From: Seungwon Jeon <tgih.jun@samsung.com>
To: 'Doug Anderson' <dianders@chromium.org>,
'Jaehoon Chung' <jh80.chung@samsung.com>
Cc: 'Chris Ball' <cjb@laptop.org>, 'Olof Johansson' <olof@lixom.net>,
'James Hogan' <james.hogan@imgtec.com>,
'Grant Grundler' <grundler@chromium.org>,
'Alim Akhtar' <alim.akhtar@samsung.com>,
'Abhilash Kesavan' <a.kesavan@samsung.com>,
'Tomasz Figa' <tomasz.figa@gmail.com>,
linux-mmc@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: RE: [PATCH v4 1/4] mmc: dw_mmc: Invalidate cache of current_speed after suspend/resume
Date: Mon, 12 Aug 2013 16:14:38 +0900 [thread overview]
Message-ID: <000c01ce972b$9ba23590$d2e6a0b0$%jun@samsung.com> (raw)
In-Reply-To: <CAD=FV=VmtoxnRzjsKF1rVTwvkJRAxKGUvNZHAEwuWaeVokzSZA@mail.gmail.com>
On Sat, August 10, 2013, Doug Anderson wrote:
> Seungwon and Jaehoon,
>
> On Fri, Aug 9, 2013 at 6:32 AM, Seungwon Jeon <tgih.jun@samsung.com> wrote:
> > On Wed, August 07, 2013, Doug Anderson wrote:
> >> The dw_mmc driver keeps a cache of the current slot->clock in order to
> >> avoid doing a whole lot of work every time set_ios() is called.
> >> However, after suspend/resume the register values are bogus so we need
> >> to ensure that the cached value is invalidated.
> > This mismatch comes only in case MMC_PM_KEEP_POWER, right?
>
> Actually, no. I saw problems with the SD Card slot, which doesn't
> have MMC_KEEP_POWER. Problems showed up when no card was inserted
> across suspend/resume. In other words:
>
> 1. At boot time, slot is all setup and configured to 400kHz.
>
> 2. Suspend
>
> 3. Resume; clock registers are reset (by suspend/resume) and not
> restored since dw_mmc still thinks slot is configured for 400kHz due
> to host->current_speed cache.
>
> 4. Insert card.
>
> 5. No code sees any need to change the clock for detecting the card,
> since everyone thinks it's at 400kHz. ...but it's not.
Doug, your analysis is right.
But, let me suggest another approach.
After step #1, core layer actually call mmc_power_off because slot is empthy(get_cd() is '0').
Then, set_ios is requested with 'ios->clock'.
However, because current implementation doesn't update current_speed in case ios->clock is '0'.
It causes current_speed has invalid clock rate in resume of dw-mmc.
So, if we can update slot->clock properly, it will be fixed.
-static void dw_mci_setup_bus(struct dw_mci_slot *slot, bool force_clkinit)
+static void dw_mci_setup_bus(struct dw_mci_slot *slot)
{
struct dw_mci *host = slot->host;
u32 div;
u32 clk_en_a;
- if (slot->clock != host->current_speed || force_clkinit) {
+ if (slot->clock && (slot->clock != host->current_speed)) {
@@ -807,13 +807,11 @@ static void dw_mci_set_ios(struct mmc_host *mmc, struct mmc_ios *ios)
mci_writel(slot->host, UHS_REG, regs);
- if (ios->clock) {
- /*
- * Use mirror of ios->clock to prevent race with mmc
- * core ios update when finding the minimum.
- */
- slot->clock = ios->clock;
- }
+ /*
+ * Use mirror of ios->clock to prevent race with mmc
+ * core ios update when finding the minimum.
+ */
+ slot->clock = ios->clock;
Thanks,
Seungwon Jeon
>
>
> >> In many cases we got by without this since the core mmc code fiddles
> >> with the clock a lot. If we've got a card present we're probably
> >> running it at something like 50MHz and the core will temporarily
> >> switch us to 400kHz after resume. One case that didn't work (for me)
> >> is the case of having no card in the slot. The slot is initted to
> >> 400kHz at boot time. After suspend/resume the slot thinks it's still
> >> at 400kHz (due to the cache) so doesn't adjust timing. When it tries
> >> to send the command at probe time it just times out and gets left in a
> >> bad state.
> > I understand this change although some part of commit message (boot time, probe time...) make me
> confused.
>
> Sorry to be confusing. I was trying to explain why the old code works
> fine in many cases. It's because the core MMC code tends to adjust
> the clock a lot around suspend/resume. When it does that, it works
> around this problem. ...but I found one case where suspend/resume
> would happen and the MMC core didn't adjust the clock.
>
>
> > I guess this change intends to update clock programming forcedly.
> > It looks like another version of 'dw_mci_setup_bus(slot, true)'.
> > Eventually, this change does same?
>
> Effectively, yes. As Jaehoon points out, that means we can actually
> eliminate the "force" parameter to dw_mci_setup_bus().
>
>
> I will send a new version out that eliminates the "force" parameter
> and updates the commit message to (hopefully) be clearer.
>
> -Doug
> --
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> More majordomo info at http://vger.kernel.org/majordomo-info.html
next prev parent reply other threads:[~2013-08-12 7:14 UTC|newest]
Thread overview: 65+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-07-09 17:31 [PATCH 0/5] mmc: dw_mmc: fixes for suspend/resume on exynos Doug Anderson
2013-07-09 17:31 ` [PATCH 1/5] mmc: dw_mmc: Invalidate cache of current_speed after suspend/resume Doug Anderson
2013-07-09 17:31 ` [PATCH 2/5] mmc: dw_mmc: Add suspend/resume callbacks; disable irq during suspend Doug Anderson
2013-07-09 21:17 ` James Hogan
2013-07-09 21:31 ` Doug Anderson
2013-07-09 17:31 ` [PATCH 3/5] mmc: dw_mmc: Add exynos resume callback to clear WAKEUP_INT Doug Anderson
2013-07-09 19:09 ` Doug Anderson
2013-07-11 0:43 ` Grant Grundler
2013-07-09 17:31 ` [PATCH 4/5] mmc: dw_mmc: Always setup the bus after suspend/resume Doug Anderson
2013-07-09 17:31 ` [PATCH 5/5] mmc: dw_mmc: Set timeout to max upon resume Doug Anderson
2013-07-09 23:19 ` [PATCH v2 0/5] mmc: dw_mmc: fixes for suspend/resume on exynos Doug Anderson
2013-07-09 23:19 ` [PATCH v2 1/5] mmc: dw_mmc: Invalidate cache of current_speed after suspend/resume Doug Anderson
2013-07-09 23:19 ` [PATCH v2 2/5] mmc: dw_mmc: Add suspend_noirq/resume_noirq callbacks for dw_mmc-pltfm Doug Anderson
2013-07-10 8:37 ` James Hogan
2013-07-10 15:08 ` Doug Anderson
2013-07-09 23:19 ` [PATCH v2 3/5] mmc: dw_mmc: Add exynos resume_noirq callback to clear WAKEUP_INT Doug Anderson
2013-07-10 14:54 ` Seungwon Jeon
2013-07-10 15:05 ` Doug Anderson
2013-07-15 12:09 ` Seungwon Jeon
2013-07-31 16:18 ` Doug Anderson
2013-08-06 21:36 ` Doug Anderson
2013-07-09 23:19 ` [PATCH v2 4/5] mmc: dw_mmc: Always setup the bus after suspend/resume Doug Anderson
2013-07-09 23:19 ` [PATCH v2 5/5] mmc: dw_mmc: Set timeout to max upon resume Doug Anderson
2013-07-10 14:54 ` Seungwon Jeon
2013-07-10 15:42 ` [PATCH v3 0/5] mmc: dw_mmc: fixes for suspend/resume on exynos Doug Anderson
2013-07-10 15:42 ` [PATCH v3 1/5] mmc: dw_mmc: Invalidate cache of current_speed after suspend/resume Doug Anderson
2013-07-10 15:42 ` [PATCH v3 2/5] mmc: dw_mmc: Add suspend_noirq/resume_noirq callbacks for dw_mmc-pltfm Doug Anderson
2013-07-15 12:09 ` Seungwon Jeon
2013-08-06 21:32 ` Doug Anderson
2013-07-10 15:42 ` [PATCH v3 3/5] mmc: dw_mmc: Add exynos resume_noirq callback to clear WAKEUP_INT Doug Anderson
2013-07-16 1:36 ` Jaehoon Chung
2013-07-10 15:42 ` [PATCH v3 4/5] mmc: dw_mmc: Always setup the bus after suspend/resume Doug Anderson
2013-07-10 15:42 ` [PATCH v3 5/5] mmc: dw_mmc: Set timeout to max upon resume Doug Anderson
2013-08-06 21:37 ` [PATCH v4 0/4] mmc: dw_mmc: fixes for suspend/resume on exynos Doug Anderson
2013-08-06 21:37 ` [PATCH v4 1/4] mmc: dw_mmc: Invalidate cache of current_speed after suspend/resume Doug Anderson
2013-08-06 21:58 ` Tomasz Figa
2013-08-08 5:14 ` Jaehoon Chung
2013-08-09 13:32 ` Seungwon Jeon
2013-08-09 15:22 ` Doug Anderson
2013-08-12 7:14 ` Seungwon Jeon [this message]
2013-08-22 0:54 ` Doug Anderson
2013-08-22 16:25 ` Doug Anderson
2013-08-06 21:37 ` [PATCH v4 2/4] mmc: dw_mmc: Add exynos resume_noirq callback to clear WAKEUP_INT Doug Anderson
2013-08-06 21:58 ` Tomasz Figa
2013-08-06 22:09 ` Doug Anderson
2013-08-06 22:20 ` Tomasz Figa
2013-08-09 13:33 ` Seungwon Jeon
2013-08-09 15:05 ` Doug Anderson
2013-08-06 21:37 ` [PATCH v4 3/4] mmc: dw_mmc: Always setup the bus after suspend/resume Doug Anderson
2013-08-06 22:01 ` Tomasz Figa
2013-08-09 13:35 ` Seungwon Jeon
2013-08-09 15:43 ` Doug Anderson
2013-08-12 7:20 ` Seungwon Jeon
2013-08-06 21:37 ` [PATCH v4 4/4] mmc: dw_mmc: Set timeout to max upon resume Doug Anderson
2013-08-06 22:02 ` Tomasz Figa
2013-08-09 16:33 ` [PATCH v5 0/4] mmc: dw_mmc: fixes for suspend/resume on exynos Doug Anderson
2013-08-09 16:33 ` [PATCH v5 1/4] mmc: dw_mmc: Invalidate cache of current_speed after suspend/resume Doug Anderson
2013-08-09 16:33 ` [PATCH v5 2/4] mmc: dw_mmc: Add exynos resume_noirq callback to clear WAKEUP_INT Doug Anderson
2013-08-09 16:41 ` Fabio Estevam
2013-08-09 16:48 ` Doug Anderson
2013-08-12 7:21 ` Seungwon Jeon
2013-08-09 16:33 ` [PATCH v5 3/4] mmc: dw_mmc: Always setup the bus after suspend/resume Doug Anderson
2013-08-09 16:33 ` [PATCH v5 4/4] mmc: dw_mmc: Set timeout to max upon resume Doug Anderson
2013-08-21 11:48 ` [PATCH v5 0/4] mmc: dw_mmc: fixes for suspend/resume on exynos Seungwon Jeon
2013-08-21 15:13 ` Doug Anderson
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