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Date: Fri, 29 Jan 2016 11:42:13 +0100 From: Ulf Hansson <ulf.hansson@...aro.org> To: Chen-Yu Tsai <wens@...e.org> Cc: Maxime Ripard <maxime.ripard@...e-electrons.com>, Hans de Goede <hdegoede@...hat.com>, linux-mmc <linux-mmc@...r.kernel.org>, "linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, linux-sunxi@...glegroups.com Subject: Re: [PATCH RFC 03/15] mmc: sunxi: Block signal voltage switching (CMD11) On 21 January 2016 at 06:26, Chen-Yu Tsai <wens@...e.org> wrote: > Allwinner's mmc controller supports signal voltage switching. This is > supported in code in Allwinner's kernel. However, publicly available > boards all tie it to a fixed 3.0/3.3V regulator, with options to tie > it to 1.8V for eMMC on some. > > Since Allwinner's kernel is an ancient 3.4, it is hard to say whether > adapting it's code to a modern mainline kernel would work. Block signal > voltage switching until someone has proper hardware to implement and > test this. > > This only affects SD UHS-1 modes, as eMMC switches the voltage directly > without any signaling. > > Signed-off-by: Chen-Yu Tsai <wens@...e.org> > --- > drivers/mmc/host/sunxi-mmc.c | 14 ++++++++++++++ > 1 file changed, 14 insertions(+) > > diff --git a/drivers/mmc/host/sunxi-mmc.c b/drivers/mmc/host/sunxi-mmc.c > index 790f01662b4e..0495ae7da6d6 100644 > --- a/drivers/mmc/host/sunxi-mmc.c > +++ b/drivers/mmc/host/sunxi-mmc.c > @@ -816,6 +816,20 @@ static void sunxi_mmc_request(struct mmc_host *mmc, struct mmc_request *mrq) > } > } > > + /* > + * TODO Support signal voltage switching > + * > + * Compared to Allwinner's kernel, recent updates in the mmc core > + * mean this should be as easy as setting the flags in cmd_val and > + * imask, and waiting for it to finish. However no boards support > + * this so this cannot be tested. Block it for now. > + */ > + if (cmd->opcode == SD_SWITCH_VOLTAGE) { > + mrq->cmd->error = -EPERM; > + mmc_request_done(mmc, mrq); > + return; > + } Unless some of the MMC_CAP_UHS* mode is set, this command shouldn't be sent. So, if you *really* want to protect from this, I think it's better to clear these caps in the ->probe() function, after mmc_of_parse() has been called. > + > if (cmd->opcode == MMC_GO_IDLE_STATE) { > cmd_val |= SDXC_SEND_INIT_SEQUENCE; > imask |= SDXC_COMMAND_DONE; > -- > 2.7.0.rc3 > Kind regards Uffe
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