File system, Hardware, NAND/NOR

Effect of file-system on sd card’s performance

I had a task to compare different protocols( and their different implementations) like SD, SPI, SDIO(in FreeBSD’s MMCCAM implementation) by accessing SD Card. Now, for unbiased comparison, I must eliminate file system type in sd card from the equation. In this blog post, I’ll discuss/share my findings of the file-systems used for the card(SD and MMC) and how they affect its performance. So, let’s start with a very quick introduction to some basic concepts: Introduction MMC- Multimedia Card is a memory card unveiled in 1997 by SanDisk and Siemens based on NAND flash memory. eMMC is a regular MMC in…

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CAM, FreeBSD, mmccam, SDIO, Software

Implementing a MMC/SD/SDIO stack using CAM framework(Part 2)

Hi, In the next part lets look at other files which makes up the SDIO stack within mmccam framework. Please have  a look at previous part for more info: http://uditagarwal.in/index.php/2018/03/19/implementing-a-mmc-sd-sdio-stack-using-cam-framework/ mmc_sdio.c +void sdio_fill_mmcio_rw_direct(union ccb *ccb, uint8_t f, uint8_t wr, uint32_t adr, uint8_t *data) { + struct ccb_mmcio *mmcio; + + CAM_DEBUG(ccb->ccb_h.path, CAM_DEBUG_TRACE, + (“sdio_fill_mmcio(f=%d, wr=%d, adr=%02x, data=%02x)\n”, f, wr, adr, (data == NULL ? 0 : *data))); + mmcio = &ccb->mmcio; + + mmcio->cmd.opcode = SD_IO_RW_DIRECT; + mmcio->cmd.arg = SD_IO_RW_FUNC(f) | SD_IO_RW_ADR(adr); + if (wr) + mmcio->cmd.arg |= SD_IO_RW_WR | SD_IO_RW_RAW | SD_IO_RW_DAT(*data); + mmcio->cmd.flags = MMC_RSP_R5 | MMC_CMD_AC; +…

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CAM, FreeBSD, Hardware, mmccam, SDIO, Software

Detailed SDIO protocol Implementation

Reference: Wikipedia, https://www.sdcard.org/developers/overview/sdio/sdio_spec/Simplified_SDIO_Card_Spec.pdf  SDIO cards are intended to provide high-speed data Input/Output on our regular sd card slot. SDIO cards are compatible with any sd card slot and will not cause any physical damage to the host if it’s not compatible with SDIO. When SDIO is plugged in an SDIO compatible host, in its early stage it is in low power mode and consumes very little current. The host identifies the SDIO card, it’s power requirement, it’s I/O capabilities, etc. If the host finds that the power requirement is manageable and there is a driver for the I/O functionality card…

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CAM, FreeBSD, mmccam

Implementing a MMC/SD/SDIO stack using CAM framework(Part 1)

In this blog post we will have a detailed look at all the files added/changed while implementing the MMC/SD/SDIO stack via CAM framework. We will basically discuss the commit  https://github.com/freebsd/freebsd/commit/a87c7a85be3e3727b6b08b19741b4282f942400d which aims at adding MMC/SD/SDIO stack to FreeBSD’s already existing CAM framework. So, lets start one by one with each file: mmc.h #ifndef CAM_MMC_H #define CAM_MMC_H #include <dev/mmc/mmcreg.h> /* * This structure describes an MMC/SD card */ struct mmc_params { u_int8_t model[40]; /* Card model */ /* Card OCR */ uint32_t card_ocr; /* OCR of the IO portion of the card */ uint32_t io_ocr; /* Card CID — raw and…

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CAM, FreeBSD

Understanding FreeBSD’s CAM Framework

This blog post presents a gist of Free BSD’s doc on CAM(here) and chapter 14 of the book FreeBSD device driver- A guide for intrepid. It gives an introduction to the CAM(Common access method), it’s applications, it’s working and it’s organization in FreeBSD. It is written to get myself a really good understanding of mmccam stack which is nothing but SDHC/SDIO protocols wired within the CAM framework. COMMON ACCESS METHOD CAM is a method for separating HBA adapters from storage adapters and is primarily used for SCSI. By separating these drivers it reduces the complexity of both the drivers.Furthermore, this…

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Hardware

Understanding SD, SDIO and MMC Interface

  TL;DR; MMC and SD-card have the same physical and electrical specifications but different software controls. They both are used as a storage device only. SDIO and SD-Combo cards, on the other hand, incorporate Input/Output functionality(like Bluetooth, Wifi, GPS, etc) without and with the storage facility respectively. So, a SD-Combo card can act as a wifi adapter along with a storage device. In this blog post, I will present a gist of the paper http://www.kaltech.co.il/pdf/Eureka_sd_wp1.pdf  (updated link). This is meant for anyone willing to understand how removable devices like sd card work and different protocols/functionalities they support. Secure Digital (SD)…

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Hardware, RTEMS, RTOS, Software

Building and testing RTEMS-libbsd for BeagleBone Black BSP

———————————————————————— Building and testing libbsd for BeagleBone Black BSP ———————————————————————— == Installation overview == === Initial setup === – Jump into your workspace and make a directory named sandbox This folder will contain all our project files – cd sandbox/ – export sandbox=$PWD – git clone git://git.rtems.org/rtems-source-builder.git – git clone git://git.rtems.org/rtems.git – git clone git://git.rtems.org/rtems-libbsd.git === Building desired toolset for ARM === – cd rtems-source-builder/rtems/ – ../source-builder/sb-check – ../source-builder/sb-set-builder –prefix=$sandbox/5 5/rtems-arm – cd $sandbox – export PATH=$PWD/5/bin:$PATH After having required toolchain, we can now proceed towards building our Board Support Package(BSP) === Building Beagleboneblack BSP === – cd $sandbox –…

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