AuxXxilium/linux_dsm_epyc7002
1
0
Fork 0
mirror of https://github.com/AuxXxilium/linux_dsm_epyc7002.git synced 2024-11-27 04:20:51 +07:00
Code Issues Actions Packages Projects Releases Wiki Activity

serial: sh-sci: Avoid overflow in sci_baud_calc_hscif()

Browse Source 
If bps >= 1048576, the multiplication of the predivider and "bps" will
overflow, and both br and err will contain bogus values.
Skip the current and all higher clock select predividers when overflow
is detected.  Simplify the calculations using intermediates while we're
at it.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Geert Uytterhoeven 2015-11-13 17:04:56 +01:00
parent 95a2703e36
commit de01e6cd0b
1 changed files with 19 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

23
drivers/tty/serial/sh-sci.c
View File

@ -1870,7 +1870,7 @@ static unsigned int sci_scbrr_calc(struct sci_port *s, unsigned int bps,
static void sci_baud_calc_hscif(unsigned int bps, unsigned long freq, int *brr,
unsigned int *srr, unsigned int *cks)
{
unsigned int sr, br, c;
unsigned int sr, br, prediv, scrate, c;
int err, recv_margin;
int min_err = 1000; /* 100% */
int recv_max_margin = 0;
@ -1880,11 +1880,24 @@ static void sci_baud_calc_hscif(unsigned int bps, unsigned long freq, int *brr,
for (sr = 8; sr <= 32; sr++) {
for (c = 0; c <= 3; c++) {
/* integerized formulas from HSCIF documentation */
br = DIV_ROUND_CLOSEST(freq, (sr *
(1 << (2 * c + 1)) * bps));
prediv = sr * (1 << (2 * c + 1));
/*
* We need to calculate:
*
* br = freq / (prediv * bps) clamped to [1..256]
* err = (freq / (br * prediv * bps / 1000)) - 1000
*
* Watch out for overflow when calculating the desired
* sampling clock rate!
*/
if (bps > UINT_MAX / prediv)
break;
scrate = prediv * bps;
br = DIV_ROUND_CLOSEST(freq, scrate);
br = clamp(br, 1U, 256U);
err = DIV_ROUND_CLOSEST(freq, (br * bps * sr *
(1 << (2 * c + 1)) / 1000)) -
err = DIV_ROUND_CLOSEST(freq, (br * scrate) / 1000) -
1000;
/* Calc recv margin
* M: Receive margin (%)