus_width;
> + int detect_pin;
> + int wp_pin;
> + int vcc_pin;
> +};
>
Notice in 2.6.29 that at91_mci and most other structures call it
"det_pin" rather than "detect_pin"

> + if (host->need_reset) {
> + at91_mci_write(host, AT91_MCI_CR, AT91_MCI_SWRST);
> + at91_mci_write(host, AT91_MCI_CR, AT91_MCI_MCIEN);
> + at91_mci_write(host, AT91_MCI_MR, host->mode_reg);
> + host->need_reset = false;
> + }
>
In my experience some at91s need a reset after every single command,
otherwise bad things happen. I think the need_reset logic is too
conservative in this driver.

> + /*
> + * WRPROOF and RDPROOF prevent overruns/underruns by
> + * stopping the clock when the FIFO is full/empty.
> + * This state is not expected to last for long.
> + */
> + host->mode_reg = (AT91_MCI_CLKDIV & clkdiv) | AT91_MCI_WRPROOF
> + | AT91_MCI_RDPROOF;
>
These registers are not in all at91 chips especially the at91sam9261.

> + if (pdata->slot[0].bus_width) {
> + ret = at91mci_init_slot(host, &pdata->slot[0],
> + AT91_MCI_SDCSEL & 0x0, 0);
> + if (!ret)
> + nr_slots++;
> + }
> + if (pdata->slot[1].bus_width) {
> + ret = at91mci_init_slot(host, &pdata->slot[1],
> + AT91_MCI_SDCSEL & 0x1, 1);
> + if (!ret)
> + nr_slots++;
> + }
> +
> + if (!nr_slots)
> + goto err_init_slot;
>
The original pdata had "wire4" which worked (but defaulted to 1-wire) as
default uninitialized. With this new variable it's easy to register
mmc_slot_pdata with bus_width set to zero. The difference bit me when
testing and at least deserves a printk if not a change.

-joey


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