You have to modify in the following file in the yocto build to enable preset
value:
tmp/work-shared/<board>/kernel-source/drivers/mmc/host/sdhci.c
The following function does the enabling of preset value:
static void sdhci_enable_preset_value(struct sdhci_host *host, bool enable)
{
u16 ctrl;
/* Host Controller v3.00 defines preset value registers */
if (host->version < SDHCI_SPEC_300)
return;
ctrl = sdhci_readw(host, SDHCI_HOST_CONTROL2);
/*
* We only enable or disable Preset Value if they are not already
* enabled or disabled respectively. Otherwise, we bail out.
*/
if (enable && !(ctrl & SDHCI_CTRL_PRESET_VAL_ENABLE)) {
ctrl |= SDHCI_CTRL_PRESET_VAL_ENABLE;
sdhci_writew(host, ctrl, SDHCI_HOST_CONTROL2);
host->flags |= SDHCI_PV_ENABLED;
} else if (!enable && (ctrl & SDHCI_CTRL_PRESET_VAL_ENABLE)) {
ctrl &= ~SDHCI_CTRL_PRESET_VAL_ENABLE;
sdhci_writew(host, ctrl, SDHCI_HOST_CONTROL2);
host->flags &= ~SDHCI_PV_ENABLED;
}
}
The function can be called in the following way:
sdhci_enable_preset_value(host, true);
Thanks,
Juinee
From: meta-intel-boun...@yoctoproject.org
[mailto:meta-intel-boun...@yoctoproject.org] On Behalf Of Francesco Camarda
(fcamarda)
Sent: Tuesday, August 8, 2017 6:24 PM
To: meta-intel@yoctoproject.org
Subject: [meta-intel] change hostctrl2_presetvalueenable default value
Hi,
>From of the Apollo Lake SoC External Design Specification (EDS) Volume 2 of
>3<https://embedded.communities.intel.com/external-link.jspa?url=https%3A%2F%2Fedc.intel.com%2FLink.aspx%3Fid%3D14201>
> document # 557556 (on pages from 4511 to 4515) it is possible to change the
>driver strength that depends on the setting of bit 15
>(hostctrl2_presetvalueenable).
If Preset Value Enable = 0, the driver strength is set by the host driver. If
Preset Value Enable = 1, the driver strength is automatically set to the values
specified in the Capabilities Register (capabilities)-Offset 40h (refer also to
Capabilities Register (capabilities)-Offset 40h).
Which of the file of the build (EC31) I should modify to put the Preset Value
Enable = 1?
Thanks & Regards,
Francesco
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