Messages in this thread | | | From | Geert Uytterhoeven <> | Date | Tue, 15 Dec 2020 15:24:04 +0100 | Subject | Re: [PATCH] spi: Limit the spi device max speed to controller's max speed |
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Hi Mark, Tudor,
On Fri, Dec 11, 2020 at 8:02 PM Mark Brown <broonie@kernel.org> wrote: > On Wed, 9 Dec 2020 19:35:14 +0200, Tudor Ambarus wrote: > > Make sure the max_speed_hz of spi_device does not override > > the max_speed_hz of controller. > > Applied to > > https://git.kernel.org/pub/scm/linux/kernel/git/broonie/spi.git for-next > > Thanks! > > [1/1] spi: Limit the spi device max speed to controller's max speed > commit: 9326e4f1e5dd1a4410c429638d3c412b6fc17040
> - if (!spi->max_speed_hz) > + if (!spi->max_speed_hz || > + spi->max_speed_hz > spi->controller->max_speed_hz) > spi->max_speed_hz = spi->controller->max_speed_hz;
If spi->controller->max_speed_hz is zero, a non-zero spi->max_speed_hz will be overwritten by zero.
Hence this broke spi-sh-msiof, which has the following check in sh_msiof_spi_set_clk_regs():
if (!spi_hz || !parent_rate) { WARN(1, "Invalid clock rate parameters %lu and %u\n", parent_rate, spi_hz); return; }
Without this, the driver would trigger a division-by-zero later...
Arguably all SPI controller drivers should fill in spi_controller.{min,max}_speed_hz, but as long as that is not the case, I think this patch should be reverted, or the check should be enhanced to make sure spi->controller->max_speed_hz is non-zero.
Gr{oetje,eeting}s,
Geert
-- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds
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