["Followup-To:" header set to gmane.linux.kernel.mmc.]
On 2014-08-19, Barry Song <[email protected]> wrote:
> From: Minda Chen <[email protected]>
>
> 8bit-width enable bit of CSR MMC hosts is 3, while stardard hosts use
> bit 5. this patch fixes the functionality of 8bit transfer in CSR mmc
> controllers and improve performance for mmc0 a lot.
>
> Signed-off-by: Minda Chen <[email protected]>
> Signed-off-by: Barry Song <[email protected]>
> ---
> -v2: check for host->version >= SDHCI_SPEC_300
>
Hi Barry,
Did you check the runtime behaviour of the device after this change ?
>From the SiRFprimaII/SiRFatlasVI data sheets, it appears that the
implementation of the SDHCI controller is a modified version of the one
described in the 1.0 specification, and not a normal 3.0 controller.
This explains why the independent development of the 8-bit wide transfer
bus does not use the same bit as the standard one.
As a result, the description of the SPEC_VER field in the
SD_SLOT_INT_STATUS register indicates a read-only value of 0, which
corresponds to SDHCI_SPEC_100 in the "sdhci.h" header. On a real
SiRFatlasVI chip, the value is 0 as well.
I believe the correct change would be to remove the control on the
version >= SDHCI_SPEC_300 in both 4-bit and 8-bit cases, instead of
adding it in both cases. There are no supported SiRF SoCs where the 8-bit
bus is not supported at the controller level.
In my opinion, this should look like this:
+static void sdhci_sirf_set_bus_width(struct sdhci_host *host, int width)
+{
+ u8 ctrl;
+
+ ctrl = sdhci_readb(host, SDHCI_HOST_CONTROL);
+ /* The 8-bit bus width configuration bit is not standard */
+ ctrl &= ~(SDHCI_CTRL_4BITBUS | SDHCI_SIRF_8BITBUS);
+ if (width == MMC_BUS_WIDTH_8) {
+ ctrl |= SDHCI_SIRF_8BITBUS;
+ } else if (width == MMC_BUS_WIDTH_4)
+ ctrl |= SDHCI_CTRL_4BITBUS;
+ }
+ sdhci_writeb(host, ctrl, SDHCI_HOST_CONTROL);
+}
+
You can use it verbatim with my signoff if you want.
Signed-off-by: Romain Izard <[email protected]>
But you should try it on your board, as I do not have a setup to test
the mainline kernel on SiRFatlasVI available.
Best regards,
--
Romain Izard
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