Hi Adrian, On ven., févr. 12 2016, Adrian Hunter <adrian.hunter@xxxxxxxxx> wrote: > On 04/02/16 12:55, Ulf Hansson wrote: >> + Adrian >> >> On 29 January 2016 at 10:43, Russell King - ARM Linux >> <linux@xxxxxxxxxxxxxxxx> wrote: >>> On Mon, Dec 21, 2015 at 11:39:56AM +0000, Russell King - ARM Linux wrote: >>>> This all started with a report from an iMX6 Hummingboard user that >>>> they were seeing regular "mmc0: Got data interrupt 0x00000002 even >>>> though no data operation was in progress." messages with 4.4-rc and >>>> additional patches to enable UHS support in DT for the platform. >>>> >>>> When I tested 4.4-rc on an iMX6 Hummingboard with UHS support enabled, >>>> I found several other issues. This patch series addresses some of >>>> the issues. >>>> >>>> However, while testing on Armada 388, an issue was found there, and >>>> a fix is also included in this patch set, however it does not depend >>>> on the rest of the patch series. >>>> >>>> We all know that the SDHCI driver is in poor state, and Ulf's desire >>>> to see it turned into a library (which actually comes from myself.) >>>> However, with the driver in such a poor state, it makes sense to fix >>>> a few of the issues first, especially if they result in the code >>>> shrinking - which they do. >>>> >>>> However, given what I've found below, I have to wonder how many of the >>>> quirks that we have in this driver are down to the poor code rather than >>>> real hardware problems: how many of them are due to poorly investigated >>>> bugs. >>>> >>>> This series starts off by shutting up some kernel messages that should >>>> not be verbose: >>>> - the voltage-ranges DT property is optional, so we should not print >>>> a message saying that it's missing from DT. That suggests it isn't >>>> optional. As no ill effect comes from not specifying it, I've >>>> dropped this message to debug level. >>>> >>>> - reworking the voltage-ranges code so that callers know whether the >>>> optional voltage-ranges property was specified. >>>> >>>> - "retrying because a re-tune was needed" - a re-tune is something that >>>> is part of the higher speed SD specs, and it's required to happen >>>> periodically. So it's expected and normal behaviour. There's no need >>>> to print this to the kernel log. >>>> >>>> - When tuning fails, rather than a bland "mmc0: tuning execution failed" >>>> message, print the error code so that we can see what the reason for >>>> the failure is. MMC fails on this point in many places. >>>> >>>> - Move the initialisation of the command ->error member. It looks to >>>> me as if this is not required; mmc_start_request() does this already, >>>> as it seems the rest of the MMC core does too. Maybe this should be >>>> removed altogether? >>>> >>>> - Testing error bits, then setting the error, then testing the error >>>> value, and completing the command is a very lengthy way to deal with >>>> errors here. Test the error bits, and then decide what error occurred >>>> before completing. (This code is actually buggy, see the next change). >>>> >>>> - If a command _response_ CRC error occurs, we can't be certain whether >>>> the card received the command successfully, and has started processing >>>> it. If it has, and it results in data being read from the card, the >>>> card will enter data transfer state, and start sending data to the >>>> host. Therefore, it is completely wrong to blindly terminate the >>>> command, especially when such termination fails to clean _anything_ >>>> up - eg, it leaves DMA in place so the host can continue DMAing to the >>>> memory, and it leaves buffers DMA mapped - which eventually annoys the >>>> DMA API debugging. Fix this by assuming that a CRC error is a receive >>>> side error. If the card did not correctly receive the command, it >>>> will not initiate a data transfer, and we should time out after the >>>> card specified timeout. >>>> >>>> With the unmodified mainline code, even if we reset the state machines >>>> when finishing a request in error, the _card_ itself may well still be >>>> in data transfer mode when this happens. How can we be sure what state >>>> the data side is actually in? Could this be why (eg) sdhci-esdhc-imx.c >>>> has this: >>>> >>>> /* FIXME: delay a bit for card to be ready for next tuning due to errors */ >>>> mdelay(1); >>>> >>>> And how many more such _hacks_ are working around similar problems? >>>> >>>> - The unaligned buffer handling is a total waste of resources in its >>>> current form. We DMA map, sync, and unmap it on every transfer, >>>> whether the buffer is used or not. For MMC/SD transfers, these will >>>> be coming from the VFS/MM layers, which operate through the page >>>> cache - hence the vast majority of buffers will be page aligned. >>>> Performance measurements on iMX6 show that this additional DMA >>>> maintanence is responsible for a 10% reduction in read transfer >>>> performance. Switch this to use a DMA coherent mapping instead, which >>>> needs no DMA maintanence. >>>> >>>> - sdhci_adma_table_post() is badly coded: we walk the scatterlist >>>> looking for any buffers which might not be aligned (which can be a >>>> rare event, see above) and then we only do something if we find an >>>> unaligned buffer _and_ it's a read transfer. So for a write transfer, >>>> this scatterlist walking is a total waste of CPU cycles. Testing the >>>> transfer direction is much cheaper than walking the scatterlist. >>>> Re-organise the code to do the cheap test first. >>>> >>>> - There are two paths to identical DMA unmapping code (the code around >>>> dma_unmap_sg()) in sdhci_finish_data() and its child function >>>> sdhci_adma_table_post(). Trivially simplify this duplication. >>>> >>>> - Move sdhci_pre_dma_transfer() so we avoid needing to declare it. >>>> >>>> - Do the same thing with sdhci_prepare_data() and sdhci_pre_dma_transfer() >>>> as with sdhci_finish_data() and sdhci_adma_table_post(). >>>> >>>> - Fix the mess that is the data segment host_cookie handling. The >>>> existing code seems like a candidate for the obfuscated coding prize! >>>> Four patches address this, turning it into something much easier to >>>> understand, which then allows (finally)... >>>> >>>> - The DMA API leak which occurs when we have mapped the DMA buffers in >>>> sdhci_prepare_data() and an error occurs early on in the processing >>>> of a request. >>>> >>>> - A change (mentioned above) which fixes a prior commit for Armada 38x >>>> using sdhci-pxav3.c, found while trying to get the higher speed modes >>>> working on these SoCs. Clearly the existing code is broken, this at >>>> least resolves some of the breakage by allowing the correct high-order >>>> SDHCI capabilities through. >>>> >>>> - Fixing another DMA API leak with the pre/post request handling, where >>>> a current request can change the state of the SDHCI_REQ_USE_DMA, and >>>> thus stop a mapped request being unmapped. >>>> >>>> - Fixing the SDHCI timeout calculation code to correctly round timeouts >>>> up rather than down, and correctly calculate the time (in microseconds) >>>> for a certain number of card clocks. >>>> >>>> - Consolidating the SDHCI address/size alignment handling so we only walk >>>> the scatterlist once instead of twice. >>>> >>>> Further patches are necessary as there are still a number of observable >>>> problems when using this driver on iMX6 with UHS cards. Patches up to >>>> and including "mmc: sdhci: further fix for DMA unmapping in >>>> sdhci_post_req()" should be considered for inclusion in the stable >>>> kernel trees. >>>> >>>> I've tested these changes on iMX6 at UHS speeds, and Armada 388 SoCs >>>> at HS speeds so far. Others should test them. >>> >>> One comment from Adrian addressed. >>> >>> drivers/mmc/card/block.c | 4 +- >>> drivers/mmc/core/core.c | 17 +- >>> drivers/mmc/host/sdhci-pxav3.c | 6 +- >>> drivers/mmc/host/sdhci.c | 444 ++++++++++++++++++----------------------- >>> drivers/mmc/host/sdhci.h | 4 +- >>> 5 files changed, 213 insertions(+), 262 deletions(-) >>> >>> -- >>> RMK's Patch system: http://www.arm.linux.org.uk/developer/patches/ >>> FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up >>> according to speedtest.net. >> >> I have applied patch 1 to 4, for next! >> >> The rest are sdhci patches, which from now on needs acks from Adrian >> for me to pick them up. > > I have taken the liberty of re-organizing Russell's patches to put the > bug fixes first with stable cc's. I also did 2 tweaks which result in > final code having the diff below to the original: > > > diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c > index f857cb2a3d05..03fbb36580f7 100644 > --- a/drivers/mmc/host/sdhci.c > +++ b/drivers/mmc/host/sdhci.c > @@ -2270,7 +2270,7 @@ static void sdhci_cmd_irq(struct sdhci_host *host, u32 intmask, u32 *mask) > * will time out. > */ > if (host->cmd->data && > - intmask & (SDHCI_INT_CRC | SDHCI_INT_TIMEOUT) == > + (intmask & (SDHCI_INT_CRC | SDHCI_INT_TIMEOUT)) == > SDHCI_INT_CRC) { > host->cmd = NULL; > return; > @@ -2920,7 +2920,8 @@ int sdhci_add_host(struct sdhci_host *host) > pr_warn("%s: Unable to allocate ADMA buffers - falling back to standard DMA\n", > mmc_hostname(mmc)); > host->flags &= ~SDHCI_USE_ADMA; > - } else if (dma & SDHCI_ADMA2_MASK) { > + } else if ((dma + host->align_buffer_sz) & > + (SDHCI_ADMA2_DESC_ALIGN - 1)) { > pr_warn("%s: unable to allocate aligned ADMA descriptor\n", > mmc_hostname(mmc)); > host->flags &= ~SDHCI_USE_ADMA; > > > Where I have made changes, they are indicated in the patch commit. > > I did some basic testing of eMMC, SD card and SDIO, for the fixes alone > and also the entire patch set. > > Russell, please let me know if this is OK, and if so, Ulf please consider > pulling: > > > The following changes since commit 7d9e20d2be0d836c4eb7afca901eced34274c8dd: > > Merge branch 'fixes' into next (2016-02-08 16:22:56 +0100) > > are available in the git repository at: > > > git://git.infradead.org/users/ahunter/linux-sdhci.git master Thanks to your branch I was able to test the series on the Armada 38x boards. At the beginning my main motivation was to ensure that now thanks to the patch "mmc: sdhci-pxav3: fix higher speed mode capabilities", we really manage to support SDR50 and DDR50 modes. However I realized that I don't have any 1.8V support on the board I have. So I can't confirm this, but at least I didn't see any regression while using the SD cards. Gregory > > for you to fetch changes up to eb6bf3c3513d2e2ab77d86bc6c2f2755073f0745: > > mmc: sdhci: further code simplication (2016-02-11 16:24:46 +0200) > > ---------------------------------------------------------------- > Russell King (22): > mmc: sdhci: move initialisation of command error member > mmc: sdhci: clean up command error handling > mmc: sdhci: fix command response CRC error handling > mmc: sdhci: avoid unnecessary mapping/unmapping of align buffer > mmc: sdhci: plug DMA mapping leak on error > mmc: sdhci-pxav3: fix higher speed mode capabilities > mmc: sdhci: further fix for DMA unmapping in sdhci_post_req() > mmc: sdhci: fix data timeout (part 1) > mmc: sdhci: fix data timeout (part 2) > mmc: sdhci: allocate alignment and DMA descriptor buffer together > mmc: sdhci: clean up coding style in sdhci_adma_table_pre() > mmc: sdhci: avoid walking SG list for writes > mmc: sdhci: factor out common DMA cleanup in sdhci_finish_data() > mmc: sdhci: move sdhci_pre_dma_transfer() > mmc: sdhci: factor out sdhci_pre_dma_transfer() from sdhci_adma_table_pre() > mmc: sdhci: pass the cookie into sdhci_pre_dma_transfer() > mmc: sdhci: always unmap a mapped data transfer in sdhci_post_req() > mmc: sdhci: clean up host cookie handling > mmc: sdhci: cleanup DMA un-mapping > mmc: sdhci: prepare DMA address/size quirk handling consolidation > mmc: sdhci: consolidate the DMA/ADMA size/address quicks > mmc: sdhci: further code simplication > > drivers/mmc/host/sdhci-pxav3.c | 6 ++- > drivers/mmc/host/sdhci.c | 444 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++------------------------------------------------------------------------------------------- > drivers/mmc/host/sdhci.h | 4 +- > 3 files changed, 200 insertions(+), 254 deletions(-) > > > Regards > Adrian -- Gregory Clement, Free Electrons Kernel, drivers, real-time and embedded Linux development, consulting, training and support. http://free-electrons.com -- To unsubscribe from this list: send the line "unsubscribe linux-mmc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
