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In may, Steven sent a patch deleting the bounce buffer handling
and the CONFIG_MMC_BLOCK_BOUNCE option.
I chose the less invasive path of making it a runtime config
option, and we merged that successfully for kernel v4.12.
The code is however just standing in the way and taking up
space for seemingly no gain on any systems in wide use today.
Pierre says the code was there to improve speed on TI SDHCI
controllers on certain HP laptops and possibly some Ricoh
controllers as well. Early SDHCI controllers lacked the
scatter-gather feature, which made software bounce buffers
a significant speed boost.
We are clearly talking about the list of SDHCI PCI-based
MMC/SD card readers found in the pci_ids[] list in
drivers/mmc/host/sdhci-pci-core.c.
The TI SDHCI derivative is not supported by the upstream
kernel. This leaves the Ricoh.
What we can however notice is that the x86 defconfigs in the
kernel did not enable CONFIG_MMC_BLOCK_BOUNCE option, which
means that any such laptop would have to have a custom
configured kernel to actually take advantage of this
bounce buffer speed-up. It simply seems like there was
a speed optimization for the Ricoh controllers that noone
was using. (I have not checked the distro defconfigs but
I am pretty sure the situation is the same there.)
Bounce buffers increased performance on the OMAP HSMMC
at one point, and was part of the original submission in
commit a45c6cb816 ("[ARM] 5369/1: omap mmc: Add new
omap hsmmc controller for 2430 and 34xx, v3")
This optimization was removed in
commit 0ccd76d4c2 ("omap_hsmmc: Implement scatter-gather
emulation")
which found that scatter-gather emulation provided even
better performance.
The same was introduced for SDHCI in
commit 2134a922c6 ("sdhci: scatter-gather (ADMA) support")
I am pretty positively convinced that software
scatter-gather emulation will do for any host controller what
the bounce buffers were doing. Essentially, the bounce buffer
was a reimplementation of software scatter-gather-emulation in
the MMC subsystem, and it should be done away with.
Cc: Pierre Ossman <pierre@ossman.eu>
Cc: Juha Yrjola <juha.yrjola@solidboot.com>
Cc: Steven J. Hill <Steven.Hill@cavium.com>
Cc: Shawn Lin <shawn.lin@rock-chips.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Suggested-by: Steven J. Hill <Steven.Hill@cavium.com>
Suggested-by: Shawn Lin <shawn.lin@rock-chips.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Now that we have a custom printf format specifier, convert users of
full_name to use %pOF instead. This is preparation to remove storing
of the full path string for each node.
Signed-off-by: Rob Herring <robh@kernel.org>
Cc: Ulf Hansson <ulf.hansson@linaro.org>
Cc: Ludovic Desroches <ludovic.desroches@microchip.com>
Cc: Jan Glauber <jglauber@cavium.com>
Cc: David Daney <david.daney@cavium.com>
Cc: "Steven J. Hill" <Steven.Hill@cavium.com>
Cc: linux-mmc@vger.kernel.org
Acked-by: David Daney <david.daney@cavium.com>
Tested-by: Steven J. Hill <Steven.Hill@cavium.com>
Acked-by: Ludovic Desroches <ludovic.desroches@microchip.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
This option is activated by all multiplatform configs and what
not so we almost always have it turned on, and the memory it
saves is negligible, even more so moving forward. The actual
bounce buffer only gets allocated only when used, the only
thing the ifdefs are saving is a little bit of code.
It is highly improper to have this as a Kconfig option that
get turned on by Kconfig, make this a pure runtime-thing and
let the host decide whether we use bounce buffers. We add a
new property "disable_bounce" to the host struct.
Notice that mmc_queue_calc_bouncesz() already disables the
bounce buffers if host->max_segs != 1, so any arch that has a
maximum number of segments higher than 1 will have bounce
buffers disabled.
The option CONFIG_MMC_BLOCK_BOUNCE is default y so the
majority of platforms in the kernel already have it on, and
it then gets turned off at runtime since most of these have
a host->max_segs > 1. The few exceptions that have
host->max_segs == 1 and still turn off the bounce buffering
are those that disable it in their defconfig.
Those are the following:
arch/arm/configs/colibri_pxa300_defconfig
arch/arm/configs/zeus_defconfig
- Uses MMC_PXA, drivers/mmc/host/pxamci.c
- Sets host->max_segs = NR_SG, which is 1
- This needs its bounce buffer deactivated so we set
host->disable_bounce to true in the host driver
arch/arm/configs/davinci_all_defconfig
- Uses MMC_DAVINCI, drivers/mmc/host/davinci_mmc.c
- This driver sets host->max_segs to MAX_NR_SG, which is 16
- That means this driver anyways disabled bounce buffers
- No special action needed for this platform
arch/arm/configs/lpc32xx_defconfig
arch/arm/configs/nhk8815_defconfig
arch/arm/configs/u300_defconfig
- Uses MMC_ARMMMCI, drivers/mmc/host/mmci.[c|h]
- This driver by default sets host->max_segs to NR_SG,
which is 128, unless a DMA engine is used, and in that case
the number of segments are also > 1
- That means this driver already disables bounce buffers
- No special action needed for these platforms
arch/arm/configs/sama5_defconfig
- Uses MMC_SDHCI, MMC_SDHCI_PLTFM, MMC_SDHCI_OF_AT91, MMC_ATMELMCI
- Uses drivers/mmc/host/sdhci.c
- Normally sets host->max_segs to SDHCI_MAX_SEGS which is 128 and
thus disables bounce buffers
- Sets host->max_segs to 1 if SDHCI_USE_SDMA is set
- SDHCI_USE_SDMA is only set by SDHCI on PCI adapers
- That means that for this platform bounce buffers are already
disabled at runtime
- No special action needed for this platform
arch/blackfin/configs/CM-BF533_defconfig
arch/blackfin/configs/CM-BF537E_defconfig
- Uses MMC_SPI (a simple MMC card connected on SPI pins)
- Uses drivers/mmc/host/mmc_spi.c
- Sets host->max_segs to MMC_SPI_BLOCKSATONCE which is 128
- That means this platform already disables bounce buffers at
runtime
- No special action needed for these platforms
arch/mips/configs/cavium_octeon_defconfig
- Uses MMC_CAVIUM_OCTEON, drivers/mmc/host/cavium.c
- Sets host->max_segs to 16 or 1
- Setting host->disable_bounce to be sure for the 1 case
arch/mips/configs/qi_lb60_defconfig
- Uses MMC_JZ4740, drivers/mmc/host/jz4740_mmc.c
- This sets host->max_segs to 128 so bounce buffers are
already runtime disabled
- No action needed for this platform
It would be interesting to come up with a list of the platforms
that actually end up using bounce buffers. I have not been
able to infer such a list, but it occurs when
host->max_segs == 1 and the bounce buffering is not explicitly
disabled.
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
In case the DT specifies neither a regulator nor a gpio
for the shared power the driver will crash accessing the regulator.
Prevent the crash by checking the regulator before use.
Use mmc_regulator_get_supply() instead of open coding the same
logic.
Signed-off-by: Jan Glauber <jglauber@cavium.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Use the mmc_card_is_blockaddr() function to properly detect if the
card uses byte or block addressing.
Signed-off-by: Steven J. Hill <Steven.Hill@cavium.com>
Acked-by: David Daney <david.daney@cavium.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
"dat" is a u64 and "shift" starts as 54 so this is a shift wrapping bug.
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Add a pointer check to prevent this smatch warning:
drivers/mmc/host/cavium.c:803 cvm_mmc_request()
error: we previously assumed 'cmd->data' could be null (see line 782)
This is a theoretical fix because MMC_CMD_ADTC seems to imply
that cmd->data is not null. Nevertheless checking cmd->data
before using it improves readability.
Signed-off-by: Jan Glauber <jglauber@cavium.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Add support for switching to DDR mode for eMMC devices.
Signed-off-by: Jan Glauber <jglauber@cavium.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Add Support for the scatter-gather DMA available in the
ThunderX MMC units. Up to 16 DMA requests can be processed
together.
Signed-off-by: Jan Glauber <jglauber@cavium.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
This core driver will be used by a MIPS platform driver
or by an ARM64 PCI driver. The core driver implements the
mmc_host_ops and slot probe & remove functions.
Callbacks are provided to allow platform specific interrupt
enable and bus locking.
The host controller supports:
- up to 4 slots that can contain sd-cards or eMMC chips
- 1, 4 and 8 bit bus width
- SDR and DDR
- transfers up to 52 Mhz (might be less when multiple slots are used)
- DMA read/write
- multi-block read/write (but not stream mode)
Voltage is limited to 3.3v and shared for all slots (vmmc and vmmcq).
A global lock for all MMC devices is required because the host
controller is shared.
Signed-off-by: Jan Glauber <jglauber@cavium.com>
Signed-off-by: David Daney <david.daney@cavium.com>
Signed-off-by: Steven J. Hill <steven.hill@cavium.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
