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The interrupt handling of the RS911x is particularly heavy. For each RX packet, the card does three SDIO transactions, one to read interrupt status register, one to RX buffer length, one to read the RX packet(s). This translates to ~330 uS per one cycle of interrupt handler. In case there is more incoming traffic, this will be more. The drivers/mmc/core/sdio_irq.c has the following comment, quote "Just like traditional hard IRQ handlers, we expect SDIO IRQ handlers to be quick and to the point, so that the holding of the host lock does not cover too much work that doesn't require that lock to be held." The RS911x interrupt handler does not fit that. This patch therefore changes it such that the entire IRQ handler is moved to the RX thread instead, and the interrupt handler only wakes the RX thread. This is OK, because the interrupt handler only does things which can also be done in the RX thread, that is, it checks for firmware loading error(s), it checks buffer status, it checks whether a packet arrived and if so, reads out the packet and passes it to network stack. Moreover, this change permits removal of a code which allocated an skbuff only to get 4-byte-aligned buffer, read up to 8kiB of data into the skbuff, queue this skbuff into local private queue, then in RX thread, this buffer is dequeued, the data in the skbuff as passed to the RSI driver core, and the skbuff is deallocated. All this is replaced by directly calling the RSI driver core with local buffer. Signed-off-by: Marek Vasut <marex@denx.de> Cc: Angus Ainslie <angus@akkea.ca> Cc: David S. Miller <davem@davemloft.net> Cc: Jakub Kicinski <kuba@kernel.org> Cc: Kalle Valo <kvalo@codeaurora.org> Cc: Lee Jones <lee.jones@linaro.org> Cc: Martin Kepplinger <martink@posteo.de> Cc: Sebastian Krzyszkowiak <sebastian.krzyszkowiak@puri.sm> Cc: Siva Rebbagondla <siva8118@gmail.com> Cc: linux-wireless@vger.kernel.org Cc: netdev@vger.kernel.org Tested-by: Martin Kepplinger <martin.kepplinger@puri.sm> Signed-off-by: Kalle Valo <kvalo@codeaurora.org> Link: https://lore.kernel.org/r/20201103180941.443528-1-marex@denx.de |
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Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.